[PATCH] D138945: [ModuleUtils][KCFI] Set !kcfi_type metadata for sanitizer constructors

[Sami Tolvanen via Phabricator via llvm-commits]

samitolvanen updated this revision to Diff 479719.
samitolvanen added a comment.

Added a test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D138945/new/

https://reviews.llvm.org/D138945

Files:
  llvm/lib/Transforms/Utils/ModuleUtils.cpp
  llvm/test/Instrumentation/AddressSanitizer/kcfi.ll


Index: llvm/test/Instrumentation/AddressSanitizer/kcfi.ll
===================================================================
--- /dev/null
+++ llvm/test/Instrumentation/AddressSanitizer/kcfi.ll
@@ -0,0 +1,12 @@
+; Test that we emit kcfi_type metadata for asan.module_ctor with KCFI.
+
+; RUN: opt < %s -passes=asan -S | FileCheck %s
+
+; CHECK: @llvm.global_ctors = {{.*}}{ i32 1, ptr @asan.module_ctor, ptr @asan.module_ctor }
+
+; CHECK: define internal void @asan.module_ctor()
+; CHECK-SAME: !kcfi_type
+
+  !llvm.module.flags = !{!0}
+  !0 = !{i32 4, !"kcfi", i32 1}
+
Index: llvm/lib/Transforms/Utils/ModuleUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/ModuleUtils.cpp
+++ llvm/lib/Transforms/Utils/ModuleUtils.cpp
@@ -15,8 +15,10 @@
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/xxhash.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "moduleutils"
@@ -112,6 +114,19 @@
   appendToUsedList(M, "llvm.compiler.used", Values);
 }
 
+static void setKCFIType(Module &M, Function &F, StringRef MangledType) {
+  if (!M.getModuleFlag("kcfi"))
+    return;
+
+  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))))));
+}
+
 FunctionCallee
 llvm::declareSanitizerInitFunction(Module &M, StringRef InitName,
                                    ArrayRef<Type *> InitArgTypes) {
@@ -128,6 +143,7 @@
       GlobalValue::InternalLinkage, M.getDataLayout().getProgramAddressSpace(),
       CtorName, &M);
   Ctor->addFnAttr(Attribute::NoUnwind);
+  setKCFIType(M, *Ctor, "_ZTSFvvE"); // void (*)(void)
   BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
   ReturnInst::Create(M.getContext(), CtorBB);
   // Ensure Ctor cannot be discarded, even if in a comdat.


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