1 /*
2 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores,
20 * CA 94065 USA or visit www.oracle.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 #include <unistd.h>
26 #include <sys/procfs.h>
27 #include <search.h>
28 #include <stdlib.h>
29 #include <string.h>
30 #include "symtab.h"
31 #include "salibelf.h"
32
33
34 // ----------------------------------------------------
35 // functions for symbol lookups
36 // ----------------------------------------------------
37
38 struct elf_section {
39 ELF_SHDR *c_shdr;
40 void *c_data;
41 };
42
43 struct elf_symbol {
44 char *name;
45 uintptr_t offset;
46 uintptr_t size;
47 };
48
49 typedef struct symtab {
50 char *strs;
51 size_t num_symbols;
52 struct elf_symbol *symbols;
53 struct hsearch_data *hash_table;
54 } symtab_t;
55
56 // read symbol table from given fd.
57 struct symtab* build_symtab(int fd) {
58 ELF_EHDR ehdr;
59 char *names = NULL;
60 struct symtab* symtab = NULL;
61
62 // Reading of elf header
63 struct elf_section *scn_cache = NULL;
64 int cnt = 0;
65 ELF_SHDR* shbuf = NULL;
66 ELF_SHDR* cursct = NULL;
67 ELF_PHDR* phbuf = NULL;
68 ELF_PHDR* phdr = NULL;
69
70 uintptr_t baseaddr = (uintptr_t)-1;
71
72 lseek(fd, (off_t)0L, SEEK_SET);
73 if (! read_elf_header(fd, &ehdr)) {
74 // not an elf
75 return NULL;
76 }
77
78 // read ELF header
79 if ((shbuf = read_section_header_table(fd, &ehdr)) == NULL) {
80 goto quit;
81 }
82
83 baseaddr = find_base_address(fd, &ehdr);
84
85 scn_cache = (struct elf_section *)
86 calloc(ehdr.e_shnum * sizeof(struct elf_section), 1);
87 if (scn_cache == NULL) {
88 goto quit;
89 }
90
91 for (cursct = shbuf, cnt = 0; cnt < ehdr.e_shnum; cnt++) {
92 scn_cache[cnt].c_shdr = cursct;
93 if (cursct->sh_type == SHT_SYMTAB || cursct->sh_type == SHT_STRTAB) {
94 if ( (scn_cache[cnt].c_data = read_section_data(fd, &ehdr, cursct)) == NULL) {
95 goto quit;
96 }
97 }
98 cursct++;
99 }
100
101 for (cnt = 1; cnt < ehdr.e_shnum; cnt++) {
102 ELF_SHDR *shdr = scn_cache[cnt].c_shdr;
103
104 if (shdr->sh_type == SHT_SYMTAB) {
105 ELF_SYM *syms;
106 int j, n, rslt;
107 size_t size;
108
109 // FIXME: there could be multiple data buffers associated with the
110 // same ELF section. Here we can handle only one buffer. See man page
111 // for elf_getdata on Solaris.
112
113 // guarantee(symtab == NULL, "multiple symtab");
114 symtab = (struct symtab*)calloc(1, sizeof(struct symtab));
115 if (symtab == NULL) {
116 goto quit;
117 }
118 // the symbol table
119 syms = (ELF_SYM *)scn_cache[cnt].c_data;
120
121 // number of symbols
122 n = shdr->sh_size / shdr->sh_entsize;
123
124 // create hash table, we use hcreate_r, hsearch_r and hdestroy_r to
125 // manipulate the hash table.
126 symtab->hash_table = (struct hsearch_data*) calloc(1, sizeof(struct hsearch_data));
127 rslt = hcreate_r(n, symtab->hash_table);
128 // guarantee(rslt, "unexpected failure: hcreate_r");
129
130 // shdr->sh_link points to the section that contains the actual strings
131 // for symbol names. the st_name field in ELF_SYM is just the
132 // string table index. we make a copy of the string table so the
133 // strings will not be destroyed by elf_end.
134 size = scn_cache[shdr->sh_link].c_shdr->sh_size;
135 symtab->strs = (char *)malloc(size);
136 memcpy(symtab->strs, scn_cache[shdr->sh_link].c_data, size);
137
138 // allocate memory for storing symbol offset and size;
139 symtab->num_symbols = n;
140 symtab->symbols = (struct elf_symbol *)calloc(n , sizeof(struct elf_symbol));
141
142 // copy symbols info our symtab and enter them info the hash table
143 for (j = 0; j < n; j++, syms++) {
144 ENTRY item, *ret;
145 char *sym_name = symtab->strs + syms->st_name;
146
147 // skip non-object and non-function symbols
148 int st_type = ELF_ST_TYPE(syms->st_info);
149 if ( st_type != STT_FUNC && st_type != STT_OBJECT)
150 continue;
151 // skip empty strings and undefined symbols
152 if (*sym_name == '\0' || syms->st_shndx == SHN_UNDEF) continue;
153
154 symtab->symbols[j].name = sym_name;
155 symtab->symbols[j].offset = syms->st_value - baseaddr;
156 symtab->symbols[j].size = syms->st_size;
157
158 item.key = sym_name;
159 item.data = (void *)&(symtab->symbols[j]);
160
161 hsearch_r(item, ENTER, &ret, symtab->hash_table);
162 }
163 }
164 }
165
166 quit:
167 if (shbuf) free(shbuf);
168 if (phbuf) free(phbuf);
169 if (scn_cache) {
170 for (cnt = 0; cnt < ehdr.e_shnum; cnt++) {
171 if (scn_cache[cnt].c_data != NULL) {
172 free(scn_cache[cnt].c_data);
173 }
174 }
175 free(scn_cache);
176 }
177 return symtab;
178 }
179
180 void destroy_symtab(struct symtab* symtab) {
181 if (!symtab) return;
182 if (symtab->strs) free(symtab->strs);
183 if (symtab->symbols) free(symtab->symbols);
184 if (symtab->hash_table) {
185 hdestroy_r(symtab->hash_table);
186 free(symtab->hash_table);
187 }
188 free(symtab);
189 }
190
191 uintptr_t search_symbol(struct symtab* symtab, uintptr_t base,
192 const char *sym_name, int *sym_size) {
193 ENTRY item;
194 ENTRY* ret = NULL;
195
196 // library does not have symbol table
197 if (!symtab || !symtab->hash_table)
198 return (uintptr_t)NULL;
199
200 item.key = (char*) strdup(sym_name);
201 hsearch_r(item, FIND, &ret, symtab->hash_table);
202 if (ret) {
203 struct elf_symbol * sym = (struct elf_symbol *)(ret->data);
204 uintptr_t rslt = (uintptr_t) ((char*)base + sym->offset);
205 if (sym_size) *sym_size = sym->size;
206 free(item.key);
207 return rslt;
208 }
209
210 quit:
211 free(item.key);
212 return (uintptr_t) NULL;
213 }
214
215 const char* nearest_symbol(struct symtab* symtab, uintptr_t offset,
216 uintptr_t* poffset) {
217 int n = 0;
218 if (!symtab) return NULL;
219 for (; n < symtab->num_symbols; n++) {
220 struct elf_symbol* sym = &(symtab->symbols[n]);
221 if (sym->name != NULL &&
222 offset >= sym->offset && offset < sym->offset + sym->size) {
223 if (poffset) *poffset = (offset - sym->offset);
224 return sym->name;
225 }
226 }
227 return NULL;
228 }