[clang][Codegen] Introduce the disable_sanitizer_instrumentation attribute

The purpose of __attribute__((disable_sanitizer_instrumentation)) is to
prevent all kinds of sanitizer instrumentation applied to a certain
function, Objective-C method, or global variable.

The no_sanitize(...) attribute drops instrumentation checks, but may
still insert code preventing false positive reports. In some cases
though (e.g. when building Linux kernel with -fsanitize=kernel-memory
or -fsanitize=thread) the users may want to avoid any kind of
instrumentation.

Differential Revision: https://reviews.llvm.org/D108029

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index dca4204..e3a6631 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -381,6 +381,9 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
                        "__cyg_profile_func_exit");
   }
 
+  if (ShouldSkipSanitizerInstrumentation())
+    CurFn->addFnAttr(llvm::Attribute::DisableSanitizerInstrumentation);
+
   // Emit debug descriptor for function end.
   if (CGDebugInfo *DI = getDebugInfo())
     DI->EmitFunctionEnd(Builder, CurFn);
@@ -519,6 +522,12 @@ bool CodeGenFunction::ShouldInstrumentFunction() {
   return true;
 }
 
+bool CodeGenFunction::ShouldSkipSanitizerInstrumentation() {
+  if (!CurFuncDecl)
+    return false;
+  return CurFuncDecl->hasAttr<DisableSanitizerInstrumentationAttr>();
+}
+
 /// ShouldXRayInstrument - Return true if the current function should be
 /// instrumented with XRay nop sleds.
 bool CodeGenFunction::ShouldXRayInstrumentFunction() const {