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7 November 2023

Melissa Wen: AMD Driver-specific Properties for Color Management on Linux (Part 2)

TL;DR: This blog post explores the color capabilities of AMD hardware and how they are exposed to userspace through driver-specific properties. It discusses the different color blocks in the AMD Display Core Next (DCN) pipeline and their capabilities, such as predefined transfer functions, 1D and 3D lookup tables (LUTs), and color transformation matrices (CTMs). It also highlights the differences in AMD HW blocks for pre and post-blending adjustments, and how these differences are reflected in the available driver-specific properties. Overall, this blog post provides a comprehensive overview of the color capabilities of AMD hardware and how they can be controlled by userspace applications through driver-specific properties. This information is valuable for anyone who wants to develop applications that can take advantage of the AMD color management pipeline. Get a closer look at each hardware block s capabilities, unlock a wealth of knowledge about AMD display hardware, and enhance your understanding of graphics and visual computing. Stay tuned for future developments as we embark on a quest for GPU color capabilities in the ever-evolving realm of rainbow treasures.
Operating Systems can use the power of GPUs to ensure consistent color reproduction across graphics devices. We can use GPU-accelerated color management to manage the diversity of color profiles, do color transformations to convert between High-Dynamic-Range (HDR) and Standard-Dynamic-Range (SDR) content and color enhacements for wide color gamut (WCG). However, to make use of GPU display capabilities, we need an interface between userspace and the kernel display drivers that is currently absent in the Linux/DRM KMS API. In the previous blog post I presented how we are expanding the Linux/DRM color management API to expose specific properties of AMD hardware. Now, I ll guide you to the color features for the Linux/AMD display driver. We embark on a journey through DRM/KMS, AMD Display Manager, and AMD Display Core and delve into the color blocks to uncover the secrets of color manipulation within AMD hardware. Here we ll talk less about the color tools and more about where to find them in the hardware. We resort to driver-specific properties to reach AMD hardware blocks with color capabilities. These blocks display features like predefined transfer functions, color transformation matrices, and 1-dimensional (1D LUT) and 3-dimensional lookup tables (3D LUT). Here, we will understand how these color features are strategically placed into color blocks both before and after blending in Display Pipe and Plane (DPP) and Multiple Pipe/Plane Combined (MPC) blocks. That said, welcome back to the second part of our thrilling journey through AMD s color management realm!

AMD Display Driver in the Linux/DRM Subsystem: The Journey In my 2022 XDC talk I m not an AMD expert, but , I briefly explained the organizational structure of the Linux/AMD display driver where the driver code is bifurcated into a Linux-specific section and a shared-code portion. To reveal AMD s color secrets through the Linux kernel DRM API, our journey led us through these layers of the Linux/AMD display driver s software stack. It includes traversing the DRM/KMS framework, the AMD Display Manager (DM), and the AMD Display Core (DC) [1]. The DRM/KMS framework provides the atomic API for color management through KMS properties represented by struct drm_property. We extended the color management interface exposed to userspace by leveraging existing resources and connecting them with driver-specific functions for managing modeset properties. On the AMD DC layer, the interface with hardware color blocks is established. The AMD DC layer contains OS-agnostic components that are shared across different platforms, making it an invaluable resource. This layer already implements hardware programming and resource management, simplifying the external developer s task. While examining the DC code, we gain insights into the color pipeline and capabilities, even without direct access to specifications. Additionally, AMD developers provide essential support by answering queries and reviewing our work upstream. The primary challenge involved identifying and understanding relevant AMD DC code to configure each color block in the color pipeline. However, the ultimate goal was to bridge the DC color capabilities with the DRM API. For this, we changed the AMD DM, the OS-dependent layer connecting the DC interface to the DRM/KMS framework. We defined and managed driver-specific color properties, facilitated the transport of user space data to the DC, and translated DRM features and settings to the DC interface. Considerations were also made for differences in the color pipeline based on hardware capabilities.

Exploring Color Capabilities of the AMD display hardware Now, let s dive into the exciting realm of AMD color capabilities, where a abundance of techniques and tools await to make your colors look extraordinary across diverse devices. First, we need to know a little about the color transformation and calibration tools and techniques that you can find in different blocks of the AMD hardware. I borrowed some images from [2] [3] [4] to help you understand the information.

Predefined Transfer Functions (Named Fixed Curves): Transfer functions serve as the bridge between the digital and visual worlds, defining the mathematical relationship between digital color values and linear scene/display values and ensuring consistent color reproduction across different devices and media. You can learn more about curves in the chapter GPU Gems 3 - The Importance of Being Linear by Larry Gritz and Eugene d Eon. ITU-R 2100 introduces three main types of transfer functions:
  • OETF: the opto-electronic transfer function, which converts linear scene light into the video signal, typically within a camera.
  • EOTF: electro-optical transfer function, which converts the video signal into the linear light output of the display.
  • OOTF: opto-optical transfer function, which has the role of applying the rendering intent .
AMD s display driver supports the following pre-defined transfer functions (aka named fixed curves):
  • Linear/Unity: linear/identity relationship between pixel value and luminance value;
  • Gamma 2.2, Gamma 2.4, Gamma 2.6: pure power functions;
  • sRGB: 2.4: The piece-wise transfer function from IEC 61966-2-1:1999;
  • BT.709: has a linear segment in the bottom part and then a power function with a 0.45 (~1/2.22) gamma for the rest of the range; standardized by ITU-R BT.709-6;
  • PQ (Perceptual Quantizer): used for HDR display, allows luminance range capability of 0 to 10,000 nits; standardized by SMPTE ST 2084.
These capabilities vary depending on the hardware block, with some utilizing hardcoded curves and others relying on AMD s color module to construct curves from standardized coefficients. It also supports user/custom curves built from a lookup table.

1D LUTs (1-dimensional Lookup Table): A 1D LUT is a versatile tool, defining a one-dimensional color transformation based on a single parameter. It s very well explained by Jeremy Selan at GPU Gems 2 - Chapter 24 Using Lookup Tables to Accelerate Color Transformations It enables adjustments to color, brightness, and contrast, making it ideal for fine-tuning. In the Linux AMD display driver, the atomic API offers a 1D LUT with 4096 entries and 8-bit depth, while legacy gamma uses a size of 256.

3D LUTs (3-dimensional Lookup Table): These tables work in three dimensions red, green, and blue. They re perfect for complex color transformations and adjustments between color channels. It s also more complex to manage and require more computational resources. Jeremy also explains 3D LUT at GPU Gems 2 - Chapter 24 Using Lookup Tables to Accelerate Color Transformations

CTM (Color Transformation Matrices): Color transformation matrices facilitate the transition between different color spaces, playing a crucial role in color space conversion.

HDR Multiplier: HDR multiplier is a factor applied to the color values of an image to increase their overall brightness.

AMD Color Capabilities in the Hardware Pipeline First, let s take a closer look at the AMD Display Core Next hardware pipeline in the Linux kernel documentation for AMDGPU driver - Display Core Next In the AMD Display Core Next hardware pipeline, we encounter two hardware blocks with color capabilities: the Display Pipe and Plane (DPP) and the Multiple Pipe/Plane Combined (MPC). The DPP handles color adjustments per plane before blending, while the MPC engages in post-blending color adjustments. In short, we expect DPP color capabilities to match up with DRM plane properties, and MPC color capabilities to play nice with DRM CRTC properties. Note: here s the catch there are some DRM CRTC color transformations that don t have a corresponding AMD MPC color block, and vice versa. It s like a puzzle, and we re here to solve it!

AMD Color Blocks and Capabilities We can finally talk about the color capabilities of each AMD color block. As it varies based on the generation of hardware, let s take the DCN3+ family as reference. What s possible to do before and after blending depends on hardware capabilities describe in the kernel driver by struct dpp_color_caps and struct mpc_color_caps. The AMD Steam Deck hardware provides a tangible example of these capabilities. Therefore, we take SteamDeck/DCN301 driver as an example and look at the Color pipeline capabilities described in the file: driver/gpu/drm/amd/display/dcn301/dcn301_resources.c
/* Color pipeline capabilities */
dc->caps.color.dpp.dcn_arch = 1; // If it is a Display Core Next (DCN): yes. Zero means DCE.
dc->caps.color.dpp.input_lut_shared = 0;
dc->caps.color.dpp.icsc = 1; // Intput Color Space Conversion  (CSC) matrix.
dc->caps.color.dpp.dgam_ram = 0; // The old degamma block for degamma curve (hardcoded and LUT).  Gamma correction  is the new one.
dc->caps.color.dpp.dgam_rom_caps.srgb = 1; // sRGB hardcoded curve support
dc->caps.color.dpp.dgam_rom_caps.bt2020 = 1; // BT2020 hardcoded curve support (seems not actually in use)
dc->caps.color.dpp.dgam_rom_caps.gamma2_2 = 1; // Gamma 2.2 hardcoded curve support
dc->caps.color.dpp.dgam_rom_caps.pq = 1; // PQ hardcoded curve support
dc->caps.color.dpp.dgam_rom_caps.hlg = 1; // HLG hardcoded curve support
dc->caps.color.dpp.post_csc = 1; // CSC matrix
dc->caps.color.dpp.gamma_corr = 1; // New  Gamma Correction  block for degamma user LUT;
dc->caps.color.dpp.dgam_rom_for_yuv = 0;
dc->caps.color.dpp.hw_3d_lut = 1; // 3D LUT support. If so, it's always preceded by a shaper curve. 
dc->caps.color.dpp.ogam_ram = 1; //  Blend Gamma  block for custom curve just after blending
// no OGAM ROM on DCN301
dc->caps.color.dpp.ogam_rom_caps.srgb = 0;
dc->caps.color.dpp.ogam_rom_caps.bt2020 = 0;
dc->caps.color.dpp.ogam_rom_caps.gamma2_2 = 0;
dc->caps.color.dpp.ogam_rom_caps.pq = 0;
dc->caps.color.dpp.ogam_rom_caps.hlg = 0;
dc->caps.color.dpp.ocsc = 0;
dc->caps.color.mpc.gamut_remap = 1; // Post-blending CTM (pre-blending CTM is always supported)
dc->caps.color.mpc.num_3dluts = pool->base.res_cap->num_mpc_3dlut; // Post-blending 3D LUT (preceded by shaper curve)
dc->caps.color.mpc.ogam_ram = 1; // Post-blending regamma.
// No pre-defined TF supported for regamma.
dc->caps.color.mpc.ogam_rom_caps.srgb = 0;
dc->caps.color.mpc.ogam_rom_caps.bt2020 = 0;
dc->caps.color.mpc.ogam_rom_caps.gamma2_2 = 0;
dc->caps.color.mpc.ogam_rom_caps.pq = 0;
dc->caps.color.mpc.ogam_rom_caps.hlg = 0;
dc->caps.color.mpc.ocsc = 1; // Output CSC matrix.
I included some inline comments in each element of the color caps to quickly describe them, but you can find the same information in the Linux kernel documentation. See more in struct dpp_color_caps, struct mpc_color_caps and struct rom_curve_caps. Now, using this guideline, we go through color capabilities of DPP and MPC blocks and talk more about mapping driver-specific properties to corresponding color blocks.

DPP Color Pipeline: Before Blending (Per Plane) Let s explore the capabilities of DPP blocks and what you can achieve with a color block. The very first thing to pay attention is the display architecture of the display hardware: previously AMD uses a display architecture called DCE
  • Display and Compositing Engine, but newer hardware follows DCN - Display Core Next.
The architectute is described by: dc->caps.color.dpp.dcn_arch

AMD Plane Degamma: TF and 1D LUT Described by: dc->caps.color.dpp.dgam_ram, dc->caps.color.dpp.dgam_rom_caps,dc->caps.color.dpp.gamma_corr AMD Plane Degamma data is mapped to the initial stage of the DPP pipeline. It is utilized to transition from scanout/encoded values to linear values for arithmetic operations. Plane Degamma supports both pre-defined transfer functions and 1D LUTs, depending on the hardware generation. DCN2 and older families handle both types of curve in the Degamma RAM block (dc->caps.color.dpp.dgam_ram); DCN3+ separate hardcoded curves and 1D LUT into two block: Degamma ROM (dc->caps.color.dpp.dgam_rom_caps) and Gamma correction block (dc->caps.color.dpp.gamma_corr), respectively. Pre-defined transfer functions:
  • they are hardcoded curves (read-only memory - ROM);
  • supported curves: sRGB EOTF, BT.709 inverse OETF, PQ EOTF and HLG OETF, Gamma 2.2, Gamma 2.4 and Gamma 2.6 EOTF.
The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. Setting TF = Identity/Default and LUT as NULL means bypass. References:

AMD Plane 3x4 CTM (Color Transformation Matrix) AMD Plane CTM data goes to the DPP Gamut Remap block, supporting a 3x4 fixed point (s31.32) matrix for color space conversions. The data is interpreted as a struct drm_color_ctm_3x4. Setting NULL means bypass. References:

AMD Plane Shaper: TF + 1D LUT Described by: dc->caps.color.dpp.hw_3d_lut The Shaper block fine-tunes color adjustments before applying the 3D LUT, optimizing the use of the limited entries in each dimension of the 3D LUT. On AMD hardware, a 3D LUT always means a preceding shaper 1D LUT used for delinearizing and/or normalizing the color space before applying a 3D LUT, so this entry on DPP color caps dc->caps.color.dpp.hw_3d_lut means support for both shaper 1D LUT and 3D LUT. Pre-defined transfer function enables delinearizing content with or without shaper LUT, where AMD color module calculates the resulted shaper curve. Shaper curves go from linear values to encoded values. If we are already in a non-linear space and/or don t need to normalize values, we can set a Identity TF for shaper that works similar to bypass and is also the default TF value. Pre-defined transfer functions:
  • there is no DPP Shaper ROM. Curves are calculated by AMD color modules. Check calculate_curve() function in the file amd/display/modules/color/color_gamma.c.
  • supported curves: Identity, sRGB inverse EOTF, BT.709 OETF, PQ inverse EOTF, HLG OETF, and Gamma 2.2, Gamma 2.4, Gamma 2.6 inverse EOTF.
The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. When setting Plane Shaper TF (!= Identity) and LUT at the same time, the color module will combine the pre-defined TF and the custom LUT values into the LUT that s actually programmed. Setting TF = Identity/Default and LUT as NULL works as bypass. References:

AMD Plane 3D LUT Described by: dc->caps.color.dpp.hw_3d_lut The 3D LUT in the DPP block facilitates complex color transformations and adjustments. 3D LUT is a three-dimensional array where each element is an RGB triplet. As mentioned before, the dc->caps.color.dpp.hw_3d_lut describe if DPP 3D LUT is supported. The AMD driver-specific property advertise the size of a single dimension via LUT3D_SIZE property. Plane 3D LUT is a blog property where the data is interpreted as an array of struct drm_color_lut elements and the number of entries is LUT3D_SIZE cubic. The array contains samples from the approximated function. Values between samples are estimated by tetrahedral interpolation The array is accessed with three indices, one for each input dimension (color channel), blue being the outermost dimension, red the innermost. This distribution is better visualized when examining the code in [RFC PATCH 5/5] drm/amd/display: Fill 3D LUT from userspace by Alex Hung:
+	for (nib = 0; nib < 17; nib++)  
+		for (nig = 0; nig < 17; nig++)  
+			for (nir = 0; nir < 17; nir++)  
+				ind_lut = 3 * (nib + 17*nig + 289*nir);
+
+				rgb_area[ind].red = rgb_lib[ind_lut + 0];
+				rgb_area[ind].green = rgb_lib[ind_lut + 1];
+				rgb_area[ind].blue = rgb_lib[ind_lut + 2];
+				ind++;
+			 
+		 
+	 
In our driver-specific approach we opted to advertise it s behavior to the userspace instead of implicitly dealing with it in the kernel driver. AMD s hardware supports 3D LUTs with 17-size or 9-size (4913 and 729 entries respectively), and you can choose between 10-bit or 12-bit. In the current driver-specific work we focus on enabling only 17-size 12-bit 3D LUT, as in [PATCH v3 25/32] drm/amd/display: add plane 3D LUT support:
+		/* Stride and bit depth are not programmable by API yet.
+		 * Therefore, only supports 17x17x17 3D LUT (12-bit).
+		 */
+		lut->lut_3d.use_tetrahedral_9 = false;
+		lut->lut_3d.use_12bits = true;
+		lut->state.bits.initialized = 1;
+		__drm_3dlut_to_dc_3dlut(drm_lut, drm_lut3d_size, &lut->lut_3d,
+					lut->lut_3d.use_tetrahedral_9,
+					MAX_COLOR_3DLUT_BITDEPTH);
A refined control of 3D LUT parameters should go through a follow-up version or generic API. Setting 3D LUT to NULL means bypass. References:

