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Add --mount flag for 9p host directory sharing #9

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hulthe merged 3 commits from feature/9p-mount into master 2026-09-11 09:36:00 +02:00
Conversation 3 Commits 3 Files Changed 5
+192 -7
3 Commits
Author SHA1 Message Date
marvin 93cbf7ca47 Support host:guest mount syntax with WORKINGDIR resolution
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--mount now accepts <host-path>:<guest-path> (Docker-style). When the
guest path is omitted, the host path is used. Non-absolute guest paths
are resolved against the image WORKINGDIR, which is written to
/slim/workdir at build time and read by slim-init.sh at boot.

Changes:
- qemu.rs: Parse host:guest spec, pass guest path (not host path) on
  the kernel cmdline as slim.mount=<tag>:<base64(guest_path)>
- inject.rs: Accept working_dir param, write /slim/workdir into rootfs
- build.rs: Pass config.working_dir to inject()
- slim-init.sh: Read /slim/workdir, resolve relative guest paths
  against it before mounting
- test.sh: Test host:guest absolute paths (multi-mount) and relative
  guest path resolved against WORKINGDIR

Addresses PR #9 review comment from @hulthe.
 2026-09-10 12:21:44 +02:00
marvin c3b6a72d39 Fix U3: escape commas in --mount path for QEMU -virtfs 
QEMU QemuOpts splits on commas; escape literal commas in the host
path as ,, per QEMU convention to prevent option injection and
boot failures on paths containing commas.

Fix U5: extract b64dec() helper in slim-init.sh

Deduplicate the 3-line base64 fallback decode block used by both
the slim.mount and slim.cmd handlers into a single b64dec() function.

Fix U6: add multi-mount test case

test_mount now passes two --mount flags and asserts both slim0
and slim1 9p tags appear, covering the multi-mount tag-generation
path.
 2026-09-10 12:21:30 +02:00
marvin 90de50dfed Add --mount flag for 9p host directory sharing 
Add support for sharing host directories into the VM via QEMU 9p
(virtio-9p).  The --mount flag can be repeated; each host directory
appears at the same absolute path inside the VM.

Design:
- QEMU: each --mount gets a short 9p tag (slim0, slim1, …) via
  -virtfs local,path=…,mount_tag=slimN,security_model=mapped-xattr.
  Tags are kept short because 9p mount_tag has a ~31-byte limit.
- Kernel cmdline: the full destination path is passed as
  slim.mount=<tag>:<base64(path)> so the init script knows where to
  mount each tag.  Base64 avoids issues with spaces/special chars.
- slim-init.sh: after networking, parse slim.mount= entries, mkdir -p
  the destination, and mount -t 9p <tag> <dest> -o trans=virtio,version=9p2000.L

Tests verify: 9p share detection via sysfs mount_tag, 9p entry in
mount output, file content accessible at the expected path, and clean
VM exit.
 2026-09-10 12:19:59 +02:00