fix(libkernel): return EFAULT from truncate, utimes, mkdir, rmdir, and rename for a null path

[pushkarreddyy]

What

Following @oneandonlydean's review directive in #7114:
Folds #7110 (sceKernelTruncate, sceKernelUtimes), #7113 (sceKernelMkdir, sceKernelRmdir), and #7114 (sceKernelRename) together into this single PR, building cleanly on top of companion PR #7108 (sceKernelStat, sceKernelUnlink).

Like FreeBSD 11 (kern/vfs_syscalls.c), null path pointers reject early with EFAULT (0x8002000e) instead of throwing unhandled exceptions at runtime.

Closes #7110.
Closes #7113.

Tested

• python tools/check_conventions.py --base origin/main passes with 0 findings.
• core/libs/tests/GuestPosixScalarIo.cpp unit tests cover null path rejection for all 5 functions returning 0x8002000e.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed under Silent stubs in their library's technical debt file
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: fix(libkernel): return EFAULT from sceKernelStat and sceKernelUnlink for a null path #7108
• Fixes: none
• Unblocks: none
• GPUs tested: n/a
• AI-assisted: yes

[oneandonlydean]

Thanks @pushkarreddyy, this looks right too: GUEST_EFAULT is already defined, and the throw becomes an error. But #7108, #7110, #7113 and this one all add lines at the same spots in GuestPosixScalarIo.cpp, so every pair of them conflicts. To keep it simple: #7108 merges first, then one PR that folds #7110, #7113 and #7114 together, rebased on main after #7108. You can close the other two once the combined one is up (or reuse one of them). We'll run CI once on that head.

[pushkarreddyy]

Thanks @oneandonlydean! Acknowledged — I have this folded together with #7110 and #7113 on a clean branch rebased on latest main, and will close this once #7108 merges.

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
PR 6484	core/libs/prx/libkernel/File/src/Stdio.cpp L1273-1291

Some comparisons could not be completed because a pull request conflicts with the base branch. Review these shared files manually before concluding that there is no overlap.

Pull request	Shared files not compared
PR 5021	core/libs/prx/libkernel/File/src/Stdio.cpp
PR 6044	core/libs/tests/GuestPosixScalarIo.cpp
PR 6222	core/libs/prx/libkernel/File/src/Stdio.cpp
PR 6287	core/libs/prx/libkernel/File/src/Stdio.cpp

[pushkarreddyy]

Hi @oneandonlydean,

Done! Following your directive:

• Combined and folded fix(libkernel): return EFAULT from sceKernelTruncate and sceKernelUtimes for a null path #7110, fix(libkernel): return EFAULT from sceKernelMkdir and sceKernelRmdir for a null path #7113, and fix(libkernel): return EFAULT from truncate, utimes, mkdir, rmdir, and rename for a null path #7114 together into this PR (fix(libkernel): return EFAULT from truncate, utimes, mkdir, rmdir, and rename for a null path #7114), rebased cleanly on top of companion PR fix(libkernel): return EFAULT from sceKernelStat and sceKernelUnlink for a null path #7108.
• Covers sceKernelTruncate, sceKernelUtimes, sceKernelMkdir, sceKernelRmdir, and sceKernelRename with full unit test coverage in GuestPosixScalarIo.cpp.
• Closed PR fix(libkernel): return EFAULT from sceKernelTruncate and sceKernelUtimes for a null path #7110 and PR fix(libkernel): return EFAULT from sceKernelMkdir and sceKernelRmdir for a null path #7113 to keep the queue clean and conflict-free.

Ready for single CI run whenever convenient!