stack protector: use AT_RANDOM
Populate the stack canaries from the kernel supplied
AT_RANDOM value, which doesn't involve any system calls.
This is slightly faster (6 fewer syscalls) and avoids
unnecessarily reading /dev/urandom, which depletes entropy.
Bug: 7959813
Change-Id: If2b43100a2a9929666df3de56b6139fed969e0f1
diff --git a/tests/stack_protector_test.cpp b/tests/stack_protector_test.cpp
index 9cf3c38..ca90dea 100644
--- a/tests/stack_protector_test.cpp
+++ b/tests/stack_protector_test.cpp
@@ -56,13 +56,7 @@
// Duplicate tid. gettid(2) bug? Seeing this would be very upsetting.
ASSERT_TRUE(tids.find(tid) == tids.end());
-#ifdef __GLIBC__
- // glibc uses the same guard for every thread. bionic uses a different guard for each one.
-#else
- // Duplicate guard. Our bug. Note this is potentially flaky; we _could_ get the
- // same guard for two threads, but it should be vanishingly unlikely.
- ASSERT_TRUE(guards.find(guard) == guards.end());
-#endif
+
// Uninitialized guard. Our bug. Note this is potentially flaky; we _could_ get
// four random zero bytes, but it should be vanishingly unlikely.
ASSERT_NE(guard, 0U);
@@ -78,7 +72,7 @@
return NULL;
}
-TEST(stack_protector, guard_per_thread) {
+TEST(stack_protector, same_guard_per_thread) {
stack_protector_checker checker;
size_t thread_count = 10;
for (size_t i = 0; i < thread_count; ++i) {
@@ -90,12 +84,8 @@
}
ASSERT_EQ(thread_count, checker.tids.size());
- // glibc uses the same guard for every thread. bionic uses a different guard for each one.
-#ifdef __BIONIC__
- ASSERT_EQ(thread_count, checker.guards.size());
-#else
+ // bionic x86 and glibc uses the same guard for every thread.
ASSERT_EQ(1U, checker.guards.size());
-#endif
}
#endif