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11 July 2017

Andreas Bombe: PDP-8/e Replicated Overview

This is an overview of the hardware and internals of the PDP-8/e replica I m building.

The front panel board
functional replica of the PDP-8/e front panel
If you know the original or remember the picture from the first post it is clear that this is a functional replica not aiming to be as pretty as those of the other projects I mentioned. I have reordered the switches into two rows to make the board more compact (which also means cheaper) without sacrificing usability. There s the two rows of display lights plus one run light the 8/e provides. The upper row is the address made up of 12 bits of memory address and 3 bits of extended memory address or field. Below are the 12 bits indicator which can show one data set out of six as selected by the user. All the switches of the original are implemented as more compact buttons1. While momentary switches are easily substituted by buttons, all buttons implementing two position switches toggle on/off with each press and they have a LED above that shows the current state. The six position rotary switch is implemented as a button cycling through all indicator displays together with six LEDs which show the active selection. Markings show the meaning of the indicator and switches as on the original, grouped in threes as the predominant numbering system for the PDPs was octal. The upper line shows the meaning for the state indicator, the middle for the status indicator and bit numbers for the rest. Note that on the PDP-8 and opposite to modern conventions, the most significant bit was numbered 0. I designed it as a pure front panel board without any PDP-8 simulation parts. The buttons and associated lights are controllable via SPI lines with a 3.3 V supply. The address and indicator lights have a separate common anode configuration with all cathodes individually available on a pin header without any resistors in the path, leaving voltage and current regulation up to the simulation board. This board is actually a few years old from a similar project where I emulated the PDP-8 in software on a microcontroller and the flexible design allowed me to reuse it unchanged.

The main board
main board with CPU and peripherals of the replicated PDP-8/e
This is where the magic happens. You can see three big ICs on the board: On the left is the STM32F405 microcontroller (with ARM Cortex-M4 core), the bigger one in the middle is the Altera2 MAX 10 FPGA and finally to the right is the SRAM that is large enough to hold all the main memory of the 32 KW maximum expansion of the PDP-8/e. The two smaller chips to the right of that are just buffers that drive the front panel address LEDs, the small chip at the top left is a RS-232 level shifter. The idea behind this is that the PDP-8 and peripherals that are simple to directly implement, such as GPIO or a serial port, are fully on the FPGA. Other peripherals such as paper and magnetic tape and disks, which are after all not connected to real PDP-8 drives but disk images on a microSD, are implemented on the microcontroller interfacing with stub devices in the FPGA. Compared to implementing everything everything in the FPGA, the STM32F4 has the advantage of useful built in peripherals such as two host/device capable USB ports. 5 V tolerant I/O pins are very useful and simply not available in any FPGA. I have to admit that this board was a bit of a rush job in order to have something at all to show at the Vintage Computer Festival Europe 18.0. Given that it was my first time designing a board with a large microcontroller and the first time with an FPGA, it wasn t exactly my fastest progressing project either and I got basic functionality (front panel allows toggling in small programs and running them) working just in time. For various reasons the project hasn t progressed much since, so the following is still just plans, but plans for which the hardware was designed. Since the aim is to have a cycle accurate PDP-8/e implementation, digital I/O was always planned. Rather than defining my own header I have included Arduino R3 compatible headers (for 3.3 V compatible boards only) that have become a popular even outside the Arduino world for this purpose. The digital Arduino pins are connected directly to the FPGA and will be directly controllable by PDP-8 software. The downside of choosing the Arduino headers is that the original PDP-8 digital I/O interface is not a perfect match since it naturally has 12 lines whereas the Arduino has 15. The analog inputs are not connected to the FPGA, the documentation of the MAX10 s ADC in the EQFP package are not very encouraging. They are connected to the STM32 instead3. Another interface connected directly to the FPGA and that would be directly under PDP-8 control is a standard 9 pin RS-232 interface. RX, TX, CTS and RTS are connected and level-shifted between 3.3 V and RS-232 levels by a MAX3232. Besides the PDP-8, I also plan to implement a full video terminal on the board. The idea is that with a power supply, keyboard and monitor this board would form a complete system without the need of connecting another computer to act as a terminal. To that end, there is a VGA port attached to the FPGA with simple resistor network DACs for 9 bits color (RGB with 3 bits each). This is another spot where I left myself room to expand, for e.g. a VT220 you really only need one color in two brightness levels. Keyboards will be connected either via the PS/2 connector on the right or the USB-A host port at the top left. Last of the interface ports is the USB micro-AB port on the left, which for now I am using only for power supply. I mainly plan to use it to provide alternative or additional serial ports to the PDP-8 or to export the video terminal serial port for testing purposes. Other possible uses are access to the image files on the microSD and firmware updates. This has gotten rather long again, so I m stopping here and leave some implementation notes for another post.
  1. They are also much cheaper. Given the large number of switches, the savings are substantial. Additionaly the buttons are nicer to operate than long rows of tiny switches. [return]
  2. Or rather Intel now. At least Altera s web site, documentation and software have already been thoroughly rebranded, but the chips I got were produced prior to that. [return]
  3. That s not to say that the analog conversions on the STM32 are necessarily better than those of the MAX10 when you can t follow their guidelines, I have no comparisons. Certainly following the guidelines would have been prohibitive given how many pins usage they restrict. [return]

Raphaël Hertzog: Freexian s report about Debian Long Term Support, June 2017

A Debian LTS logoLike each month, here comes a report about the work of paid contributors to Debian LTS. Individual reports In May, about 161 work hours have been dispatched among 11 paid contributors. Their reports are available: Evolution of the situation The number of sponsored hours increased slightly with one new bronze sponsor and another silver sponsor is in the process of joining. The security tracker currently lists 49 packages with a known CVE and the dla-needed.txt file 54. The number of open issues is close to last month. Thanks to our sponsors New sponsors are in bold.

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10 July 2017

Markus Koschany: My Free Software Activities in June 2017

Welcome to gambaru.de. Here is my monthly report that covers what I have been doing for Debian. If you re interested in Java, Games and LTS topics, this might be interesting for you. Debian Games Debian Java + Android Debian LTS This was my sixteenth month as a paid contributor and I have been paid to work 16 hours on Debian LTS, a project started by Rapha l Hertzog. In that time I did the following: Misc Thanks for reading and see you next time.

Kees Cook: security things in Linux v4.12

Previously: v4.11. Here s a quick summary of some of the interesting security things in last week s v4.12 release of the Linux kernel: x86 read-only and fixed-location GDT
With kernel memory base randomization, it was stil possible to figure out the per-cpu base address via the sgdt instruction, since it would reveal the per-cpu GDT location. To solve this, Thomas Garnier moved the GDT to a fixed location. And to solve the risk of an attacker targeting the GDT directly with a kernel bug, he also made it read-only. usercopy consolidation
After hardened usercopy landed, Al Viro decided to take a closer look at all the usercopy routines and then consolidated the per-architecture uaccess code into a single implementation. The per-architecture code was functionally very similar to each other, so it made sense to remove the redundancy. In the process, he uncovered a number of unhandled corner cases in various architectures (that got fixed by the consolidation), and made hardened usercopy available on all remaining architectures. ASLR entropy sysctl on PowerPC
Continuing to expand architecture support for the ASLR entropy sysctl, Michael Ellerman implemented the calculations needed for PowerPC. This lets userspace choose to crank up the entropy used for memory layouts. LSM structures read-only
James Morris used __ro_after_init to make the LSM structures read-only after boot. This removes them as a desirable target for attackers. Since the hooks are called from all kinds of places in the kernel this was a favorite method for attackers to use to hijack execution of the kernel. (A similar target used to be the system call table, but that has long since been made read-only.) KASLR enabled by default on x86
With many distros already enabling KASLR on x86 with CONFIG_RANDOMIZE_BASE and CONFIG_RANDOMIZE_MEMORY, Ingo Molnar felt the feature was mature enough to be enabled by default. Expand stack canary to 64 bits on 64-bit systems
The stack canary values used by CONFIG_CC_STACKPROTECTOR is most powerful on x86 since it is different per task. (Other architectures run with a single canary for all tasks.) While the first canary chosen on x86 (and other architectures) was a full unsigned long, the subsequent canaries chosen per-task for x86 were being truncated to 32-bits. Daniel Micay fixed this so now x86 (and future architectures that gain per-task canary support) have significantly increased entropy for stack-protector. Expanded stack/heap gap
Hugh Dickens, with input from many other folks, improved the kernel s mitigation against having the stack and heap crash into each other. This is a stop-gap measure to help defend against the Stack Clash attacks. Additional hardening needs to come from the compiler to produce stack probes when doing large stack expansions. Any Variable Length Arrays on the stack or alloca() usage needs to have machine code generated to touch each page of memory within those areas to let the kernel know that the stack is expanding, but with single-page granularity. That s it for now; please let me know if I missed anything. The v4.13 merge window is open!

