[HWASan] Leave pointer tagged when calling memmove.

[morehouse]

Summary

Fixes a false positive that occurs when a user-implemented memmove is
instrumented by HWASan.

compiler-rt/lib/hwasan/hwasan_memintrinsics.cpp

void *__hwasan_memcpy(void *to, const void *from, uptr size) {
   return memcpy(to, from, size);
 }
 
 void *__hwasan_memmove(void *to, const void *from, uptr size) {
   CheckAddressSized<ErrorAction::Recover, AccessType::Store>(
       reinterpret_cast<uptr>(to), size);
   CheckAddressSized<ErrorAction::Recover, AccessType::Load>(
       reinterpret_cast<uptr>(from), size);
-  return memmove(UntagPtr(to), UntagPtr(from), size);
+  return memmove(to, from, size);
 }

compiler-rt/test/hwasan/TestCases/custom-memmove.c

+// Test that custom memmove implementations instrumented by HWASan do not cause
+// false positives.
+
+// RUN: %clang_hwasan %s -o %t
+// RUN: %run %t
+
+#include <assert.h>
+#include <sanitizer/hwasan_interface.h>
+#include <stdlib.h>
+
+void *memmove(void *Dest, const void *Src, size_t N) {
+  char *Tmp = (char *)malloc(N);
+  char *D = (char *)Dest;
+  const char *S = (const char *)Src;
+
+  for (size_t I = 0; I < N; ++I)
+    Tmp[I] = S[I];
+  for (size_t I = 0; I < N; ++I)
+    D[I] = Tmp[I];
+
+  free(Tmp);
+  return Dest;
+}
+
+int main() {
+  __hwasan_enable_allocator_tagging();
+
+  const size_t BufSize = 64;
+  char *Buf = (char *)malloc(BufSize);
+
+  for (size_t I = 0; I < BufSize; ++I)
+    Buf[I] = I;
+  memmove(Buf + BufSize / 2, Buf, BufSize / 2);
+  for (size_t I = 0; I < BufSize; ++I)
+    assert(Buf[I] == I % (BufSize / 2));
+
+  free(Buf);
+  return 0;
+}