libc: preserve short program invocation names

[brandonpayton]

Why

libc is the C standard library linked into Kandelo guest programs. It exposes one variable for the full executable name and another for only the final filename. Programs rely on that distinction to decide how they were invoked.

Restore the libc contract for program_invocation_short_name so programs receive the basename of argv[0], while program_invocation_name retains the full value.

Root cause

Kandelo's Wasm-specific __libc_start_main overlay copied argv[0] into both musl globals but omitted musl's basename scan. As a result, an invocation such as /opt/kandelo/bin/pkill exposed the same full path through both names. Procps uses the short name to distinguish pkill from pgrep, so real pkill incorrectly selected pgrep behavior.

What changed

• Restore musl's upstream-equivalent slash scan in the Wasm overlay.
• Extend the exec fixture to pass a path-valued argv[0] and assert both the full and basename forms.
• Make the focused exec tests independent of the default rootfs fixture.

This does not change the host/kernel ABI. Statically linked user programs must be rebuilt to receive the corrected libc startup code.

Validation

• ./scripts/dev-shell.sh bash scripts/build-musl.sh
• ./scripts/dev-shell.sh scripts/build-programs.sh
• ./scripts/dev-shell.sh bash -c 'cargo build --release -p kandelo -Z build-std=core,alloc'
• rm -rf host/dist && ./scripts/dev-shell.sh bash -c 'cd host && npx vitest run test/exec.test.ts' - 2 passed
• ./scripts/dev-shell.sh scripts/run-libc-tests.sh - 303 PASS, 20 expected XFAIL, 0 FAIL, 0 XPASS, 1 FLAKE-PASS
• ./scripts/dev-shell.sh bash scripts/check-abi-version.sh - snapshot, C header, and TypeScript bindings in sync; no ABI change

[brandonpayton]

Independent devil\u0027s-advocate review at exact head 0527559e7bc73c9153ee837c83e5c0d7ff7ebbe6 found no issues. The change restores upstream musl\u0027s basename scan exactly; procps-ng uses program_invocation_short_name to select PKILL mode. The regression exercises a real execve with path-valued argv[0] and validates both full and short exported names. Independent musl rebuild, complete fixture rebuild, focused exec tests (2/2), ABI consistency, and git diff --check passed. No ABI bump is required; statically linked programs must rebuild to receive the libc fix. No merge action taken.

[github-actions]

Phase B-1 matrix build status — pr-914-staging

ABI v18. 68 built, 1 failed, 69 total.

Package	Arch	Status	Sha
libcurl	wasm32	built	fb35c538
libcxx	wasm32	built	a4061a7c
libcxx	wasm64	built	21405639
libpng	wasm32	built	4e98a9f7
libxml2	wasm32	built	dc49eb90
libxml2	wasm64	built	3df44f95
openssl	wasm32	built	d3a39163
openssl	wasm64	built	ae9791a7
sqlite	wasm32	built	6441ae95
sqlite	wasm64	built	c461fe72
zlib	wasm32	built	6b026711
zlib	wasm64	built	71917474
bc	wasm32	built	b6095f08
bzip2	wasm32	built	aa16fbf2
coreutils	wasm32	built	4f5f89ab
curl	wasm32	built	2f798aa5
dash	wasm32	built	2568b6fd
diffutils	wasm32	built	96d34530
dinit	wasm32	built	3c8c98d7
fbdoom	wasm32	built	65e769fa
file	wasm32	built	630f0226
findutils	wasm32	built	5032c58c
gawk	wasm32	built	428a8ffe
git	wasm32	built	0548a0c4
grep	wasm32	built	c1bb0ab0
gzip	wasm32	built	8400ccbe
hello	wasm32	built	6a7c1997
kandelo-sdk	wasm32	built	177cad47
kernel	wasm32	built	a167648b
less	wasm32	built	b48d17fc
lsof	wasm32	built	6c1473c0
m4	wasm32	built	9803a42c
make	wasm32	built	785673ea
mariadb	wasm32	built	267eb040
mariadb	wasm64	built	780c0653
modeset	wasm32	built	9bd96fc6
msmtpd	wasm32	built	f3a03988
nano	wasm32	built	067080e1
ncurses	wasm32	built	849a8bd1
netcat	wasm32	built	11063a6f
nginx	wasm32	built	f2b47d32
php	wasm32	built	ab6df12b
posix-utils-lite	wasm32	built	6792230f
ruby	wasm32	built	78926340
sed	wasm32	built	73026730
spidermonkey	wasm32	built	8d3464fa
tar	wasm32	built	53f5cfb1
tcl	wasm32	built	c6b3a3b9
unzip	wasm32	built	7a7815a1
userspace	wasm32	built	31c26384
vim	wasm32	built	7465e9d7
wget	wasm32	built	7c648b4f
xz	wasm32	built	0c9bfdbb
zip	wasm32	built	0f2a52da
zstd	wasm32	built	02135b20
bash	wasm32	built	2957e5dc
mariadb-test	wasm32	built	62b4869f
mariadb-vfs	wasm32	built	82e97653
mariadb-vfs	wasm64	built	e9d771d2
nethack	wasm32	built	95437edf
node	wasm32	built	631ebb31
spidermonkey-node	wasm32	built	e5d5d551
vim-browser-bundle	wasm32	built	f2165f03
nethack-browser-bundle	wasm32	built	01c16aa7
rootfs	wasm32	built	42a91d75
shell	wasm32	failed	—
lamp	wasm32	built	ef4ad405
node-vfs	wasm32	built	f23a2f5a
wordpress	wasm32	built	38cf4367

_{Auto-generated; replaced on each push. Raw data in the publish-status workflow artifact.}

[brandonpayton]

Absorbed by rebase-merged #967. Main is now 6efb411 with the sealed tree b133bfa018f7e2bc84c4845edf2f945b2f844954, and ABI 41 activation completed successfully in run 29550069085. The absorption audit confirmed this PR\x27s behavior and tests are present in that merged tree, so this source PR is closed and its branch is deleted.