argv[0] can now be automatically fixed

[tvierling]

Is this a bug report, feature (enhancement) request or question? (leave only one on its own line)

/kind enhancement

Description:

qemu-user-static can now automatically handle binfmt P mode for reflecting the correct argv[0] value, based on the name of the binary (a suffix -binfmt-P). I have a manually hacked container to do exactly this; looking into fixing it here but have to familiarize myself with this container's build automation.

Since this can now be automatic, it probably should be the default mode once implemented. There's really no reason not to use binfmt P mode if it can be used, because non-P mode is seriously buggy in many contexts.

This is fairly simple to do, if someone with more familiarity with this container's build wants to give it a go:

1. Rename the binaries from qemu-ARCH-static to qemu-ARCH-static-binfmt-P
2. Copy those binaries into the container, with that renaming.
3. Change the last line of register.sh from:
   exec /qemu-binfmt-conf.sh --qemu-suffix "-static" --qemu-path "${QEMU_BIN_DIR}" $@
   to:
   exec /qemu-binfmt-conf.sh --qemu-suffix "-static-binfmt-P" --preserve-argv0 yes --qemu-path "${QEMU_BIN_DIR}" $@

Once done, argv[0] will be correct in the foreign container environment. No wrapper C program needed.

Environment:

• QEMU version: (if you can know it): 7.2.0
• Container application: Docker

Output of docker version, podman version or singularity version

Client:
 Version:           20.10.12
 API version:       1.41
 Go version:        go1.17.3
 Git commit:        20.10.12-0ubuntu4
 Built:             Mon Mar  7 17:10:06 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true