1 /* libunwind - a platform-independent unwind library
2 Copyright (C) 2003, 2005 Hewlett-Packard Co
3 Copyright (C) 2007 David Mosberger-Tang
4 Contributed by David Mosberger-Tang <dmosberger@gmail.com>
5
6 This file is part of libunwind.
7
8 Permission is hereby granted, free of charge, to any person obtaining
9 a copy of this software and associated documentation files (the
10 "Software"), to deal in the Software without restriction, including
11 without limitation the rights to use, copy, modify, merge, publish,
12 distribute, sublicense, and/or sell copies of the Software, and to
13 permit persons to whom the Software is furnished to do so, subject to
14 the following conditions:
15
16 The above copyright notice and this permission notice shall be
17 included in all copies or substantial portions of the Software.
18
19 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
21 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
23 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
24 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
25 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
26
27 #include <fcntl.h>
28 #include <stddef.h>
29 #include <unistd.h>
30
31 #include <sys/mman.h>
32 #include <sys/stat.h>
33
34 #include "libunwind_i.h"
35 #include "map_info.h"
36
37 #if ELF_CLASS == ELFCLASS32
38 # define ELF_W(x) ELF32_##x
39 # define Elf_W(x) Elf32_##x
40 # define elf_w(x) _Uelf32_##x
41 #else
42 # define ELF_W(x) ELF64_##x
43 # define Elf_W(x) Elf64_##x
44 # define elf_w(x) _Uelf64_##x
45 #endif
46
47 #define GET_FIELD(ei, offset, struct_name, elf_struct, field, check_cached) \
48 { \
49 if (!check_cached || (elf_struct)->field == 0) { \
50 if (sizeof((elf_struct)->field) != elf_w (memory_read) ( \
51 ei, ei->u.memory.start + offset + offsetof(struct_name, field), \
52 (uint8_t*) &((elf_struct)->field), sizeof((elf_struct)->field), false)) { \
53 return false; \
54 } \
55 } \
56 }
57
58 #define GET_EHDR_FIELD(ei, ehdr, field, check_cached) \
59 GET_FIELD(ei, 0, Elf_W(Ehdr), ehdr, field, check_cached)
60
61 #define GET_PHDR_FIELD(ei, offset, phdr, field) \
62 GET_FIELD(ei, offset, Elf_W(Phdr), phdr, field, false)
63
64 #define GET_SHDR_FIELD(ei, offset, shdr, field) \
65 GET_FIELD(ei, offset, Elf_W(Shdr), shdr, field, false)
66
67 #define GET_SYM_FIELD(ei, offset, sym, field) \
68 GET_FIELD(ei, offset, Elf_W(Sym), sym, field, false)
69
70 #define GET_DYN_FIELD(ei, offset, dyn, field) \
71 GET_FIELD(ei, offset, Elf_W(Dyn), dyn, field, false)
72
73 extern bool elf_w (get_proc_name) (
74 unw_addr_space_t as, pid_t pid, unw_word_t ip, char* buf, size_t len,
75 unw_word_t* offp, void* as_arg);
76
77 extern bool elf_w (get_proc_name_in_image) (
78 unw_addr_space_t as, struct elf_image* ei, unsigned long segbase,
79 unsigned long mapoff, unw_word_t ip, char* buf, size_t buf_len, unw_word_t* offp);
80
81 extern bool elf_w (get_load_base) (struct elf_image* ei, unw_word_t mapoff, unw_word_t* load_base);
82
83 extern size_t elf_w (memory_read) (
84 struct elf_image* ei, unw_word_t addr, uint8_t* buffer, size_t bytes, bool string_read);
85
86 extern bool elf_w (xz_decompress) (uint8_t* src, size_t src_size,
87 uint8_t** dst, size_t* dst_size);
88
89 extern bool elf_w (find_section_mapped) (struct elf_image *ei, const char* name,
90 uint8_t** section, size_t* size, Elf_W(Addr)* vaddr);
91
elf_w(valid_object_mapped)92 static inline bool elf_w (valid_object_mapped) (struct elf_image* ei) {
93 if (ei->u.mapped.size <= EI_VERSION) {
94 return false;
95 }
96
97 uint8_t* e_ident = (uint8_t*) ei->u.mapped.image;
98 return (memcmp (ei->u.mapped.image, ELFMAG, SELFMAG) == 0
99 && e_ident[EI_CLASS] == ELF_CLASS && e_ident[EI_VERSION] != EV_NONE
100 && e_ident[EI_VERSION] <= EV_CURRENT);
101 }
102
elf_w(valid_object_memory)103 static inline bool elf_w (valid_object_memory) (struct elf_image* ei) {
104 uint8_t e_ident[EI_NIDENT];
105 uintptr_t start = ei->u.memory.start;
106 if (SELFMAG != elf_w (memory_read) (ei, start, e_ident, SELFMAG, false)) {
107 return false;
108 }
109 if (memcmp (e_ident, ELFMAG, SELFMAG) != 0) {
110 return false;
111 }
112 // Read the rest of the ident data.
