---

yaml
---
r: 14337
b: refs/heads/try
c: 853e200
h: refs/heads/master
i:
  14335: 4cc2ad4
v: v3

Author: brson

[refs]

@@ -2,5 +2,5 @@
 refs/heads/master: 61b1875c16de39c166b0f4d54bba19f9c6777d1a
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 4a81779abd786ff22d71434c6d9a5917ea4cdfff
-refs/heads/try: 2796ab6de9eefb3d009a410e45f5c154469c94b7
+refs/heads/try: 853e2003b8383749596e5b7b153186e2eef32455
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105

branches/try/src/rt/rust_stack.cpp

@@ -3,6 +3,12 @@
 #include "vg/valgrind.h"
 #include "vg/memcheck.h"
 
+#ifdef _LP64
+const uintptr_t canary_value = 0xABCDABCDABCDABCD;
+#else
+const uintptr_t canary_value = 0xABCDABCD;
+#endif
+
 void
 register_valgrind_stack(stk_seg *stk) {
     stk->valgrind_id =
@@ -17,8 +23,7 @@ prepare_valgrind_stack(stk_seg *stk) {
     // old stack segments, since the act of popping the stack previously
     // caused valgrind to consider the whole thing inaccessible.
     size_t sz = stk->end - (uintptr_t)&stk->data[0];
-    VALGRIND_MAKE_MEM_UNDEFINED(stk->data + sizeof(stack_canary),
-                                sz - sizeof(stack_canary));
+    VALGRIND_MAKE_MEM_UNDEFINED(stk->data, sz);
 #endif
 }
 
@@ -29,12 +34,10 @@ deregister_valgrind_stack(stk_seg *stk) {
 
 void
 add_stack_canary(stk_seg *stk) {
-    memcpy(stk->data, stack_canary, sizeof(stack_canary));
-    assert(sizeof(stack_canary) == 16 && "Stack canary was not the expected size");
+    stk->canary = canary_value;
 }
 
 void
 check_stack_canary(stk_seg *stk) {
-    assert(!memcmp(stk->data, stack_canary, sizeof(stack_canary))
-      && "Somebody killed the canary");
+    assert(stk->canary == canary_value && "Somebody killed the canary");
 }

branches/try/src/rt/rust_stack.h

@@ -10,15 +10,11 @@ struct stk_seg {
     uint32_t pad;
 #endif
 
+    uintptr_t canary;
+
     uint8_t data[];
 };
 
-// A value that goes at the end of the stack and must not be touched
-const uint8_t stack_canary[] = {0xAB, 0xCD, 0xAB, 0xCD,
-                                0xAB, 0xCD, 0xAB, 0xCD,
-                                0xAB, 0xCD, 0xAB, 0xCD,
-                                0xAB, 0xCD, 0xAB, 0xCD};
-
 // Used by create_stack
 void
 register_valgrind_stack(stk_seg *stk);
@@ -34,7 +30,7 @@ add_stack_canary(stk_seg *stk);
 template <class T>
 stk_seg *
 create_stack(T allocer, size_t sz) {
-  size_t total_sz = sizeof(stk_seg) + sz + sizeof(stack_canary);
+  size_t total_sz = sizeof(stk_seg) + sz;
   stk_seg *stk = (stk_seg *)allocer->malloc(total_sz, "stack");
   memset(stk, 0, sizeof(stk_seg));
   stk->end = (uintptr_t) &stk->data[sz];