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
|
/* Return backtrace of current program state.
Copyright (C) 2003-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <execinfo.h>
#include <stdlib.h>
#include <unwind.h>
#include <unwind-link.h>
#include <sframe.h>
struct trace_arg
{
void **array;
struct unwind_link *unwind_link;
_Unwind_Word cfa;
int cnt;
int size;
};
/* Initialize the SFrame backtrace routine and attempt to backtrace
the current stack using SFrame information. For the SFrame
backtrace to be considered valid, the tracer must return more than
one frame. If it doesn't, this could indicate a mixed
environment for example, glibc may have been compiled with SFrame
support, while the application was not. An even more complex
scenario arises when the application uses shared objects compiled
with differing configurations.
Additionally, glibc includes certain callback paths that must be
considered. For example: an application calls shared object A,
which calls shared object B, which in turn calls qsort() in
glibc. qsort() then invokes a helper in shared object C, which
raises a SIGFPE signal, handled by object D, which requests a
backtrace. Any of these components may or may not include SFrame
encoding.
In cases where a stack frame lacks SFrame information, the SFrame
backtracer can fall back to using the DWARF unwinder.
This function must be always inline. Otherwise the
__builtin_frame_address and the __getXX helper functions will not
return the right addresses. */
static inline int __attribute__ ((always_inline))
do_sframe_backtrace (void **array, int size)
{
frame frame;
frame.pc = __getPC ();
frame.sp = __getSP ();
frame.fp = (_Unwind_Ptr) __builtin_frame_address (0);
return __stacktrace_sframe (array, size, &frame);
}
static _Unwind_Reason_Code
backtrace_helper (struct _Unwind_Context *ctx, void *a)
{
struct trace_arg *arg = a;
/* We are first called with address in the __backtrace function.
Skip it. */
if (arg->cnt != -1)
{
arg->array[arg->cnt]
= (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx);
if (arg->cnt > 0)
arg->array[arg->cnt]
= unwind_arch_adjustment (arg->array[arg->cnt - 1],
arg->array[arg->cnt]);
/* Check whether we make any progress. */
_Unwind_Word cfa
= UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetCFA) (ctx);
if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
&& cfa == arg->cfa)
return _URC_END_OF_STACK;
arg->cfa = cfa;
}
if (++arg->cnt == arg->size)
return _URC_END_OF_STACK;
return _URC_NO_REASON;
}
int
__backtrace (void **array, int size)
{
struct trace_arg arg =
{
.array = array,
.unwind_link = __libc_unwind_link_get (),
.cfa = 0,
.size = size,
.cnt = -1
};
if (size <= 0)
return 0;
/* Try first the SFrame backtracer. */
int cnt = do_sframe_backtrace (array, size);
if (cnt > 1)
return cnt;
/* Try the dwarf unwinder. */
if (arg.unwind_link == NULL)
return 0;
UNWIND_LINK_PTR (arg.unwind_link, _Unwind_Backtrace)
(backtrace_helper, &arg);
/* _Unwind_Backtrace seems to put NULL address above
_start. Fix it up here. */
if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
--arg.cnt;
return arg.cnt != -1 ? arg.cnt : 0;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
|
