[IshmamDC217]

What

--trace-imports (#4547) only worked for Windows output. This adds it for Linux output, as the second half of #3815's Linux support, on top of the libc runtime in #7411.

With the flag, LinuxElfPatcher now:

• adds an undefined TraceImport_nid_no_patch symbol and a GLOB_DAT relocation for it, bound eagerly like every other import, so a libc.prx without it fails at load with ld.so's undefined symbol error;
• writes a table of the traced import slots with their NID and library, as offsets so it works for PIE and --linux-fixed-base output alike;
• puts a prologue in front of the existing entry stub. For each entry it calls TraceImport_nid_no_patch(*slot, name, library) and stores the result back in the slot, then falls through to the usual stub. rdx (ld.so's fini pointer) and the stack are preserved.

The same imports are traced as on Windows: functions bound through a PLT slot, or through a GOT slot whose symbol is a function, with no addend, and not weak.

Before storing, the prologue makes each slot's page readable, writable and executable with mprotect. Today the Linux output drops PT_GNU_RELRO, but #6406 keeps it, and real eboots have their JUMP_SLOT targets inside it. Without this, the store would fault once both are merged. I merged #6406 locally with a RELRO range over the slot's page and the traced output still ran correctly. The trade-off (those pages stay writable, and data pages become executable while tracing) is recorded in docs/dev/debt/relinker.md.

Other changes:

• --trace-imports no longer requires --windows. It is refused with --macos, and it still requires libc.prx among the libraries and conflicts with --lazy-binding.
• Usage, TRACING.md and the debt entries now cover Linux.

Tested

Linux x86-64, GCC 13. Relinker-only build: the full suite of 195 tests passes.

• New linux_trace_imports test. It builds a fake a.prx and a fake libc.prx with cc, like linux_executable_exports, and runs the relinked fixture. Its hook replaces a.prx's shared with a function that exits with 77.
  • Untraced: exits with 11.
  • Traced: exits with 77, both PIE and with --linux-fixed-base.
  • Data and weak imports are left alone: exits with 11.
  • A libc.prx without the hook fails at load naming the symbol.
  • The relinker refuses no libc.prx dependency, --lazy-binding and --macos.
  • I checked that the test fails when the expected exit code is wrong.
• windows_trace_imports loses only its "requires --windows" assertion.
• End to end with the real libc.prx from feat(libc): record traced system library calls on Linux #7411: APS5_TRACE_CALLS=a ./out.elf on a fixture whose import calls abort() prints:

[libc] SIGABRT
  last traced system library calls (APS5_TRACE_CALLS):
    #1 thread 8574 a.prx shared from 0x000055903df90006 out.elf+0x6
  most called traced imports (1 calls in total):
               1 a.prx shared

Not tested on a real title, Windows or macOS.

python3 tools/check_conventions.py --base origin/main passes.

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: feat(libc): record traced system library calls on Linux #7411
• Unblocks: none
• GPUs tested: n/a
• AI-assisted: yes

[MarcZX10]

The SIGABRT handler calls fprintf here, then ReportCallTrace() calls dladdr, stdio, and the trace-copy routines. These are not async-signal-safe; if abort() is raised while the thread holds a stdio/loader/trace lock, this handler can deadlock before the prior handler runs or the process terminates. Could the trace be emitted from a non-signal-context abort path (or otherwise use a signal-safe handoff) so the diagnostic cannot turn an abort into a hang?

[IshmamDC217]

Cheers, sorted in #7411 (f670141), and this one's now rebased on it. The handler only uses write(2) now, with no stdio, dladdr or locks. There's a regression test for the held stderr lock case too. Details are over on #7411.

[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 7532	core/relinker/elfpatcher/src/linux/LinuxElfPatcher.cpp L280, L286, L295, L324, L326, L347-348, L398
PR 7918	docs/dev/debt/relinker.md L30-31

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/libc/CMakeLists.txt core/relinker/CMakeLists.txt docs/dev/debt/libc.md docs/dev/debt/relinker.md docs/user/USAGE.md
PR 5431	docs/dev/ENVIRONMENT.md
PR 5925	docs/user/USAGE.md
PR 6044	core/libs/prx/libc/CMakeLists.txt core/libs/tests/GuestCallTrace.cpp core/relinker/CMakeLists.txt
PR 6226	docs/dev/debt/libc.md
PR 6469	docs/dev/debt/libc.md
PR 6618	core/relinker/CMakeLists.txt
PR 6636	docs/dev/ENVIRONMENT.md
PR 6788	docs/user/USAGE.md
PR 6819	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 6879	core/relinker/CMakeLists.txt docs/dev/ENVIRONMENT.md
PR 6924	docs/dev/ENVIRONMENT.md docs/user/USAGE.md
PR 6946	docs/dev/ENVIRONMENT.md docs/user/USAGE.md
PR 6947	docs/dev/ENVIRONMENT.md docs/user/USAGE.md
PR 6977	core/relinker/CMakeLists.txt docs/dev/debt/relinker.md
PR 7081	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 7201	core/libs/prx/libc/CMakeLists.txt
PR 7464	docs/dev/ENVIRONMENT.md
PR 7473	docs/dev/debt/libc.md
PR 7484	docs/dev/ENVIRONMENT.md
PR 7604	docs/dev/ENVIRONMENT.md docs/dev/TRACING.md
PR 7642	docs/dev/ENVIRONMENT.md docs/user/USAGE.md
PR 7648	docs/dev/debt/libc.md
PR 7715	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 7800	docs/user/USAGE.md
PR 7922	docs/dev/ENVIRONMENT.md
PR 8004	docs/dev/ENVIRONMENT.md
PR 8076	docs/dev/debt/relinker.md
PR 8077	docs/dev/ENVIRONMENT.md
PR 8150	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 8206	docs/dev/ENVIRONMENT.md
PR 8352	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 8542	docs/dev/ENVIRONMENT.md