1 // Copyright 2017 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 // Produce stack trace.
16 //
17 // There are three different ways we can try to get the stack trace:
18 //
19 // 1) Our hand-coded stack-unwinder. This depends on a certain stack
20 // layout, which is used by gcc (and those systems using a
21 // gcc-compatible ABI) on x86 systems, at least since gcc 2.95.
22 // It uses the frame pointer to do its work.
23 //
24 // 2) The libunwind library. This is still in development, and as a
25 // separate library adds a new dependency, but doesn't need a frame
26 // pointer. It also doesn't call malloc.
27 //
28 // 3) The gdb unwinder -- also the one used by the c++ exception code.
29 // It's obviously well-tested, but has a fatal flaw: it can call
30 // malloc() from the unwinder. This is a problem because we're
31 // trying to use the unwinder to instrument malloc().
32 //
33 // Note: if you add a new implementation here, make sure it works
34 // correctly when absl::GetStackTrace() is called with max_depth == 0.
35 // Some code may do that.
36
37 #include "absl/debugging/stacktrace.h"
38
39 #include <atomic>
40
41 #include "absl/base/attributes.h"
42 #include "absl/base/port.h"
43 #include "absl/debugging/internal/stacktrace_config.h"
44
45 #if defined(ABSL_STACKTRACE_INL_HEADER)
46 #include ABSL_STACKTRACE_INL_HEADER
47 #else
48 # error Cannot calculate stack trace: will need to write for your environment
49
50 # include "absl/debugging/internal/stacktrace_aarch64-inl.inc"
51 # include "absl/debugging/internal/stacktrace_arm-inl.inc"
52 # include "absl/debugging/internal/stacktrace_generic-inl.inc"
53 # include "absl/debugging/internal/stacktrace_powerpc-inl.inc"
54 # include "absl/debugging/internal/stacktrace_unimplemented-inl.inc"
55 # include "absl/debugging/internal/stacktrace_win32-inl.inc"
56 # include "absl/debugging/internal/stacktrace_x86-inl.inc"
57 #endif
58
59 namespace absl {
60 ABSL_NAMESPACE_BEGIN
61 namespace {
62
63 typedef int (*Unwinder)(void**, int*, int, int, const void*, int*);
64 std::atomic<Unwinder> custom;
65
66 template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
Unwind(void ** result,int * sizes,int max_depth,int skip_count,const void * uc,int * min_dropped_frames)67 ABSL_ATTRIBUTE_ALWAYS_INLINE inline int Unwind(void** result, int* sizes,
68 int max_depth, int skip_count,
69 const void* uc,
70 int* min_dropped_frames) {
71 Unwinder f = &UnwindImpl<IS_STACK_FRAMES, IS_WITH_CONTEXT>;
72 Unwinder g = custom.load(std::memory_order_acquire);
73 if (g != nullptr) f = g;
74
75 // Add 1 to skip count for the unwinder function itself
76 int size = (*f)(result, sizes, max_depth, skip_count + 1, uc,
77 min_dropped_frames);
78 // To disable tail call to (*f)(...)
79 ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
80 return size;
81 }
82
83 } // anonymous namespace
84
GetStackFrames(void ** result,int * sizes,int max_depth,int skip_count)85 ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int GetStackFrames(
86 void** result, int* sizes, int max_depth, int skip_count) {
87 return Unwind<true, false>(result, sizes, max_depth, skip_count, nullptr,
88 nullptr);
89 }
90
91 ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
GetStackFramesWithContext(void ** result,int * sizes,int max_depth,int skip_count,const void * uc,int * min_dropped_frames)92 GetStackFramesWithContext(void** result, int* sizes, int max_depth,
93 int skip_count, const void* uc,
94 int* min_dropped_frames) {
95 return Unwind<true, true>(result, sizes, max_depth, skip_count, uc,
96 min_dropped_frames);
97 }
98
GetStackTrace(void ** result,int max_depth,int skip_count)99 ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int GetStackTrace(
100 void** result, int max_depth, int skip_count) {
101 return Unwind<false, false>(result, nullptr, max_depth, skip_count, nullptr,
102 nullptr);
103 }
104
105 ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
GetStackTraceWithContext(void ** result,int max_depth,int skip_count,const void * uc,int * min_dropped_frames)106 GetStackTraceWithContext(void** result, int max_depth, int skip_count,
107 const void* uc, int* min_dropped_frames) {
108 return Unwind<false, true>(result, nullptr, max_depth, skip_count, uc,
109 min_dropped_frames);
110 }
111
SetStackUnwinder(Unwinder w)112 void SetStackUnwinder(Unwinder w) {
113 custom.store(w, std::memory_order_release);
114 }
115
DefaultStackUnwinder(void ** pcs,int * sizes,int depth,int skip,const void * uc,int * min_dropped_frames)116 int DefaultStackUnwinder(void** pcs, int* sizes, int depth, int skip,
117 const void* uc, int* min_dropped_frames) {
118 skip++; // For this function
119 Unwinder f = nullptr;
120 if (sizes == nullptr) {
121 if (uc == nullptr) {
122 f = &UnwindImpl<false, false>;
123 } else {
124 f = &UnwindImpl<false, true>;
125 }
126 } else {
127 if (uc == nullptr) {
128 f = &UnwindImpl<true, false>;
129 } else {
130 f = &UnwindImpl<true, true>;
131 }
132 }
133 volatile int x = 0;
134 int n = (*f)(pcs, sizes, depth, skip, uc, min_dropped_frames);
135 x = 1; (void) x; // To disable tail call to (*f)(...)
136 return n;
137 }
138
139 ABSL_NAMESPACE_END
140 } // namespace absl
141