feat(libkernel): load system libraries from their console paths - #6519

What

PS4 programs load system libraries with sceKernelLoadStartModule and their console path. The OpenOrbis piglet sample loads /<sandbox word>/common/lib/libScePigletv2VSH.sprx and libScePrecompiledShaders.sprx, the sandboxed form of /system/common/lib/ that sceKernelGetFsSandboxRandomWord names. AnyPS5 opened that path as a guest file, so the load failed with ENOENT and the sample stopped with:

Module prefix = /gkbHtXc3Wq/common/lib/
Failed to load the Piglet module, err=0x80020002
Module load failed.

A path in /system/common/lib/ or in the sandboxed /<word>/common/lib/ whose file name ends in .sprx now loads the host libs/<name>.prx, as libSceSysmodule does for module IDs. A name with a directory part is not mapped, so such a path cannot leave libs/. Any other path is opened as before. The new line in docs/dev/debt/libkernel.md records that a host library has no module_start, so res is 0, and that other system directories, such as /system/priv/lib, are not mapped. Part of the PS4 homebrew work tracked in #3093.

Overlap with open pull requests that change Module.cpp or docs/dev/debt/libkernel.md, checked with git merge-file against main 03c4cb5e7:

• fix(libkernel): pass module arguments to loaded modules #4972 adds #include <mutex> on the line where this adds #include <optional>; whichever merges second keeps both includes.
• feat(libkernel): read param.sfo when param.json is absent #5993 (mine) also appends an entry at the end of docs/dev/debt/libkernel.md; whichever merges second keeps both entries.
• fix(libkernel): provide default arguments block for DT_INIT on Linux #6149 merges cleanly with this.

Tested

Windows 11 Pro 26200, WinLibs GCC 15.2.0 r7, Release, BUILD_TESTING=ON, on main 03c4cb5e7:

• guest_dynamic_loader now copies its fixture module into libs/ and loads it through /system/common/lib/<name>.sprx and /gkbHtXc3Wq/common/lib/<name>.sprx (gkbHtXc3Wq is AnyPS5's sandbox word). It calls the module's export and unloads it each time. A missing name and a .prx name return 0x80020002, and so does /gkbHtXc3Wq/common/lib/../<name>.sprx, even though the file exists one directory up.
• Each of these makes the test fail: the mapped path not passed to the loader, the sandboxed prefix not mapped, the /system/common/lib/ prefix not mapped, a name with a directory part mapped.
• The OpenOrbis piglet sample on main 03c4cb5e7 with this, feat(libScePrecompiledShaders): export the texmap shaders the piglet sample uses #6520, feat(libScePigletv2VSH): implement the EGL and GLES 2 calls of the piglet sample #6521, fix(relinker): search libc.prx for libkernel-only Windows executables #5990 to fix(relinker): stop module syscall scans at the PLT and skip the PS4 loader path #5994, feat(libSceFreeType): implement the six FreeType functions OpenOrbis samples use #6376, fix(relinker): accept section-relative guest module relocations #5138 and a change that answers the Linux TIOCGWINSZ with ENOTTY, as fix(libkernel): return ENOTTY for malformed ioctl requests #5569 did: it prints Module prefix = /gkbHtXc3Wq/common/lib/ and Modules loaded OK., and draws its rotating textured square at 59.96 FPS. With Module.cpp from main instead, it stops with the lines above.
• Full ctest of that build: 1304 of 1306 pass; agc_driver_gpu_indirect_arguments_misaligned_writer_ahead does not compile with MinGW on main (test(agc): align the indirect arguments block at run time #6452 fixes it), and prx_thread_local_destructors fails as it did on main 92cdc7b62 on this machine without my changes.
• tools/check_conventions.py passes.

Not tested on Linux or macOS.

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: none for the code; the piglet sample also needs feat(libScePrecompiledShaders): export the texmap shaders the piglet sample uses #6520 and feat(libScePigletv2VSH): implement the EGL and GLES 2 calls of the piglet sample #6521
• Unblocks: OpenOrbis PS4 toolchain sample piglet, Relinker rejects PS4 executables: SCE dynamic tables and data in the code segment (two ready branches) + remaining PS4 work #3093
• GPUs tested: n/a
• AI-assisted: yes (Claude Code)

🤖 Generated with Claude Code