AMD Plane Blend/Out Gamma: TF + 1D LUT Described by: dc->caps.color.dpp.ogam_ram The Blend/Out Gamma block applies the final touch-up before blending, allowing users to linearize content after 3D LUT and just before the blending. It supports both 1D LUT and pre-defined TF. We can see Shaper and Blend LUTs as 1D LUTs that are sandwich the 3D LUT. So, if we don t need 3D LUT transformations, we may want to only use Degamma block to linearize and skip Shaper, 3D LUT and Blend. Pre-defined transfer function:
  • there is no DPP Blend ROM. Curves are calculated by AMD color modules;
  • supported curves: Identity, sRGB EOTF, BT.709 inverse OETF, PQ EOTF, HLG inverse OETF, and Gamma 2.2, Gamma 2.4, Gamma 2.6 EOTF.
The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. If plane_blend_tf_property != Identity TF, AMD color module will combine the user LUT values with pre-defined TF into the LUT parameters to be programmed. Setting TF = Identity/Default and LUT to NULL means bypass. References:

MPC Color Pipeline: After Blending (Per CRTC)

DRM CRTC Degamma 1D LUT The degamma lookup table (LUT) for converting framebuffer pixel data before apply the color conversion matrix. The data is interpreted as an array of struct drm_color_lut elements. Setting NULL means bypass. Not really supported. The driver is currently reusing the DPP degamma LUT block (dc->caps.color.dpp.dgam_ram and dc->caps.color.dpp.gamma_corr) for supporting DRM CRTC Degamma LUT, as explaning by [PATCH v3 20/32] drm/amd/display: reject atomic commit if setting both plane and CRTC degamma.

DRM CRTC 3x3 CTM Described by: dc->caps.color.mpc.gamut_remap It sets the current transformation matrix (CTM) apply to pixel data after the lookup through the degamma LUT and before the lookup through the gamma LUT. The data is interpreted as a struct drm_color_ctm. Setting NULL means bypass.

DRM CRTC Gamma 1D LUT + AMD CRTC Gamma TF Described by: dc->caps.color.mpc.ogam_ram After all that, you might still want to convert the content to wire encoding. No worries, in addition to DRM CRTC 1D LUT, we ve got a AMD CRTC gamma transfer function (TF) to make it happen. Possible TF values are defined by enum amdgpu_transfer_function. Pre-defined transfer functions:
  • there is no MPC Gamma ROM. Curves are calculated by AMD color modules.
  • supported curves: Identity, sRGB inverse EOTF, BT.709 OETF, PQ inverse EOTF, HLG OETF, and Gamma 2.2, Gamma 2.4, Gamma 2.6 inverse EOTF.
The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. When setting CRTC Gamma TF (!= Identity) and LUT at the same time, the color module will combine the pre-defined TF and the custom LUT values into the LUT that s actually programmed. Setting TF = Identity/Default and LUT to NULL means bypass. References:

Others

AMD CRTC Shaper and 3D LUT We have previously worked on exposing CRTC shaper and CRTC 3D LUT, but they were removed from the AMD driver-specific color series because they lack userspace case. CRTC shaper and 3D LUT works similar to plane shaper and 3D LUT but after blending (MPC block). The difference here is that setting (not bypass) Shaper and Gamma blocks together are not expected, since both blocks are used to delinearize the input space. In summary, we either set Shaper + 3D LUT or Gamma.

Input and Output Color Space Conversion There are two other color capabilities of AMD display hardware that were integrated to DRM by previous works and worth a brief explanation here. The DC Input CSC sets pre-defined coefficients from the values of DRM plane color_range and color_encoding properties. It is used for color space conversion of the input content. On the other hand, we have de DC Output CSC (OCSC) sets pre-defined coefficients from DRM connector colorspace properties. It is uses for color space conversion of the composed image to the one supported by the sink. References:

The search for rainbow treasures is not over yet If you want to understand a little more about this work, be sure to watch Joshua and I presented two talks at XDC 2023 about AMD/Steam Deck colors on Gamescope: In the time between the first and second part of this blog post, Uma Shashank and Chaitanya Kumar Borah published the plane color pipeline for Intel and Harry Wentland implemented a generic API for DRM based on VKMS support. We discussed these two proposals and the next steps for Color on Linux during the Color Management workshop at XDC 2023 and I briefly shared workshop results in the 2023 XDC lightning talk session. The search for rainbow treasures is not over yet! We plan to meet again next year in the 2024 Display Hackfest in Coru a-Spain (Igalia s HQ) to keep up the pace and continue advancing today s display needs on Linux. Finally, a HUGE thank you to everyone who worked with me on exploring AMD s color capabilities and making them available in userspace.

1 November 2023

Matthew Garrett: Why ACPI?

"Why does ACPI exist" - - the greatest thread in the history of forums, locked by a moderator after 12,239 pages of heated debate, wait no let me start again.

Why does ACPI exist? In the beforetimes power management on x86 was done by jumping to an opaque BIOS entry point and hoping it would do the right thing. It frequently didn't. We called this Advanced Power Management (Advanced because before this power management involved custom drivers for every machine and everyone agreed that this was a bad idea), and it involved the firmware having to save and restore the state of every piece of hardware in the system. This meant that assumptions about hardware configuration were baked into the firmware - failed to program your graphics card exactly the way the BIOS expected? Hurrah! It's only saved and restored a subset of the state that you configured and now potential data corruption for you. The developers of ACPI made the reasonable decision that, well, maybe since the OS was the one setting state in the first place, the OS should restore it.

So far so good. But some state is fundamentally device specific, at a level that the OS generally ignores. How should this state be managed? One way to do that would be to have the OS know about the device specific details. Unfortunately that means you can't ship the computer without having OS support for it, which means having OS support for every device (exactly what we'd got away from with APM). This, uh, was not an option the PC industry seriously considered. The alternative is that you ship something that abstracts the details of the specific hardware and makes that abstraction available to the OS. This is what ACPI does, and it's also what things like Device Tree do. Both provide static information about how the platform is configured, which can then be consumed by the OS and avoid needing device-specific drivers or configuration to be built-in.

The main distinction between Device Tree and ACPI is that Device Tree is purely a description of the hardware that exists, and so still requires the OS to know what's possible - if you add a new type of power controller, for instance, you need to add a driver for that to the OS before you can express that via Device Tree. ACPI decided to include an interpreted language to allow vendors to expose functionality to the OS without the OS needing to know about the underlying hardware. So, for instance, ACPI allows you to associate a device with a function to power down that device. That function may, when executed, trigger a bunch of register accesses to a piece of hardware otherwise not exposed to the OS, and that hardware may then cut the power rail to the device to power it down entirely. And that can be done without the OS having to know anything about the control hardware.

How is this better than just calling into the firmware to do it? Because the fact that ACPI declares that it's going to access these registers means the OS can figure out that it shouldn't, because it might otherwise collide with what the firmware is doing. With APM we had no visibility into that - if the OS tried to touch the hardware at the same time APM did, boom, almost impossible to debug failures (This is why various hardware monitoring drivers refuse to load by default on Linux - the firmware declares that it's going to touch those registers itself, so Linux decides not to in order to avoid race conditions and potential hardware damage. In many cases the firmware offers a collaborative interface to obtain the same data, and a driver can be written to get that. this bug comment discusses this for a specific board)

Unfortunately ACPI doesn't entirely remove opaque firmware from the equation - ACPI methods can still trigger System Management Mode, which is basically a fancy way to say "Your computer stops running your OS, does something else for a while, and you have no idea what". This has all the same issues that APM did, in that if the hardware isn't in exactly the state the firmware expects, bad things can happen. While historically there were a bunch of ACPI-related issues because the spec didn't define every single possible scenario and also there was no conformance suite (eg, should the interpreter be multi-threaded? Not defined by spec, but influences whether a specific implementation will work or not!), these days overall compatibility is pretty solid and the vast majority of systems work just fine - but we do still have some issues that are largely associated with System Management Mode.

One example is a recent Lenovo one, where the firmware appears to try to poke the NVME drive on resume. There's some indication that this is intended to deal with transparently unlocking self-encrypting drives on resume, but it seems to do so without taking IOMMU configuration into account and so things explode. It's kind of understandable why a vendor would implement something like this, but it's also kind of understandable that doing so without OS cooperation may end badly.

This isn't something that ACPI enabled - in the absence of ACPI firmware vendors would just be doing this unilaterally with even less OS involvement and we'd probably have even more of these issues. Ideally we'd "simply" have hardware that didn't support transitioning back to opaque code, but we don't (ARM has basically the same issue with TrustZone). In the absence of the ideal world, by and large ACPI has been a net improvement in Linux compatibility on x86 systems. It certainly didn't remove the "Everything is Windows" mentality that many vendors have, but it meant we largely only needed to ensure that Linux behaved the same way as Windows in a finite number of ways (ie, the behaviour of the ACPI interpreter) rather than in every single hardware driver, and so the chances that a new machine will work out of the box are much greater than they were in the pre-ACPI period.

There's an alternative universe where we decided to teach the kernel about every piece of hardware it should run on. Fortunately (or, well, unfortunately) we've seen that in the ARM world. Most device-specific simply never reaches mainline, and most users are stuck running ancient kernels as a result. Imagine every x86 device vendor shipping their own kernel optimised for their hardware, and now imagine how well that works out given the quality of their firmware. Does that really seem better to you?

It's understandable why ACPI has a poor reputation. But it's also hard to figure out what would work better in the real world. We could have built something similar on top of Open Firmware instead but the distinction wouldn't be terribly meaningful - we'd just have Forth instead of the ACPI bytecode language. Longing for a non-ACPI world without presenting something that's better and actually stands a reasonable chance of adoption doesn't make the world a better place.

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31 October 2023

Iustin Pop: Raspberry PI OS: upgrading and cross-grading

One of the downsides of running Raspberry PI OS is the fact that - not having the resources of pure Debian - upgrades are not recommended, and cross-grades (migrating between armhf and arm64) is not even mentioned. Is this really true? It is, after all a Debian-based system, so it should in theory be doable. Let s try!

Upgrading The recently announced release based on Debian Bookworm here says:
We have always said that for a major version upgrade, you should re-image your SD card and start again with a clean image. In the past, we have suggested procedures for updating an existing image to the new version, but always with the caveat that we do not recommend it, and you do this at your own risk. This time, because the changes to the underlying architecture are so significant, we are not suggesting any procedure for upgrading a Bullseye image to Bookworm; any attempt to do this will almost certainly end up with a non-booting desktop and data loss. The only way to get Bookworm is either to create an SD card using Raspberry Pi Imager, or to download and flash a Bookworm image from here with your tool of choice.
Which means, it s time to actually try it turns out it s actually trivial, if you use RPIs as headless servers. I had only three issues:
  • if using an initrd, the new initrd-building scripts/hooks are looking for some binaries in /usr/bin, and not in /bin; solution: install manually the usrmerge package, and then re-run dpkg --configure -a;
  • also if using an initrd, the scripts are looking for the kernel config file in /boot/config-$(uname -r), and the raspberry pi kernel package doesn t provide this; workaround: modprobe configs && zcat /proc/config.gz > /boot/config-$(uname -r);
  • and finally, on normal RPI systems, that don t use manual configurations of interfaces in /etc/network/interface, migrating from the previous dhcpcd to NetworkManager will break network connectivity, and require you to log in locally and fix things.
I expect most people to hit only the 3rd, and almost no-one to use initrd on raspberry pi. But, overall, aside from these two issues and a couple of cosmetic ones (login.defs being rewritten from scratch and showing a baffling diff, for example), it was easy. Is it worth doing? Definitely. Had no data loss, and no non-booting system.

Cross-grading (32 bit to 64 bit userland) This one is actually painful. Internet searches go from it s possible, I think to it s definitely not worth trying . Examples: Aside from these, there are a gazillion other posts about switching the kernel to 64 bit. And that s worth doing on its own, but it s only half the way. So, armed with two different systems - a RPI4 4GB and a RPI Zero W2 - I tried to do this. And while it can be done, it takes many hours - first system was about 6 hours, second the same, and a third RPI4 probably took ~3 hours only since I knew the problematic issues. So, what are the steps? Basically:
  • install devscripts, since you will need dget
  • enable new architecture in dpkg: dpkg --add-architecture arm64
  • switch over apt sources to include the 64 bit repos, which are different than the 32 bit ones (Raspberry PI OS did a migration here; normally a single repository has all architectures, of course)
  • downgrade all custom rpi packages/libraries to the standard bookworm/bullseye version, since dpkg won t usually allow a single library package to have different versions (I think it s possible to override, but I didn t bother)
  • install libc for the arm64 arch (this takes some effort, it s actually a set of 3-4 packages)
  • once the above is done, install whiptail:amd64 and rejoice at running a 64-bit binary!
  • then painfully go through sets of packages and migrate the set to arm64:
    • sometimes this work via apt, sometimes you ll need to use dget and dpkg -i
    • make sure you download both the armhf and arm64 versions before doing dpkg -i, since you ll need to rollback some installs
  • at one point, you ll be able to switch over dpkg and apt to arm64, at which point the default architecture flips over; from here, if you ve done it at the right moment, it becomes very easy; you ll probably need an apt install --fix-broken, though, at first
  • and then, finish by replacing all packages with arm64 versions
  • and then, dpkg --remove-architecture armhf, reboot, and profit!
But it s tears and blood to get to that point

Pain point 1: RPI custom versions of packages Since the 32bit armhf architecture is a bit weird - having many variations - it turns out that raspberry pi OS has many packages that are very slightly tweaked to disable a compilation flag or work around build/test failures, or whatnot. Since we talk here about 64-bit capable processors, almost none of these are needed, but they do make life harder since the 64 bit version doesn t have those overrides. So what is needed would be to say downgrade all armhf packages to the version in debian upstream repo , but I couldn t find the right apt pinning incantation to do that. So what I did was to remove the 32bit repos, then use apt-show-versions to see which packages have versions that are no longer in any repo, then downgrade them. There s a further, minor, complication that there were about 3-4 packages with same version but different hash (!), which simply needed apt install --reinstall, I think.