113 if (EI_NIDENT - SELFMAG != elf_w (memory_read) (
114 ei, start + SELFMAG, e_ident + SELFMAG, EI_NIDENT - SELFMAG, false)) {
115 return false;
116 }
117 return e_ident[EI_CLASS] == ELF_CLASS && e_ident[EI_VERSION] != EV_NONE
118 && e_ident[EI_VERSION] <= EV_CURRENT;
119 }
120
elf_map_image(struct elf_image * ei,const char * path)121 static inline bool elf_map_image (struct elf_image* ei, const char* path) {
122 struct stat stat;
123 int fd;
124
125 fd = open (path, O_RDONLY);
126 if (fd < 0) {
127 return false;
128 }
129
130 if (fstat (fd, &stat) == -1) {
131 close (fd);
132 return false;
133 }
134
135 ei->u.mapped.size = stat.st_size;
136 ei->u.mapped.image = mmap (NULL, ei->u.mapped.size, PROT_READ, MAP_PRIVATE, fd, 0);
137 close (fd);
138 if (ei->u.mapped.image == MAP_FAILED) {
139 return false;
140 }
141
142 ei->valid = elf_w (valid_object_mapped) (ei);
143 if (!ei->valid) {
144 munmap (ei->u.mapped.image, ei->u.mapped.size);
145 return false;
146 }
147
148 ei->mapped = true;
149 // Set to true for cases where this is called outside of elf_map_cached.
150 ei->load_attempted = true;
151
152 return true;
153 }
154
elf_map_cached_image(unw_addr_space_t as,void * as_arg,struct map_info * map,unw_word_t ip,bool local_unwind)155 static inline bool elf_map_cached_image (
156 unw_addr_space_t as, void* as_arg, struct map_info* map, unw_word_t ip,
157 bool local_unwind) {
158 intrmask_t saved_mask;
159
160 // Don't even try and cache this unless the map is readable and executable.
161 if ((map->flags & (PROT_READ | PROT_EXEC)) != (PROT_READ | PROT_EXEC)) {
162 return false;
163 }
164
165 // Do not try and cache the map if it's a file from /dev/ that is not
166 // /dev/ashmem/.
167 if (map->path != NULL && strncmp ("/dev/", map->path, 5) == 0
168 && strncmp ("ashmem/", map->path + 5, 7) != 0) {
169 return false;
170 }
171
172 // Lock while loading the cached elf image.
173 lock_acquire (&map->ei_lock, saved_mask);
174 if (!map->ei.load_attempted) {
175 map->ei.load_attempted = true;
176
177 if (!elf_map_image (&map->ei, map->path)) {
178 // If the image cannot be loaded, we'll read data directly from
179 // the process using the access_mem function.
180 if (map->flags & PROT_READ) {
181 map->ei.u.memory.start = map->start;
182 map->ei.u.memory.end = map->end;
183 map->ei.u.memory.as = as;
184 map->ei.u.memory.as_arg = as_arg;
185 map->ei.valid = elf_w (valid_object_memory) (&map->ei);
186 }
187 } else if (!local_unwind) {
188 // Do not process the compressed section for local unwinds.
189 // Uncompressing this section can consume a large amount of memory
190 // and cause the unwind to take longer, which can cause problems
191 // when an ANR occurs in the system. Compressed sections are
192 // only used to contain java stack trace information. Since ART is
193 // one of the only ways that a local trace is done, and it already
194 // dumps the java stack, this information is redundant.
195
196 // Try to cache the minidebuginfo data.
197 uint8_t *compressed = NULL;
198 size_t compressed_len;
199 if (elf_w (find_section_mapped) (&map->ei, ".gnu_debugdata", &compressed,
200 &compressed_len, NULL)) {
201 if (elf_w (xz_decompress) (compressed, compressed_len,
202 (uint8_t**) &map->ei.mini_debug_info_data, &map->ei.mini_debug_info_size)) {
203 Debug (1, "Decompressed and cached .gnu_debugdata");
204 } else {
205 map->ei.mini_debug_info_data = NULL;
206 map->ei.mini_debug_info_size = 0;
207 }
208 }
209 }
210 unw_word_t load_base;
211 if (map->ei.valid && elf_w (get_load_base) (&map->ei, map->offset, &load_base)) {
212 map->load_base = load_base;
213 }
214 } else if (map->ei.valid && !map->ei.mapped && map->ei.u.memory.as != as) {
215 // If this map is only in memory, this might be a cached map
216 // that crosses over multiple unwinds. In this case, we've detected
217 // that the as is stale, so set it to a valid as.
218 map->ei.u.memory.as = as;
219 }
220 lock_release (&map->ei_lock, saved_mask);
221 return map->ei.valid;
222 }
223