Disable sanitizer's on ifunc resolvers.

[danielkiss]

Summary

Resolvers are running before the module is initialised which leads to
crashes due to the santizer is not yet initialised.

Fixes #40287

[hctim]

Looks good to me, but I'd like @pcc to also confirm.

[danielkiss]

Ping @pcc

[danielkiss]

@pcc Do you mind to land this?
chromium run into this recently: https://bugs.chromium.org/p/chromium/issues/detail?id=1454613

[hctim]

Peter's out of office. This patch looks fine to me, and I'll land it for you.

[danielkiss]

In D150262#4584618, @hctim wrote:

Peter's out of office. This patch looks fine to me, and I'll land it for you.

ok, I can land it too, no worries.

[hctim]

In D150262#4584627, @danielkiss wrote:

ok, I can land it too, no worries.

Sounds good.

[farzon]

This comment was removed by farzon.

clang/lib/CodeGen/CodeGenModule.cpp

if (Entry) {
     // Remove it and replace uses of it with the ifunc.
     GIF->takeName(Entry);
 
     Entry->replaceAllUsesWith(llvm::ConstantExpr::getBitCast(GIF,
                                                           Entry->getType()));
     Entry->eraseFromParent();
   } else
     GIF->setName(MangledName);
-
+  if (auto *F = dyn_cast<llvm::Function>(Resolver)) {
+    F->addFnAttr(llvm::Attribute::DisableSanitizerInstrumentation);
+  }
   SetCommonAttributes(GD, GIF);
 }
 
 llvm::Function *CodeGenModule::getIntrinsic(unsigned IID,
                                             ArrayRef<llvm::Type*> Tys) {
   return llvm::Intrinsic::getDeclaration(&getModule(), (llvm::Intrinsic::ID)IID,
                                          Tys);
 }

clang/test/CodeGen/ifunc.c

 // RUN: %clang_cc1 -triple i386-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple i386-unknown-linux-gnu -O2 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -fsanitize=thread -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -fsanitize=address -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -fsanitize=memory -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
 
 int foo(int) __attribute__ ((ifunc("foo_ifunc")));
 
 static int f1(int i) {
   return i + 1;
 }
 
 static int f2(int i) {

 void* goo_ifunc(void) {
   return 0;
 }
 // CHECK: @foo = ifunc i32 (i32), ptr @foo_ifunc
 // CHECK: @goo = ifunc void (), ptr @goo_ifunc
 
 // CHECK: call i32 @foo(i32
 // CHECK: call void @goo()
+
+// SAN: define internal nonnull ptr @foo_ifunc() #[[#FOO_IFUNC:]] {
+
+// SAN: define dso_local noalias ptr @goo_ifunc() #[[#GOO_IFUNC:]] {
+
+// SAN-DAG: attributes #[[#FOO_IFUNC]] = {{{.*}} disable_sanitizer_instrumentation {{.*}}
+
+// SAN-DAG: attributes #[[#GOO_IFUNC]] = {{{.*}} disable_sanitizer_instrumentation {{.*}}