Pain point 2: architecture independent packages There is one very big issue with dpkg in all this story, and the one that makes things very problematic: while you can have a library package installed multiple times for different architectures, as the files live in different paths, a non-library package can only be installed once (usually). For binary packages (arch:any), that is fine. But architecture-independent packages (arch:all) are problematic since usually they depend on a binary package, but they always depend on the default architecture version! Hrmm, and I just realise I don t have logs from this, so I m only ~80% confident. But basically:
  • vim-solarized (arch:all) depends on vim (arch:any)
  • if you replace vim armhf with vim arm64, this will break vim-solarized, until the default architecture becomes arm64
So you need to keep track of which packages apt will de-install, for later re-installation. It is possible that Multi-Arch: foreign solves this, per the debian wiki which says:
Note that even though Architecture: all and Multi-Arch: foreign may look like similar concepts, they are not. The former means that the same binary package can be installed on different architectures. Yet, after installation such packages are treated as if they were native architecture (by definition the architecture of the dpkg package) packages. Thus Architecture: all packages cannot satisfy dependencies from other architectures without being marked Multi-Arch foreign.
It also has warnings about how to properly use this. But, in general, not many packages have it, so it is a problem.

Pain point 3: remove + install vs overwrite It seems that depending on how the solver computes a solution, when migrating a package from 32 to 64 bit, it can choose either to:
  • overwrite in place the package (akin to dpkg -i)
  • remove + install later
The former is OK, the later is not. Or, actually, it might be that apt never can do this, for example (edited for brevity):
# apt install systemd:arm64 --no-install-recommends
The following packages will be REMOVED:
  systemd
The following NEW packages will be installed:
  systemd:arm64
0 upgraded, 1 newly installed, 1 to remove and 35 not upgraded.
Do you want to continue? [Y/n] y
dpkg: systemd: dependency problems, but removing anyway as you requested:
 systemd-sysv depends on systemd.
Removing systemd (247.3-7+deb11u2) ...
systemd is the active init system, please switch to another before removing systemd.
dpkg: error processing package systemd (--remove):
 installed systemd package pre-removal script subprocess returned error exit status 1
dpkg: too many errors, stopping
Errors were encountered while processing:
 systemd
Processing was halted because there were too many errors.
But at the same time, overwrite in place is all good - via dpkg -i from /var/cache/apt/archives. In this case it manifested via a prerm script, in other cases is manifests via dependencies that are no longer satisfied for packages that can t be removed, etc. etc. So you will have to resort to dpkg -i a lot.

Pain point 4: lib- packages that are not lib During the whole process, it is very tempting to just go ahead and install the corresponding arm64 package for all armhf lib package, in one go, since these can coexist. Well, this simple plan is complicated by the fact that some packages are named libfoo-bar, but are actual holding (e.g.) the bar binary for the libfoo package. Examples:
  • libmagic-mgc contains /usr/lib/file/magic.mgc, which conflicts between the 32 and 64 bit versions; of course, it s the exact same file, so this should be an arch:all package, but
  • libpam-modules-bin and liblockfile-bin actually contain binaries (per the -bin suffix)
It s possible to work around all this, but it changes a 1 minute:
# apt install $(dpkg -i   grep ^ii   awk ' print $2 ' grep :amrhf sed -e 's/:armhf/:arm64')
into a 10-20 minutes fight with packages (like most other steps).

Is it worth doing? Compared to the simple bullseye bookworm upgrade, I m not sure about this. The result? Yes, definitely, the system feels - weirdly - much more responsive, logged in over SSH. I guess the arm64 base architecture has some more efficient ops than the lowest denominator armhf , so to say (e.g. there was in the 32 bit version some rpi-custom package with string ops), and thus migrating to 64 bit makes more things faster , but this is subjective so it might be actually not true. But from the point of view of the effort? Unless you like to play with dpkg and apt, and understand how these work and break, I d rather say, migrate to ansible and automate the deployment. It s doable, sure, and by the third system, I got this nailed down pretty well, but it was a lot of time spent. The good aspect is that I did 3 migrations:
  • rpi zero w2: bullseye 32 bit to 64 bit, then bullseye to bookworm
  • rpi 4: bullseye to bookworm, then bookworm 32bit to 64 bit
  • same, again, for a more important system
And all three worked well and no data loss. But I m really glad I have this behind me, I probably wouldn t do a fourth system, even if forced And now, waiting for the RPI 5 to be available See you!

22 October 2023

Ravi Dwivedi: Software Freedom Day at sflc.in

Software Freedom Law Center, India, also known as sflc.in, organized an event to celebrate the Software Freedom Day on 30th September 2023. Me, Sahil, Contrapunctus and Suresh joined. The venue was at the SFLC India office in Delhi. The sflc.in office was on the second floor of what looked like someone s apartment:). I also met Chirag, Orendra, Surbhi and others. My plan was to have a stall on LibreOffice and Prav app to raise awareness about these projects. I didn t have QR code for downloading prav app printed already, so I asked the people at sflc.in if they can get it printed for me. They were very kind and helped me in getting a color printout for me. So, I got a stall in their main room. Surbhi was having an Inkscape stall next to mine and gave me company. People came and asked about the prav project and then I realized I was still too tired to explain the idea behind the prav project and about LibreOffice (after a long Kerala trip). We got a few prav app installs during the event, which is cool.
My stall. Photo credits: Tejaswini.
Sahil had Debian stall and contrapunctus had OpenStreetMap stall. After about an hour, Revolution OS was screened for all of us to watch, along with popcorn. The documentary gave an overview of history of Free Software Movement. The office had a kitchen where fresh chai was being made and served to us. The organizers ordered a lot of good snacks for us.
Snacks and tea at the front desk. CC-BY-SA 4.0 by Ravi Dwivedi.
I came out of the movie hall to take more tea and snacks from the front desk. I saw a beautiful painting was hanging at the wall opposite to the front desk and Tejaswini (from sflc.in) revealed that she had made it. The tea was really good as it was freshly made in the kitchen. After the movie, we played a game of pictionary. We were divided into two teams. The game goes as follows: A person from a team is selected and given a term related to freedom respecting software written on a piece of paper, but concealed from other participants. Then that person draws something on the board (no logo, no alphabets) without speaking. If the team from which the person belongs correctly guesses the term, the team gets one step ahead on the leader board. The team who reaches the finish line wins. I recall some fun pictionaries. Like, the one in the picture below seems far from the word Wireguard and even then someone from the team guessed that word. Our team won in the end \o/.
Pictionary drawing nowhere close to the intended word Wireguard :), which was guessed. Photo by Ravi Dwivedi, CC-BY-SA 4.0.
Then, we posed for a group picture. At the end, SFLC.in had a delicious cake in store for us. They had some merchandise - handbags, T-shirts, etc. which we could take if we donate some amount to SFLC.in. I bought a handbag with Ban Plastic, not Internet written on it in exchange for donation. I hope that gives people around me a powerful message :) .
Group photo. Photo credits: Tejaswini.
Tasty cake. CC-BY-SA 4.0 by Ravi Dwivedi.
Merchandise by sflc.in. CC-BY-SA 4.0 by Ravi Dwivedi.
All in all, a nice event by sflc.in :)

Aigars Mahinovs: Figuring out finances part 3

So now that I have something that looks very much like a budgeting setup going, I am going to .. delete it! Why? Well, at the end of the last part of this, the Firefly III instance was running on a tiny Debian server in a Docker container right next to another Docker container that is running the main user of this server - a Home Assistant instance that has been managing my home for several years already. So why change that? See, there is one bit of knowledge that is very crucial to your Home Assistant experience, which is not really emphasised enough in the Home Assistant documentation. In fact back when I was getting into the Home Assistant both the main documentation and basically all the guides around were just coming off the hype of Docker disrupting everything and that is a big reason why everyone suggested to install and use Home Assistant as a Docker container on top of any kind of stable OS. In fact I used to run it for years on my TerraMaster NAS, just so that I don't have a separate home server running 24/7 at home and just have everything inside the very compact NAS case. So here is the thing you NEED to know - Home Assistant Container is DEMO version of Home Assistant! If you want to have a full Home Assistant experience and use the knowledge of the huge community around the HA space, you have to use the Home Assistant OS. Ideally on dedicated hardware. Ideally on HA Green box, but any tiny PC would also work great. Raspberry Pi 4+ is common, but quite weak as the network size grows and especially the SD card for storage gets old very fast. Get a real small x86 PC with at least 4Gb RAM and a NVME SSD (eMMC is fine too). You want to have an Ethernet port and a few free USB ports. I would also suggest immediately getting HA SkyConnect adapter that can do Zigbee networking and will do Matter soon (tm). I am making do with a SonOff Zigbee gateway, but it is quite hacky to get working and your whole Zigbee communication breaks down if the WiFi goes down - suboptimal. So I took a backup of the Home Assistant instance using it's build-in tools. I took an export of my fully configured Firefly III instance and proceeded to wipe the drive of the NUC. That was not a smart idea. :D On the Home Assitant side I was really frustrated by the documentation that was really focused on users that are (likely) using Windows and are using an SD card in something like Raspberry Pi to get Home Assistant OS running. It recommended downloading Etcher to write the image to the boot medium. That is a really weird piece of software that managed to actually crash consistently when I was trying to run it from Debian Live or Ubuntu Live on my NUC. It took me way too long to give up and try something much simpler - dd. xzcat haos_generic-x86-64-11.0.img.xz dd of=/dev/mmcblk0 bs=1M That just worked, prefectly and really fast. If you want to use a GUI in a live environment, then just using the gnome-disk-utility ("Disks" in Gnome menu) and using the "Restore Disk Image ..." on a partition would work just as well. It even supports decompressing the XZ images directly while writing. But that image is small, will it not have a ton of unused disk space behind the fixed install partition? Yes, it will ... until first boot. The HA OS takes over the empty space after its install partition on the first boot-up and just grows its main partition to take up all the remaining space. Smart. After first boot is completed, the first boot wizard can be accessed via your web browser and one of the prominent buttons there is restoring from backup. So you just give it the backup file and wait. Sadly the restore does not actually give any kind of progress, so your only way to figure out when it is done is opening the same web adress in another browser tab and refresh periodically - after restoring from backup it just boots into the same config at it had before - all the settings, all the devices, all the history is preserved. Even authentification tokens are preserved so if yu had a Home Assitant Mobile installed on your phone (both for remote access and to send location info and phone state, like charging, to HA to trigger automations) then it will just suddenly start working again without further actions needed from your side. That is an almost perfect backup/restore experience. The first thing you get for using the OS version of HA is easy automatic update that also automatically takes a backup before upgrade, so if anything breaks you can roll back with one click. There is also a command-line tool that allows to upgrade, but also downgrade ha-core and other modules. I had to use it today as HA version 23.10.4 actually broke support for the Sonoff bridge that I am using to control Zigbee devices, which are like 90% of all smart devices in my home. Really helpful stuff, but not a must have. What is a must have and that you can (really) only get with Home Assistant Operating System are Addons. Some addons are just normal servers you can run alongside HA on the same HA OS server, like MariaDB or Plex or a file server. That is not the most important bit, but even there the software comes pre-configured to use in a home server configuration and has a very simple config UI to pre-configure key settings, like users, passwords and database accesses for MariaDB - you can litereally in a few clicks and few strings make serveral users each with its own access to its own database. Couple more clicks and the DB is running and will be kept restarted in case of failures. But the real gems in the Home Assistant Addon Store are modules that extend Home Assitant core functionality in way that would be really hard or near impossible to configure in Home Assitant Container manually, especially because no documentation has ever existed for such manual config - everyone just tells you to install the addon from HA Addon store or from HACS. Or you can read the addon metadata in various repos and figure out what containers it actually runs with what settings and configs and what hooks it puts into the HA Core to make them cooperate. And then do it all over again when a new version breaks everything 6 months later when you have already forgotten everything. In the Addons that show up immediately after installation are addons to install the new Matter server, a MariaDB and MQTT server (that other addons can use for data storage and message exchange), Z-Wave support and ESPHome integration and very handy File manager that includes editors to edit Home Assitant configs directly in brower and SSH/Terminal addon that boht allows SSH connection and also a web based terminal that gives access to the OS itself and also to a comand line interface, for example, to do package downgrades if needed or see detailed logs. And also there is where you can get the features that are the focus this year for HA developers - voice enablers. However that is only a beginning. Like in Debian you can add additional repositories to expand your list of available addons. Unlike Debian most of the amazing software that is available for Home Assistant is outside the main, official addon store. For now I have added the most popular addon repository - HACS (Home Assistant Community Store) and repository maintained by Alexbelgium. The first includes things like NodeRED (a workflow based automation programming UI), Tailscale/Wirescale for VPN servers, motionEye for CCTV control, Plex for home streaming. HACS also includes a lot of HA UI enhacement modules, like themes, custom UI control panels like Mushroom or mini-graph-card and integrations that provide more advanced functions, but also require more knowledge to use, like Local Tuya - that is harder to set up, but allows fully local control of (normally) cloud-based devices. And it has AppDaemon - basically a Python based automation framework where you put in Python scrips that get run in a special environment where they get fed events from Home Assistant and can trigger back events that can control everything HA can and also do anything Python can do. This I will need to explore later. And the repository by Alex includes the thing that is actually the focus of this blog post (I know :D) - Firefly III addon and Firefly Importer addon that you can then add to your Home Assistant OS with a few clicks. It also has all kinds of addons for NAS management, photo/video server, book servers and Portainer that lets us setup and run any Docker container inside the HA OS structure. HA OS will detect this and warn you about unsupported processes running on your HA OS instance (nice security feature!), but you can just dismiss that. This will be very helpful very soon. This whole environment of OS and containers and apps really made me think - what was missing in Debian that made the talented developers behind all of that to spend the immense time and effor to setup a completely new OS and app infrastructure and develop a completel paraller developer community for Home Assistant apps, interfaces and configurations. Is there anything that can still be done to make HA community and the general open source and Debian community closer together? HA devs are not doing anything wrong: they are using the best open source can provide, they bring it to people whould could not install and use it otherwise, they are contributing fixes and improvements as well. But there must be some way to do this better, together. So I installed MariaDB, create a user and database for Firefly. I installed Firefly III and configured it to use the MariaDB with the web config UI. When I went into the Firefly III web UI I was confronted with the normal wizard to setup a new instance. And no reference to any backup restore. Hmm, ok. Maybe that goes via the Importer? So I make an access token again, configured the Importer to use that, configured the Nordlinger bank connection settings. Then I tried to import the export that I downloaded from Firefly III before. The importer did not auto-recognose the format. Turns out it is just a list of transactions ... It can only be barely useful if you first manually create all the asset accounts with the same names as before and even then you'll again have to deal with resolving the problem of transfers showing up twice. And all of your categories (that have not been used yet) are gone, your automation rules and bills are gone, your budgets and piggy banks are gone. Boooo. It will be easier for me to recreate my account data from bank exports again than to resolve data in that transaction export. Turns out that Firefly III documenation explicitly recommends making a mysqldump of your own and not rely on anything in the app itself for backup purposes. Kind of sad this was not mentioned in the export page that sure looked a lot like a backup :D After doing all that work all over again I needed to make something new not to feel like I wasted days of work for no real gain. So I started solving a problem I had for a while already - how do I add cash transations to the system when I am out of the house with just my phone in the hand? So far my workaround has been just sending myself messages in WhatsApp with the amount and description of any cash expenses. Two solutions are possible: app and bot. There are actually multiple Android-based phone apps that work with Firefly III API to do full financial management from the phone. However, after trying it out, that is not what I will be using most of the time. First of all this requires your Firefly III instance to be accessible from the Internet. Either via direct API access using some port forwarding and secured with HTTPS and good access tokens, or via a VPN server redirect that is installed on both HA and your phone. Tailscale was really easy to get working. But the power has its drawbacks - adding a new cash transaction requires opening the app, choosing new transaction view, entering descriptio, amount, choosing "Cash" as source account and optionally choosing destination expense account, choosing category and budget and then submitting the form to the server. Sadly none of that really works if you have no Internet or bad Internet at the place where you are using cash. And it's just too many steps. Annoying. An easier alternative is setting up a Telegram bot - it is running in a custom Docker container right next to your Firefly (via Portainer) and you talk to it via a custom Telegram chat channel that you create very easily and quickly. And then you can just tell it "Coffee 5" and it will create a transaction from the (default) cash account in 5 amount with description "Coffee". This part also works if you are offline at the moment - the bot will receive the message once you get back online. You can use Telegram bot menu system to edit the transaction to add categories or expense accounts, but this part only work if you are online. And the Firefly instance does not have to be online at all. Really nifty. So next week I will need to write up all the regular payments as bills in Firefly (again) and then I can start writing a Python script to predict my (financial) future!

