blob: 664a11e7b5337802e5cd597f86d8820430760646 [file] [log] [blame]
* Copyright (C) 2012 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
* Contributed by: Intel Corporation
#include <gtest/gtest.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <set>
#ifdef __GLIBC__
// glibc doesn't expose gettid(2).
pid_t gettid() { return syscall(__NR_gettid); }
#ifdef __i386__
// For x86, bionic and glibc have per-thread stack guard values.
static uint32_t GetGuardFromTls() {
uint32_t guard;
asm ("mov %%gs:0x14, %0": "=d" (guard));
return guard;
struct stack_protector_checker {
std::set<pid_t> tids;
std::set<uint32_t> guards;
void Check() {
pid_t tid = gettid();
uint32_t guard = GetGuardFromTls();
printf("[thread %d] %%gs:0x14 = 0x%08x\n", tid, guard);
// Duplicate tid. gettid(2) bug? Seeing this would be very upsetting.
ASSERT_TRUE(tids.find(tid) == tids.end());
// 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);
static void* ThreadGuardHelper(void* arg) {
stack_protector_checker* checker = reinterpret_cast<stack_protector_checker*>(arg);
return NULL;
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) {
pthread_t t;
ASSERT_EQ(0, pthread_create(&t, NULL, ThreadGuardHelper, &checker));
void* result;
ASSERT_EQ(0, pthread_join(t, &result));
ASSERT_EQ(NULL, result);
ASSERT_EQ(thread_count, checker.tids.size());
// bionic and glibc use the same guard for every thread.
ASSERT_EQ(1U, checker.guards.size());
#if defined(__BIONIC__) || defined(__arm__) || defined(__mips__)
// For ARM and MIPS, glibc has a global stack check guard value.
// Bionic has the global for x86 too, to support binaries that can run on
// Android releases that didn't implement the TLS guard value.
extern "C" uintptr_t __stack_chk_guard;
TEST(stack_protector, global_guard) {
ASSERT_NE(0, gettid());
ASSERT_NE(0U, __stack_chk_guard);
* When this function returns, the stack canary will be inconsistent
* with the previous value, which will generate a call to __stack_chk_fail(),
* eventually resulting in a SIGABRT.
* This must be marked with "__attribute__ ((noinline))", to ensure the
* compiler generates the proper stack guards around this function.
__attribute__ ((noinline))
static void do_modify_stack_chk_guard() {
__stack_chk_guard = 0x12345678;
// We have to say "DeathTest" here so gtest knows to run this test (which exits)
// in its own process.
TEST(stack_protector_DeathTest, modify_stack_protector) {
::testing::FLAGS_gtest_death_test_style = "threadsafe";
ASSERT_EXIT(do_modify_stack_chk_guard(), testing::KilledBySignal(SIGABRT), "");