[babyhuey]

What

Implements readlink (pd02UI9TbOA) in libkernel_sys. Part of #1578: PPSA99001 (ProsperoRadio) imports it from libkernel_sys, which only had the placeholder export. On Windows an import is looked up in its own module and then libc, so it has to live in libkernel_sys.

• Follows FreeBSD kern_readlinkat/kern_readlink_vp: a path that is not a symbolic link fails with EINVAL, a zero bufsiz returns 0, a longer target is truncated to bufsiz without a terminator, and bufsiz above SSIZE_MAX fails with EINVAL. A null path fails with EFAULT, an empty one with ENOENT.
• The path goes through ResolvePath_nid_no_patch. The target is read with std::filesystem::read_symlink and returned with / separators, then copied into the guest buffer, so no host call writes guest memory directly.
• Host errors map to guest errno values up to 34 and EIO otherwise, as SceErrorFromErrno does in libkernel.

Tested

Linux (Ubuntu 24.04, GCC 13, Release): new guest_kernel_sys passes with --repeat until-fail:3. It covers a file, a directory, a missing path, empty and null paths, and a link: full target, truncation, zero size, null buffer, and a case-insensitive guest path. Where symbolic links can't be created (Windows without the privilege) it prints that the link cases were not tested. The test fails when truncation is removed. check_test_registration.py and check_conventions.py pass. Windows: Export.cpp compiles with MinGW-w64 GCC 13 (-Wall -Wextra -fsyntax-only); not run on Windows. No title run.

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 in TechnicalDebt
• 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: none
• AI-assisted: yes

[klosixgaming-arch]

LGTM. Thorough implementation of readlink following FreeBSD semantics with proper argument validation, path resolution, symlink status checking, and error mapping via GuestError. The test coverage is excellent - testing non-symlink paths, missing/empty/null paths, full reading, truncation, zero-size buffer, null buffer cases, and case-insensitive path handling on Windows. Good graceful degradation when symlinks aren't available (Windows without privilege). Clean addition to libkernel_sys for ProsperoRadio's import requirements.

[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
#1641		__error_nid_postfix
#1675		__error_nid_postfix
#1686	core/libs/CMakeLists.txt L133
#1727		__error_nid_postfix
#1729		__error_nid_postfix
#1738		__error_nid_postfix
#1772		__error_nid_postfix
#1795	core/libs/CMakeLists.txt L133
#1828	core/libs/CMakeLists.txt L133
#1841		__error_nid_postfix
#1860		__error_nid_postfix

[babyhuey]

Fork CI while the upstream run waits for approval: Build run, all jobs green on a2de24b (Linux 467/467, Windows 458/458, relinker on Linux, macOS and Windows). It builds the branch head, not the merge with main.

[github-actions]

Progress report (54f28f2 → d024717)

📈 System libraries: 85.31% (+0.01%, +1 implemented functions)

✅ 1 implemented

Library	Name
libkernel_sys	readlink_nid_postfix

[babyhuey]

A title that stops on readlink on current main. Linux, Ubuntu 24.04 container, GCC 13, Release, main d64134f (relinker and libs); titles from the homebrew catalog, relinked for Linux and run from the title folder.

Title	main	with this branch
PPSA99010 vkQuake 1.0	app.elf: symbol lookup error: app.elf: undefined symbol: pd02UI9TbOA (readlink)	next stop QuJYZ2KVGGQ (shm_open)

The "with this branch" build also had my other open PRs merged; only this branch exports pd02UI9TbOA.

[babyhuey]

Same title on Windows. Windows 11, RTX 3080, WinLibs GCC 15.2.0 r7, Release, main f145139 (relinker and libs); titles relinked with --windows.

Title	main	with this branch
PPSA99010 vkQuake 1.0	FAIL: unresolved ELF import pd02UI9TbOA from libkernel_sys.prx (readlink)	FAIL: unresolved ELF import QuJYZ2KVGGQ from libkernel.prx (shm_open)

As on Linux, the second build also had my other open PRs merged; only this branch exports pd02UI9TbOA.

[adriadam10]

Checked on Linux (merged onto current main): build and ctest green (524/524, guest_kernel_sys included); the test no longer links without the readlink export. Error codes and truncation match FreeBSD kern_readlinkat, and the vkQuake runs on Linux and Windows back it up. Merging.