Ian Jackson: DigiSpark (ATTiny85) - Arduino, C, Rust, build systems

Recently I completed a small project, including an embedded microcontroller. For me, using the popular Arduino IDE, and C, was a mistake. The experience with Rust was better, but still very exciting, and not in a good way. Here follows the rant. Introduction In a recent project (I ll write about the purpose, and the hardware in another post) I chose to use a DigiSpark board. This is a small board with a USB-A tongue (but not a proper plug), and an ATTiny85 microcontroller, This chip has 8 pins and is quite small really, but it was plenty for my application. By choosing something popular, I hoped for convenient hardware, and an uncomplicated experience. Convenient hardware, I got. Arduino IDE The usual way to program these boards is via an IDE. I thought I d go with the flow and try that. I knew these were closely related to actual Arduinos and saw that the IDE package arduino was in Debian. But it turns out that the Debian package s version doesn t support the DigiSpark. (AFAICT from the list it offered me, I m not sure it supports any ATTiny85 board.) Also, disturbingly, its board manager seemed to be offering to install board support, suggesting it would download stuff from the internet and run it. That wouldn t be acceptable for my main laptop. I didn t expect to be doing much programming or debugging, and the project didn t have significant security requirements: the chip, in my circuit, has only a very narrow ability do anything to the real world, and no network connection of any kind. So I thought it would be tolerable to do the project on my low-security video laptop . That s the machine where I m prepared to say yes to installing random software off the internet. So I went to the upstream Arduino site and downloaded a tarball containing the Arduino IDE. After unpacking that in /opt it ran and produced a pointy-clicky IDE, as expected. I had already found a 3rd-party tutorial saying I needed to add a magic URL (from the DigiSpark s vendor) in the preferences. That indeed allowed it to download a whole pile of stuff. Compilers, bootloader clients, god knows what. However, my tiny test program didn t make it to the board. Half-buried in a too-small window was an error message about the board s bootloader ( Micronucleus ) being too new. The boards I had came pre-flashed with micronucleus 2.2. Which is hardly new, But even so the official Arduino IDE (or maybe the DigiSpark s board package?) still contains an old version. So now we have all the downsides of curl bash-ware, but we re lacking the it s up to date and it just works upsides. Further digging found some random forum posts which suggested simply downloading a newer micronucleus and manually stuffing it into the right place: one overwrites a specific file, in the middle the heaps of stuff that the Arduino IDE s board support downloader squirrels away in your home directory. (In my case, the home directory of the untrusted shared user on the video laptop,) So, whatever . I did that. And it worked! Having demo d my ability to run code on the board, I set about writing my program. Writing C again The programming language offered via the Arduino IDE is C. It s been a little while since I started a new thing in C. After having spent so much of the last several years writing Rust. C s primitiveness quickly started to grate, and the program couldn t easily be as DRY as I wanted (Don t Repeat Yourself, see Wilson et al, 2012, 4, p.6). But, I carried on; after all, this was going to be quite a small job. Soon enough I had a program that looked right and compiled. Before testing it in circuit, I wanted to do some QA. So I wrote a simulator harness that #included my Arduino source file, and provided imitations of the few Arduino library calls my program used. As an side advantage, I could build and run the simulation on my main machine, in my normal development environment (Emacs, make, etc.). The simulator runs confirmed the correct behaviour. (Perhaps there would have been some more faithful simulation tool, but the Arduino IDE didn t seem to offer it, and I wasn t inclined to go further down that kind of path.) So I got the video laptop out, and used the Arduino IDE to flash the program. It didn t run properly. It hung almost immediately. Some very ad-hoc debugging via led-blinking (like printf debugging, only much worse) convinced me that my problem was as follows: Arduino C has 16-bit ints. My test harness was on my 64-bit Linux machine. C was autoconverting things (when building for the micrcocontroller). The way the Arduino IDE ran the compiler didn t pass the warning options necessary to spot narrowing implicit conversions. Those warnings aren t the default in C in general because C compilers hate us all for compatibility reasons. I don t know why those warnings are not the default in the Arduino IDE, but my guess is that they didn t want to bother poor novice programmers with messages from the compiler explaining how their program is quite possibly wrong. After all, users don t like error messages so we shouldn t report errors. And novice programmers are especially fazed by error messages so it s better to just let them struggle themselves with the arcane mysteries of undefined behaviour in C? The Arduino IDE does offer a dropdown for compiler warnings . The default is None. Setting it to All didn t produce anything about my integer overflow bugs. And, the output was very hard to find anyway because the log window has a constant stream of strange messages from javax.jmdns, with hex DNS packet dumps. WTF. Other things that were vexing about the Arduino IDE: it has fairly fixed notions (which don t seem to be documented) about how your files and directories ought to be laid out, and magical machinery for finding things you put nearby its sketch (as it calls them) and sticking them in its ear, causing lossage. It has a tendency to become confused if you edit files under its feet (e.g. with git checkout). It wasn t really very suited to a workflow where principal development occurs elsewhere. And, important settings such as the project s clock speed, or even the target board, or the compiler warning settings to use weren t stored in the project directory along with the actual code. I didn t look too hard, but I presume they must be in a dotfile somewhere. This is madness. Apparently there is an Arduino CLI too. But I was already quite exasperated, and I didn t like the idea of going so far off the beaten path, when the whole point of using all this was to stay with popular tooling and share fate with others. (How do these others cope? I have no idea.) As for the integer overflow bug: I didn t seriously consider trying to figure out how to control in detail the C compiler options passed by the Arduino IDE. (Perhaps this is possible, but not really documented?) I did consider trying to run a cross-compiler myself from the command line, with appropriate warning options, but that would have involved providing (or stubbing, again) the Arduino/DigiSpark libraries (and bugs could easily lurk at that interface). Instead, I thought, if only I had written the thing in Rust . But that wasn t possible, was it? Does Rust even support this board? Rust on the DigiSpark I did a cursory web search and found a very useful blog post by Dylan Garrett. This encouraged me to think it might be a workable strategy. I looked at the instructions there. It seemed like I could run them via the privsep arrangement I use to protect myself when developing using upstream cargo packages from crates.io. I got surprisingly far surprisingly quickly. It did, rather startlingly, cause my rustup to download a random recent Nightly Rust, but I have six of those already for other Reasons. Very quickly I got the trinket LED blink example, referenced by Dylan s blog post, to compile. Manually copying the file to the video laptop allowed me to run the previously-downloaded micronucleus executable and successfully run the blink example on my board! I thought a more principled approach to the bootloader client might allow a more convenient workflow. I found the upstream Micronucleus git releases and tags, and had a look over its source code, release dates, etc. It seemed plausible, so I compiled v2.6 from source. That was a success: now I could build and install a Rust program onto my board, from the command line, on my main machine. No more pratting about with the video laptop. I had got further, more quickly, with Rust, than with the Arduino IDE, and the outcome and workflow was superior. So, basking in my success, I copied the directory containing the example into my own project, renamed it, and adjusted the path references. That didn t work. Now it didn t build. Even after I copied about .cargo/config.toml and rust-toolchain.toml it didn t build, producing a variety of exciting messages, depending what precisely I tried. I don t have detailed logs of my flailing: the instructions say to build it by cd ing to the subdirectory, and, given that what I was trying to do was to not follow those instructions, it didn t seem sensible to try to prepare a proper repro so I could file a ticket. I wasn t optimistic about investigating it more deeply myself: I have some experience of fighting cargo, and it s not usually fun. Looking at some of the build control files, things seemed quite complicated. Additionally, not all of the crates are on crates.io. I have no idea why not. So, I would need to supply local copies of them anyway. I decided to just git subtree add the avr-hal git tree. (That seemed better than the approach taken by the avr-hal project s cargo template, since that template involve a cargo dependency on a foreign git repository. Perhaps it would be possible to turn them into path dependencies, but given that I had evidence of file-location-sensitive behaviour, which I didn t feel like I wanted to spend time investigating, using that seems like it would possibly have invited more trouble. Also, I don t like package templates very much. They re a form of clone-and-hack: you end up stuck with whatever bugs or oddities exist in the version of the template which was current when you started.) Since I couldn t get things to build outside avr-hal, I edited the example, within avr-hal, to refer to my (one) program.rs file outside avr-hal, with a #[path] instruction. That s not pretty, but it worked. I also had to write a nasty shell script to work around the lack of good support in my nailing-cargo privsep tool for builds where cargo must be invoked in a deep subdirectory, and/or Cargo.lock isn t where it expects, and/or the target directory containing build products is in a weird place. It also has to filter the output from cargo to adjust the pathnames in the error messages. Otherwise, running both cd A; cargo build and cd B; cargo build from a Makefile produces confusing sets of error messages, some of which contain filenames relative to A and some relative to B, making it impossible for my Emacs to reliably find the right file. RIIR (Rewrite It In Rust) Having got my build tooling sorted out I could go back to my actual program. I translated the main program, and the simulator, from C to Rust, more or less line-by-line. I made the Rust version of the simulator produce the same output format as the C one. That let me check that the two programs had the same (simulated) behaviour. Which they did (after fixing a few glitches in the simulator log formatting). Emboldened, I flashed the Rust version of my program to the DigiSpark. It worked right away! RIIR had caused the bug to vanish. Of course, to rewrite the program in Rust, and get it to compile, it was necessary to be careful about the types of all the various integers, so that s not so surprising. Indeed, it was the point. I was then able to refactor the program to be a bit more natural and DRY, and improve some internal interfaces. Rust s greater power, compared to C, made those cleanups easier, so making them worthwhile. However, when doing real-world testing I found a weird problem: my timings were off. Measured, the real program was too fast by a factor of slightly more than 2. A bit of searching (and searching my memory) revealed the cause: I was using a board template for an Adafruit Trinket. The Trinket has a clock speed of 8MHz. But the DigiSpark runs at 16.5MHz. (This is discussed in a ticket against one of the C/C++ libraries supporting the ATTiny85 chip.) The Arduino IDE had offered me a choice of clock speeds. I have no idea how that dropdown menu took effect; I suspect it was adding prelude code to adjust the clock prescaler. But my attempts to mess with the CPU clock prescaler register by hand at the start of my Rust program didn t bear fruit. So instead, I adopted a bodge: since my code has (for code structure reasons, amongst others) only one place where it dealt with the underlying hardware s notion of time, I simply changed my delay function to adjust the passed-in delay values, compensating for the wrong clock speed. There was probably a more principled way. For example I could have (re)based my work on either of the two unmerged open MRs which added proper support for the DigiSpark board, rather than abusing the Adafruit Trinket definition. But, having a nearly-working setup, and an explanation for the behaviour, I preferred the narrower fix to reopening any cans of worms. An offer of help As will be obvious from this posting, I m not an expert in dev tools for embedded systems. Far from it. This area seems like quite a deep swamp, and I m probably not the person to help drain it. (Frankly, much of the improvement work ought to be done, and paid for, by hardware vendors.) But, as a full Member of the Debian Project, I have considerable gatekeeping authority there. I also have much experience of software packaging, build systems, and release management. If anyone wants to try to improve the situation with embedded tooling in Debian, and is willing to do the actual packaging work. I would be happy to advise, and to review and sponsor your contributions. An obvious candidate: it seems to me that micronucleus could easily be in Debian. Possibly a DigiSpark board definition could be provided to go with the arduino package. Unfortunately, IMO Debian s Rust packaging tooling and workflows are very poor, and the first of my suggestions for improvement wasn t well received. So if you need help with improving Rust packages in Debian, please talk to the Debian Rust Team yourself. Conclusions Embedded programming is still rather a mess and probably always will be. Embedded build systems can be bizarre. Documentation is scant. You re often expected to download board support packages full of mystery binaries, from the board vendor (or others). Dev tooling is maddening, especially if aimed at novice programmers. You want version control? Hermetic tracking of your project s build and install configuration? Actually to be told by the compiler when you write obvious bugs? You re way off the beaten track. As ever, Free Software is under-resourced and the maintainers are often busy, or (reasonably) have other things to do with their lives. All is not lost Rust can be a significantly better bet than C for embedded software: The Rust compiler will catch a good proportion of programming errors, and an experienced Rust programmer can arrange (by suitable internal architecture) to catch nearly all of them. When writing for a chip in the middle of some circuit, where debugging involves staring an LED or a multimeter, that s precisely what you want. Rust embedded dev tooling was, in this case, considerably better. Still quite chaotic and strange, and less mature, perhaps. But: significantly fewer mystery downloads, and significantly less crazy deviations from the language s normal build system. Overall, less bad software supply chain integrity. The ATTiny85 chip, and the DigiSpark board, served my hardware needs very well. (More about the hardware aspects of this project in a future posting.)

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Russell Coker: Brother MFC-J4440DW Printer

I just had to setup a Brother MFC-J4440DW for a relative. They were replacing an old HP laser printer that mysteriously stopped printing as dark as it should, I don t know whether the HP printer had worn out or if the HP firmware decided to hobble it to make them buy a new printer. In either case HP is well known for shady behaviour with their printer firmware and should be avoided. The new Brother printer has problems when using wifi and auto DNS. I don t know how much of that was due to the printer itself and how much was due to the wifi AP provided by Foxtel. Anyway it works better with Ethernet and a fixed address (the wifi AP didn t allow me to set a fixed address). I think the main thing was configuring CUPS to connect via the IP address and not use Avahi etc. One problem I had with printing was that programs like Chrome and LibreOffice would hang for about a minute before printing, that turned out to be due to /etc/cups/lpoptions having the old printer (which had been removed) listed as the default. It would be nice if the web configuration for cups would change that when I set the default printer. CUPS doesn t seem to support USB printing. If it is possible to get this printer to print via USB then I welcome a comment describing how to do it. Scanning only seems to work on Ethernet not on USB, the command for scanning that I ended up with was scanimage -d escl:http://10.0.0.3:80 . Again I welcome comments from anyone who has had success in scanning via USB. There are probably some Linux users who would find it really inconvenient to setup a network interface specifically for printing. It s easy for me as I have a pile of spare ethernet cards and a box of cables but some people would have to buy this. Also it s disappointing that Brother didn t include an Ethernet cable or a USB cable in the box. But if that makes it cheaper I can deal with that. The resolution for scanning is only 832*1163 and it s black and white, I think that generally scanning in printers is a bad idea, taking a photo with a phone is a better way of scanning documents. Generally this printer works well and is cheap at only $299, a price for disposable hardware by today s standards. There are Debian packages from Brother for the printer. The scanner package looks like it just configures scanimage, and I m not sure whether the stock version of CUPS in Debian will do it without the Brother package. One thing I found interesting is that the package mfcj4440dwpdrv has the following shell code in the postinst to label for SE Linux:
if [ "$(which semanage 2> /dev/null)" != '' ];then
semanage fcontext -a -t cupsd_rw_etc_t '/opt/brother/Printers/mfcj4440dw/inf(/.*)?'
semanage fcontext -a -t bin_t          '/opt/brother/Printers/mfcj4440dw/lpd(/.*)?'
semanage fcontext -a -t bin_t          '/opt/brother/Printers/mfcj4440dw/cupswrapper(/.*)?'
if [ "$(which restorecon 2> /dev/null)" != '' ];then
restorecon -R /opt/brother/Printers/mfcj4440dw
fi
fi
This is the first time I ve seen a Debian package from a hardware vendor with SE Linux specific code. I can t just add those rules to the Debian policy as that would make the semanage commands fail to add an identical context spec will break the postinst. In the latest policy I m uploading to Debian/Unstable (version 2.20231010-1) there are the following 3 lines to deal with this, the first was already there for some time and the other 2 I just added:
/opt/brother/Printers/([^/]+/)?inf(/.*)?        gen_context(system_u:object_r:cupsd_rw_etc_t,s0)
/opt/brother/Printers/[^/]+/lpd(/.*)?   gen_context(system_u:object_r:bin_t,s0)
/opt/brother/Printers/[^/]+/cupswrapper(/.*)?   gen_context(system_u:object_r:bin_t,s0)
The Brother employee(s) who added the SE Linux code to their package are welcome to connect to me on LinkedIn.

