chroot: use execvp directly instead of process::Command

[mattsu2020]

• Replace process::Command execution with direct execvp call via libc for improved performance by avoiding process forking
• Add validation to detect and error on commands containing null bytes
• Capture and handle execution errors using the last OS error after execvp failure

fix this issue
#9010

[Arcterus]

Rather than using execvp() directly, it'd probably be better to rely on the Command::exec() function provided by CommandExt.

CommandExt actually provides a number of things we do here manually with libc, so we might be able to move e.g. the actual chroot() and uid/gid changes and so on to the stdlib.

[codspeed-hq]

CodSpeed Performance Report

Merging #9013 will not alter performance

_{Comparing mattsu2020:fix_chroot (55a3100) with main (cc103ec)}

Summary

✅ 127 untouched
⏩ 6 skipped¹

Footnotes

1. 6 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[mattsu2020]

Rather than using execvp() directly, it'd probably be better to rely on the Command::exec() function provided by CommandExt.

CommandExt actually provides a number of things we do here manually with libc, so we might be able to move e.g. the actual chroot() and uid/gid changes and so on to the stdlib.

I made some revisions based on your feedback.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[fulalas]

I confirm this change fixes #9010

Nice job! :)

[sylvestre]

would it be possible to add a test? thanks

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[mattsu2020]

would it be possible to add a test? thanks

Done

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[Ecordonnier]

@mattsu2020 I suggest replacing the word "refactor" with "chroot" in the title of this PR.

[Ecordonnier]

I think it's better to not mix cosmetic changes (ProcessCommand instead of process::Command) with functional fixes.

[mattsu2020]

I restored it to its original state.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/cksum/b2sum is no longer failing!

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.