[ASan] Add metadata to renamed instructions so ASan doesn't use the i… (#119387)

…ncorrect name

Clang needs variables to be represented with unique names. This means
that if a variable shadows another, its given a different name
internally to ensure it has a unique name. If ASan tries to use this
name when printing an error, it will print the modified unique name,
rather than the variable's source code name

Fixes #47326

Author: gbMattN

clang/lib/CodeGen/CGExpr.cpp

@@ -143,6 +143,9 @@ llvm::AllocaInst *CodeGenFunction::CreateTempAlloca(llvm::Type *Ty,
     Alloca =
         new llvm::AllocaInst(Ty, CGM.getDataLayout().getAllocaAddrSpace(),
                              ArraySize, Name, AllocaInsertPt->getIterator());
+  if (SanOpts.Mask & SanitizerKind::Address) {
+    Alloca->addAnnotationMetadata({"alloca_name_altered", Name.str()});
+  }
   if (Allocas) {
     Allocas->Add(Alloca);
   }

compiler-rt/test/asan/TestCases/shadowed-stack-serialization.cpp

@@ -0,0 +1,12 @@
+// RUN: %clangxx_asan -O0 %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+int main() {
+  int x;
+  {
+    int x;
+    delete &x;
+  }
+}
+
+// CHECK: [32, 36) 'x'

compiler-rt/test/asan/TestCases/use-after-scope-inlined.cpp

@@ -27,5 +27,5 @@ int main(int argc, char *argv[]) {
   // CHECK: Address 0x{{.*}} is located in stack of thread T0 at offset [[OFFSET:[^ ]*]] in frame
   // CHECK:      {{.*}} in main
   // CHECK:   This frame has
-  // CHECK:     {{\[}}[[OFFSET]], {{.*}}) 'x.i' (line [[@LINE-15]])
+  // CHECK:     {{\[}}[[OFFSET]], {{.*}}) 'x' (line [[@LINE-15]])
 }

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -3437,6 +3437,29 @@ static void findStoresToUninstrumentedArgAllocas(
   }
 }
 
+static StringRef getAllocaName(AllocaInst *AI) {
+  // Alloca could have been renamed for uniqueness. Its true name will have been
+  // recorded as an annotation.
+  if (AI->hasMetadata(LLVMContext::MD_annotation)) {
+    MDTuple *AllocaAnnotations =
+        cast<MDTuple>(AI->getMetadata(LLVMContext::MD_annotation));
+    for (auto &Annotation : AllocaAnnotations->operands()) {
+      if (!isa<MDTuple>(Annotation))
+        continue;
+      auto AnnotationTuple = cast<MDTuple>(Annotation);
+      for (int Index = 0; Index < AnnotationTuple->getNumOperands(); Index++) {
+        // All annotations are strings
+        auto MetadataString =
+            cast<MDString>(AnnotationTuple->getOperand(Index));
+        if (MetadataString->getString() == "alloca_name_altered")
+          return cast<MDString>(AnnotationTuple->getOperand(Index + 1))
+              ->getString();
+      }
+    }
+  }
+  return AI->getName();
+}
+
 void FunctionStackPoisoner::processStaticAllocas() {
   if (AllocaVec.empty()) {
     assert(StaticAllocaPoisonCallVec.empty());
@@ -3477,7 +3500,8 @@ void FunctionStackPoisoner::processStaticAllocas() {
   SmallVector<ASanStackVariableDescription, 16> SVD;
   SVD.reserve(AllocaVec.size());
   for (AllocaInst *AI : AllocaVec) {
-    ASanStackVariableDescription D = {AI->getName().data(),
+    StringRef Name = getAllocaName(AI);
+    ASanStackVariableDescription D = {Name.data(),
                                       ASan.getAllocaSizeInBytes(*AI),
                                       0,
                                       AI->getAlign().value(),