Refactor GitHub CD workflow

[jonkerj]

A long time ago, I started working on #653. I found it hard to find the time to improve the CD, but in the previous week I managed to finish it. The original PR has gone stale/rotten/closed so I'm filing this new one.

This PR achieves a couple of things:

• No messy individual deb-extracts: it leverages multiarch
• Arm64 support (fixes #280)
• Consistent artifact naming (ie, spotifyd-<os>-<arch>-<type>)
• Consistent feature set (linux/slim is always alsa)
• Almost no DRY

There are two drawbacks I am not sure about:

• I did not include armv6. Is this really used?
• The linux artifact types had different feature set (specifically audio backends) across architectures: x86_64 used pulseaudio, even in slim, but arm did not. Was this intentional?

I've tested this in my repo, and have a full artifact set for v0.3.2-cd.3.

[MichaIng]

I did not include armv6. Is this really used?

Yes it is, Raspberry Pi 1 and Raspberry Pi Zero models (which are still heavily used), so would be great to keep it. Alternatively the ARMv7 binaries could be replaced with ARMv6 ones (could be called "armhf" or "arm32"), which works well due to backwards compatibility. But ARMv6 binaries are usually larger (= higher memory usage) and possibly have other minor downsides on ARMv7 capable systems, so it isn't optional, just common practice elsewhere 😉.

[jonkerj]

That would require a bit of re-thinking, but if it is used, it should work. I'll look into it.

[jonkerj]

Small update: I've been fighting with toolchains for a couple of days now, and supporting armv6 seems very hard. Default toolchains on recent ubuntu (20.04) is unable to build armv6/thumb-1 binaries and third party toolchains are very clunky to use (ignoring the supply chain attack vector here).

In order to safely build armv6 binaries on recent ubuntu, you'll need to roll your own toolchain (yay..) or trust a third party.

[MichaIng]

gcc-arm-linux-gnueabihf compiler with --with-arch=armv6 --with-float=hard --with-fpu=vfp flags does not work?

[jonkerj]

The packages gcc-{8,9,10}-arm-linux-gnueabihf are not compiled "with" armv6/thumb-1, etc:

jorik@zinc:$ arm-linux-gnueabihf-gcc -mcpu=arm1176jzf-s -mfloat-abi=hard -mfpu=vfp /tmp/silly.c -o /tmp/silly
/tmp/silly.c: In function ‘main’:
/tmp/silly.c:1:1: sorry, unimplemented: Thumb-1 hard-float VFP ABI
    1 | int main() {}
      | ^~~
jorik@zinc:$ arm-linux-gnueabihf-gcc -v
Using built-in specs.
COLLECT_GCC=arm-linux-gnueabihf-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/arm-linux-gnueabihf/9/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 9.3.0-17ubuntu1~20.04' --with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,gm2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-9 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --without-target-system-zlib --enable-libpth-m2 --enable-multiarch --enable-multilib --disable-sjlj-exceptions --with-arch=armv7-a --with-fpu=vfpv3-d16 --with-float=hard --with-mode=thumb --disable-werror --enable-multilib --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=arm-linux-gnueabihf --program-prefix=arm-linux-gnueabihf- --includedir=/usr/arm-linux-gnueabihf/include
Thread model: posix
gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04)

I'm going to do yet another attempt using bootlin's precompiled toolchains. These are for specific archs (in this case armv6/eabihf/glibc), up to date, and reasonably trustworthy.

[MichaIng]

Here is the official toolchain: https://github.com/raspberrypi/tools But it states to be deprecated and suggests what I posted above. What generally works is compiling on a Raspbian system, e.g. booted/chrooted as QEMU container.

[jonkerj]

OK, I can build a binary using a armv6 toolchain (bootlin's armv6/glibc). When I readelf -A the resulting binary, it still shows wrong arch, even though the toolchain is not able to -march=armv7:

jorik@zinc:~/spotifyd/spotifyd$ readelf -A target/arm-unknown-linux-gnueabihf/release/spotifyd
Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "7-A"
  Tag_CPU_arch: v7
  Tag_CPU_arch_profile: Application
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-2
  Tag_FP_arch: VFPv3-D16
[..]
jorik@zinc:~/spotifyd/spotifyd$ echo 'int main() {}' > ../silly.c
jorik@zinc:~/spotifyd/spotifyd$ arm-buildroot-linux-gnueabihf-gcc -march=armv7 -o ../silly ../silly.c
cc1: error: target CPU does not support ARM mode