2017, Kees Cook. This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.
Creative Commons License

8 July 2017

Daniel Silverstone: Gitano - Approaching Release - Access Control Changes

As mentioned previously I am working toward getting Gitano into Stretch. A colleague and friend of mine (Richard Maw) did a large pile of work on Lace to support what we are calling sub-defines. These let us simplify Gitano's ACL files, particularly for individual projects. In this posting, I'd like to cover what has changed with the access control support in Gitano, so if you've never used it then some of this may make little sense. Later on, I'll be looking at some better user documentation in conjunction with another friend of mine (Lars Wirzenius) who has promised to help produce a basic administration manual before Stretch is totally frozen.

Sub-defines With a more modern lace (version 1.3 or later) there is a mechanism we are calling 'sub-defines'. Previously if you wanted to write a ruleset which said something like "Allow Steve to read my repository" you needed: 
define is_steve user exact steve
allow "Steve can read my repo" is_steve op_read
And, as you'd expect, if you also wanted to grant read access to Jeff then you'd need yet set of defines: 
define is_jeff user exact jeff
define is_steve user exact steve
define readers anyof is_jeff is_steve
allow "Steve and Jeff can read my repo" readers op_read
This, while flexible (and still entirely acceptable) is wordy for small rulesets and so we added sub-defines to create this syntax: 
allow "Steve and Jeff can read my repo" op_read [anyof [user exact jeff] [user exact steve]]
Of course, this is generally neater for simpler rules, if you wanted to add another user then it might make sense to go for: 
define readers anyof [user exact jeff] [user exact steve] [user exact susan]
allow "My friends can read my repo" op_read readers
The nice thing about this sub-define syntax is that it's basically usable anywhere you'd use the name of a previously defined thing, they're compiled in much the same way, and Richard worked hard to get good error messages out from them just in case.

No more auto_user_XXX and auto_group_YYY As a result of the above being implemented, the support Gitano previously grew for automatically defining users and groups has been removed. The approach we took was pretty inflexible and risked compilation errors if a user was deleted or renamed, and so the sub-define approach is much much better. If you currently use auto_user_XXX or auto_group_YYY in your rulesets then your upgrade path isn't bumpless but it should be fairly simple:
  1. Upgrade your version of lace to 1.3
  2. Replace any auto_user_FOO with [user exact FOO] and similarly for any auto_group_BAR to [group exact BAR].
  3. You can now upgrade Gitano safely.

No more 'basic' matches Since Gitano first gained support for ACLs using Lace, we had a mechanism called 'simple match' for basic inputs such as groups, usernames, repo names, ref names, etc. Simple matches looked like user FOO or group !BAR. The match syntax grew more and more arcane as we added Lua pattern support refs ~^refs/heads/$ user /. When we wanted to add proper PCRE regex support we added a syntax of the form: user pcre ^/.+?... where pcre could be any of: exact, prefix, suffix, pattern, or pcre. We had a complex set of rules for exactly what the sigils at the start of the match string might mean in what order, and it was getting unwieldy. To simplify matters, none of the "backward compatibility" remains in Gitano. You instead MUST use the what how with match form. To make this slightly more natural to use, we have added a bunch of aliases: is for exact, starts and startswith for prefix, and ends and endswith for suffix. In addition, kind of match can be prefixed with a ! to invert it, and for natural looking rules not is an alias for !is. This means that your rulesets MUST be updated to support the more explicit syntax before you update Gitano, or else nothing will compile. Fortunately this form has been supported for a long time, so you can do this in three steps.
  1. Update your gitano-admin.git global ruleset. For example, the old form of the defines used to contain define is_gitano_ref ref ~^refs/gitano/ which can trivially be replaced with: define is_gitano_ref ref prefix refs/gitano/
  2. Update any non-zero rulesets your projects might have.
  3. You can now safely update Gitano
If you want a reference for making those changes, you can look at the Gitano skeleton ruleset which can be found at https://git.gitano.org.uk/gitano.git/tree/skel/gitano-admin/rules/ or in /usr/share/gitano if Gitano is installed on your local system. Next time, I'll likely talk about the deprecated commands which are no longer in Gitano, and how you'll need to adjust your automation to use the new commands.

