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/*
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Contributed by: Intel Corporation
*/
#include <gtest/gtest.h>
#include "BionicDeathTest.h"
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <set>
extern "C" pid_t gettid();
// For x86, bionic and glibc have per-thread stack guard values (all identical).
#if defined(__i386__)
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);
tids.insert(tid);
guards.insert(guard);
}
};
static void* ThreadGuardHelper(void* arg) {
stack_protector_checker* checker = reinterpret_cast<stack_protector_checker*>(arg);
checker->Check();
return NULL;
}
#endif // __i386__
TEST(stack_protector, same_guard_per_thread) {
#if defined(__i386__)
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());
#else // __i386__
GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __i386__
}
// For ARM and MIPS, glibc has a global stack check guard value.
#if defined(__BIONIC__) || defined(__arm__) || defined(__mips__)
#define TEST_STACK_CHK_GUARD
// 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;
/*
* 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.
*/
static char* dummy_buf;
__attribute__ ((noinline))
static void do_modify_stack_chk_guard() {
char buf[128];
// Store local array's address to global variable to force compiler to generate stack guards.
dummy_buf = buf;
__stack_chk_guard = 0x12345678;
}
#endif
TEST(stack_protector, global_guard) {
#if defined(TEST_STACK_CHK_GUARD)
ASSERT_NE(0, gettid());
ASSERT_NE(0U, __stack_chk_guard);
#else // TEST_STACK_CHK_GUARD
GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // TEST_STACK_CHK_GUARD
}
class stack_protector_DeathTest : public BionicDeathTest {};
TEST_F(stack_protector_DeathTest, modify_stack_protector) {
#if defined(TEST_STACK_CHK_GUARD)
ASSERT_EXIT(do_modify_stack_chk_guard(), testing::KilledBySignal(SIGABRT), "");
#else // TEST_STACK_CHK_GUARD
GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // TEST_STACK_CHK_GUARD
}
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