1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
// Copyright 2017 The Abseil Authors.
//
// 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
//
// https://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.
//
// This is inspired by Craig Silverstein's PowerPC stacktrace code.
#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
#include <cstdint>
#include "absl/debugging/stacktrace.h"
// WARNING:
// This only works if all your code is in either ARM or THUMB mode. With
// interworking, the frame pointer of the caller can either be in r11 (ARM
// mode) or r7 (THUMB mode). A callee only saves the frame pointer of its
// mode in a fixed location on its stack frame. If the caller is a different
// mode, there is no easy way to find the frame pointer. It can either be
// still in the designated register or saved on stack along with other callee
// saved registers.
// Given a pointer to a stack frame, locate and return the calling
// stackframe, or return nullptr if no stackframe can be found. Perform sanity
// checks (the strictness of which is controlled by the boolean parameter
// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
template<bool STRICT_UNWINDING>
static void **NextStackFrame(void **old_sp) {
void **new_sp = (void**) old_sp[-1];
// Check that the transition from frame pointer old_sp to frame
// pointer new_sp isn't clearly bogus
if (STRICT_UNWINDING) {
// With the stack growing downwards, older stack frame must be
// at a greater address that the current one.
if (new_sp <= old_sp) return nullptr;
// Assume stack frames larger than 100,000 bytes are bogus.
if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
} else {
// In the non-strict mode, allow discontiguous stack frames.
// (alternate-signal-stacks for example).
if (new_sp == old_sp) return nullptr;
// And allow frames upto about 1MB.
if ((new_sp > old_sp)
&& ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
}
if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return nullptr;
return new_sp;
}
// This ensures that absl::GetStackTrace sets up the Link Register properly.
#ifdef __GNUC__
void StacktraceArmDummyFunction() __attribute__((noinline));
void StacktraceArmDummyFunction() { __asm__ volatile(""); }
#else
# error StacktraceArmDummyFunction() needs to be ported to this platform.
#endif
template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
const void * /* ucp */, int *min_dropped_frames) {
#ifdef __GNUC__
void **sp = reinterpret_cast<void**>(__builtin_frame_address(0));
#else
# error reading stack point not yet supported on this platform.
#endif
// On ARM, the return address is stored in the link register (r14).
// This is not saved on the stack frame of a leaf function. To
// simplify code that reads return addresses, we call a dummy
// function so that the return address of this function is also
// stored in the stack frame. This works at least for gcc.
StacktraceArmDummyFunction();
int n = 0;
while (sp && n < max_depth) {
// The absl::GetStackFrames routine is called when we are in some
// informational context (the failure signal handler for example).
// Use the non-strict unwinding rules to produce a stack trace
// that is as complete as possible (even if it contains a few bogus
// entries in some rare cases).
void **next_sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
if (skip_count > 0) {
skip_count--;
} else {
result[n] = *sp;
if (IS_STACK_FRAMES) {
if (next_sp > sp) {
sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
} else {
// A frame-size of 0 is used to indicate unknown frame size.
sizes[n] = 0;
}
}
n++;
}
sp = next_sp;
}
if (min_dropped_frames != nullptr) {
// Implementation detail: we clamp the max of frames we are willing to
// count, so as not to spend too much time in the loop below.
const int kMaxUnwind = 200;
int j = 0;
for (; sp != nullptr && j < kMaxUnwind; j++) {
sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
}
*min_dropped_frames = j;
}
return n;
}
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace debugging_internal {
bool StackTraceWorksForTest() {
return false;
}
} // namespace debugging_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
|