6 July 2017

Thadeu Lima de Souza Cascardo: News on Debian on apexqtmo

I had been using my Samsung Galaxy S Relay 4G for almost three years when I decided to get a new phone. I would use this new phone for daily tasks and take the chance to get a new model for hacking in the future. My apexqtmo would still be my companion and would now be more available for real hacking. And so it also happened that its power button got stuck. It was not the first time, but now it would happen every so often, and would require me to disassemble it. So I managed to remove the plastic button and leave it with a hole so I could press the button with a screwdriver or a paperclip. That was the excuse I needed to get it to running Debian only. Though it's now always plugged on my laptop, I got the chance to hack on it on my scarce free time. As I managed to get a kernel I built myself running on it, I started fixing things like enabling devtmpfs. I didn't insist much on running systemd, though, and kept with System V. The Xorg issues were either on the server or the client, depending on which client I ran. I decided to give a chance to running the Android userspace on a chroot, but gave up after some work to get some firmware loaded. I managed to get the ALSA controls right after saving them inside a chroot on my CyanogenMod system. Then, restoring them on Debian allowed to play songs. Unfortunately, it seems I broke the audio jack when disassembling it. Otherwise, it would have been a great portable audio player. I even wrote a small program that would allow me to control mpd by swiping on the touchscreen. Then, as Debian release approached, I decided to investigate the framebuffer issue closely. I ended finding out that it was really a bug in the driver, and after fixing it, the X server and client crashes were gone. It was beautiful to get some desktop environment running with the right colors, get a calculator started and really using the phone as a mobile device. There are two lessons or findings here for me. The first one is that the current environments are really lacking. Even something like GPE can't work. The buttons are tiny, scrollbars are still the only way for scrolling, some of the time. No automatic virtual keyboards. So, there needs to be some investing in the existing environments, and maybe even the development of new environments for these kinds of devices. This was something I expected somehow, but it's still disappointing to know that we had so much of those developed in the past and now gone. I really miss Maemo. Running something like Qtopia would mean grabing a very old unmaintained software not available in Debian. There is still matchbox, but it's as subpar as the others I tested. The second lesson is that building a userspace to run on old kernels will still hit the problem of broken drivers. In my particular case, unless I wrote code for using Ion instead of the framebuffer, I would have had that problem. Or it would require me to add code to xorg-xserver that is not appropriate. Or fix the kernel drivers of available kernel sourcecodes. But this does not scale much more than doing the right thing and adding upstream support for these devices. So, I decided it was time I started working on upstream support for my device. I have it in progress and may send some upstream patches soon. I have USB and MMC/SDcard working fine. DRM is still a challenge, but thanks to Rob Clark, it's something I expect to get working soon, and after that, I would certainly celebrate. Maybe even consider starting the work on other devices a little sooner. Trying to review my post on GNU on smartphones, here is where I would put some of the status of my device and some extra notes. On Halium I am really glad people started this project. This was one of the things I criticized: that though Ubuntu Phone and FirefoxOS built on Android userspace, they were not easily portable to many devices out there. But as I am looking for a more pure GNU experience, let's call it that, Halium does not help much in that direction. But I'd like to see it flourish and allow people to use more OSes on more devices. Unfortunately, it suffers from similar problems as the strategy I was trying to go with. If you have a device with a very old kernel, you won't be able to run some of the latest userspace, even with Android userspace help. So, lots of devices would be left unsupported, unless we start working on some upstream support. On RYF Hardware My device is one of the worst out there. It's a modem that has a peripherical CPU. Much has already been said about Qualcomm chips being some of the least freedom-friendly. Ironically, it's some with the best upstream support, as far as I found out while doing this upstreaming work. Guess we'll have to wait for opencores, openrisc and risc-v to catch up here. Diversity Though I have been experimenting with Debian, the upstream work would sure benefit lots of other OSes out there, mainly GNU+Linux based ones, but also other non-GNU Linux based ones. Not so much for other kernels. On other options After the demise of Ubuntu Phone, I am glad to see UBports catching up. I hope the project is sustainable and produce more releases for more devices. Rooting This needs documentation. Most of the procedures rely on booting a recovery system, which means we are already past the root requirement. We simply boot our own system, then. However, for some debugging strategies, getting root on the OEM system is useful. So, try to get root on your system, but beware of malware out there. Booting Most of these devices will have their bootloaders in there. They may be unlocked, allowing unsigned kernels to be booted. Replacing these bootloaders is still going to be a challenge for another future phase. Though adding a second bootloader there, one that is freedom respecting, and that allows more control on that booting step to the user is something possible once you have some good upstream support. One could either use kexec for that, or try to use the same device tree for U-Boot, and use the knowledge of the device drivers for Linux on writing drivers for U-Boot, GRUB or Libreboot. Installation If you have root on your OEM system, this is something that could be worked on. Otherwise, there is magic-device-tool, whose approach is one that could be used. Kernels While I am working on adding Linux upstream support for my device, it would be wonderful to see more kernels supporting those gadgets. Hopefully, some of the device driver writing and reverse engineering could help with that, though I am not too much optimistic. But there is hope. Basic kernel drivers Adding the basic support, like USB and MMC, after clocks, gpios, regulators and what not, is the first step to a long road. But it would allow using the device as a board computer, under better control of the user. Hopefully, lots of eletronic garbage out there would have some use as control gadgets. Instead of buying a new board, just grab your old phone and put it to some nice use. Sensors, input devices, LEDs There are usually easy too. Some sensors may depend on your modem or some userspace code that is not that easily reverse engineered. But others would just require some device tree work, or some small input driver. Graphics Here, things may get complicated. Even basic video output is something I have some trouble with. Thanks to some other people's work, I have hope at least for my device. And using the vendor's linux source code, some framebuffer should be possible, even some DRM driver. But OpenGL or other 3D acceleration support requires much more work than that, and, at this moment, it's not something I am counting on. I am thankful for the work lots of people have been doing on this area, nonetheless. Wireless Be it Wifi or Bluetooth, things get ugly here. The vendor driver might be available. Rewriting it would take a long time. Even then, it would most likely require some non-free firmware loading. Using USB OTG here might be an option. Modem/GSM The work of the Replicant folks on that is what gives me some hope that it might be possible to get this working. Something I would leave to after I have a good interface experience in my hands. GPS Problem is similar to the Modem/GSM one, as some code lives in userspace, sometimes talking to the modem is a requirement to get GPS access, etc. Shells This is where I would like to see new projects, even if they work on current software to get them more friendly to these form factors. I consider doing some work there, though that's not really my area of expertise. Next steps For me, my next steps are getting what I have working upstream, keep working on DRM support, packaging GPE, then experimenting with some compositor code. In the middle of that, trying to get some other devices started. But documenting some of my work is something I realized I need to do more often, and this post is some try on that.

Thadeu Lima de Souza Cascardo: News on Debian on apexqtmo

I had been using my Samsung Galaxy S Relay 4G for almost three years when I decided to get a new phone. I would use this new phone for daily tasks and take the chance to get a new model for hacking in the future. My apexqtmo would still be my companion and would now be more available for real hacking. And so it also happened that its power button got stuck. It was not the first time, but now it would happen every so often, and would require me to disassemble it. So I managed to remove the plastic button and leave it with a hole so I could press the button with a screwdriver or a paperclip. That was the excuse I needed to get it to running Debian only. Though it's now always plugged on my laptop, I got the chance to hack on it on my scarce free time. As I managed to get a kernel I built myself running on it, I started fixing things like enabling devtmpfs. I didn't insist much on running systemd, though, and kept with System V. The Xorg issues were either on the server or the client, depending on which client I ran. I decided to give a chance to running the Android userspace on a chroot, but gave up after some work to get some firmware loaded. I managed to get the ALSA controls right after saving them inside a chroot on my CyanogenMod system. Then, restoring them on Debian allowed to play songs. Unfortunately, it seems I broke the audio jack when disassembling it. Otherwise, it would have been a great portable audio player. I even wrote a small program that would allow me to control mpd by swiping on the touchscreen. Then, as Debian release approached, I decided to investigate the framebuffer issue closely. I ended finding out that it was really a bug in the driver, and after fixing it, the X server and client crashes were gone. It was beautiful to get some desktop environment running with the right colors, get a calculator started and really using the phone as a mobile device. There are two lessons or findings here for me. The first one is that the current environments are really lacking. Even something like GPE can't work. The buttons are tiny, scrollbars are still the only way for scrolling, some of the time. No automatic virtual keyboards. So, there needs to be some investing in the existing environments, and maybe even the development of new environments for these kinds of devices. This was something I expected somehow, but it's still disappointing to know that we had so much of those developed in the past and now gone. I really miss Maemo. Running something like Qtopia would mean grabing a very old unmaintained software not available in Debian. There is still matchbox, but it's as subpar as the others I tested. The second lesson is that building a userspace to run on old kernels will still hit the problem of broken drivers. In my particular case, unless I wrote code for using Ion instead of the framebuffer, I would have had that problem. Or it would require me to add code to xorg-xserver that is not appropriate. Or fix the kernel drivers of available kernel sourcecodes. But this does not scale much more than doing the right thing and adding upstream support for these devices. So, I decided it was time I started working on upstream support for my device. I have it in progress and may send some upstream patches soon. I have USB and MMC/SDcard working fine. DRM is still a challenge, but thanks to Rob Clark, it's something I expect to get working soon, and after that, I would certainly celebrate. Maybe even consider starting the work on other devices a little sooner. Trying to review my post on GNU on smartphones, here is where I would put some of the status of my device and some extra notes. On Halium I am really glad people started this project. This was one of the things I criticized: that though Ubuntu Phone and FirefoxOS built on Android userspace, they were not easily portable to many devices out there. But as I am looking for a more pure GNU experience, let's call it that, Halium does not help much in that direction. But I'd like to see it flourish and allow people to use more OSes on more devices. Unfortunately, it suffers from similar problems as the strategy I was trying to go with. If you have a device with a very old kernel, you won't be able to run some of the latest userspace, even with Android userspace help. So, lots of devices would be left unsupported, unless we start working on some upstream support. On RYF Hardware My device is one of the worst out there. It's a modem that has a peripherical CPU. Much has already been said about Qualcomm chips being some of the least freedom-friendly. Ironically, it's some with the best upstream support, as far as I found out while doing this upstreaming work. Guess we'll have to wait for opencores, openrisc and risc-v to catch up here. Diversity Though I have been experimenting with Debian, the upstream work would sure benefit lots of other OSes out there, mainly GNU+Linux based ones, but also other non-GNU Linux based ones. Not so much for other kernels. On other options After the demise of Ubuntu Phone, I am glad to see UBports catching up. I hope the project is sustainable and produce more releases for more devices. Rooting This needs documentation. Most of the procedures rely on booting a recovery system, which means we are already past the root requirement. We simply boot our own system, then. However, for some debugging strategies, getting root on the OEM system is useful. So, try to get root on your system, but beware of malware out there. Booting Most of these devices will have their bootloaders in there. They may be unlocked, allowing unsigned kernels to be booted. Replacing these bootloaders is still going to be a challenge for another future phase. Though adding a second bootloader there, one that is freedom respecting, and that allows more control on that booting step to the user is something possible once you have some good upstream support. One could either use kexec for that, or try to use the same device tree for U-Boot, and use the knowledge of the device drivers for Linux on writing drivers for U-Boot, GRUB or Libreboot. Installation If you have root on your OEM system, this is something that could be worked on. Otherwise, there is magic-device-tool, whose approach is one that could be used. Kernels While I am working on adding Linux upstream support for my device, it would be wonderful to see more kernels supporting those gadgets. Hopefully, some of the device driver writing and reverse engineering could help with that, though I am not too much optimistic. But there is hope. Basic kernel drivers Adding the basic support, like USB and MMC, after clocks, gpios, regulators and what not, is the first step to a long road. But it would allow using the device as a board computer, under better control of the user. Hopefully, lots of eletronic garbage out there would have some use as control gadgets. Instead of buying a new board, just grab your old phone and put it to some nice use. Sensors, input devices, LEDs There are usually easy too. Some sensors may depend on your modem or some userspace code that is not that easily reverse engineered. But others would just require some device tree work, or some small input driver. Graphics Here, things may get complicated. Even basic video output is something I have some trouble with. Thanks to some other people's work, I have hope at least for my device. And using the vendor's linux source code, some framebuffer should be possible, even some DRM driver. But OpenGL or other 3D acceleration support requires much more work than that, and, at this moment, it's not something I am counting on. I am thankful for the work lots of people have been doing on this area, nonetheless. Wireless Be it Wifi or Bluetooth, things get ugly here. The vendor driver might be available. Rewriting it would take a long time. Even then, it would most likely require some non-free firmware loading. Using USB OTG here might be an option. Modem/GSM The work of the Replicant folks on that is what gives me some hope that it might be possible to get this working. Something I would leave to after I have a good interface experience in my hands. GPS Problem is similar to the Modem/GSM one, as some code lives in userspace, sometimes talking to the modem is a requirement to get GPS access, etc. Shells This is where I would like to see new projects, even if they work on current software to get them more friendly to these form factors. I consider doing some work there, though that's not really my area of expertise. Next steps For me, my next steps are getting what I have working upstream, keep working on DRM support, packaging GPE, then experimenting with some compositor code. In the middle of that, trying to get some other devices started. But documenting some of my work is something I realized I need to do more often, and this post is some try on that.

