[dfsan] Introduce dfsan_read_label runtime function.

Differential Revision: http://llvm-reviews.chandlerc.com/D1349

llvm-svn: 188319

1 files changed, 8 insertions, 1 deletions

diff --git a/compiler-rt/lib/dfsan/dfsan.cc b/compiler-rt/lib/dfsan/dfsan.cc
index c8b0e6851ec..ba8e8b5112e 100644
--- a/compiler-rt/lib/dfsan/dfsan.cc
+++ b/compiler-rt/lib/dfsan/dfsan.cc
@@ -120,7 +120,7 @@ dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
 }
 
 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
-dfsan_label __dfsan_union_load(dfsan_label *ls, size_t n) {
+dfsan_label __dfsan_union_load(const dfsan_label *ls, size_t n) {
   dfsan_label label = ls[0];
   for (size_t i = 1; i != n; ++i) {
     dfsan_label next_label = ls[i];
@@ -171,6 +171,13 @@ SANITIZER_INTERFACE_ATTRIBUTE dfsan_label dfsan_get_label(long data) {
   return __dfsan_arg_tls[0];
 }
 
+SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
+dfsan_read_label(const void *addr, size_t size) {
+  if (size == 0)
+    return 0;
+  return __dfsan_union_load(shadow_for(addr), size);
+}
+
 SANITIZER_INTERFACE_ATTRIBUTE
 const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
   __dfsan_retval_tls = 0;  // Ensures return value is unlabelled in the caller.