arm-unknown-linux-gnueabihf generates dependency on GLIBC_2.28

[jadamcrain]

Hi,

We're using rust-cross in our CI to generate FFI libraries for a number of targets:

https://github.com/stepfunc/dnp3/blob/refactor/jni-ci-gen/.github/workflows/ci.yml#L274

The generated GLIBC dependencies are as advertised with the exception of arm-unknown-linux-gnueabihf. The table in the README says 2.27 for this target, whereas we have the following two 2.28 dependencies in the .so:

00000000      DF *UND*  00000000  GLIBC_2.28  fcntl
00000000  w   DF *UND*  00000000  GLIBC_2.28  statx

The full objdump.txt

Is this expected? Can the minimum required GLIBC be lowered for this target?

thanks!

Adam

[jadamcrain]

The ARM toolchain referenced in the dockerfile explicitly says it contains 2.28 so maybe best to update the table from 2.27 -> 2.28.

I have a user who'd like to use our ARM cross builds on Ubuntu 18.04 which only has 2.27 and is LTS until 2028.

[Emilgardis]

Thanks for the issue!

Yeah, the table is not accurate, feel free to submit a pr to correct it. We also have #591 which probably will change stuff as well, we haven't gotten to that though yet.

See #680 for a way to possibly select glibc version

[jadamcrain]

@Emilgardis Thanks for these.

cargo-zigbuild is pretty fascinating. I just tried to do this locally installing it, zig, and the arm-unknown-linux-gneuabihf target.

My project has ring as an indirect dependency which has a complicated, platform-dependent build script.

  error: Unknown CPU: 'armv6'
  thread 'main' panicked at 'execution failed', /home/jadamcrain/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/ring-0.16.20/build.rs:656:9

I'll take this issue over to the cargo-zigbuild project for suggestions to see if they can help.

Regardless of outcome with zigbuild, is rust-cross interested in supporting older GLIBC for this architecture?. Not supporting Ubuntu 18.04 doesn't seem portable.

[jadamcrain]

It looks like I'm hamstrung by ziglang/zig#4911 and unable to use cargo-zigbuild until that resolves.

[Emilgardis]

Regardless of outcome with zigbuild, is rust-cross interested in supporting older GLIBC for this architecture?. Not supporting Ubuntu 18.04 doesn't seem portable.

Yes, as hinted in #680, we want to try to do that

[Alexhuszagh]

This has actually been fixed: we've lowered this (for this target only) to glibc 2.17 (see supported targets). This was part of another bug fix (reported in #426 and fixed in #734). While moving to crosstool for this image build to correctly target ARMv6 rather than ARMv7, we were able to build for a much older glibc so we can have compatibility with RHEL7.

[jadamcrain]

That's great! How often are releases done? Does it matter if the referenced docker image are updated more frequently?

I guess I'm just wondering when this fix would show up if I'm using Github actions with cross: true.

[Emilgardis]

You can try it out already if you add

- run: cargo install --git https://github.com/cross-rs/cross --locked to your action

#761