5 July 2017

Shirish Agarwal: Debian 9 release party at Co-hive

Dear all, This would be a biggish one so please have a chai/coffee or something stronger as it would take a while. I would start with attempt at some alcohol humor. While some people know that I have had a series of convulsive epileptic seizure I had shared bits about it in another post as well. Recovery is going through allopathic medicines as well as physiotherapy which I go to every alternate day. One of the exercises that I do in physiotherapy sessions is walk cross-legged on a line. While doing it today, it occurred to me that this is the same test that a Police inspector would do if they caught you drinking or are suspected of drunk driving. While some in the police force have now also have breath analyzer machines to determine alcohol content in the breath and body (and ways to deceive it are also there) the above exercise is still an integral part of examination. Now few of my friends who do drink have and had made expertise of walking on a line, while I due to this neurological disorder still have issues of walking on a line. So while I don t think of a drinking party in the near future (6 months at least), if I ever do get caught with a friend who is drunk (by association I would also be a suspect) by a policeman who doesn t have a breath analyzer machine, I could be in a lot of trouble. In addition if I tell him I have a neurological disorder I am bound to land up in a cell as he will think I m trying to make a fool of him. If you are able to picturize the situation, I m sure you will get a couple of laughs. Now coming to the release party, I was a bit apprehensive. It s been quite a while I had faced an audience and just coming out of illness didn t know how well or ill-prepared I would be for the session. I had forsaken/given up exercising two days earlier before the event as I wanted to have loose body, loose limbs all over. I also took a mild sedative (1mg) the day before just so I will have a fit night sleep and be able to focus all my energies on the big day. (I don t recommend sedatives unless the doctor prescribes) and I did have a doctor prescription so was able to have a nice sleep. I didn t do any Debian study as I hoped my somewhat long experience with both Ubuntu and Debian should help me. On the d-day, I had asked dhanesh (the organizer of the event) to accompany me from home to venue and back as I was unsure of the journey as it was around 9-10 kms. from my place and while I had been to the venue about couple of years back, I had just a mild remembrance of the place. Anyways, Dhanesh compiled with my request and together we reached the venue before the appointed 1500 hrs. As it was a Sunday I was unsure as how many people would turn up as people usually like to cozy up on a Sunday. Around 1530 hrs everybody showed up The whole group It included couple of co-organizers with most people being newbies so while I had thought of showing how to contribute via reporting bugs or putting up patches, had to set that aside and explain how things work in free software and open-source world. We didn t get into the debate of free vs open-source or free/open-source/open-core as that would have been counter-productive and probably confusing for newbies. We did however share the debian tree structure debian-tree-structure-discussion I was stumped by /var and /proc . I hadn t taken my lappy as it is expensive (a lenovo thinkpad I love very dearly) and I was unsure if I would be able to take care of it (weight wise). Dhanesh had told me that he had Debian on his lappy + zsh both of which are my favourites. While back at home I realized /var has been relegated to having apache/server logs and stuff like that, I do recall (vaguely) a thread on debian-devel about removing /var although that discussion went nowhere. One of the bugs that we hit early on is that nobody had enough space on their hdd to have Debian comfortably. It took a while to get an external hdd and push some of the content from somebody s lappy to the external drive to have space for the installation. I did share the /. /home, optional swap while Dhanesh helped by sharing about having a separate /boot partition as well which I had forgotten. I can t even begin to remember the number of times having a separate /boot partition has helped me in all of my systems. That done, we did try to install/show Debian 9 without network but were hit with #866629 so wasn t able to complete the installation. We had got the latest 9.0.1 as I had seen Steve s message about issues with the live images but even then we were hit with the above bug. As shared in the bug history, it might be a good idea to have the last couple of RC s (Release Candidate releases) as pre-release parties so people have a chance to report bugs and get them fixed. It was also nice to see Praveen raising the seriousness of the bug shared above. The next day I also filed #866971 as I had mistaken the release to be a regular release and not the live instance. I have pushed my rationale and hope the right thing happens. As installation takes a bit of time, we used the time to share about Google s Summer of Code and absence of Debian from GSoC this year. I should have directed them to an itfoss article I wrote sometime ago and also shared that Debian is also looking to having a similar apprenticeship within Debian itself. There were questions about why Debian would like to take the administrative overhead, my response was that it probably had to do with Debian wanting more control over the process. While Debian has had some great luck getting all number of seats that it asks for in GSoC, the ball is always in Google s court. Having that uncertainty off would be beneficial to Debian both in short-term as well as long-term. One interesting stat that was shared with me was that something akin to 89 students from India had been selected this year to GSoC even with the lower stipend and that is a far cry from the 10-15 students who are able to complete GSoC every year. Let s see what happens this year. One of the interesting fact/gossip I shared with them is that Google uses a modified/forked Debian internally which it probably would never release ever. There were quite a few queries about GSoC which resulted into how contributions are made and how git had become the master of all VCS (Version Control Systems). While I do have pet bugs about git (the biggest one being for places/countries having not big bandwidth git fails many a times while cloning). I *think* the bug has been reported enough times but haven t seen any improvements yet. There is a need of a solution like wget and wget -c so git just works even under the most trying circumstances (bandwidth wise) We also shared what a repo is and Dhanesh helpfully did a git shortlog to show people how commits are commented. It was from his official work so he couldn t show anything apart from the shortlog. I also shared how non-technical people can help with regard to documentation, artwork but didn t get into any concrete examples although wiki.debian.org would have been a good start. I also don t know if it s a fact or not but it seems/seemed that moinmoin (the current wiki solution used by debian) seems to have got sectional edit feature which I used sometime back. If moinmoin has got this feature then it is on par with mediawiki, although do know that mediawiki has lot more features going for it. Dhanesh did manage to install a Debian 8.0.7 (while 8.8.0 was the last release) which might have been better. The debian-installer (d-i) looks the same even though I know there are improvements with respect to UEFI and many updated components. There are and were many bugs which I wanted to share but didn t know if it was the right forum or not, for e.g. #597176 which probably needs improvements in other libraries along with the JPEG 2000 support #604859 all of which I m subscribed to. We also had a talk about code documentation and code readability, python (as almost everything in Debian is based on python) I had actually wanted to show metrics.debian.net but had seen it was down the day before and again checked to see it is down now as well, hence reported it, will hopefully come on Debian BTS some time soonish. The idea was to share that Debian does have/uses other programming languages as well and is only limited by people interested in a specific language and be willing to package and maintain packages in that specific programming language. As Dhanesh was part of Firefox OS and a Campus Ambassador we did discuss what went wrong in Firefox OS deployment and Firefox as a whole, specifically between the community and Mozilla the Corporation. In this there were lots that was lot that I wasn t able to share as had become tired otherwise would have shared that ncurses debian-installer interface although bit ugly to look at is still good as it has speech for visually differently abled people as well as people with poor sight. There is and was lots to share about Debian but was conscious that I might over-burden the audience and my stamina was also stretched. We also shared about automated builds bud didn t show either travis.debian.net or jeankins.debian.net We also had a small discussion about Artificial Intelligence, Robotics and how the outlook for people coming in Computer Science looks today. One thing I forgot to share we did do the cake-cutting together Dhanesh-Shirish cutting cake together Dhanesh is on the left while I m on the right. We did have a cute 3-4 year old boy as our guest as well bud didn t get good pictures of him. Lastly, the Debian cake itself Debian 9 cake We also talked about the kernel and subsystem maintainers and how Linus is the overlord. Look forward to comments. I am hoping Dhanesh might recollect some points that I might have missed/forgotten. Update 07/07/17 All programming languages stats. can be seen here
Filed under: Miscellenous Tagged: #alcohol humor, #co-hive, #crystal-gazing, #Debian bugs, #Debian cake, #Debian-release-party-9-pune, #live-installer, #moinmoin, #planet-debian, debian-installer, Pune

