[PATCH] D106246: [sanitizer] Place module_ctor/module_dtor in llvm.used

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: eugenis, tejohnson, vitalybuka.
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This removes an abuse of ELF linker behaviors while keeping Mach-O/COFF linker
behaviors unchanged.

ELF: when module_ctor is in a comdat, this patch removes reliance on a linker
abuse (an SHT_INIT_ARRAY in a section group retains the whole group) by using
SHF_GNU_RETAIN. No linker behavior difference when module_ctor is not in a comdat.

Mach-O: module_ctor gets `N_NO_DEAD_STRIP`. No linker behavior difference
because module_ctor is already referenced by a `S_MOD_INIT_FUNC_POINTERS`
section (GC root).

PE/COFF: no-op. SanitizerCoverage already appends module_ctor to `llvm.used`.
Other sanitizers: llvm.used for local linkage is not implemented in
`TargetLoweringObjectFileCOFF::emitLinkerDirectives` (once implemented or
switched to a non-local linkage, COFF can use module_ctor in comdat (i.e.
generalize ELF-specific rL301586 <https://reviews.llvm.org/rL301586>)).

There is no object file size difference.

---

I think module_ctor should have `linkonce_odr hidden` linkage/visibility.
This will

- make COFF deduplication work
- drop the reliance on the comdat lowering behavior on ELF (internal module_ctor should not be deduplicated, so rGc4b4253f7c63de8452eabf0105d87a17ff47748f <https://reviews.llvm.org/rGc4b4253f7c63de8452eabf0105d87a17ff47748f> doesn't actually conform to LangRef).

I'll investigate it in another patch.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106246

Files:
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
  llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
  llvm/lib/Transforms/Utils/ModuleUtils.cpp
  llvm/test/Instrumentation/AddressSanitizer/basic.ll
  llvm/test/Instrumentation/AddressSanitizer/instrument_global.ll
  llvm/test/Instrumentation/HWAddressSanitizer/basic.ll
  llvm/test/Instrumentation/HeapProfiler/basic.ll
  llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
  llvm/test/Instrumentation/SanitizerCoverage/inline-bool-flag.ll
  llvm/test/Instrumentation/SanitizerCoverage/trace-pc-guard.ll
  llvm/test/Instrumentation/ThreadSanitizer/tsan_basic.ll

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