From 7b789562244ee941b7bf2cefeb3fc08a59a01865 Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Wed, 21 Jul 2021 14:03:26 -0700 Subject: [sanitizer] Place module_ctor/module_dtor in llvm.used 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)). There is no object file size difference. Reviewed By: vitalybuka Differential Revision: https://reviews.llvm.org/D106246 --- llvm/lib/Transforms/Utils/ModuleUtils.cpp | 2 ++ 1 file changed, 2 insertions(+) (limited to 'llvm/lib/Transforms/Utils/ModuleUtils.cpp') diff --git a/llvm/lib/Transforms/Utils/ModuleUtils.cpp b/llvm/lib/Transforms/Utils/ModuleUtils.cpp index 8c6435b..7c03162 100644 --- a/llvm/lib/Transforms/Utils/ModuleUtils.cpp +++ b/llvm/lib/Transforms/Utils/ModuleUtils.cpp @@ -128,6 +128,8 @@ Function *llvm::createSanitizerCtor(Module &M, StringRef CtorName) { Ctor->addAttribute(AttributeList::FunctionIndex, Attribute::NoUnwind); BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor); ReturnInst::Create(M.getContext(), CtorBB); + // Ensure Ctor cannot be discarded, even if in a comdat. + appendToUsed(M, {Ctor}); return Ctor; } -- cgit v1.1