1 /*
2 * Copyright (C) 2020 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include "platform/bionic/android_unsafe_frame_pointer_chase.h"
30
31 #include "platform/bionic/mte.h"
32 #include "platform/bionic/pac.h"
33 #include "private/bionic_defs.h"
34 #include "pthread_internal.h"
35
36 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
__get_thread_stack_top()37 extern "C" __LIBC_HIDDEN__ uintptr_t __get_thread_stack_top() {
38 return __get_thread()->stack_top;
39 }
40
41 /*
42 * Implement fast stack unwinding for stack frames with frame pointers. Stores at most num_entries
43 * return addresses to buffer buf. Returns the number of available return addresses, which may be
44 * greater than num_entries.
45 *
46 * This function makes no guarantees about its behavior on encountering a frame built without frame
47 * pointers, except that it should not crash or enter an infinite loop, and that any frames prior to
48 * the frame built without frame pointers should be correct.
49 *
50 * This function is only meant to be used with memory safety tools such as sanitizers which need to
51 * take stack traces efficiently. Normal applications should use APIs such as libunwindstack or
52 * _Unwind_Backtrace.
53 */
android_unsafe_frame_pointer_chase(uintptr_t * buf,size_t num_entries)54 __attribute__((no_sanitize("address", "hwaddress"))) size_t android_unsafe_frame_pointer_chase(
55 uintptr_t* buf, size_t num_entries) {
56 // Disable MTE checks for the duration of this function, since we can't be sure that following
57 // next_frame pointers won't cause us to read from tagged memory. ASAN/HWASAN are disabled here
58 // for the same reason.
59 ScopedDisableMTE x;
60
61 struct frame_record {
62 uintptr_t next_frame, return_addr;
63 };
64
65 auto begin = reinterpret_cast<uintptr_t>(__builtin_frame_address(0));
66 auto end = __get_thread_stack_top();
67
68 stack_t ss;
69 if (sigaltstack(nullptr, &ss) == 0 && (ss.ss_flags & SS_ONSTACK)) {
70 end = reinterpret_cast<uintptr_t>(ss.ss_sp) + ss.ss_size;
71 }
72
73 size_t num_frames = 0;
74 while (1) {
75 auto* frame = reinterpret_cast<frame_record*>(begin);
76 if (num_frames < num_entries) {
77 buf[num_frames] = __bionic_clear_pac_bits(frame->return_addr);
78 }
79 ++num_frames;
80 if (frame->next_frame < begin + sizeof(frame_record) || frame->next_frame >= end ||
81 frame->next_frame % sizeof(void*) != 0) {
82 break;
83 }
84 begin = frame->next_frame;
85 }
86
87 return num_frames;
88 }
89