1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17// Deliberately overwrite the stack canary.
18__attribute__((noinline)) void modify_stack_protector_test() {
19  char buf[128];
20  // We can't use memset here because it's fortified, and we want to test
21  // the line of defense *after* that.
22  // Without volatile, the generic x86/x86-64 targets don't write to the stack.
23  volatile char* p = buf;
24  int size = static_cast<int>(sizeof(buf) + 1);
25#if __x86_64__
26  // The generic x86-64 target leaves an 8-byte gap between `buf` and the stack guard.
27  // We only need to corrupt one byte though.
28  size += 8;
29#endif
30  while ((p - buf) < size) *p++ = '\0';
31}
32