Yakking: Open your minds, and your data (formats)

Whether I am writing my own program, or chosing between existing solutions, one aspect of the decision making process which always weighs heavily on my mind is that of the input and output data formats. I have been spending a lot of my work days recently working on converting data from a proprietary tool's export format into another tool's input format. This has involved a lot of XML diving, a lot more swearing, and a non-trivial amount of pain. This drove home to me once more that the format of input and output of data is such a critical part of software tooling that it must weigh as heavily as, or perhaps even more heavily than, the software's functionality. As Tannenbaum tells us, the great thing about standards is that there's so many of them to choose from. XKCD tells us, how that comes about. Data formats are many and varied, and suffer from specifications as vague as "plain text" to things as complex as the structure of data stored in custom database formats. If you find yourself writing software which requires a brand new data format then, while I might caution you to examine carefully if it really does need a new format, you should ensure that you document the format carefully and precisely. Ideally give your format specification to a third party and get them to implement a reader and writer for your format, so that they can check that you've not missed anything. Tests and normative implementations can help prop up such an endeavour admirably. Be sceptical of data formats which have "implementation specific" areas, or "vendor specific extension" space because this is where everyone will put the most important and useful data. Do not put such beasts into your format design. If you worry that you've made your design too limiting, deal with that after you have implemented your use-cases for the data format. Don't be afraid to version the format and extend later; but always ensure that a given version of the data format is well understood; and document what it means to be presented with data in a format version you do not normally process. Phew.
Given all that, I exhort you to consider carefully how your projects manage their input and output data, and for these things to be uppermost when you are choosing between different solutions to a problem at hand. Your homework is, as you may have grown to anticipate at this time, to look at your existing projects and check that their input and output data formats are well documented if appropriate.

4 July 2017

Reproducible builds folks: Reproducible Builds: week 114 in Stretch cycle

Here's what happened in the Reproducible Builds effort between Sunday June 25 and Saturday July 1 2017: Upcoming and past events Our next IRC meeting is scheduled for July 6th at 17:00 UTC (agenda). Topics to be discussed include an update on our next Summit, a potential NMU campaign, a press release for buster, branding, etc. Toolchain development and fixes Packages fixed and bugs filed Ximin Luo uploaded dash, sensible-utils and xz-utils to the deferred uploads queue with a delay of 14 days. (We have had patches for these core packages for over a year now and the original maintainers seem inactive so Debian conventions allow for this.) Patches submitted upstream: Reviews of unreproducible packages 4 package reviews have been added, 4 have been updated and 35 have been removed in this week, adding to our knowledge about identified issues. One issue types has been updated: One issue type has been added: Weekly QA work During our reproducibility testing, FTBFS bugs have been detected and reported by: diffoscope development tests.reproducible-builds.org Misc. This week's edition was written by Chris Lamb, Ximin Luo, Holger Levsen, Bernhard Wiedemann, Vagrant Cascadian & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.

Raphaël Hertzog: My Free Software Activities in June 2017

My monthly report covers a large part of what I have been doing in the free software world. I write it for my donors (thanks to them!) but also for the wider Debian community because it can give ideas to newcomers and it s one of the best ways to find volunteers to work with me on projects that matter to me. Debian LTS I was allocated 12 hours to work on security updates for Debian 7 Wheezy. During this time I did the following: Debian packaging Django. A last-minute update to Django in stretch before the release, I uploaded python-django 1:1.10.7-2 fixing two bugs (among which one was release critical) and filed the corresponding unblock request. schroot. I tried to prepare another last-minute update, this time for schroot. The goal was to fix the bash completion (#855283) and a problem encountered by the Debian sysadmins (#835104). Those issues are fixed in unstable/testing but my unblock request got turned into a post-release stretch update because the release managers wanted to give the package some more testing time in unstable. Even now, they are wondering whether they should accept the new systemd service file. live-build, live-config and live-boot. On live-build, I merged a patch to add a keyboard shortcut for the advanced option menu entry (#864386). For live-config, I uploaded version 5.20170623 to fix a broken boot sequence when you have multiple partitions (#827665). For live-boot, I uploaded version 1:20170623 to fix the path to udevadm (#852570) and avoiding a file duplication in the initrd (864385). zim. I packaged a release candidate (0.67~rc2) in Debian Experimental and started to use it. I quickly discovered two annoying regressions that I reported upstream (here and here). logidee-tools. This is a package I authored a long time ago and that I m no longer actively using. It does still work but I sometimes wonder if it still has real users. Anyway I wanted to quickly replace the broken dependency on pgf but I ended up converting the Subversion repository to Git and I also added autopkgtests. At least those tests will inform me when the package no longer works otherwise I would not notice since I m no longer using it. Bugs filed. I filed #865531 on lintian because the new check testsuite-autopkgtest-missing is giving some bad advice and probably does its check in a bad way. I also filed #865541 on sbuild because sbuild --apt-distupgrade can under some circumstances remove build-essential and break the build chroot. I filed an upstream ticket on publican to forward the request I received in #864648. Sponsorship. I sponsored a jessie update for php-tcpdf (#814030) and dolibarr 5.0.4+dfsg3-1 for unstable. I sponsored many other packages, but all in the context of the pkg-security team. pkg-security work Now that the Stretch freeze is over, the team became more active again and I have been overwhelmed with the number of packages to review and sponsor: I also updated hashcat to a new upstream release (3.6.0) and had to discuss with upstream about its weird versioning change. Looks like we will have to introduce an epoch to be able to get back in sync with upstream. To be able to get in sync with Kali, I introduced an hashcat-meta source package (in contrib) providing hashcat-nvidia to make it easy to install hashcat for owners of NVidia hardware. Misc stuff Distro Tracker. I merged a small CSS fix from Aur lien Couderc (#858101) and added a missing constraint on the data model (found through an unexpected traceback that I received by email). I also updated the list of repositories shortly after the stretch release (#865070). Salt formulas. As part of my Kali work, I did setup a build daemon on Debian stretch host and I encountered a couple of issues with my Salt rules. I reported one against salt-formula (here) and I pushed updates for debootstrap-formula, apache-formula and schroot-formula. Thanks See you next month for a new summary of my activities.

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Foteini Tsiami: Internationalization, part two

Now that sch-scripts has been renamed to ltsp-manager and translated to English, it was time to set up a proper project site for it in launchpad: http://www.launchpad.net/ltsp-manager The following subpages were created for LTSP Manager there: We currently have an initial version of LTSP Manager running in Debian Stretch; although more testing and more bug reports will be needed before we start the localization phase. Attaching a first screenshot!

