[cfi][CodeGen] Call SetLLVMFunctionAttributes{,ForDefinition} on __cf… (#78253)

…i_check

This causes __cfi_check, just as __cfi_check_fail, to get the proper
target-specific attributes, in particular uwtable for unwind table
generation. Previously, nounwind attribute could be inferred for
__cfi_check, which caused it to lose its unwind table even with
-funwind-table option.

~~

Huawei RRI, OS Lab

Co-authored-by: Nikolai Kholiavin <[email protected]>

Author: kpdev

clang/docs/ReleaseNotes.rst

@@ -626,6 +626,10 @@ Sanitizers
   manually disable potentially noisy signed integer overflow checks with
   ``-fno-sanitize=signed-integer-overflow``
 
+- ``-fsanitize=cfi -fsanitize-cfi-cross-dso`` (cross-DSO CFI instrumentation)
+  now generates the ``__cfi_check`` function with proper target-specific
+  attributes, for example allowing unwind table generation.
+
 Python Binding Changes
 ----------------------
 

clang/lib/CodeGen/CGExpr.cpp

@@ -3663,12 +3663,29 @@ void CodeGenFunction::EmitCfiSlowPathCheck(
 // symbol in LTO mode.
 void CodeGenFunction::EmitCfiCheckStub() {
   llvm::Module *M = &CGM.getModule();
-  auto &Ctx = M->getContext();
+  ASTContext &C = getContext();
+  QualType QInt64Ty = C.getIntTypeForBitwidth(64, false);
+
+  FunctionArgList FnArgs;
+  ImplicitParamDecl ArgCallsiteTypeId(C, QInt64Ty, ImplicitParamKind::Other);
+  ImplicitParamDecl ArgAddr(C, C.VoidPtrTy, ImplicitParamKind::Other);
+  ImplicitParamDecl ArgCFICheckFailData(C, C.VoidPtrTy,
+                                        ImplicitParamKind::Other);
+  FnArgs.push_back(&ArgCallsiteTypeId);
+  FnArgs.push_back(&ArgAddr);
+  FnArgs.push_back(&ArgCFICheckFailData);
+  const CGFunctionInfo &FI =
+      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, FnArgs);
+
   llvm::Function *F = llvm::Function::Create(
-      llvm::FunctionType::get(VoidTy, {Int64Ty, Int8PtrTy, Int8PtrTy}, false),
+      llvm::FunctionType::get(VoidTy, {Int64Ty, VoidPtrTy, VoidPtrTy}, false),
       llvm::GlobalValue::WeakAnyLinkage, "__cfi_check", M);
+  CGM.SetLLVMFunctionAttributes(GlobalDecl(), FI, F, /*IsThunk=*/false);
+  CGM.SetLLVMFunctionAttributesForDefinition(nullptr, F);
   F->setAlignment(llvm::Align(4096));
   CGM.setDSOLocal(F);
+
+  llvm::LLVMContext &Ctx = M->getContext();
   llvm::BasicBlock *BB = llvm::BasicBlock::Create(Ctx, "entry", F);
   // CrossDSOCFI pass is not executed if there is no executable code.
   SmallVector<llvm::Value*> Args{F->getArg(2), F->getArg(1)};

clang/test/CodeGen/cfi-check-attrs.c

@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -triple arm-unknown-linux -funwind-tables=1 -fsanitize-cfi-cross-dso -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: define weak {{.*}}void @__cfi_check({{.*}} [[ATTR:#[0-9]*]]
+
+// CHECK: attributes [[ATTR]] = {{.*}} uwtable(sync)

clang/test/CodeGen/cfi-check-fail.c

@@ -72,7 +72,7 @@ void caller(void (*f)(void)) {
 // CHECK: [[CONT5]]:
 // CHECK:   ret void
 
-// CHECK: define weak void @__cfi_check(i64 %[[TYPE:.*]], ptr %[[ADDR:.*]], ptr %[[DATA:.*]]) align 4096
+// CHECK: define weak void @__cfi_check(i64 noundef %[[TYPE:.*]], ptr noundef %[[ADDR:.*]], ptr noundef %[[DATA:.*]]){{.*}} align 4096
 // CHECK-NOT: }
 // CHECK: call void @__cfi_check_fail(ptr %[[DATA]], ptr %[[ADDR]])
 // CHECK-NEXT: ret void