1 | /* Return backtrace of current program state. |
2 | Copyright (C) 1998-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <execinfo.h> |
20 | #include <stdlib.h> |
21 | #include <unwind-link.h> |
22 | |
23 | struct trace_arg |
24 | { |
25 | void **array; |
26 | struct unwind_link *unwind_link; |
27 | int cnt, size; |
28 | void *lastebp, *lastesp; |
29 | }; |
30 | |
31 | static _Unwind_Reason_Code |
32 | backtrace_helper (struct _Unwind_Context *ctx, void *a) |
33 | { |
34 | struct trace_arg *arg = a; |
35 | |
36 | /* We are first called with address in the __backtrace function. |
37 | Skip it. */ |
38 | if (arg->cnt != -1) |
39 | arg->array[arg->cnt] |
40 | = (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx); |
41 | if (++arg->cnt == arg->size) |
42 | return _URC_END_OF_STACK; |
43 | |
44 | /* %ebp is DWARF2 register 5 on IA-32. */ |
45 | arg->lastebp |
46 | = (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetGR) (ctx, 5); |
47 | arg->lastesp |
48 | = (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetCFA) (ctx); |
49 | return _URC_NO_REASON; |
50 | } |
51 | |
52 | |
53 | /* This is a global variable set at program start time. It marks the |
54 | highest used stack address. */ |
55 | extern void *__libc_stack_end; |
56 | |
57 | |
58 | /* This is the stack layout we see with every stack frame |
59 | if not compiled without frame pointer. |
60 | |
61 | +-----------------+ +-----------------+ |
62 | %ebp -> | %ebp last frame--------> | %ebp last frame--->... |
63 | | | | | |
64 | | return address | | return address | |
65 | +-----------------+ +-----------------+ |
66 | |
67 | First try as far to get as far as possible using |
68 | _Unwind_Backtrace which handles -fomit-frame-pointer |
69 | as well, but requires .eh_frame info. Then fall back to |
70 | walking the stack manually. */ |
71 | |
72 | struct layout |
73 | { |
74 | struct layout *ebp; |
75 | void *ret; |
76 | }; |
77 | |
78 | |
79 | int |
80 | __backtrace (void **array, int size) |
81 | { |
82 | struct trace_arg arg = |
83 | { |
84 | .array = array, |
85 | .unwind_link = __libc_unwind_link_get (), |
86 | .size = size, |
87 | .cnt = -1, |
88 | }; |
89 | |
90 | if (size <= 0 || arg.unwind_link == NULL) |
91 | return 0; |
92 | |
93 | UNWIND_LINK_PTR (arg.unwind_link, _Unwind_Backtrace) |
94 | (backtrace_helper, &arg); |
95 | |
96 | if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL) |
97 | --arg.cnt; |
98 | else if (arg.cnt < size) |
99 | { |
100 | struct layout *ebp = (struct layout *) arg.lastebp; |
101 | |
102 | while (arg.cnt < size) |
103 | { |
104 | /* Check for out of range. */ |
105 | if ((void *) ebp < arg.lastesp || (void *) ebp > __libc_stack_end |
106 | || ((long) ebp & 3)) |
107 | break; |
108 | |
109 | array[arg.cnt++] = ebp->ret; |
110 | ebp = ebp->ebp; |
111 | } |
112 | } |
113 | return arg.cnt != -1 ? arg.cnt : 0; |
114 | } |
115 | weak_alias (__backtrace, backtrace) |
116 | libc_hidden_def (__backtrace) |
117 | |