John Goerzen: Time, Frozen

We re expecting a baby any time now. The last few days have had an odd quality of expectation: any time, our family will grow. It makes time seem to freeze, to stand still. We have Jacob, about to start fifth grade and middle school. But here he is, still a sweet and affectionate kid as ever. He loves to care for cats and seeks them out often. He still keeps an eye out for the stuffed butterfly he s had since he was an infant, and will sometimes carry it and a favorite blanket around the house. He will also many days prepare the Yellow House News on his computer, with headlines about his day and some comics pasted in before disappearing to play with Legos for awhile. And Oliver, who will walk up to Laura and give baby a hug many times throughout the day and sneak up to me, try to touch my arm, and say doink before running off before I can doink him back. It was Oliver that had asked for a baby sister for Christmas before he knew he d be getting one! In the past week, we ve had out the garden hose a couple of times. Both boys will enjoy sending mud down our slide, or getting out the water slide to play with, or just playing in mud. The rings of dirt in the bathtub testify to the fun that they had. One evening, I built a fire, we made brats and hot dogs, and then Laura and I sat visiting and watching their water antics for an hour after, laughter and cackles of delight filling the air, and cats resting on our laps. These moments, or countless others like Oliver s baseball games, flying the boys to a festival in Winfield, or their cuddles at bedtime, warm the heart. I remember their younger days too, with fond memories of taking them camping or building a computer with them. Sometimes a part of me wants to just keep soaking in things just as they are; being a parent means both taking pride in children s accomplishments as they grow up, and sometimes also missing the quiet little voice that can be immensely excited by a caterpillar. And yet, all four of us are so excited and eager to welcome a new life into our home. We are ready. I can t wait to hold the baby, or to lay her to sleep, to see her loving and excited older brothers. We hope for a smooth birth, for mom and baby. Here is the crib, ready, complete with a mobile with a cute bear (and even a plane). I can t wait until there is a little person here to enjoy it.

3 July 2017

Antoine Beaupr : My free software activities, June 2017

Debian Long Term Support (LTS) This is my monthly Debian LTS report. This time I worked on Mercurial, sudo and Puppet.

Mercurial remote code execution I issued DLA-1005-1 to resolve problems with the hg server --stdio command that could be abused by "remote authenticated users to launch the Python debugger, and consequently execute arbitrary code, by using --debugger as a repository name" (CVE-2017-9462). Backporting the patch was already a little tricky because, as is often the case in our line of work, the code had changed significantly in newer version. In particular, the commandline dispatcher had been refactored which made the patch non-trivial to port. On the other hand, mercurial has an extensive test suite which allowed me to make those patches in all confidence. I also backported a part of the test suite to detect certain failures better and to fix the output so that it matches the backported code. The test suite is slow, however, which meant slow progress when working on this package. I also noticed a strange issue with the test suite: all hardlink operations would fail. Somehow it seems that my new sbuild setup doesn't support doing hardlinks. I ended up building a tarball schroot to build those types of packages, as it seems the issue is related to the use of overlayfs in sbuild. The odd part is my tests of overlayfs, following those instructions, show that it does support hardlinks, so there maybe something fishy here that I misunderstand. This, however, allowed me to get a little more familiar with sbuild and the schroots. I also took this opportunity to optimize the builds by installing an apt-cacher-ng proxy to speed up builds, which will also be useful for regular system updates.

Puppet remote code execution I have issued DLA-1012-1 to resolve a remote code execution attack against puppetmaster servers, from authenticated clients. To quote the advisory: "Versions of Puppet prior to 4.10.1 will deserialize data off the wire (from the agent to the server, in this case) with a attacker-specified format. This could be used to force YAML deserialization in an unsafe manner, which would lead to remote code execution." The fix was non-trivial. Normally, this would have involved fixing the YAML parsing, but this was considered problematic because the ruby libraries themselves were vulnerable and it wasn't clear we could fix the problem completely by fixing YAML parsing. The update I proposed took the bold step of switching all clients to PSON and simply deny YAML parsing from the server. This means all clients need to be updated before the server can be updated, but thankfully, updated clients will run against an older server as well. Thanks to LeLutin at Koumbit for helping in testing patches to solve this issue.

Sudo privilege escalation I have issued DLA-1011-1 to resolve an incomplete fix for a privilege escalation issue (CVE-2017-1000368 from CVE-2017-1000367). The backport was not quite trivial as the code had changed quite a lot since wheezy as well. Whereas mercurial's code was more complex, it's nice to see that sudo's code was actually simpler and more straightforward in newer versions, which is reassuring. I uploaded the packages for testing and uploaded them a year later. I also took extra time to share the patch in the Debian bugtracker, so that people working on the issue in stable may benefit from the backported patch, if needed. One issue that came up during that work is that sudo doesn't have a test suite at all, so it is quite difficult to test changes and make sure they do not break anything.

Should we upload on fridays? I brought up a discussion on the mailing list regarding uploads on fridays. With the sudo and puppet uploads pending, it felt really ... daring to upload both packages, on a friday. Years of sysadmin work hardwired me to be careful on fridays; as the saying goes: "don't deploy on a friday if you don't want to work on the weekend!" Feedback was great, but I was surprised to find that most people are not worried worried about those issues. I have tried to counter some of the arguments that were brought up: I wonder if there could be a disconnection here between the package maintainer / programmer work and the sysadmin work that is at the receiving end of that work. Having myself to deal with broken updates in the past, I'm surprised this has never come up in the discussions yet, or that the response is so underwhelming. So far, I'll try to balance the need for prompt security updates and the need for stable infrastructure. One does not, after all, go without the other...

Triage I also did small fry triage: Hopefully some of those will come to fruitition shortly.

Other work My other work this month was a little all over the place.

Stressant Uploaded a new release (0.4.1) of stressant to split up the documentation from the main package, as the main package was taking up too much space according to grml developers. The release also introduces limited anonymity option, by blocking serial numbers display in the smartctl output.

Debiman Also did some small followup on the debiman project to fix the FAQ links.

Local server maintenance I upgraded my main server to Debian stretch. This generally went well, althought the upgrade itself took way more time than I would have liked (4 hours!). This is partly because I have a lot of cruft installed on the server, but also because of what I consider to be issues in the automation of major Debian upgrades. For example, I was prompted for changes in configuration files at seemingly random moments during the upgrade, and got different debconf prompts to answer. This should really be batched together, and unfortunately I had forgotten to use the home-made script I established when i was working at Koumbit which shortens the upgrade a bit. I wish we would improve on our major upgrade mechanism. I documented possible solutions for this in the AutomatedUpgrade wiki page, but I'm not sure I see exactly where to go from here. I had a few regressions after the upgrade:
  • the infrared remote control stopped working: still need to investigate
  • my home-grown full-disk encryption remote unlocking script broke, but upstream has a nice workaround, see Debian bug #866786
  • gdm3 breaks bluetooth support (Debian bug #805414 - to be fair, this is not a regression in stretch, it's just that I switched my workstation from lightdm to gdm3 after learning that the latter can do rootless X11!)

Docker and Subsonic I did my first (and late?) foray into Docker and containers. My rationale was that I wanted to try out Subsonic, an impressive audio server which some friends have shown me. Since Subsonic is proprietary, I didn't want it to contaminate the rest of my server and it seemed like a great occasion to try out containers to keep things tidy. Containers may also allow me to transparently switch to the FLOSS fork LibreSonic once the trial period is over. I have learned a lot and may write more about the details of that experience soon, for now you can look at the contributions I made to the unofficial Subsonic docker image, but also the LibreSonic one. Since Subsonic also promotes album covers as first-class citizens, I used beets to download a lot of album covers, which was really nice. I look forward to using beets more, but first I'll need to implement two plugins.

Wallabako I did a small release of wallabako to fix the build with the latest changes in the underlying wallabago library, which led me to ask upstream to make versionned releases. I also looked into creating a separate documentation site but it looks like mkdocs doesn't like me very much: the table of contents is really ugly...

Small fry That's about it! And that was supposed to be a slow month...

