[ubsan] PR33081: Skip the standard type checks for volatile

[vsk]

Summary

Skip checks for null dereference, alignment violation, object size
violation, and dynamic type violation if the pointer points to volatile
data.

https://bugs.llvm.org/show_bug.cgi?id=33081

[rnk]

Looks good, and I did ask Richard about this in person before filing the bug and he was in favor of it, so feel free to commit. If I'd known how easy it was to implement and how few tests it would break, I would've made the patch instead of filing it. :) Thanks for getting around to it.

test/CodeGen/ubsan-volatile.c

9 ↗

(On Diff #102758)

IMO the CHECKs would be cleaner if this were a parameter. You can do CHECK-NOT: call{{.*}}ubsan or something.

[vsk]

Thanks for the review. I'll make the suggested test changes and commit.

cfe/trunk/lib/CodeGen/CGExpr.cpp

if (!sanitizePerformTypeCheck())
     return;
 
   // Don't check pointers outside the default address space. The null check
   // isn't correct, the object-size check isn't supported by LLVM, and we can't
   // communicate the addresses to the runtime handler for the vptr check.
   if (Ptr->getType()->getPointerAddressSpace())
     return;
 
+  // Don't check pointers to volatile data. The behavior here is implementation-
+  // defined.
+  if (Ty.isVolatileQualified())
+    return;
+
   SanitizerScope SanScope(this);
 
   SmallVector<std::pair<llvm::Value *, SanitizerMask>, 3> Checks;
   llvm::BasicBlock *Done = nullptr;
 
   // Quickly determine whether we have a pointer to an alloca. It's possible
   // to skip null checks, and some alignment checks, for these pointers. This
   // can reduce compile-time significantly.

cfe/trunk/test/CodeGen/ubsan-volatile.c

+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsanitize=null,alignment,object-size,vptr -S -emit-llvm %s -o - | FileCheck %s
+
+// CHECK: @volatile_null_deref
+void volatile_null_deref(volatile int *p) {
+  // CHECK-NOT: call{{.*}}ubsan
+  *p;
+}