20 October 2023

Iustin Pop: How to set a per-app locale in MacOS

After spending ~20+ years with a Linux desktop, I m trying to expand my desktop setup to include MacOS (well, desktop/laptop, I mean end user in general). And to my surprise, there s no clear repository of MacOS info. Man pages yes, some StackOverflow, some Apple forums, but no canonical version. Or, I didn t find it, please enlighten me Another issue is that Apple apparently changes behaviour without clearly documenting it. In this specific case, the region part of the locale went through significant churn lately. So, my goal: In Linux, this would simply mean running the app with the correct environment variables. But MacOS deprecated this a while back (it used to work). After reading what I could, the solution is quite easy, just not obvious:
% defaults read .GlobalPreferences grep en_
    AKLastLocale = "en_CH";
    AppleLocale = "en_CH";
% defaults read -app FooBar
(has no AppleLocale key)
% defaults write -app FooBar AppleLocale en_US
And that s it. Now, the defaults man page says the global-global is NSGlobalDomain, I don t know where I got the .GlobalPreferences. But I only needed to know the key name (in this case, AppleLocale - of course it couldn t be LC_ALL/LANG). One day I ll know MacOS better, but I try to learn more for 2+ years now, and it s not a smooth ride. Old dog new tricks, right?

Freexian Collaborators: Debian Contributions: Freexian meetup, debusine updates, lpr/lpd in Debian, and more! (by Utkarsh Gupta, Stefano Rivera)

Contributing to Debian is part of Freexian s mission. This article covers the latest achievements of Freexian and their collaborators. All of this is made possible by organizations subscribing to our Long Term Support contracts and consulting services.

Freexian Meetup, by Stefano Rivera, Utkarsh Gupta, et al. During DebConf, Freexian organized a meetup for its collaborators and those interested in learning more about Freexian and its services. It was well received and many people interested in Freexian showed up. Some developers who were interested in contributing to LTS came to get more details about joining the project. And some prospective customers came to get to know us and ask questions. Sadly, the tragic loss of Abraham shook DebConf, both individually and structurally. The meetup got rescheduled to a small room without video coverage. With that, we still had a wholesome interaction and here s a quick picture from the meetup taken by Utkarsh (which is also why he s missing!).

Debusine, by Rapha l Hertzog, et al. Freexian has been investing into debusine for a while, but development speed is about to increase dramatically thanks to funding from SovereignTechFund.de. Rapha l laid out the 5 milestones of the funding contract, and filed the issues for the first milestone. Together with Enrico and Stefano, they established a workflow for the expanded team. Among the first steps of this milestone, Enrico started to work on a developer-friendly description of debusine that we can use when we reach out to the many Debian contributors that we will have to interact with. And Rapha l started the design work of the autopkgtest and lintian tasks, i.e. what s the interface to schedule such tasks, what behavior and what associated options do we support? At this point you might wonder what debusine is supposed to be let us try to answer this: Debusine manages scheduling and distribution of Debian-related build and QA tasks to a network of worker machines. It also manages the resulting artifacts and provides the results in an easy to consume way. We want to make it easy for Debian contributors to leverage all the great QA tools that Debian provides. We want to build the next generation of Debian s build infrastructure, one that will continue to reliably do what it already does, but that will also enable distribution-wide experiments, custom package repositories and custom workflows with advanced package reviews. If this all sounds interesting to you, don t hesitate to watch the project on salsa.debian.org and to contribute.

lpr/lpd in Debian, by Thorsten Alteholz During Debconf23, Till Kamppeter presented CPDB (Common Print Dialog Backend), a new way to handle print queues. After this talk it was discussed whether the old lpr/lpd based printing system could be abandoned in Debian or whether there is still demand for it. So Thorsten asked on the debian-devel email list whether anybody uses it. Oddly enough, these old packages are still useful:
  • Within a small network it is easier to distribute a printcap file, than to properly configure cups clients.
  • One of the biggest manufacturers of WLAN router and DSL boxes only supports raw queues when attaching an USB printer to their hardware. Admittedly the CPDB still has problems with such raw queues.
  • The Pharos printing system at MIT is still lpd-based.
As a result, the lpr/lpd stuff is not yet ready to be abandoned and Thorsten will adopt the relevant packages (or rather move them under the umbrella of the debian-printing team). Though it is not planned to develop new features, those packages should at least have a maintainer. This month Thorsten adopted rlpr, an utility for lpd printing without using /etc/printcap. The next one he is working on is lprng, a lpr/lpd printer spooling system. If you know of any other package that is also needed and still maintained by the QA team, please tell Thorsten.

/usr-merge, by Helmut Grohne Discussion about lifting the file move moratorium has been initiated with the CTTE and the release team. A formal lift is dependent on updating debootstrap in older suites though. A significant number of packages can automatically move their systemd unit files if dh_installsystemd and systemd.pc change their installation targets. Unfortunately, doing so makes some packages FTBFS and therefore patches have been filed. The analysis tool, dumat, has been enhanced to better understand which upgrade scenarios are considered supported to reduce false positive bug filings and gained a mode for local operation on a .changes file meant for inclusion in salsa-ci. The filing of bugs from dumat is still manual to improve the quality of reports. Since September, the moratorium has been lifted.

Miscellaneous contributions
  • Rapha l updated Django s backport in bullseye-backports to match the latest security release that was published in bookworm. Tracker.debian.org is still using that backport.
  • Helmut Grohne sent 13 patches for cross build failures.
  • Helmut Grohne performed a maintenance upload of debvm enabling its use in autopkgtests.
  • Helmut Grohne wrote an API-compatible reimplementation of autopkgtest-build-qemu. It is powered by mmdebstrap, therefore unprivileged, EFI-only and will soon be included in mmdebstrap.
  • Santiago continued the work regarding how to make it easier to (automatically) test reverse dependencies. An example of the ongoing work was presented during the Salsa CI BoF at DebConf 23.
    In fact, omniorb-dfsg test pipelines as the above were used for the omniorb-dfsg 4.3.0 transition, verifying how the reverse dependencies (tango, pytango and omnievents) were built and how their autopkgtest jobs run with the to-be-uploaded omniorb-dfsg new release.
  • Utkarsh and Stefano attended and helped run DebConf 23. Also continued winding up DebConf 22 accounting.
  • Anton Gladky did some science team uploads to fix RC bugs.

18 October 2023

Russ Allbery: Review: Wolf Country

Review: Wolf Country, by Mar Delaney
Publisher: Kalikoi
Copyright: September 2021
ASIN: B09H55TGXK
Format: Kindle
Pages: 144
Wolf Country is a short lesbian shifter romance by Mar Delaney, a pen name for Layla Lawlor (who is also one of the writers behind the shared pen name Zoe Chant). Dasha Volkova is a werewolf, a member of a tribe of werewolves who keep to themselves deep in the wilds of Alaska. She's just become an adult and is wandering, curious and exploring, seeing what's in the world outside of her sheltered childhood. A wild chase after a hare, purely for the fun of it, is sufficiently distracting that she doesn't notice the snare before she steps in it going full speed. Laney Rosen is not a werewolf. She's a landscape painter who lives a quiet and self-contained life in an isolated cabin in the wilderness. She only stumbles across Dasha because she got lost on the snowmobile tracks taking photographs. Laney assumes Dasha is a dog caught in a poacher's trap, and is quite surprised when the pain of getting her out of the snare causes Dasha to shapeshift into a naked woman. This short book is precisely what it sounds like, which I appreciate in a romance novel. Woman meets wolf and discovers her secret accidentally, woman is of course entirely trustworthy although wolf can't know that, attraction at first sight, they have to pitch a tent in the wilderness and there's only one sleeping bag, etc. Nothing here is going to surprise you, but it's gentle and kind and fulfills the romance contract of a happy ending. It's not particularly steamy; the focus is on the relationship and the mutual attraction rather than on the sex. The best part of this book is probably the backdrop. Delaney lives in Alaska, and it shows in both the attention to the details of survival and heat and in the landscape descriptions (and the descriptions of Laney's landscapes). Dasha's love of Laney's paintings is one of the most heart-warming parts of the book. Laney has retinitis pigmentosa and is slowly losing her vision, which I thought was handled gracefully and well in the story. It creates real problems and limitations for her, but it also doesn't define her or become central to her character. Both Dasha and Laney are viewpoint characters and roughly alternate tight third-person viewpoint chapters. There are a few twists: potential parental disapproval on Dasha's part and some real physical danger from the person who set the trap, but most of the story is the two woman getting to know each other and getting past the early hesitancy to name what they're feeling. Laney feels a bit older than Dasha just because she's out on her own and Dasha was homeschooled and very sheltered, but both of them feel very young. This is Dasha's first serious relationship. Delaney does use the fated lover trope, which seems worth a warning in case you're not in the mood for that. Werewolves apparently know when they've found their fated mate and don't have a lot of choice in the matter. This is a common paranormal and fantasy romance trope that I find disturbing if I think about it too hard. Thankfully, here it's not much of a distraction. Dasha is such an impulsive, think-with-her-heart sort of character that the immediate conclusion that Laney is her fated mate felt in character even without the werewolf lore. I read this based on a random recommendation from Yoon Ha Lee when I was in the mood for something light and kind and uncomplicated, and I got exactly what I expected and was in the mood for. The writing isn't the best, but the landscape descriptions aren't bad and the characterization is reasonably good if you're in the mood for brightly curious but not particularly wise. Recommended if you're looking for this sort of thing. Rating: 7 out of 10

12 October 2023

Matthew Garrett: Defending abuse does not defend free software

The Free Software Foundation Europe and the Software Freedom Conservancy recently released a statement that they would no longer work with Eben Moglen, chairman of the Software Freedom Law Center. Eben was the general counsel for the Free Software Foundation for over 20 years, and was centrally involved in the development of version 3 of the GNU General Public License. He's devoted a great deal of his life to furthering free software.

But, as described in the joint statement, he's also acted abusively towards other members of the free software community. He's acted poorly towards his own staff. In a professional context, he's used graphically violent rhetoric to describe people he dislikes. He's screamed abuse at people attempting to do their job.

And, sadly, none of this comes as a surprise to me. As I wrote in 2017, after it became clear that Eben's opinions diverged sufficiently from the FSF's that he could no longer act as general counsel, he responded by threatening an FSF board member at an FSF-run event (various members of the board were willing to tolerate this, which is what led to me quitting the board). There's over a decade's evidence of Eben engaging in abusive behaviour towards members of the free software community, be they staff, colleagues, or just volunteers trying to make the world a better place.

When we build communities that tolerate abuse, we exclude anyone unwilling to tolerate being abused[1]. Nobody in the free software community should be expected to deal with being screamed at or threatened. Nobody should be afraid that they're about to have their sexuality outed by a former boss.

But of course there are some that will defend Eben based on his past contributions. There were people who were willing to defend Hans Reiser on that basis. We need to be clear that what these people are defending is not free software - it's the right for abusers to abuse. And in the long term, that's bad for free software.

[1] "Why don't people just get better at tolerating abuse?" is a terrible response to this. Why don't abusers stop abusing? There's fewer of them, and it should be easier.

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Freexian Collaborators: Monthly report about Debian Long Term Support, September 2023 (by Santiago Ruano Rinc n)

Like each month, have a look at the work funded by Freexian s Debian LTS offering.

Debian LTS contributors In September, 21 contributors have been paid to work on Debian LTS, their reports are available:
  • Abhijith PA did 10.0h (out of 0h assigned and 14.0h from previous period), thus carrying over 4.0h to the next month.
  • Adrian Bunk did 7.0h (out of 17.0h assigned), thus carrying over 10.0h to the next month.
  • Anton Gladky did 9.5h (out of 7.5h assigned and 7.5h from previous period), thus carrying over 5.5h to the next month.
  • Bastien Roucari s did 16.0h (out of 15.5h assigned and 1.5h from previous period), thus carrying over 1.0h to the next month.
  • Ben Hutchings did 17.0h (out of 17.0h assigned).
  • Chris Lamb did 17.0h (out of 17.0h assigned).
  • Emilio Pozuelo Monfort did 30.0h (out of 30.0h assigned).
  • Guilhem Moulin did 18.25h (out of 18.25h assigned).
  • Helmut Grohne did 10.0h (out of 10.0h assigned).
  • Lee Garrett did 17.0h (out of 16.5h assigned and 0.5h from previous period).
  • Markus Koschany did 40.0h (out of 40.0h assigned).
  • Ola Lundqvist did 4.5h (out of 0h assigned and 24.0h from previous period), thus carrying over 19.5h to the next month.
  • Roberto C. S nchez did 5.0h (out of 12.0h assigned), thus carrying over 7.0h to the next month.
  • Santiago Ruano Rinc n did 7.75h (out of 16.0h assigned), thus carrying over 8.25h to the next month.
  • Sean Whitton did 7.0h (out of 7.0h assigned).
  • Sylvain Beucler did 10.5h (out of 17.0h assigned), thus carrying over 6.5h to the next month.
  • Thorsten Alteholz did 14.0h (out of 14.0h assigned).
  • Tobias Frost did 13.25h (out of 16.0h assigned), thus carrying over 2.75h to the next month.

Evolution of the situation In September, we have released 44 DLAs. The month of September was a busy month for the LTS Team. A notable security issue fixed in September was the high-severity CVE-2023-4863, a heap buffer overflow that allowed remote attackers to perform an out-of-bounds memory write via a crafted WebP file. This CVE was covered by the three DLAs of different packages: firefox-esr, libwebp and thunderbird. The libwebp backported patch was sent to upstream, who adapted and applied it to the 0.6.1 branch. It is also worth noting that LTS contributor Markus Koschany included in his work updates to packages in Debian Bullseye and Bookworm, that are under the umbrella of the Security Team: xrdp, jetty9 and mosquitto. As every month, there was important behind-the-scenes work by the Front Desk staff, who triaged, analyzed and reviewed dozens of vulnerabilities, to decide if they warrant a security update. This is very important work, since we need to trade-off between the frequency of updates and the stability of the LTS release.

