Compile rust for powerpc OpenWRT device with libc 1.2.3?

Hi there!

I'd like to create a cross platform CLI tool / daemon that I would like to also be able to have running on OpenWRT routers.

I've managed to compile a hello world (with only the std println macro) using cross-rs + podman, but sadly that binary doesn't run on my target device, instead printing:

-ash: /path/file: not found

Reading linux - ELF file exists in /usr/bin but turns out "-ash: file: not found" - Stack Overflow made me believe the reason is incompatible libc versions between build and runtime environments.

My runtime has this libc version:

$ opkg list-installed | grep libc
libc - 1.2.3-4

That package contains only one file with two symbolic links pointing onto itself:

$ opkg files libc
Package libc (1.2.3-4) is installed on root and has the following files:
/lib/libc.so
/lib/ld-musl-powerpc-sf.so.1
/usr/bin/ldd

How can I get a compatible build environment? Is that "musl" in there a hint that I should use a target architecture with "musl" suffix?

My next try:

cargo +nightly build -Z build-std=std --release --target powerpc-unknown-linux-musl

failed with:

error[E0463]: can't find crate for panic_abort

next try:

cargo +nightly build -Z build-std=std,panic_abort --release --target powerpc-unknown-linux-musl

failure:

error: linking with `cc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/self-contained:/home/user/.rustup/toolchains/esp/riscv32-esp-elf/esp-12.2.0_20230208/riscv32-esp-elf/bin:/home/user/.rustup/toolchains/esp/xtensa-esp32s2-elf/esp-12.2.0_20230208/xtensa-esp32s2-elf/bin:/home/user/.rustup/toolchains/esp/xtensa-esp32s3-elf/esp-12.2.0_20230208/xtensa-esp32s3-elf/bin:/home/user/.rustup/toolchains/esp/xtensa-esp32-elf/esp-12.2.0_20230208/xtensa-esp32-elf/bin:/home/user/bin:/home/user/.cargo/bin:/opt/flutter/bin:/opt/android-sdk/tools/bin:/home/user/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/opt/android-sdk/cmdline-tools/latest/bin:/opt/flutter/bin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl:/usr/lib/rustup/bin" VSLANG="1033" "cc" "-m32" "crt1.o" "crti.o" "crtbegin.o" "/tmp/rustcdu8X2U/symbols.o" "/home/user/Development/git/project/target/powerpc-unknown-linux-musl/release/deps/rust_p2p_chat-361aa1a14a2e669f.rust_p2p_chat.2fc1f9e84b3f03e1-cgu.0.rcgu.o" "-Wl,--as-needed" "-L" "/home/user/Development/git/project/target/powerpc-unknown-linux-musl/release/deps" "-L" "/home/user/Development/git/project/target/release/deps" "-L" "/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/powerpc-unknown-linux-musl/lib" "-Wl,-Bstatic" "-lunwind" "-lc" "/home/user/Development/git/project/target/powerpc-unknown-linux-musl/release/deps/libcompiler_builtins-af938bdf6febe714.rlib" "-Wl,-Bdynamic" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-nostartfiles" "-L" "/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/powerpc-unknown-linux-musl/lib" "-L" "/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/powerpc-unknown-linux-musl/lib/self-contained" "-o" "/home/user/Development/git/project/target/powerpc-unknown-linux-musl/release/deps/rust_p2p_chat-361aa1a14a2e669f" "-Wl,--gc-sections" "-static" "-no-pie" "-Wl,-z,relro,-z,now" "-Wl,--strip-all" "-nodefaultlibs" "crtend.o" "crtn.o"
  = note: /usr/bin/ld: cannot find crt1.o: No such file or directory
          /usr/bin/ld: cannot find crti.o: No such file or directory
          /usr/bin/ld: cannot find crtbegin.o: No such file or directory
          /usr/bin/ld: /home/user/Development/git/project/target/powerpc-unknown-linux-musl/release/deps/rust_p2p_chat-361aa1a14a2e669f.rust_p2p_chat.2fc1f9e84b3f03e1-cgu.0.rcgu.o: relocations in generic ELF (EM: 20)

I've installed the package musl on my system (=a x86_64 Manjaro linux box) which did contain the files /usr/lib/musl/lib/crt1.o & /usr/lib/musl/lib/crti.o (unsure where crtbegin.o should come from) but that didn't change the latest error messages. Unsure if that's because /usr/lib/musl/lib/ is not on the library search path or if powerpc specific versions of those files need to be available somewhere..

I found a quite good explanation of the options for compiling for older libc versions here:

Since my final goal is to get this build done using Gitlab CI (and since I dislike static linking because I need to optimize for size) the 3rd option with a docker image would be the one I prefer.

So now I need to find or learn how to create a docker image that enables building rust with libc version 1.2.3

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