[HWASAN] Modify HwasanAllocate to set the size to 1 if requested size is 0

[kstoimenov]

Summary

This should keep it consistent with LSAN and ASAN,

[MaskRay]

An alternative is to do if (orig_size == 0) orig_size = 1 in HwasanAllocate. asan/lsan do this.

[kstoimenov]

Make size 1 if 0.

[kstoimenov]

Revert chang in Metadata::IsAllocated.

[MaskRay]

I know that hwasan x86-64 needs involved setup. Wish that is documented somewhere (e.g. https://github.com/google/sanitizers/wiki) so that interested folks (like I) can play with it :)

[kstoimenov]

Reverted test.

[kstoimenov]

In D143438#4108290, @MaskRay wrote:

An alternative is to do if (orig_size == 0) orig_size = 1 in HwasanAllocate. asan/lsan do this.

Good point. I changed that to make it consistent with ASAN and LSAN.

[vitalybuka]

compiler-rt/lib/hwasan/hwasan_allocator.cpp

166 ↗

(On Diff #495303)

168 ↗

(On Diff #495303)

same

[kstoimenov]

Updated title and added UNLIKELY.

[kstoimenov]

Need to fix 2 tests that this patch broke.

compiler-rt/test/hwasan/TestCases/malloc-test.c

 // Test basic malloc functionality.
 // RUN: %clang_hwasan %s -o %t
 // RUN: %run %t
 
 #include <stdlib.h>
 #include <assert.h>
 #include <sanitizer/hwasan_interface.h>
 #include <sanitizer/allocator_interface.h>
 
 int main() {
   __hwasan_enable_allocator_tagging();
   char *a1 = (char*)malloc(0);
   assert(a1 != 0);
-  assert(__sanitizer_get_allocated_size(a1) == 0);
+  assert(__sanitizer_get_allocated_size(a1) == 1);
   free(a1);
 }

compiler-rt/test/hwasan/TestCases/new-test.cpp

 #include <sanitizer/hwasan_interface.h>
 
 int main() {
   __hwasan_enable_allocator_tagging();
 
   size_t volatile n = 0;
   char *a1 = new char[n];
   assert(a1 != nullptr);
-  assert(__sanitizer_get_allocated_size(a1) == 0);
+  assert(__sanitizer_get_allocated_size(a1) == 1);
   delete[] a1;
 
 #if defined(__cpp_aligned_new) &&                                              \
     (!defined(__GLIBCXX__) ||                                                  \
      (defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE >= 7))
   // Aligned new/delete
   constexpr auto kAlign = std::align_val_t{8};
   void *a2 = ::operator new(4, kAlign);
   assert(a2 != nullptr);
   assert(reinterpret_cast<uintptr_t>(a2) % static_cast<uintptr_t>(kAlign) == 0);
   assert(__sanitizer_get_allocated_size(a2) >= 4);
   ::operator delete(a2, kAlign);
 #endif
 }