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8 October 2023

Sahil Dhiman: Lap 24

Twenty-four is a big number. More than one/fourth (or more) of my life is behind me now. At this point, I truly feel like I have become an adult; mentally and physically. Another year seem to have gone by quickly. I still vividly remember writing 23 and Counting and here I m writing the next one so soon. Probably the lowest I felt ever on my birthday; with loss of Abraham and on the other hand, medical issues with a dear one. Didn t even felt like birthday was almost here. The loss of Abraham, taught me to care for people more and meet cherish everyone. I m grateful for all the people who supported and cared for me and others during times of grief when things went numb. Thank you! Also, for the first time ever, I went to office on my birthday. This probably would become a norm in coming years. Didn t felt like doing anything, so just went to office. The cake, wishes and calls kept coming in throughout the day. I m grateful for the all people around for remembering :) This year marked my first official job switch where I moved from MakeMyTrip to Unmukti as a GNU/Linux Network Systems engineer (that s a mouthful of a job role, I know) where I do anything and everything ranging from system admin, network engineering, a bit of social media, chronicling stuff on company blog and bringing up new applications as per requirement. Moving from MMT to Unmukti was a big cultural shift. From a full-blown corporate with more than 3 thousand employees to a small 5-person team. People still think I work for a startup on hearing the low head count, though Unmukti is a 13 year old organization. I get the freedom to work at my own pace and put my ideas in larger technical discussions, while also actively participating in the community, which I m truly grateful of. I go full geek here and almost everyone here is on the same spectrum, so things technical or societal discussions just naturally flow. The months of August-September again marked the Great Refresh. For reasons unforeseen, I have had to pack my stuff again and move, albeit to just next door for now, but that gave me the much need opportunity to sift through my belongings here. As usual, I threw a boatload of stuff which was of no use and/or just hogging space. My wardrobe cupboard finally got cleaned and sorted, with old and new clothes getting (re)discovered. The Refresh is always a pain with loads of collating stuff in carry worthy bags and hauling stuff but as usual, there s nothing else I can do other than just pack and move. This year also culminated our four plus years of work for organizing annual Debian conference, DebConf to India. DebConf23 happened in Kochi, Kerala from 3rd September to 17th September (including DebCamp). First concrete work to bring conference to India was done Raju Dev who made the first bid during DebConf18 in Hsinchu, Taiwan. We lost but won during the next year bid at DebConf19 Curitiba, Brazil in 2019. I joined the efforts after meeting the team online after DebConf20. Initially started with the publicity team, but we didn t need much publicity for event, I was later asked to join sponsors/fundraising team. That turned out to be quite an experience. Then the conference itself turned to be a good experience. More on that in an upcoming DebConf23 blog post, which will come eventually. After seeing how things work out in Debian in 2020, I had the goal to become a Debian Developer (DD) before DebConf23, which gave me almost three years to get involved and get recognized to become a DD. I was more excited to grab sahil AT debian.org, a short email with only my name and no number of characters after it. After, quite a while, I dropped the hope of become a DD because I wasn t successful in my attempts to meaningfully package and technically contribute to the project. But people in Debian India later convinced me that I have done enough to become a Debian Developer, non uploading, purely by showing up and helping around all for the Debian conferences. I applied and got sponsored (i.e. supported) for my request by srud and Praveen. Finally, on 23rd Feb, I officially became part of Debian project as 14th (at the moment) Debian Developer from India. Got sahil AT debian.org too :) For some grace, I also became a DD before DebConf23. Becoming a DD didn t change anything much though, I still believe, it might have helped secure me a job though. Also, worth mentioning is my increased interest in OpenStreetMap (OSM) mapping. I heavily mapped this year and went around for mapathon-meetups too. One step towards a better OSM and more community engagement around it. Looking back at my blog, this year around, it seems mostly dotted with Debian and one OSM post. Significant shift from the range of topics I use to write about in the past year but blogging this year wasn t a go-to activity. Other stuff kept me busy. Living in Gurugram has shown me many facades of life from which I was shielded or didn t come across earlier. It made me realize all the privileges which has helped me along the way, which became apparent while living almost alone here and managing thing by oneself.

6 October 2023

Russ Allbery: Review: The Far Reaches

Review: The Far Reaches, edited by John Joseph Adams
Publisher: Amazon Original Stories
Copyright: June 2023
ISBN: 1-6625-1572-3
ISBN: 1-6625-1622-3
ISBN: 1-6625-1503-0
ISBN: 1-6625-1567-7
ISBN: 1-6625-1678-9
ISBN: 1-6625-1533-2
Format: Kindle
Pages: 219
Amazon has been releasing anthologies of original short SFF with various guest editors, free for Amazon Prime members. I previously tried Black Stars (edited by Nisi Shawl and Latoya Peterson) and Forward (edited by Blake Crouch). Neither were that good, but the second was much worse than the first. Amazon recently released a new collection, this time edited by long-standing SFF anthology editor John Joseph Adams and featuring a new story by Ann Leckie, which sounded promising enough to give them another chance. The definition of insanity is doing the same thing over and over again and expecting different results. As with the previous anthologies, each story is available separately for purchase or Amazon Prime "borrowing" with separate ISBNs. The sidebar cover is for the first in the sequence. Unlike the previous collections, which were longer novelettes or novellas, my guess is all of these are in the novelette range. (I did not do a word count.) If you're considering this anthology, read the Okorafor story ("Just Out of Jupiter's Reach"), consider "How It Unfolds" by James S.A. Corey, and avoid the rest. "How It Unfolds" by James S.A. Corey: Humans have invented a new form of physics called "slow light," which can duplicate any object that is scanned. The energy expense is extremely high, so the result is not a post-scarcity paradise. What the technology does offer, however, is a possible route to interstellar colonization: duplicate a team of volunteers and a ship full of bootstrapping equipment, and send copies to a bunch of promising-looking exoplanets. One of them might succeed. The premise is interesting. The twists Corey adds on top are even better. What can be duplicated once can be duplicated again, perhaps with more information. This is a lovely science fiction idea story that unfortunately bogs down because the authors couldn't think of anywhere better to go with it than relationship drama. I found the focus annoying, but the ideas are still very neat. (7) "Void" by Veronica Roth: A maintenance worker on a slower-than-light passenger ship making the run between Sol and Centauri unexpectedly is called to handle a dead body. A passenger has been murdered, two days outside the Sol system. Ace is in no way qualified to investigate the murder, nor is it her job, but she's watched a lot of crime dramas and she has met the victim before. The temptation to start poking around is impossible to resist. It's been a long time since I've read a story built around the differing experiences of time for people who stay on planets and people who spend most of their time traveling at relativistic speeds. It's a bit of a retro idea from an earlier era of science fiction, but it's still a good story hook for a murder mystery. None of the characters are that memorable and Roth never got me fully invested in the story, but this was still a pleasant way to pass the time. (6) "Falling Bodies" by Rebecca Roanhorse: Ira is the adopted son of a Genteel senator. He was a social experiment in civilizing the humans: rescue a human orphan and give him the best of Genteel society to see if he could behave himself appropriately. The answer was no, which is how Ira finds himself on Long Reach Station with a parole officer and a schooling opportunity, hopefully far enough from his previous mistakes for a second chance. Everyone else seems to like Rebecca Roanhorse's writing better than I do, and this is no exception. Beneath the veneer of a coming-of-age story with a twist of political intrigue, this is brutal, depressing, and awful, with an ending that needs a lot of content warnings. I'm sorry that I read it. (3) "The Long Game" by Ann Leckie: The Imperial Radch trilogy are some of my favorite science fiction novels of all time, but I am finding Leckie's other work a bit hit and miss. I have yet to read a novel of hers that I didn't like, but the short fiction I've read leans more heavily into exploring weird and alien perspectives, which is not my favorite part of her work. This story is firmly in that category: the first-person protagonist is a small tentacled alien creature, a bit like a swamp-dwelling octopus. I think I see what Leckie is doing here: balancing cynicism and optimism, exploring how lifespans influence thinking and planning, and making some subtle points about colonialism. But as a reading experience, I didn't enjoy it. I never liked any of the characters, and the conclusion of the story is the unsettling sort of main-character optimism that seems rather less optimistic to the reader. (4) "Just Out of Jupiter's Reach" by Nnedi Okorafor: K rm n scientists have found a way to grow living ships that can achieve a symbiosis with a human pilot, but the requirements for that symbiosis are very strict and hard to predict. The result was a planet-wide search using genetic testing to find the rare and possibly nonexistent matches. They found seven people. The deal was simple: spend ten years in space, alone, in her ship. No contact with any other human except at the midpoint, when the seven ships were allowed to meet up for a week. Two million euros a year, for as long as she followed the rules, and the opportunity to be part of a great experiment, providing data that will hopefully lead to humans becoming a spacefaring species. The core of this story is told during the seven days in the middle of the mission, and thus centers on people unfamiliar with human contact trying to navigate social relationships after five years in symbiotic ships that reshape themselves to their whims and personalities. The ships themselves link so that the others can tour, which offers both a good opportunity for interesting description and a concretized metaphor about meeting other people. I adore symbiotic spaceships, so this story had me at the premise. The surface plot is very psychological, and I didn't entirely click with it, but the sense of wonder vibes beneath that surface were wonderful. It also feels fresh and new: I've seen most of the ideas before, but not presented or written this way, or approached from quite this angle. Definitely the best story of the anthology. (8) "Slow Time Between the Stars" by John Scalzi: This, on the other hand, was a complete waste of time, redeemed only by being the shortest "story" in the collection. "Story" is generous, since there's only one character and a very dry, linear plot that exists only to make a philosophical point. "Speculative essay" may be closer. The protagonist is the artificial intelligence responsible for Earth's greatest interstellar probe. It is packed with a repository of all of human knowledge and the raw material to create life. Its mission is to find an exoplanet capable of sustaining that life, and then recreate it and support it. The plot, such as it is, follows the AI's decision to abandon that mission and cut off contact with Earth, for reasons that it eventually explains. Every possible beat of this story hit me wrong. The sense of wonder attaches to the most prosaic things and skips over the moments that could have provoked real wonder. The AI is both unbelievable and irritating, with all of the smug self-confidence of an Internet reply guy. The prose is overwrought in all the wrong places ("the finger of God, offering the spark to animate the dirt of another world" would totally be this AI's profile quote under their forum avatar). The only thing I liked about the story is the ethical point that it slowly meanders into, which I think I might agree with and at least find plausible. But it's delivered by the sort of character I would actively leave rooms to avoid, in a style that's about as engrossing as a tax form. Avoid. (2) Rating: 5 out of 10

3 October 2023

Bastian Blank: Introducing uploads to Debian by git tag

Several years ago, several people proposed a mechanism to upload packages to Debian just by doing "git tag" and "git push". Two not too long discussions on debian-devel (first and second) did not end with an agreement how this mechanism could work.1 The central problem was the ability to properly trace uploads back to the ones who authorised it. Now, several years later and after re-reading those e-mail threads, I again was stopped at the question: can we do this? Yes, it would not be just "git tag", but could we do with close enough? I have some rudimentary code ready to actually do uploads from the CI. However the list of caveats are currently pretty long. Yes, it works in principle. It is still disabled here, because in practice it does not yet work. Problems with this setup So what are the problems? It requires the git tags to include the both signed files for a successful source upload. This is solved by a new tool that could be a git sub-command. It just creates the source package, signs it and adds the signed file describing the upload (the .dsc and .changes file) to the tag to be pushed. The CI then extracts the signed files from the tag message and does it's work as normal. It requires a sufficiently reproducible build for source packages. Right now it is only known to work with the special 3.0 (gitarchive) source format, but even that requires the latest version of this format. No idea if it is possible to use others, like 3.0 (quilt) for this purpose. The shared GitLab runner provides by Salsa do not allow ftp access to the outside. But Debian still uses ftp to do uploads. At least if you don't want to share your ssh key, which can't be restricted to uploads only, but ssh would not work either. And as the current host for those builds, the Google Cloud Platform, does not provide connection tracking support for ftp, there is no easy way to allow that without just allowing everything. So we have no way to currently actually perform uploads from this platform. Further work As this is code running in a CI under the control of the developer, we can easily do other workflows. Some teams do workflows that do tags after acceptance into the Debian archive. Or they don't use tags at all. With some other markers, like variables or branch names, this support can be expanded easily. Unrelated to this task here, we might want to think about tying the .changes files for uploads to the target archive. As this code makes all of them readily available in form of tag message, replaying them into possible other archives might be more of a concern now. Conclusion So to come back to the question, yes we can. We can prepare uploads using our CI in a way that they would be accepted into the Debian archive. It just needs some more work on infrastructure.

  1. Here I have to admit that, after reading it again, I'm not really proud of my own behaviour and have to apologise.

27 September 2023

Antoine Beaupr : How big is Debian?

Now this was quite a tease! For those who haven't seen it, I encourage you to check it out, it has a nice photo of a Debian t-shirt I did not know about, to quote the Fine Article:
Today, when going through a box of old T-shirts, I found the shirt I was looking for to bring to the occasion: [...] For the benefit of people who read this using a non-image-displaying browser or RSS client, they are respectively:
   10 years
  100 countries
 1000 maintainers
10000 packages
and
        1 project
       10 architectures
      100 countries
     1000 maintainers
    10000 packages
   100000 bugs fixed
  1000000 installations
 10000000 users
100000000 lines of code
20 years ago we celebrated eating grilled meat at J0rd1 s house. This year, we had vegan tostadas in the menu. And maybe we are no longer that young, but we are still very proud and happy of our project! Now How would numbers line up today for Debian, 20 years later? Have we managed to get the bugs fixed line increase by a factor of 10? Quite probably, the lines of code we also have, and I can only guess the number of users and installations, which was already just a wild guess back then, might have multiplied by over 10, at least if we count indirect users and installs as well
Now I don't know about you, but I really expected someone to come up with an answer to this, directly on Debian Planet! I have patiently waited for such an answer but enough is enough, I'm a Debian member, surely I can cull all of this together. So, low and behold, here are the actual numbers from 2023! So it doesn't line up as nicely, but it looks something like this:
         1 project
        10 architectures
        30 years
       100 countries (actually 63, but we'd like to have yours!)
      1000 maintainers (yep, still there!)
     35000 packages
    211000 *binary* packages
   1000000 bugs fixed
1000000000 lines of code
 uncounted installations and users, we don't track you
So maybe the the more accurate, rounding to the nearest logarithm, would look something like:
         1 project
        10 architectures
       100 countries (actually 63, but we'd like to have yours!)
      1000 maintainers (yep, still there!)
    100000 packages
   1000000 bugs fixed
1000000000 lines of code
 uncounted installations and users, we don't track you
I really like how the "packages" and "bugs fixed" still have an order of magnitude between them there, but that the "bugs fixed" vs "lines of code" have an extra order of magnitude, that is we have fixed ten times less bugs per line of code since we last did this count, 20 years ago. Also, I am tempted to put 100 years in there, but that would be rounding up too much. Let's give it another 30 years first. Hopefully, some real scientist is going to balk at this crude methodology and come up with some more interesting numbers for the next t-shirt. Otherwise I'm available for bar mitzvahs and children parties.

21 September 2023

Jonathan Carter: DebConf23

I very, very nearly didn t make it to DebConf this year, I had a bad cold/flu for a few days before I left, and after a negative covid-19 test just minutes before my flight, I decided to take the plunge and travel. This is just everything in chronological order, more or less, it s the only way I could write it.