Interesting thing is that all intermediate objects are armv6/thumb1:

jorik@zinc:~/spotifyd/spotifyd$ readelf -A target/arm-unknown-linux-gnueabihf/release/deps/libtextwrap-ba6f73e7c9969203.rlib

File: target/arm-unknown-linux-gnueabihf/release/deps/libtextwrap-ba6f73e7c9969203.rlib(textwrap-ba6f73e7c9969203.textwrap.7dc394a6-cgu.0.rcgu.o)
Attribute Section: aeabi
File Attributes
  Tag_conformance: "2.09"
  Tag_CPU_arch: v6
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-1
  Tag_FP_arch: VFPv2
  Tag_ABI_PCS_R9_use: V6

Since the compiler refuses to create armv7 binaries, this makes me think it's the linker causing this issue. Maybe that is because of libc6-dev:armhf contains several static objects (.a files) which are getting linked, and being armv7/thumb2:

File: /usr/lib/arm-linux-gnueabihf/libm.a(s_lib_version.o)
Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "7-A"
  Tag_CPU_arch: v7
  Tag_CPU_arch_profile: Application
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-2

So I need to think of an elegant solution to download the build/link dependencies; they probably need to be really old.

[tomodachi]

@jonkerj I tested the a release from your repository assuming it's built using this CD workflow. With the relase spotifyd-linux-armhf-full I get :

"./spotifyd: /lib/arm-linux-gnueabihf/libm.so.6: version `GLIBC_2.29' not found (required by ./spotifyd)"

On a PI 3 with Rasbian (Debian Buster)

The same release from spotifyd repository works fine.

[MichaIng]

It would need to be linked against an older glibc version to be compatible with older OS versions. Debian/Raspbian Buster ships v2.28, and it is the most used distro version on armhf SBCs, so this makes sense as a minimum, I'd say. Ubuntu Bionic ships glibc v2.27.

[slondr]

I'm not sure if supporting first-generation RPis in our CD specifically is worth delaying the other changes here.

[tomodachi]

Hmm maybe it wasn't clear from my comment, but this didn't work on a rapsberrypi-3 so it's not only first-gen raspberrys that will will not work with this.

[slondr]

Oh huh does this actually bring back armv6 support now?

[robinvd]

@slondr its a little too big for me to fully review right now. If you tested it and looks look then go ahead

[jonkerj]

1. The CD doesn't currently build, it apparently just starts a debug shell (?) on the prepared system.

I did change put that in at some point, to investigate why/how things were going bad. Very hard (at least for me) to guess what was going wrong otherwise 😆

2. full fails for all non-x86_64 architectures.

I had that working at some point, but it has been at least half a year since I touched that.

I must confess I have gotten less than motivated to finish this work, as it turns out it's very hard to reliably cross-build without a lot of DRY. It could be that it only needs some touching up, but with all these native dependencies it becomes messy/complex real quick.

[eladyn]

Thanks for reporting back!

I did change put that in at some point, to investigate why/how things were going bad. Very hard (at least for me) to guess what was going wrong otherwise :laughing:

I assumed that too. :grin: Obviously nothing that should be merged, though.

2. full fails for all non-x86_64 architectures.

I had that working at some point, but it has been at least half a year since I touched that.

Yeah, it seems that it is somehow a problem with the configuration of ubuntu-20.04 that github is using? With 18.04 and 22.04 it seems to build just fine.

I must confess I have gotten less than motivated to finish this work, as it turns out it's very hard to reliably cross-build without a lot of DRY. It could be that it only needs some touching up, but with all these native dependencies it becomes messy/complex real quick.

Totally understandable. If someone else wants to take up this PR (or I get around to it) I think we could merge it for the next release, otherwise I'd postpone that. Although the arm64 support seems certainly desirable and the simplifications that this PR brings are great!

[georgefst]

Totally understandable. If someone else wants to take up this PR (or I get around to it) I think we could merge it for the next release, otherwise I'd postpone that. Although the arm64 support seems certainly desirable and the simplifications that this PR brings are great!

I take it no one's interested then? I expect I'm not the only one out there who'd happily buy a few beers/coffees for anyone who gets this over the line - aarch64 is rapidly becoming a more popular architecture, especially now that it's effectively the default for RPis.

Otherwise, I'll try to find the time to look in to it myself, but I'm pretty swamped and this is not exactly my area of expertise.