1/*
2 * Copyright 2013-present Facebook, Inc.
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#include <folly/experimental/symbolizer/StackTrace.h>
17
18// Must be first to ensure that UNW_LOCAL_ONLY is defined
19#define UNW_LOCAL_ONLY 1
20#include <libunwind.h>
21
22namespace folly {
23namespace symbolizer {
24
25ssize_t getStackTrace(uintptr_t* addresses, size_t maxAddresses) {
26 static_assert(
27 sizeof(uintptr_t) == sizeof(void*), "uintptr_t / pointer size mismatch");
28 // The libunwind documentation says that unw_backtrace is async-signal-safe
29 // but, as of libunwind 1.0.1, it isn't (tdep_trace allocates memory on
30 // x86_64)
31 int r = unw_backtrace(reinterpret_cast<void**>(addresses), maxAddresses);
32 return r < 0 ? -1 : r;
33}
34
35namespace {
36inline bool getFrameInfo(unw_cursor_t* cursor, uintptr_t& ip) {
37 unw_word_t uip;
38 if (unw_get_reg(cursor, UNW_REG_IP, &uip) < 0) {
39 return false;
40 }
41 int r = unw_is_signal_frame(cursor);
42 if (r < 0) {
43 return false;
44 }
45 // Use previous instruction in normal (call) frames (because the
46 // return address might not be in the same function for noreturn functions)
47 // but not in signal frames.
48 ip = uip - (r == 0);
49 return true;
50}
51} // namespace
52
53ssize_t getStackTraceSafe(uintptr_t* addresses, size_t maxAddresses) {
54 if (maxAddresses == 0) {
55 return 0;
56 }
57 unw_context_t context;
58 if (unw_getcontext(&context) < 0) {
59 return -1;
60 }
61 unw_cursor_t cursor;
62 if (unw_init_local(&cursor, &context) < 0) {
63 return -1;
64 }
65 if (!getFrameInfo(&cursor, *addresses)) {
66 return -1;
67 }
68 ++addresses;
69 size_t count = 1;
70 for (; count != maxAddresses; ++count, ++addresses) {
71 int r = unw_step(&cursor);
72 if (r < 0) {
73 return -1;
74 }
75 if (r == 0) {
76 break;
77 }
78 if (!getFrameInfo(&cursor, *addresses)) {
79 return -1;
80 }
81 }
82 return count;
83}
84} // namespace symbolizer
85} // namespace folly
86