Allow the no_stack_protector attribute on local variables

clang/include/clang/Basic/Attr.td

@@ -2726,7 +2726,7 @@ def : MutualExclusions<[AlwaysInline, NotTailCalled]>;
 def NoStackProtector : InheritableAttr {
   let Spellings = [Clang<"no_stack_protector">, CXX11<"gnu", "no_stack_protector">,
                    C23<"gnu", "no_stack_protector">, Declspec<"safebuffers">];
-  let Subjects = SubjectList<[Function]>;
+  let Subjects = SubjectList<[Function, LocalVar]>;
   let Documentation = [NoStackProtectorDocs];
   let SimpleHandler = 1;
 }

clang/lib/CodeGen/CGDecl.cpp

@@ -1604,6 +1604,14 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
                                  allocaAlignment, D.getName(),
                                  /*ArraySize=*/nullptr, &AllocaAddr);
 
+      if (D.hasAttr<NoStackProtectorAttr>()) {
+        if (auto *AI = dyn_cast<llvm::AllocaInst>(address.getBasePointer())) {
+          llvm::LLVMContext &Ctx = Builder.getContext();
+          auto *Operand = llvm::ConstantAsMetadata::get(Builder.getInt32(0));
+          AI->setMetadata("stack-protector", llvm::MDNode::get(Ctx, {Operand}));
+        }
+      }
+
       // Don't emit lifetime markers for MSVC catch parameters. The lifetime of
       // the catch parameter starts in the catchpad instruction, and we can't
       // insert code in those basic blocks.

clang/test/CodeGen/stack-protector-vars.c

@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+
+typedef __SIZE_TYPE__ size_t;
+
+int printf(const char * _Format, ...);
+char *strcpy(char *s1, const char *s2);
+
+// CHECK: define {{.*}}void @test1
+// CHECK: %a = alloca [1000 x i8], align 1, !stack-protector ![[A:.*]]
+void test1(const char *msg) {
+  __attribute__((no_stack_protector))
+  char a[1000];
+  strcpy(a, msg);
+  printf("%s\n", a);
+}
+
+// CHECK: define {{.*}}void @test2
+// CHECK-NOT: %b = alloca [1000 x i8], align 1, !stack-protector
+void test2(const char *msg) {
+  char b[1000];
+  strcpy(b, msg);
+  printf("%s\n", b);
+}
+
+// CHECK: ![[A]] = !{i32 0}

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -138,7 +138,7 @@
 // CHECK-NEXT: NoSanitizeThread (SubjectMatchRule_function)
 // CHECK-NEXT: NoSpeculativeLoadHardening (SubjectMatchRule_function, SubjectMatchRule_objc_method)
 // CHECK-NEXT: NoSplitStack (SubjectMatchRule_function)
-// CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
+// CHECK-NEXT: NoStackProtector (SubjectMatchRule_function, SubjectMatchRule_variable_is_local)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)

clang/test/Sema/no_stack_protector.c

@@ -4,5 +4,10 @@
 [[clang::no_stack_protector]] void test2(void) {}
 
 void __attribute__((no_stack_protector)) foo(void) {}
-int __attribute__((no_stack_protector)) var; // expected-warning {{'no_stack_protector' attribute only applies to functions}}
+int __attribute__((no_stack_protector)) var; // expected-warning {{'no_stack_protector' attribute only applies to functions and local variables}}
 void  __attribute__((no_stack_protector(2))) bar(void) {} // expected-error {{'no_stack_protector' attribute takes no arguments}}
+
+void func()
+{
+	int __attribute__((no_stack_protector)) localvar;
+}