[llvm][StackProtector] Add noreturn to __stack_chk_fail call (#143976)

It's possible for __stack_chk_fail to be an alias when using CrossDSOCFI
since it will make a jump table entry for this function and replace it
with an alias. StackProtector can crash since it always expects this to
be a regular function. Instead add the noreturn attribute to the call.

Author: PiJoules

llvm/lib/CodeGen/StackProtector.cpp

@@ -725,8 +725,8 @@ BasicBlock *CreateFailBB(Function *F, const Triple &Trip) {
     StackChkFail =
         M->getOrInsertFunction("__stack_chk_fail", Type::getVoidTy(Context));
   }
-  cast<Function>(StackChkFail.getCallee())->addFnAttr(Attribute::NoReturn);
-  B.CreateCall(StackChkFail, Args);
+  CallInst *Call = B.CreateCall(StackChkFail, Args);
+  Call->addFnAttr(Attribute::NoReturn);
   B.CreateUnreachable();
   return FailBB;
 }

llvm/test/Transforms/StackProtector/cross-dso-cfi-stack-chk-fail.ll

@@ -0,0 +1,33 @@
+;; This is a minimal reproducer that caused StackProtector to crash with a bad cast when
+;; CrossDSOCFI is used. This test just needs to not crash.
+; RUN: opt -mtriple=x86_64-pc-linux-gnu %s -passes=lowertypetests,cross-dso-cfi,stack-protector
+
+define hidden void @__stack_chk_fail() !type !1{
+  unreachable
+}
+
+define void @store_captures() sspstrong {
+entry:
+  %a = alloca i32, align 4
+  %j = alloca ptr, align 8
+  store ptr %a, ptr %j, align 8
+  ret void
+}
+
+define void @func(ptr %0) {
+entry:
+  %1 = call i1 @llvm.type.test(ptr %0, metadata !"typeid")
+  br i1 %1, label %cont, label %trap
+
+trap:                                             ; preds = %entry
+  call void @llvm.trap()
+  unreachable
+
+cont:                                             ; preds = %entry
+  call void %0()
+  ret void
+}
+
+!llvm.module.flags = !{!0}
+!0 = !{i32 4, !"Cross-DSO CFI", i32 1}
+!1 = !{i64 0, !"typeid"}

llvm/test/Transforms/StackProtector/stack-chk-fail-alias.ll

@@ -0,0 +1,21 @@
+;; __stack_chk_fail should have the noreturn attr even if it is an alias
+; RUN: opt -mtriple=x86_64-pc-linux-gnu %s -passes=stack-protector -S | FileCheck %s
+
+define hidden void @__stack_chk_fail_impl() {
+  unreachable
+}
+
+@__stack_chk_fail = hidden alias void (), ptr @__stack_chk_fail_impl
+
+; CHECK-LABEL: @store_captures(
+; CHECK:       CallStackCheckFailBlk:
+; CHECK-NEXT:      call void @__stack_chk_fail() [[ATTRS:#.*]]
+define void @store_captures() sspstrong {
+entry:
+  %a = alloca i32, align 4
+  %j = alloca ptr, align 8
+  store ptr %a, ptr %j, align 8
+  ret void
+}
+
+; CHECK: attributes [[ATTRS]] = { noreturn }