1 July 2017

Thorsten Alteholz: My Debian Activities in June 2017

FTP assistant This month I marked 100 packages for accept and rejected zero packages. I promise, I will reject more in July! Debian LTS This was my thirty-sixth month that I did some work for the Debian LTS initiative, started by Raphael Hertzog at Freexian. This month my all in all workload went down again to 16h. During that time I did LTS uploads of: I also tested the proposed apache2 package prepared by Roberto and started to work on a new bind9 upload Last but not least I had five days of frontdesk duties. Other stuff This month was filled with updating lots of machines to Stretch. Everything went fine, so thanks a lot to everybody involved in that release. Nevertheless I also did a DOPOM upload and now take care of otpw. Luckily most of the accumulated bugs already contained a patch, so that I just had to upload a new version and close them.

Daniel Silverstone: F/LOSS activity, June 2017

It seems to be becoming popular to send a mail each month detailing your free software work for that month. I have been slowly ramping my F/LOSS activity back up, after years away where I worked on completing my degree. My final exam for that was in June 2017 and as such I am now in a position to try and get on with more F/LOSS work. My focus, as you might expect, has been on Gitano which reached 1.0 in time for Stretch's release and which is now heading gently toward a 1.1 release which we have timed for Debconf 2017. My friend a colleague Richard has been working hard on Gitano and related components during this time too, and I hope that Debconf will be an opportunity for him to meet many of my Debian friends too. But enough of that, back to the F/LOSS. We've been running Gitano developer days roughly monthly since March of 2017, and the June developer day was attended by myself, Richard Maw, and Richard Ipsum. You are invited to read the wiki page for the developer day if you want to know exactly what we got up to, but a summary of my involvement that day is: Other than that, related to Gitano during June I: My non-Gitano F/LOSS related work in June has been entirely centred around the support I provide to the Lua community in the form of the Lua mailing list and website. The host on which it's run is ailing, and I've had to spend time trying to improve and replace that. Hopefully I'll have more to say next month. Perhaps by doing this reporting I'll get more F/LOSS done. Of course, July's report will be sent out while I'm in Montr al for debconf 2017 (or at least for debcamp at that point) so hopefully more to say anyway.

Keith Packard: DRM-lease-4

DRM leasing part three (vblank) The last couple of weeks have been consumed by getting frame sequence numbers and events handled within the leasing environment (and Vulkan) correctly. Vulkan EXT_display_control extension This little extension provides the bits necessary for applications to track the display of frames to the user. 
VkResult
vkGetSwapchainCounterEXT(VkDevice           device,
             VkSwapchainKHR         swapchain,
             VkSurfaceCounterFlagBitsEXT    counter,
             uint64_t           *pCounterValue);
This function just retrieves the current frame count from the display associated with swapchain. 
VkResult
vkRegisterDisplayEventEXT(VkDevice          device,
              VkDisplayKHR          display,
              const VkDisplayEventInfoEXT   *pDisplayEventInfo,
              const VkAllocationCallbacks   *pAllocator,
              VkFence           *pFence);
This function creates a fence that will be signaled when the specified event happens. Right now, the only event supported is when the first pixel of the next display refresh cycle leaves the display engine for the display. If you want something fancier (like two frames from now), you get to do that on your own using this basic function. drmWaitVBlank drmWaitVBlank is the existing interface for all things sequence related and has three modes (always nice to have one function do three things, I think). It can:
  1. Query the current vblank number
  2. Block until a specified vblank number
  3. Queue an event to be delivered at a specific vblank number
This interface has a few issues: For leases, figuring out the index into the kernel list of crtcs is pretty tricky -- our lease has a subset of those crtcs, so we can't actually compute the global crtc index. drmCrtcGetSequence 
int drmCrtcGetSequence(int fd, uint32_t crtcId,
               uint64_t *sequence, uint64_t *ns);
Here's a simple new function hand it a crtc ID and it provides the current frame sequence number and the time when that frame started (in nanoseconds). drmCrtcQueueSequence 
int drmCrtcQueueSequence(int fd, uint32_t crtcId,
                 uint32_t flags, uint64_t sequence,
             uint64_t user_data);
struct drm_event_crtc_sequence  
    struct drm_event    base;
    __u64           user_data;
    __u64           time_ns;
    __u64           sequence;
 ;
This will cause a CRTC_SEQUENCE event to be delivered at the start of the specified frame sequence. That event will include the frame when the event was actually generated (in case it's late), along with the time (in nanoseconds) when that frame was started. The event also includes a 64-bit user_data value, which can be used to hold a pointer to whatever data the application wants to see in the event handler. The 'flags' argument contains a combination of: 
#define DRM_CRTC_SEQUENCE_RELATIVE      0x00000001  /* sequence is relative to current */
#define DRM_CRTC_SEQUENCE_NEXT_ON_MISS      0x00000002  /* Use next sequence if we've missed */
#define DRM_CRTC_SEQUENCE_FIRST_PIXEL_OUT   0x00000004  /* Signal when first pixel is displayed */
These are similar to the values provided for the drmWaitVBlank function, except I've added a selector for when the event should be delivered to align with potential future additions to Vulkan. Right now, the only time you can ask for is first-pixel-out, which says that the event should correspond to the display of the first pixel on the screen. DRM events Vulkan fences With the kernel able to deliver a suitable event at the next frame, all the Vulkan code needed was a to create a fence and hook it up to such an event. The existing fence code only deals with rendering fences, so I added window system interface (WSI) fencing infrastructure and extended the radv driver to be able to handle both kinds of fences within that code. Multiple waiting threads I've now got three places which can be waiting for a DRM event to appear:
  1. Frame sequence fences.
  2. Wait for an idle image. Necessary when you want an image to draw the next frame to.
  3. Wait for the previous flip to complete. The kernel can only queue one flip at a time, so we have to make sure the previous flip is complete before queuing another one.
Vulkan allows these to be run from separate threads, so I needed to deal with multiple threads waiting for a specific DRM event at the same time. XCB has the same problem and goes to great lengths to manage this with a set of locking and signaling primitives so that only one thread is ever doing poll or read from the socket at time. If another thread wants to read at the same time, it will block on a condition variable which is then signaled by the original reader thread at the appropriate time. It's all very complicated, and it didn't work reliably for a number of years. I decided to punt and just create a separate thread for processing all DRM events. It blocks using poll(2) until some events are readable, processes those and then broadcasts to a condition variable to notify any waiting threads that 'something' has happened. Each waiting thread simply checks for the desired condition and if not satisfied, blocks on that condition variable. It's all very simple looking, and seems to work just fine. Code Complete, Validation Remains At this point, all of the necessary pieces are in place for the VR application to take advantage of an HMD using only existing Vulkan extensions. Those will be automatically mapped into DRM leases and DRM events as appropriate. The VR compositor application is working pretty well; tests with Dota 2 show occasional jerky behavior in complex scenes, so there's clearly more work to be done somewhere. I need to go write a pile of tests to independently verify that my code is working. I wonder if I'll need to wire up some kind of light sensor so I can actually tell when frames get displayed as it's pretty easy to get consistent-but-wrong answers in this environment. Source Code

