[clang] [llvm] Fix KCFI types for generated functions with integer normalization (PR #104826)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-codegen

@llvm/pr-subscribers-clang

Author: Sami Tolvanen (samitolvanen)

<details>
<summary>Changes</summary>

With -fsanitize-cfi-icall-experimental-normalize-integers, Clang appends ".normalized" to KCFI types in CodeGenModule::CreateKCFITypeId, which changes type hashes also for functions that don't have integer types in their signatures. However, llvm::setKCFIType does not take integer normalization into account, which means LLVM generated functions with KCFI types, e.g. sanitizer constructors, will fail KCFI checks when integer normalization is enabled in Clang.

Add a kcfi-normalized module flag to indicate integer normalization is used, and append ".normalized" to KCFI types also in llvm::setKCFIType to fix the type mismatch.

cc @<!-- -->rcvalle 

---
Full diff: https://github.com/llvm/llvm-project/pull/104826.diff


3 Files Affected:

- (modified) clang/lib/CodeGen/CodeGenModule.cpp (+2) 
- (modified) clang/test/CodeGen/kcfi-normalize.c (+1) 
- (modified) llvm/lib/Transforms/Utils/ModuleUtils.cpp (+7-5) 


``````````diff
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 0b61ef0f89989..7eca77dc9a86f 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1136,6 +1136,8 @@ void CodeGenModule::Release() {
 
   if (LangOpts.Sanitize.has(SanitizerKind::KCFI)) {
     getModule().addModuleFlag(llvm::Module::Override, "kcfi", 1);
+    if (CodeGenOpts.SanitizeCfiICallNormalizeIntegers)
+      getModule().addModuleFlag(llvm::Module::Override, "kcfi-normalized", 1);
     // KCFI assumes patchable-function-prefix is the same for all indirectly
     // called functions. Store the expected offset for code generation.
     if (CodeGenOpts.PatchableFunctionEntryOffset)
diff --git a/clang/test/CodeGen/kcfi-normalize.c b/clang/test/CodeGen/kcfi-normalize.c
index 7660c908a7bdd..62b907dbfb928 100644
--- a/clang/test/CodeGen/kcfi-normalize.c
+++ b/clang/test/CodeGen/kcfi-normalize.c
@@ -28,6 +28,7 @@ void baz(void (*fn)(int, int, int), int arg1, int arg2, int arg3) {
     fn(arg1, arg2, arg3);
 }
 
+// CHECK: ![[#]] = !{i32 4, !"kcfi-normalized", i32 1}
 // CHECK: ![[TYPE1]] = !{i32 -1143117868}
 // CHECK: ![[TYPE2]] = !{i32 -460921415}
 // CHECK: ![[TYPE3]] = !{i32 -333839615}
diff --git a/llvm/lib/Transforms/Utils/ModuleUtils.cpp b/llvm/lib/Transforms/Utils/ModuleUtils.cpp
index 309cf8e70b979..de8f00f415c35 100644
--- a/llvm/lib/Transforms/Utils/ModuleUtils.cpp
+++ b/llvm/lib/Transforms/Utils/ModuleUtils.cpp
@@ -205,11 +205,13 @@ void llvm::setKCFIType(Module &M, Function &F, StringRef MangledType) {
   // Matches CodeGenModule::CreateKCFITypeId in Clang.
   LLVMContext &Ctx = M.getContext();
   MDBuilder MDB(Ctx);
-  F.setMetadata(
-      LLVMContext::MD_kcfi_type,
-      MDNode::get(Ctx, MDB.createConstant(ConstantInt::get(
-                           Type::getInt32Ty(Ctx),
-                           static_cast<uint32_t>(xxHash64(MangledType))))));
+  std::string Type = MangledType.str();
+  if (M.getModuleFlag("kcfi-normalized"))
+    Type += ".normalized";
+  F.setMetadata(LLVMContext::MD_kcfi_type,
+                MDNode::get(Ctx, MDB.createConstant(ConstantInt::get(
+                                     Type::getInt32Ty(Ctx),
+                                     static_cast<uint32_t>(xxHash64(Type))))));
   // If the module was compiled with -fpatchable-function-entry, ensure
   // we use the same patchable-function-prefix.
   if (auto *MD = mdconst::extract_or_null<ConstantInt>(

``````````

</details>


https://github.com/llvm/llvm-project/pull/104826