DebCamp I planned to spend DebCamp working on various issues. Very few of them actually got done, I spent the first few days in bed further recovering, took a covid-19 test when I arrived and after I felt better, and both were negative, so not sure what exactly was wrong with me, but between that and catching up with other Debian duties, I couldn t make any progress on catching up on the packaging work I wanted to do. I ll still post what I intended here, I ll try to take a few days to focus on these some time next month: Calamares / Debian Live stuff:
  • #980209 installation fails at the install boot loader phase
  • #1021156 calamares-settings-debian: Confusing/generic program names
  • #1037299 Install Debian -> Untrusted application launcher
  • #1037123 Minimal HD space required too small for some live images
  • #971003 Console auto-login doesn t work with sysvinit
At least Calamares has been trixiefied in testing, so there s that! Desktop stuff:
  • #1038660 please set a placeholder theme during development, different from any release
  • #1021816 breeze: Background image not shown any more
  • #956102 desktop-base: unwanted metadata within images
  • #605915 please mtheake it a non-native package
  • #681025 Put old themes in a new package named desktop-base-extra
  • #941642 desktop-base: split theme data files and desktop integrations in separate packages
The Egg theme that I want to develop for testing/unstable is based on Juliette Taka s Homeworld theme that was used for Bullseye. Egg, as in, something that hasn t quite hatched yet. Get it? (for #1038660) Debian Social:
  • Set up Lemmy instance
    • I started setting up a Lemmy instance before DebCamp, and meant to finish it.
  • Migrate PeerTube to new server
    • We got a new physical server for our PeerTube instance, we should have more space for growth and it would help us fix the streaming feature on our platform.
Loopy: I intended to get the loop for DebConf in good shape before I left, so that we can spend some time during DebCamp making some really nice content, unfortunately this went very tumbly, but at least we ended up with a loopy that kind of worked and wasn t too horrible. There s always another DebConf to try again, right?
So DebCamp as a usual DebCamp was pretty much a wash (fitting with all the rain we had?) for me, at least it gave me enough time to recover a bit for DebConf proper, and I had enough time left to catch up on some critical DPL duties and put together a few slides for the Bits from the DPL talk.

DebConf Bits From the DPL I had very, very little available time to prepare something for Bits fro the DPL, but I managed to put some slides together (available on my wiki page). I mostly covered:
  • A very quick introduction of myself (I ve done this so many times, it feels redundant giving my history every time), and some introduction on what it is that the DPL does. I declared my intent not to run for DPL again, and the reasoning behind it, and a few bits of information for people who may intend to stand for DPL next year.
  • The sentiment out there for the Debian 12 release (which has been very positive). How we include firmware by default now, and that we re saying goodbye to architectures both GNU/KFreeBSD and mipsel.
  • Debian Day and the 30th birthday party celebrations from local groups all over the world (and a reminder about the Local Groups BoF later in the week).
  • I looked forward to Debian 13 (trixie!), and how we re gaining riscv64 as a release architecture, as well as loongarch64, and that plans seem to be forming to fix 2k38 in Debian, and hopefully largely by the time the Trixie release comes by.
  • I made some comments about Enterprise Linux as people refer to the RHEL eco-system these days, how really bizarre some aspects of it is (like the kernel maintenance), and that some big vendors are choosing to support systems outside of that eco-system now (like CPanel now supporting Ubuntu too). I closed with the quote below from Ian Murdock, and assured the audience that if they want to go out and make money with Debian, they are more than welcome too.
Job Fair I walked through the hallway where the Job Fair was hosted, and enjoyed all the buzz. It s not always easy to get this right, but this year it was very active and energetic, I hope lots of people made some connections! Cheese & Wine Due to state laws and alcohol licenses, we couldn t consume alcohol from outside the state of Kerala in the common areas of the hotel (only in private rooms), so this wasn t quite as big or as fun as our usual C&W parties since we couldn t share as much from our individual countries and cultures, but we always knew that this was going to be the case for this DebConf, and it still ended up being alright. Day Trip I opted for the forest / waterfalls daytrip. It was really, really long with lots of time in the bus. I think our trip s organiser underestimated how long it would take between the points on the route (all in all it wasn t that far, but on a bus on a winding mountain road, it takes long). We left at 8:00 and only found our way back to the hotel around 23:30. Even though we arrived tired and hungry, we saw some beautiful scenery, animals and also met indigenous river people who talked about their struggles against being driven out of their place of living multiple times as government invests in new developments like dams and hydro power. Photos available in the DebConf23 public git repository. Losing a beloved Debian Developer during DebConf To our collective devastation, not everyone made it back from their day trips. Abraham Raji was out to the kayak day trip, and while swimming, got caught by a whirlpool from a drainage system. Even though all of us were properly exhausted and shocked in disbelief at this point, we had to stay up and make some tough decisions. Some initially felt that we had to cancel the rest of DebConf. We also had to figure out how to announce what happened asap both to the larger project and at DebConf in an official manner, while ensuring that due diligence took place and that the family is informed by the police first before making anything public. We ended up cancelling all the talks for the following day, with an address from the DPL in the morning to explain what had happened. Of all the things I ve ever had to do as DPL, this was by far the hardest. The day after that, talks were also cancelled for the morning so that we could attend his funeral. Dozens of DebConf attendees headed out by bus to go pay their final respects, many wearing the t-shirts that Abraham had designed for DebConf. A book of condolences was set up so that everyone who wished to could write a message on how they remembered him. The book will be kept by his family.
Today marks a week since his funeral, and I still feel very raw about it. And even though there was uncertainty whether DebConf should even continue after his death, in hindsight I m glad that everyone pushed forward. While we were all heart broken, it was also heart warming to see people care for each other in all of this. If anything, I think I needed more time at DebConf just to be in that warm aura of emotional support for just a bit longer. There are many people who I wanted to talk to who I barely even had a chance to see. Abraham, or Abru as he was called by some people (which I like because bru in Afrikaans is like bro in English, not sure if that s what it implied locally too) enjoyed artistic pursuits, but he was also passionate about knowledge transfer. He ran classes at DebConf both last year and this year (and I think at other local events too) where he taught people packaging via a quick course that he put together. His enthusiasm for Debian was contagious, a few of the people who he was mentoring came up to me and told me that they were going to see it through and become a DD in honor of him. I can t even remember how I reacted to that, my brain was already so worn out and stitching that together with the tragedy of what happened while at DebConf was just too much for me. I first met him in person last year in Kosovo, I already knew who he was, so I think we interacted during the online events the year before. He was just one of those people who showed so much promise, and I was curious to see what he d achieve in the future. Unfortunately, we was taken away from us too soon. Poetry Evening Later in the week we had the poetry evening. This was the first time I had the courage to recite something. I read Ithaka by C.P. Cavafy (translated by Edmund Keely). The first time I heard about this poem was in an interview with Julian Assange s wife, where she mentioned that he really loves this poem, and it caught my attention because I really like the Weezer song Return to Ithaka and always wondered what it was about, so needless to say, that was another rabbit hole at some point. Group Photo Our DebConf photographer organised another group photo for this event, links to high-res versions available on Aigar s website.
BoFs I didn t attend nearly as many talks this DebConf as I would ve liked (fortunately I can catch up on video, should be released soon), but I did make it to a few BoFs. In the Local Groups BoF, representatives from various local teams were present who introduced themselves and explained what they were doing. From memory (sorry if I left someone out), we had people from Belgium, Brazil, Taiwan and South Africa. We talked about types of events a local group could do (BSPs, Mini DC, sprints, Debian Day, etc. How to help local groups get started, booth kits for conferences, and setting up some form of calendar that lists important Debian events in a way that makes it easier for people to plan and co-ordinate. There s a mailing list for co-ordination of local groups, and the irc channel is -localgroups on oftc.
If you got one of these Cheese & Wine bags from DebConf, that s from the South African local group!
In the Debian.net BoF, we discussed the Debian.net hosting service, where Debian pays for VMs hosted for projects by individual DDs on Debian.net. The idea is that we start some form of census that monitors the services, whether they re still in use, whether the system is up to date, whether someone still cares for it, etc. We had some discussion about where the lines of responsibility are drawn, and we can probably make things a little bit more clear in the documentation. We also want to offer more in terms of backups and monitoring (currently DDs do get 500GB from rsync.net that could be used for backups of their services though). The intention is also to deploy some form of configuration management for some essentials across the hosts. We should also look at getting some sponsored hosting for this. In the Debian Social BoF, we discussed some services that need work / expansion. In particular, Matrix keeps growing at an increased rate as more users use it and more channels are bridged, so it will likely move to its own host with big disks soon. We might replace Pleroma with a fork called Akkoma, this will need some more home work and checking whether it s even feasible. Some services haven t really been used (like Writefreely and Plume), and it might be time to retire them. We might just have to help one or two users migrate some of their posts away if we do retire them. Mjolner seems to do a fine job at spam blocking, we haven t had any notable incidents yet. WordPress now has improved fediverse support, it s unclear whether it works on a multi-site instance yet, I ll test it at some point soon and report back. For upcoming services, we are implementing Lemmy and probably also Mobilizon. A request was made that we also look into Loomio. More Information Overload There s so much that happens at DebConf, it s tough to take it all in, and also, to find time to write about all of it, but I ll mention a few more things that are certainly worth of note. During DebConf, we had some people from the Kite Linux team over. KITE supplies the ICT needs for the primary and secondary schools in the province of Kerala, where they all use Linux. They decided to switch all of these to Debian. There was an ad-hoc BoF where locals were listening and fielding questions that the Kite Linux team had. It was great seeing all the energy and enthusiasm behind this effort, I hope someone will properly blog about this! I learned about the VGLUG Foundation, who are doing a tremendous job at promoting GNU/Linux in the country. They are also training up 50 people a year to be able to provide tech support for Debian. I came across the booth for Mostly Harmless, they liberate old hardware by installing free firmware on there. It was nice seeing all the devices out there that could be liberated, and how it can breathe new life into old harware.
Some hopefully harmless soldering.
Overall, the community and their activities in India are very impressive, and I wish I had more time to get to know everyone better. Food Oh yes, one more thing. The food was great. I tasted more different kinds of curry than I ever did in my whole life up to this point. The lunch on banana leaves was interesting, and also learning how to eat this food properly by hand (thanks to the locals who insisted on teaching me!), it was a fruitful experience? This might catch on at home too less dishes to take care of! Special thanks to the DebConf23 Team I think this may have been one of the toughest DebConfs to organise yet, and I don t think many people outside of the DebConf team knows about all the challenges and adversity this team has faced in organising it. Even just getting to the previous DebConf in Kosovo was a long and tedious and somewhat risky process. Through it all, they were absolute pro s. Not once did I see them get angry or yell at each other, whenever a problem came up, they just dealt with it. They did a really stellar job and I did make a point of telling them on the last day that everyone appreciated all the work that they did. Back to my nest I bought Dax a ball back from India, he seems to have forgiven me for not taking him along.
I ll probably take a few days soon to focus a bit on my bugs and catch up on my original DebCamp goals. If you made it this far, thanks for reading! And thanks to everyone for being such fantastic people.

16 September 2023

Sergio Talens-Oliag: GitLab CI/CD Tips: Using a Common CI Repository with Assets

This post describes how to handle files that are used as assets by jobs and pipelines defined on a common gitlab-ci repository when we include those definitions from a different project.

Problem descriptionWhen a .giltlab-ci.yml file includes files from a different repository its contents are expanded and the resulting code is the same as the one generated when the included files are local to the repository. In fact, even when the remote files include other files everything works right, as they are also expanded (see the description of how included files are merged for a complete explanation), allowing us to organise the common repository as we want. As an example, suppose that we have the following script on the assets/ folder of the common repository:
dumb.sh
#!/bin/sh
echo "The script arguments are: '$@'"
If we run the following job on the common repository:
job:
  script:
    - $CI_PROJECT_DIR/assets/dumb.sh ARG1 ARG2
the output will be:
The script arguments are: 'ARG1 ARG2'
But if we run the same job from a different project that includes the same job definition the output will be different:
/scripts-23-19051/step_script: eval: line 138: d./assets/dumb.sh: not found
The problem here is that we include and expand the YAML files, but if a script wants to use other files from the common repository as an asset (configuration file, shell script, template, etc.), the execution fails if the files are not available on the project that includes the remote job definition.

SolutionsWe can solve the issue using multiple approaches, I ll describe two of them:
  • Create files using scripts
  • Download files from the common repository

Create files using scriptsOne way to dodge the issue is to generate the non YAML files from scripts included on the pipelines using HERE documents. The problem with this approach is that we have to put the content of the files inside a script on a YAML file and if it uses characters that can be replaced by the shell (remember, we are using HERE documents) we have to escape them (error prone) or encode the whole file into base64 or something similar, making maintenance harder. As an example, imagine that we want to use the dumb.sh script presented on the previous section and we want to call it from the same PATH of the main project (on the examples we are using the same folder, in practice we can create a hidden folder inside the project directory or use a PATH like /tmp/assets-$CI_JOB_ID to leave things outside the project folder and make sure that there will be no collisions if two jobs are executed on the same place (i.e. when using a ssh runner). To create the file we will use hidden jobs to write our script template and reference tags to add it to the scripts when we want to use them. Here we have a snippet that creates the file with cat:
.file_scripts:
  create_dumb_sh:
    -  
      # Create dumb.sh script
      mkdir -p "$ CI_PROJECT_DIR /assets"
      cat >"$ CI_PROJECT_DIR /assets/dumb.sh" <<EOF
      #!/bin/sh
      echo "The script arguments are: '\$@'"
      EOF
      chmod +x "$ CI_PROJECT_DIR /assets/dumb.sh"
Note that to make things work we ve added 6 spaces before the script code and escaped the dollar sign. To do the same using base64 we replace the previous snippet by this:
.file_scripts:
  create_dumb_sh:
    -  
      # Create dumb.sh script
      mkdir -p "$ CI_PROJECT_DIR /assets"
      base64 -d >"$ CI_PROJECT_DIR /assets/dumb.sh" <<EOF
      IyEvYmluL3NoCmVjaG8gIlRoZSBzY3JpcHQgYXJndW1lbnRzIGFyZTogJyRAJyIK
      EOF
      chmod +x "$ CI_PROJECT_DIR /assets/dumb.sh"
Again, we have to indent the base64 version of the file using 6 spaces (all lines of the base64 output have to be indented) and to make changes we have to decode and re-code the file manually, making it harder to maintain. With either version we just need to add a !reference before using the script, if we add the call on the first lines of the before_script we can use the downloaded file in the before_script, script or after_script sections of the job without problems:
job:
  before_script:
    - !reference [.file_scripts, create_dumb_sh]
  script:
    - $ CI_PROJECT_DIR /assets/dumb.sh ARG1 ARG2
The output of a pipeline that uses this job will be the same as the one shown in the original example:
The script arguments are: 'ARG1 ARG2'