Russ Allbery: Review: Make It Stick

Review: Make It Stick, by Peter C. Brown, et al.
Author: Peter C. Brown
Author: Henry L. Roediger III
Author: Mark A. McDaniel
Publisher: Belknap Press
Copyright: 2014
ISBN: 0-674-72901-3
Format: Kindle
Pages: 255
Another read for the work book club. "People generally are going about learning in the wrong ways." This is the first sentence of the preface of this book by two scientists (Roediger and McDaniel are both psychology researchers specializing in memory) and a novelist and former management consultant (Brown). The goal of Make It Stick is to apply empirical scientific research to the problem of learning, specifically retention of information for long-term use. The authors aim to convince the reader that subjective impressions of the effectiveness of study habits are highly deceptive, and that scientific evidence points strongly towards mildly counter-intuitive learning methods that don't feel like they're producing as good of results. I have such profound mixed feelings about this book. Let's start with the good. Make It Stick is a book containing actual science. The authors quote the studies, results, and scientific argument at length. There are copious footnotes and an index, as well as recommended reading. And the science is concrete and believable, as is the overlaid interpretation based on cognitive and memory research. The book's primary argument is that short-term and long-term memory are very different things, that what we're trying to achieve when we say "learning" is based heavily on long-term memory and recall of facts for an extended time after study, and that building this type of recall requires not letting our short-term memory do all the work. We tend towards study patterns that show obvious short-term improvement and that produce an increased feeling of effortless recall of the material, but those study patterns are training short-term memory and mean the knowledge slips away quickly. Choosing learning methods that instead make us struggle a little with what we're learning are significantly better. It's that struggle that leads to committing the material to long-term memory and building good recall pathways for it. On top of this convincingly-presented foundation, the authors walk through learning methods that feel worse in the moment but have better long-term effects: mixing practice of different related things (different types of solids when doing geometry problems, different pitches in batting practice) and switching types before you've mastered the one you're working on, forcing yourself to interpret and analyze material (such as writing a few paragraphs of summary in your own words) instead of re-reading it, and practicing material at spaced intervals far enough apart that you've forgotten some of the material and have to struggle to recall it. Possibly the most useful insight here (at least for me) was the role of testing in learning, not as just a way of measuring progress, but as a learning tool. Frequent, spaced, cumulative testing forces exactly the type of recall that builds long-term memory. The tests themselves help improve our retention of what we're learning. It's bad news for people like me who were delighted to leave school and not have to take a test again, but viewing tests as a more effective learning tool than re-reading and review (which they are) does cast them in a far more positive light. This is all solid stuff, and I'm very glad the research underlying this book exists and that I now know about it. But there are some significant problems with its presentation. The first is that there just isn't much here. The two long paragraphs above summarize nearly all of the useful content of this book. The authors certainly provide more elaboration, and I haven't talked about all of the study methods they mention or some of the useful examples of their application. But 80% of it is there, and the book is intentionally repetitive (because it tries to follow the authors' advice on learning theory). Make It Stick therefore becomes tedious and boring, particularly in the first four chapters. I was saying a lot of "yes, yes, you said that already" and falling asleep while trying to read it. The summaries at the end of the book are a bit better, but you will probably not need most of this book to get the core ideas. And then there's chapter five, which ends in a train wreck. Chapter five is on cognitive biases, and I see why the authors wanted to include it. The Dunning-Kruger effect is directly relevant to their topic. It undermines our ability to learn, and is yet another thing that testing helps avoid. Their discussion of Daniel Kahneman's two system theory (your fast, automatic, subconscious reactions and your slow, thoughtful, conscious processing) is somewhat less directly relevant, but it's interesting stuff, and it's at least somewhat related to the short-term and long-term memory dichotomy. But some of the stories they choose to use to illustrate this are... deeply unfortunate. Specifically, the authors decided to use US police work in multiple places as their example of choice for two-system thinking, and treat it completely uncritically. Some of you are probably already wincing because you can see where this is going. They interview a cop who, during scenario training for traffic stops, was surprised by the car trunk popping open and a man armed with a shotgun popping out of it. To this day, he still presses down on the trunk of the car as he walks up; it's become part of his checklist for every traffic stop. This would be a good example if the authors realized how badly his training has failed and deconstructed it, but they're apparently oblivious. I wanted to reach into the book and shake them. People have a limited number of things they can track and follow as part of a procedure, and some bad trainer has completely wasted part of this cop's attention in every traffic stop and thereby made him less safe! Just calculate the chances that someone would be curled up in an unlocked trunk with a shotgun and a cop would just happen to stop that car for some random reason, compared to any other threat the cop could use that same attention to watch for. This is exactly the type of scenario that's highly memorable but extremely improbable and therefore badly breaks human risk analysis. It's what Bruce Schneier calls a movie plot threat. The correct reaction to movie plot threats is to ignore them; wasting effort on mitigating them means not having that effort to spend on mitigating some other less memorable but more likely threat. This isn't the worst, though. The worst is the very next paragraph, also from police training, of showing up at a domestic call, seeing an armed person on the porch who stands up and walks away when ordered to drop their weapon, and not being sure how to react, resulting in that person (in the simulated exercise) killing the cop before they did anything. The authors actually use this as an example of how the cop was using system two and needed to train to use system one in that situation to react faster, and that this is part of the point of the training. Those of us who have been paying attention to the real world know what using system one here means: the person on the porch gets shot if they're black and doesn't get shot if they're white. The authors studiously refuse to even hint at this problem. I would have been perfectly happy if this book avoided the unconscious bias aspect of system one thinking. It's a bit far afield of the point of the book, and the authors are doubtless trying to stay apolitical. But that's why you pick some other example. You cannot just drop this kind of thing on the page and then refuse to even comment on it! It's like writing a chapter about the effect of mass transit on economic development, choosing Atlanta as one of your case studies, and then never mentioning race. Also, some editor seriously should have taken an ax to the sentence where the authors (for no justified reason) elaborate a story to describe a cop maiming a person, solely to make a cliched joke about how masculinity is defined by testicles and how people who lose body parts are less human. Thanks, book. This was bad enough that it dominated my memory of this chapter, but, reviewing the book for this review, I see it was just a few badly chosen examples at the end of the chapter and one pointless story at the start. The rest of the chapter is okay, although it largely summarizes things covered better in other books. The most useful part that's relevant to the topic of the book is probably the discussion of peer instruction. Just skip over all the police bits; you won't be missing anything. Thankfully, the rest of the book mostly avoids failing quite this hard. Chapter six does open with the authors obliviously falling for a string of textbook examples of survivorship bias (immediately after the chapter on cognitive biases!), but they shortly thereafter settle down to the accurate and satisfying work of critiquing theories of learning methods and types of intelligence. And by critiquing, I mean pointing out that they're mostly unscientific bullshit, which is fighting the good fight as far as I'm concerned. So, mixed feelings. The science seems solid, and is practical and directly applicable to my life. Make It Stick does an okay job at presenting it, but gets tedious and boring in places, particularly near the beginning. And there are a few train-wreck examples that had me yelling at the book and scribbling notes, which wasn't really the cure for boredom I was looking for. I recommend being aware of this research, and I'm glad the authors wrote this book, but I can't really recommend the book itself as a reading experience. Rating: 6 out of 10

Paul Wise: FLOSS Activities June 2017

Changes

Issues

Review

Administration
  • Debian: redirect 2 users to support channels, redirect 1 person to the mirrors team, investigate SMTP TLS question, fix ACL issue, restart dead exim4 service
  • Debian mentors: service restarts, security updates & reboot
  • Debian QA: deploy my changes
  • Debian website: release related rebuilds, rebuild installation-guide
  • Debian wiki: whitelist several email addresses, whitelist 1 domain
  • Debian package tracker: deploy my changes
  • Debian derivatives census: deploy my changes
  • Openmoko: security updates & reboots.

Communication

Sponsors All work was done on a volunteer basis.

28 June 2017

Yakking: What is Time?

Time is a big enough subject that I'd never finish writing about it. Fortunately this is a Linux technical blog, so I only have to talk about it from that perspective. In a departure from our usual article series format, we are going to start with an introductory article and follow up starting from basics, introducing new concepts in order of complexity. What is time? Time is seconds since the unix epoch. The Unix epoch is midnight, Thursday, 1st January 1970 in the UTC time zone. If you know the unix time and how many seconds in each day since then you can use the unix timestamp to work out what time it is now in UTC time. If you want to know the time in another timezone the na ve thing is to apply a timezone offset based on how far or behind the zone is compared to UTC. This is non-trivial since time is a political issue, requiring global coordination with hundreds of countries coming in and out of [daylight saving time][] and various other administrative changes, time often changes. Some times don't exist in some timezones. Samoa skipped a day and changed time zone. A side-effect of your system clock being in Unix time is that to know local time you need to know where you are. The talk linked to in https://fosdem.org/2017/schedule/event/python_datetime/ is primarily about time in python, but covers the relationship between time stamps, clock time and time zones. http://www.creativedeletion.com/2015/01/28/falsehoods-programmers-date-time-zones.html is a good summary of some of the common misconceptions of time zone handling.
Now that we've covered some of the concepts we can discuss in future articles how this is implemented in Linux.

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