1 /*
2 * Copyright (c) 2020 Google Inc. All rights reserved
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files
6 * (the "Software"), to deal in the Software without restriction,
7 * including without limitation the rights to use, copy, modify, merge,
8 * publish, distribute, sublicense, and/or sell copies of the Software,
9 * and to permit persons to whom the Software is furnished to do so,
10 * subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
22 */
23
24 #include <lib/backtrace/symbolize.h>
25 #include <trace.h>
26
27 #include "elf_sym.h"
28
29 #define LOCAL_TRACE 0
30
31 #undef ELF_64BIT
32 #if !IS_64BIT || USER_32BIT
33 #define ELF_64BIT 0
34 #else
35 #define ELF_64BIT 1
36 #endif
37
38 #if ELF_64BIT
39 #define ELF_SHDR Elf64_Shdr
40 #define ELF_EHDR Elf64_Ehdr
41 #define ELF_SYM Elf64_Sym
42 #else
43 #define ELF_SHDR Elf32_Shdr
44 #define ELF_EHDR Elf32_Ehdr
45 #define ELF_SYM Elf32_Sym
46 #endif
47
range_within_app_img(uintptr_t start,size_t size,struct trusty_app_img * app_img)48 static inline bool range_within_app_img(uintptr_t start,
49 size_t size,
50 struct trusty_app_img* app_img) {
51 uintptr_t end;
52 if (__builtin_add_overflow(start, size, &end)) {
53 return false;
54 }
55 return app_img->img_start <= start && end <= app_img->img_end;
56 }
57
range_within_range(uintptr_t start0,size_t size0,uintptr_t start1,size_t size1)58 static inline bool range_within_range(uintptr_t start0,
59 size_t size0,
60 uintptr_t start1,
61 size_t size1) {
62 uintptr_t end0;
63 if (__builtin_add_overflow(start0, size0, &end0)) {
64 return false;
65 }
66 uintptr_t end1;
67 if (__builtin_add_overflow(start1, size1, &end1)) {
68 return false;
69 }
70 return start1 <= start0 && end0 <= end1;
71 }
72
trusty_app_symbolize(struct trusty_app * app,uintptr_t pc,struct pc_symbol_info * info)73 int trusty_app_symbolize(struct trusty_app* app,
74 uintptr_t pc,
75 struct pc_symbol_info* info) {
76 if (!app) {
77 goto out_no_symbol;
78 }
79 /* Adjust pc to be relative to app image */
80 if (__builtin_sub_overflow(pc, app->load_bias, &pc)) {
81 goto out_no_symbol;
82 }
83 /* pc must be within the app image */
84 struct trusty_app_img* app_img = &app->app_img;
85 if (app_img->img_end <= app_img->img_start) {
86 goto out_no_symbol;
87 }
88 if (pc > app_img->img_end - app_img->img_start) {
89 goto out_no_symbol;
90 }
91
92 ELF_EHDR* ehdr = (ELF_EHDR*)app_img->img_start;
93 ELF_SHDR* shdr = (ELF_SHDR*)((uintptr_t)ehdr + ehdr->e_shoff);
94
95 ELF_SHDR* symtab_shdr = NULL;
96 ELF_SHDR* strtab_shdr = NULL;
97
98 /* Find section headers for .symtab and .strtab */
99 for (size_t i = 0; i < ehdr->e_shnum; i++) {
100 if (shdr[i].sh_type == SHT_SYMTAB) {
101 symtab_shdr = shdr + i;
102 }
103 if (shdr[i].sh_type == SHT_STRTAB) {
104 strtab_shdr = shdr + i;
105 }
106 }
107
108 /* Handle the case when app is not built with .symtab or .strtab */
109 if (!symtab_shdr || !strtab_shdr) {
110 LTRACEF("App built without symbol table\n");
111 goto out_no_symbol;
112 }
113
114 uintptr_t symtab_start = app_img->img_start + symtab_shdr->sh_offset;
115 size_t symtab_size = symtab_shdr->sh_size;
116 uintptr_t strtab_start = app_img->img_start + strtab_shdr->sh_offset;
117 size_t strtab_size = strtab_shdr->sh_size;
118
119 /* Validate .symtab and .strtab locations */
120 if (!range_within_app_img(symtab_start, symtab_size, app_img)) {
121 TRACEF(".symtab section is not within the app image\n");
122 goto out_no_symbol;
123 }
124 if (!range_within_app_img(strtab_start, strtab_size, app_img)) {
125 TRACEF(".strtab section is not within the app image\n");
126 goto out_no_symbol;
127 }
128
129 /* Find closest symbol preceding pc */
130 info->offset = ULONG_MAX;
131 for (uintptr_t curr = symtab_start;
132 curr < symtab_start + symtab_shdr->sh_size;
133 curr += symtab_shdr->sh_entsize) {
134 /* Entry must be within .symtab section */
135 if (!range_within_range(curr, symtab_shdr->sh_entsize, symtab_start,
136 symtab_size)) {
137 TRACEF(".symtab section is malformed\n");
138 goto out_no_symbol;
139 }
140
141 ELF_SYM* symtab_entry = (ELF_SYM*)curr;
142 /* We are looking for a symbol of a function */
143 if (ELF_ST_TYPE(symtab_entry->st_info) != STT_FUNC) {
144 continue;
145 }
146
147 uintptr_t func_start = symtab_entry->st_value;
148 if (func_start <= pc && info->offset > pc - func_start) {
149 /* Offset must be within .strtab section */
150 if (symtab_entry->st_name >= strtab_size) {
151 TRACEF(".strtab section is malformed\n");
152 goto out_no_symbol;
153 }
154
155 info->symbol = (const char*)(strtab_start + symtab_entry->st_name);
156 info->offset = pc - func_start;
157 info->size = symtab_entry->st_size;
158 }
159 }
160
161 if (info->offset == ULONG_MAX) {
162 goto out_no_symbol;
163 }
164 return NO_ERROR;
165
166 out_no_symbol:
167 info->symbol = NULL;
168 info->offset = 0;
169 info->size = 0;
170 return ERR_NOT_FOUND;
171 }
172