Download the files from the common repositoryAs we ve seen the previous solution works but is not ideal as it makes the files harder to read, maintain and use. An alternative approach is to keep the assets on a directory of the common repository (in our examples we will name it assets) and prepare a YAML file that declares some variables (i.e. the URL of the templates project and the PATH where we want to download the files) and defines a script fragment to download the complete folder. Once we have the YAML file we just need to include it and add a reference to the script fragment at the beginning of the before_script of the jobs that use files from the assets directory and they will be available when needed. The following file is an example of the YAML file we just mentioned:
bootstrap.yml
variables:
  CI_TMPL_API_V4_URL: "$ CI_API_V4_URL /projects/common%2Fci-templates"
  CI_TMPL_ARCHIVE_URL: "$ CI_TMPL_API_V4_URL /repository/archive"
  CI_TMPL_ASSETS_DIR: "/tmp/assets-$ CI_JOB_ID "
.scripts_common:
  bootstrap_ci_templates:
    -  
      # Downloading assets
      echo "Downloading assets"
      mkdir -p "$CI_TMPL_ASSETS_DIR"
      wget -q -O - --header="PRIVATE-TOKEN: $CI_TMPL_READ_TOKEN" \
        "$CI_TMPL_ARCHIVE_URL?path=assets&sha=$ CI_TMPL_REF:-main "  
        tar --strip-components 2 -C "$ASSETS_DIR" -xzf -
The file defines the following variables:
  • CI_TMPL_API_V4_URL: URL of the common project, in our case we are using the project ci-templates inside the common group (note that the slash between the group and the project is escaped, that is needed to reference the project by name, if we don t like that approach we can replace the url encoded path by the project id, i.e. we could use a value like $ CI_API_V4_URL /projects/31)
  • CI_TMPL_ARCHIVE_URL: Base URL to use the gitlab API to download files from a repository, we will add the arguments path and sha to select which sub path to download and from which commit, branch or tag (we will explain later why we use the CI_TMPL_REF, for now just keep in mind that if it is not defined we will download the version of the files available on the main branch when the job is executed).
  • CI_TMPL_ASSETS_DIR: Destination of the downloaded files.
And uses variables defined in other places:
  • CI_TMPL_READ_TOKEN: token that includes the read_api scope for the common project, we need it because the tokens created by the CI/CD pipelines of other projects can t be used to access the api of the common one.We define the variable on the gitlab CI/CD variables section to be able to change it if needed (i.e. if it expires)
  • CI_TMPL_REF: branch or tag of the common repo from which to get the files (we need that to make sure we are using the right version of the files, i.e. when testing we will use a branch and on production pipelines we can use fixed tags to make sure that the assets don t change between executions unless we change the reference).We will set the value on the .gitlab-ci.yml file of the remote projects and will use the same reference when including the files to make sure that everything is coherent.
This is an example YAML file that defines a pipeline with a job that uses the script from the common repository:
pipeline.yml
include:
  - /bootstrap.yaml
stages:
  - test
dumb_job:
  stage: test
  before_script:
    - !reference [.bootstrap_ci_templates, create_dumb_sh]
  script:
    - $ CI_TMPL_ASSETS_DIR /dumb.sh ARG1 ARG2
To use it from an external project we will use the following gitlab ci configuration:
gitlab-ci.yml
include:
  - project: 'common/ci-templates'
    ref: &ciTmplRef 'main'
    file: '/pipeline.yml'
variables:
  CI_TMPL_REF: *ciTmplRef
Where we use a YAML anchor to ensure that we use the same reference when including and when assigning the value to the CI_TMPL_REF variable (as far as I know we have to pass the ref value explicitly to know which reference was used when including the file, the anchor allows us to make sure that the value is always the same in both places). The reference we use is quite important for the reproducibility of the jobs, if we don t use fixed tags or commit hashes as references each time a job that downloads the files is executed we can get different versions of them. For that reason is not a bad idea to create tags on our common repo and use them as reference on the projects or branches that we want to behave as if their CI/CD configuration was local (if we point to a fixed version of the common repo the way everything is going to work is almost the same as having the pipelines directly in our repo). But while developing pipelines using branches as references is a really useful option; it allows us to re-run the jobs that we want to test and they will download the latest versions of the asset files on the branch, speeding up the testing process. However keep in mind that the trick only works with the asset files, if we change a job or a pipeline on the YAML files restarting the job is not enough to test the new version as the restart uses the same job created with the current pipeline. To try the updated jobs we have to create a new pipeline using a new action against the repository or executing the pipeline manually.

ConclusionFor now I m using the second solution and as it is working well my guess is that I ll keep using that approach unless giltab itself provides a better or simpler way of doing the same thing.

13 September 2023

Matthew Garrett: Reconstructing an invalid TPM event log

TPMs contain a set of registers ("Platform Configuration Registers", or PCRs) that are used to track what a system boots. Each time a new event is measured, a cryptographic hash representing that event is passed to the TPM. The TPM appends that hash to the existing value in the PCR, hashes that, and stores the final result in the PCR. This means that while the PCR's value depends on the precise sequence and value of the hashes presented to it, the PCR value alone doesn't tell you what those individual events were. Different PCRs are used to store different event types, but there are still more events than there are PCRs so we can't avoid this problem by simply storing each event separately.

This is solved using the event log. The event log is simply a record of each event, stored in RAM. The algorithm the TPM uses to calculate the PCR values is known, so we can reproduce that by simply taking the events from the event log and replaying the series of events that were passed to the TPM. If the final calculated value is the same as the value in the PCR, we know that the event log is accurate, which means we now know the value of each individual event and can make an appropriate judgement regarding its security.

If any value in the event log is invalid, we'll calculate a different PCR value and it won't match. This isn't terribly helpful - we know that at least one entry in the event log doesn't match what was passed to the TPM, but we don't know which entry. That means we can't trust any of the events associated with that PCR. If you're trying to make a security determination based on this, that's going to be a problem.

PCR 7 is used to track information about the secure boot policy on the system. It contains measurements of whether or not secure boot is enabled, and which keys are trusted and untrusted on the system in question. This is extremely helpful if you want to verify that a system booted with secure boot enabled before allowing it to do something security or safety critical. Unfortunately, if the device gives you an event log that doesn't replay correctly for PCR 7, you now have no idea what the security state of the system is.

We ran into that this week. Examination of the event log revealed an additional event other than the expected ones - a measurement accompanied by the string "Boot Guard Measured S-CRTM". Boot Guard is an Intel feature where the CPU verifies the firmware is signed with a trusted key before executing it, and measures information about the firmware in the process. Previously I'd only encountered this as a measurement into PCR 0, which is the PCR used to track information about the firmware itself. But it turns out that at least some versions of Boot Guard also measure information about the Boot Guard policy into PCR 7. The argument for this is that this is effectively part of the secure boot policy - having a measurement of the Boot Guard state tells you whether Boot Guard was enabled, which tells you whether or not the CPU verified a signature on your firmware before running it (as I wrote before, I think Boot Guard has user-hostile default behaviour, and that enforcing this on consumer devices is a bad idea).

But there's a problem here. The event log is created by the firmware, and the Boot Guard measurements occur before the firmware is executed. So how do we get a log that represents them? That one's fairly simple - the firmware simply re-calculates the same measurements that Boot Guard did and creates a log entry after the fact[1]. All good.

Except. What if the firmware screws up the calculation and comes up with a different answer? The entry in the event log will now not match what was sent to the TPM, and replaying will fail. And without knowing what the actual value should be, there's no way to fix this, which means there's no way to verify the contents of PCR 7 and determine whether or not secure boot was enabled.

But there's still a fundamental source of truth - the measurement that was sent to the TPM in the first place. Inspired by Henri Nurmi's work on sniffing Bitlocker encryption keys, I asked a coworker if we could sniff the TPM traffic during boot. The TPM on the board in question uses SPI, a simple bus that can have multiple devices connected to it. In this case the system flash and the TPM are on the same SPI bus, which made things easier. The board had a flash header for external reprogramming of the firmware in the event of failure, and all SPI traffic was visible through that header. Attaching a logic analyser to this header made it simple to generate a record of that. The only problem was that the chip select line on the header was attached to the firmware flash chip, not the TPM. This was worked around by simply telling the analysis software that it should invert the sense of the chip select line, ignoring all traffic that was bound for the flash and paying attention to all other traffic. This worked in this case since the only other device on the bus was the TPM, but would cause problems in the event of multiple devices on the bus all communicating.

With the aid of this analyser plugin, I was able to dump all the TPM traffic and could then search for writes that included the "0182" sequence that corresponds to the command code for a measurement event. This gave me a couple of accesses to the locality 3 registers, which was a strong indication that they were coming from the CPU rather than from the firmware. One was for PCR 0, and one was for PCR 7. This corresponded to the two Boot Guard events that we expected from the event log. The hash in the PCR 0 measurement was the same as the hash in the event log, but the hash in the PCR 7 measurement differed from the hash in the event log. Replacing the event log value with the value actually sent to the TPM resulted in the event log now replaying correctly, supporting the hypothesis that the firmware was failing to correctly reconstruct the event.

What now? The simple thing to do is for us to simply hard code this fixup, but longer term we'd like to figure out how to reconstruct the event so we can calculate the expected value ourselves. Unfortunately there doesn't seem to be any public documentation on this. Sigh.

[1] What stops firmware on a system with no Boot Guard faking those measurements? TPMs have a concept of "localities", effectively different privilege levels. When Boot Guard performs its initial measurement into PCR 0, it does so at locality 3, a locality that's only available to the CPU. This causes PCR 0 to be initialised to a different initial value, affecting the final PCR value. The firmware can't access locality 3, so can't perform an equivalent measurement, so can't fake the value.

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12 September 2023

John Goerzen: A Maze of Twisty Little Pixels, All Tiny

Two years ago, I wrote Managing an External Display on Linux Shouldn t Be This Hard. Happily, since I wrote that post, most of those issues have been resolved. But then you throw HiDPI into the mix and it all goes wonky. If you re running X11, basically the story is that you can change the scale factor, but it only takes effect on newly-launched applications (which means a logout/in because some of your applications you can t really re-launch). That is a problem if, like me, you sometimes connect an external display that is HiDPI, sometimes not, or your internal display is HiDPI but others aren t. Wayland is far better, supporting on-the-fly resizes quite nicely. I ve had two devices with HiDPI displays: a Surface Go 2, and a work-issued Thinkpad. The Surface Go 2 is my ultraportable Linux tablet. I use it sparingly at home, and rarely with an external display. I just put Gnome on it, in part because Gnome had better on-screen keyboard support at the time, and left it at that. On the work-issued Thinkpad, I really wanted to run KDE thanks to its tiling support (I wound up using bismuth with it). KDE was buggy with Wayland at the time, so I just stuck with X11 and ran my HiDPI displays at lower resolutions and lived with the fuzziness. But now that I have a Framework laptop with a HiDPI screen, I wanted to get this right. I tried both Gnome and KDE. Here are my observations with both: Gnome I used PaperWM with Gnome. PaperWM is a tiling manager with a unique horizontal ribbon approach. It grew on me; I think I would be equally at home, or maybe even prefer it, to my usual xmonad-style approach. Editing the active window border color required editing ~/.local/share/gnome-shell/extensions/paperwm@hedning:matrix.org/stylesheet.css and inserting background-color and border-color items in the paperwm-selection section. Gnome continues to have an absolutely terrible picture for configuring things. It has no less than four places to make changes (Settings, Tweaks, Extensions, and dconf-editor). In many cases, configuration for a given thing is split between Settings and Tweaks, and sometimes even with Extensions, and then there are sometimes options that are only visible in dconf. That is, where the Gnome people have even allowed something to be configurable. Gnome installs a power manager by default. It offers three options: performance, balanced, and saver. There is no explanation of the difference between them. None. What is it setting when I change the pref? A maximum frequency? A scaling governor? A balance between performance and efficiency cores? Not only that, but there s no way to tell it to just use performance when plugged in and balanced or saver when on battery. In an issue about adding that, a Gnome dev wrote We re not going to add a preference just because you want one . KDE, on the other hand, aside from not mucking with your system s power settings in this way, has a nice panel with on AC and on battery and you can very easily tweak various settings accordingly. The hostile attitude from the Gnome developers in that thread was a real turnoff. While Gnome has excellent support for Wayland, it doesn t (directly) support fractional scaling. That is, you can set it to 100%, 200%, and so forth, but no 150%. Well, unless you manage to discover that you can run gsettings set org.gnome.mutter experimental-features "['scale-monitor-framebuffer']" first. (Oh wait, does that make a FIFTH settings tool? Why yes it does.) Despite its name, that allows you to select fractional scaling under Wayland. For X11 apps, they will be blurry, a problem that is optional under KDE (more on that below). Gnome won t show the battery life time remaining on the task bar. Yikes. An extension might work in some cases. Not only that, but the Gnome battery icon frequently failed to indicate AC charging when AC was connected, a problem that didn t exist on KDE. Both Gnome and KDE support night light (warmer color temperatures at night), but Gnome s often didn t change when it should have, or changed on one display but not the other. The appindicator extension is pretty much required, as otherwise a number of applications (eg, Nextcloud) don t have their icon display anywhere. It does, however, generate a significant amount of log spam. There may be a fix for this. Unlike KDE, which has a nice inobtrusive popup asking what to do, Gnome silently automounts USB sticks when inserted. This is often wrong; for instance, if I m about to dd a Debian installer to it, I definitely don t want it mounted. I learned this the hard way. It is particularly annoying because in a GUI, there is no reason to mount a drive before the user tries to access it anyhow. It looks like there is a dconf setting, but then to actually mount a drive you have to open up Files (because OF COURSE Gnome doesn t have a nice removable-drives icon like KDE does) and it s a bunch of annoying clicks, and I didn t want to use the GUI file manager anyway. Same for unmounting; two clicks in KDE thanks to the task bar icon, but in Gnome you have to open up the file manager, unmount the drive, close the file manager again, etc. The ssh agent on Gnome doesn t start up for a Wayland session, though this is easily enough worked around. The reason I completely soured on Gnome is that after using it for awhile, I noticed my laptop fans spinning up. One core would be constantly busy. It was busy with a kworker events task, something to do with sound events. Logging out would resolve it. I believe it to be a Gnome shell issue. I could find no resolution to this, and am unwilling to tolerate the decreased battery life this implies. The Gnome summary: it looks nice out of the box, but you quickly realize that this is something of a paper-thin illusion when you try to actually use it regularly. KDE The KDE experience on Wayland was a little bit opposite of Gnome. While with Gnome, things start out looking great but you realize there are some serious issues (especially battery-eating), with KDE things start out looking a tad rough but you realize you can trivially fix them and wind up with a very solid system. Compared to Gnome, KDE never had a battery-draining problem. It will show me estimated battery time remaining if I want it to. It will do whatever I want it to when I insert a USB drive. It doesn t muck with my CPU power settings, and lets me easily define on AC vs on battery settings for things like suspend when idle. KDE supports fractional scaling, to any arbitrary setting (even with the gsettings thing above, Gnome still only supports it in 25% increments). Then the question is what to do with X11-only applications. KDE offers two choices. The first is Scaled by the system , which is also the only option for Gnome. With that setting, the X11 apps effectively run natively at 100% and then are scaled up within Wayland, giving them a blurry appearance on HiDPI displays. The advantage is that the scaling happens within Wayland, so the size of the app will always be correct even when the Wayland scaling factor changes. The other option is Apply scaling themselves , which uses native X11 scaling. This lets most X11 apps display crisp and sharp, but then if the system scaling changes, due to limitations of X11, you ll have to restart the X apps to get them to be the correct size. I appreciate the choice, and use Apply scaling by themselves because only a few of my apps aren t Wayland-aware. I did encounter a few bugs in KDE under Wayland: sddm, the display manager, would be slow to stop and cause a long delay on shutdown or reboot. This seems to be a known issue with sddm and Wayland, and is easily worked around by adding a systemd TimeoutStopSec. Konsole, the KDE terminal emulator, has weird display artifacts when using fractional scaling under Wayland. I applied some patches and rebuilt Konsole and then all was fine. The Bismuth tiling extension has some pretty weird behavior under Wayland, but a 1-character patch fixes it. On Debian, KDE mysteriously installed Pulseaudio instead of Debian s new default Pipewire, but that was easily fixed as well (and Pulseaudio also works fine). Conclusions I m sticking with KDE. Given that I couldn t figure out how to stop Gnome from deciding to eat enough battery to make my fan come on, the decision wasn t hard. But even if it weren t for that, I d have gone with KDE. Once a couple of things were patched, the experience is solid, fast, and flawless. Emacs (my main X11-only application) looks great with the self-scaling in KDE. Gimp, which I use occasionally, was terrible with the blurry scaling in Gnome. Update: Corrected the gsettings command

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