1 /*
2 * Copyright (c) 2013 Luca Clementi <luca.clementi@gmail.com>
3 * Copyright (c) 2013-2018 The strace developers.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #include "defs.h"
29 #include "unwind.h"
30
31 #include "mmap_cache.h"
32 #include <libunwind-ptrace.h>
33
34 static unw_addr_space_t libunwind_as;
35
36 static void
init(void)37 init(void)
38 {
39 mmap_cache_enable();
40
41 libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
42 if (!libunwind_as)
43 error_msg_and_die("failed to create address space"
44 " for stack tracing");
45 unw_set_caching_policy(libunwind_as, UNW_CACHE_GLOBAL);
46 }
47
48 static void *
tcb_init(struct tcb * tcp)49 tcb_init(struct tcb *tcp)
50 {
51 void *r = _UPT_create(tcp->pid);
52
53 if (!r)
54 perror_msg_and_die("_UPT_create");
55 return r;
56 }
57
58 static void
tcb_fin(struct tcb * tcp)59 tcb_fin(struct tcb *tcp)
60 {
61 _UPT_destroy(tcp->unwind_ctx);
62 }
63
64 static void
get_symbol_name(unw_cursor_t * cursor,char ** name,size_t * size,unw_word_t * offset)65 get_symbol_name(unw_cursor_t *cursor, char **name,
66 size_t *size, unw_word_t *offset)
67 {
68 for (;;) {
69 int rc = unw_get_proc_name(cursor, *name, *size, offset);
70
71 if (rc == 0)
72 break;
73 if (rc != -UNW_ENOMEM) {
74 **name = '\0';
75 *offset = 0;
76 break;
77 }
78 *name = xgrowarray(*name, size, 1);
79 }
80 }
81
82 static int
print_stack_frame(struct tcb * tcp,unwind_call_action_fn call_action,unwind_error_action_fn error_action,void * data,unw_cursor_t * cursor,char ** symbol_name,size_t * symbol_name_size)83 print_stack_frame(struct tcb *tcp,
84 unwind_call_action_fn call_action,
85 unwind_error_action_fn error_action,
86 void *data,
87 unw_cursor_t *cursor,
88 char **symbol_name,
89 size_t *symbol_name_size)
90 {
91 unw_word_t ip;
92
93 if (unw_get_reg(cursor, UNW_REG_IP, &ip) < 0) {
94 perror_msg("cannot walk the stack of process %d", tcp->pid);
95 return -1;
96 }
97
98 struct mmap_cache_entry_t *entry = mmap_cache_search(tcp, ip);
99
100 if (entry
101 /* ignore mappings that have no PROT_EXEC bit set */
102 && (entry->protections & MMAP_CACHE_PROT_EXECUTABLE)) {
103 unw_word_t function_offset;
104
105 get_symbol_name(cursor, symbol_name, symbol_name_size,
106 &function_offset);
107 unsigned long true_offset =
108 ip - entry->start_addr + entry->mmap_offset;
109 call_action(data,
110 entry->binary_filename,
111 *symbol_name,
112 function_offset,
113 true_offset);
114
115 return 0;
116 }
117
118 /*
119 * there is a bug in libunwind >= 1.0
120 * after a set_tid_address syscall
121 * unw_get_reg returns IP == 0
122 */
123 if (ip)
124 error_action(data, "unexpected_backtracing_error", ip);
125 return -1;
126 }
127
128 static void
walk(struct tcb * tcp,unwind_call_action_fn call_action,unwind_error_action_fn error_action,void * data)129 walk(struct tcb *tcp,
130 unwind_call_action_fn call_action,
131 unwind_error_action_fn error_action,
132 void *data)
133 {
134 char *symbol_name;
135 size_t symbol_name_size = 40;
136 unw_cursor_t cursor;
137 int stack_depth;
138
139 if (!tcp->mmap_cache)
140 error_func_msg_and_die("mmap_cache is NULL");
141
142 symbol_name = xmalloc(symbol_name_size);
143
144 if (unw_init_remote(&cursor, libunwind_as, tcp->unwind_ctx) < 0)
145 perror_func_msg_and_die("cannot initialize libunwind");
146
147 for (stack_depth = 0; stack_depth < 256; ++stack_depth) {
148 if (print_stack_frame(tcp, call_action, error_action, data,
149 &cursor, &symbol_name, &symbol_name_size) < 0)
150 break;
151 if (unw_step(&cursor) <= 0)
152 break;
153 }
154 if (stack_depth >= 256)
155 error_action(data, "too many stack frames", 0);
156
157 free(symbol_name);
158 }
159
160 static void
tcb_walk(struct tcb * tcp,unwind_call_action_fn call_action,unwind_error_action_fn error_action,void * data)161 tcb_walk(struct tcb *tcp,
162 unwind_call_action_fn call_action,
163 unwind_error_action_fn error_action,
164 void *data)
165 {
166 switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
167 case MMAP_CACHE_REBUILD_RENEWED:
168 /*
169 * Rebuild the unwinder internal cache.
170 * Called when mmap cache subsystem detects a
171 * change of tracee memory mapping.
172 */
173 unw_flush_cache(libunwind_as, 0, 0);
174 ATTRIBUTE_FALLTHROUGH;
175 case MMAP_CACHE_REBUILD_READY:
176 walk(tcp, call_action, error_action, data);
177 break;
178 default:
179 /* Do nothing */
180 ;
181 }
182 }
183
184 const struct unwind_unwinder_t unwinder = {
185 .name = "libunwind",
186 .init = init,
187 .tcb_init = tcb_init,
188 .tcb_fin = tcb_fin,
189 .tcb_walk = tcb_walk,
190 };
191