Author: eugenis Date: Fri Apr 7 18:00:38 2017 New Revision: 299806 URL: http://llvm.org/viewvc/llvm-project?rev=299806&view=rev Log: [cfi] Emit __cfi_check stub in the frontend.
Previously __cfi_check was created in LTO optimization pipeline, which means LLD has no way of knowing about the existence of this symbol without rescanning the LTO output object. As a result, LLD fails to export __cfi_check, even when given --export-dynamic-symbol flag. Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp cfe/trunk/lib/CodeGen/CodeGenFunction.h cfe/trunk/lib/CodeGen/CodeGenModule.cpp cfe/trunk/test/CodeGen/cfi-check-fail.c Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=299806&r1=299805&r2=299806&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CGExpr.cpp (original) +++ cfe/trunk/lib/CodeGen/CGExpr.cpp Fri Apr 7 18:00:38 2017 @@ -2783,6 +2783,24 @@ void CodeGenFunction::EmitCfiSlowPathChe EmitBlock(Cont); } +// Emit a stub for __cfi_check function so that the linker knows about this +// symbol in LTO mode. +void CodeGenFunction::EmitCfiCheckStub() { + llvm::Module *M = &CGM.getModule(); + auto &Ctx = M->getContext(); + llvm::Function *F = llvm::Function::Create( + llvm::FunctionType::get(VoidTy, {Int64Ty, Int8PtrTy, Int8PtrTy}, false), + llvm::GlobalValue::WeakAnyLinkage, "__cfi_check", M); + llvm::BasicBlock *BB = llvm::BasicBlock::Create(Ctx, "entry", F); + // FIXME: consider emitting an intrinsic call like + // call void @llvm.cfi_check(i64 %0, i8* %1, i8* %2) + // which can be lowered in CrossDSOCFI pass to the actual contents of + // __cfi_check. This would allow inlining of __cfi_check calls. + llvm::CallInst::Create( + llvm::Intrinsic::getDeclaration(M, llvm::Intrinsic::trap), "", BB); + llvm::ReturnInst::Create(Ctx, nullptr, BB); +} + // This function is basically a switch over the CFI failure kind, which is // extracted from CFICheckFailData (1st function argument). Each case is either // llvm.trap or a call to one of the two runtime handlers, based on Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=299806&r1=299805&r2=299806&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original) +++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Fri Apr 7 18:00:38 2017 @@ -3524,6 +3524,9 @@ public: /// "trap-func-name" if specified. llvm::CallInst *EmitTrapCall(llvm::Intrinsic::ID IntrID); + /// \brief Emit a stub for the cross-DSO CFI check function. + void EmitCfiCheckStub(); + /// \brief Emit a cross-DSO CFI failure handling function. void EmitCfiCheckFail(); Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=299806&r1=299805&r2=299806&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original) +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Fri Apr 7 18:00:38 2017 @@ -406,8 +406,10 @@ void CodeGenModule::Release() { EmitDeferredUnusedCoverageMappings(); if (CoverageMapping) CoverageMapping->emit(); - if (CodeGenOpts.SanitizeCfiCrossDso) + if (CodeGenOpts.SanitizeCfiCrossDso) { CodeGenFunction(*this).EmitCfiCheckFail(); + CodeGenFunction(*this).EmitCfiCheckStub(); + } emitAtAvailableLinkGuard(); emitLLVMUsed(); if (SanStats) Modified: cfe/trunk/test/CodeGen/cfi-check-fail.c URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/cfi-check-fail.c?rev=299806&r1=299805&r2=299806&view=diff ============================================================================== --- cfe/trunk/test/CodeGen/cfi-check-fail.c (original) +++ cfe/trunk/test/CodeGen/cfi-check-fail.c Fri Apr 7 18:00:38 2017 @@ -72,3 +72,8 @@ void caller(void (*f)()) { // CHECK: [[CONT5]]: // CHECK: ret void + +// CHECK: define weak void @__cfi_check(i64, i8*, i8*) +// CHECK-NOT: } +// CHECK: call void @llvm.trap() +// CHECK-NEXT: ret void _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits