1 /* $OpenBSD: i386_nlist.c,v 1.9 2022/12/28 21:30:16 jmc Exp $ */
2 /*
3 * Copyright (c) 1989, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the University nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #define ELFSIZE 32
32
33 #include <sys/types.h>
34 #include <sys/mman.h>
35 #include <sys/stat.h>
36
37 #include <elf.h>
38 #include <errno.h>
39 #include <fcntl.h>
40 #include <nlist.h>
41 #include <stdint.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45
46 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b))
47
48 static int __elf_fdnlist(int, struct nlist *);
49 static int __elf_is_okay__(Elf_Ehdr *ehdr);
50
51 int nlist_elf32(const char *, struct nlist *);
52
53 #define ISLAST(p) (p->n_name == 0 || p->n_name[0] == 0)
54
55 /*
56 * __elf_is_okay__ - Determine if ehdr really
57 * is ELF and valid for the target platform.
58 *
59 * WARNING: This is NOT a ELF ABI function and
60 * as such its use should be restricted.
61 */
62 static int
__elf_is_okay__(Elf_Ehdr * ehdr)63 __elf_is_okay__(Elf_Ehdr *ehdr)
64 {
65 int retval = 0;
66 /*
67 * We need to check magic, class size, endianness,
68 * and version before we look at the rest of the
69 * Elf_Ehdr structure. These few elements are
70 * represented in a machine independent fashion.
71 */
72
73 /*
74 * We are constructing a 32-bit executable. So we can't
75 * use the libc nlist.c, which would be upset. Manually
76 * check for the i386 values for EI_CLASS and e_machine.
77 */
78
79 if (IS_ELF(*ehdr) &&
80 ehdr->e_ident[EI_CLASS] == ELFCLASS32 &&
81 ehdr->e_ident[EI_DATA] == ELF_TARG_DATA &&
82 ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) {
83
84 /* Now check the machine dependent header */
85 if (ehdr->e_machine == EM_386 &&
86 ehdr->e_version == ELF_TARG_VER)
87 retval = 1;
88 }
89
90 return retval;
91 }
92
93 static int
__elf_fdnlist(int fd,struct nlist * list)94 __elf_fdnlist(int fd, struct nlist *list)
95 {
96 struct nlist *p;
97 caddr_t strtab;
98 Elf_Off symoff = 0, symstroff = 0;
99 Elf_Word symsize = 0, symstrsize = 0;
100 Elf_Sword nent, cc, i;
101 Elf_Sym sbuf[1024];
102 Elf_Sym *s;
103 Elf_Ehdr ehdr;
104 Elf_Shdr *shdr = NULL;
105 Elf_Word shdr_size;
106 struct stat st;
107 int usemalloc = 0;
108 size_t left, len;
109
110 /* Make sure obj is OK */
111 if (pread(fd, &ehdr, sizeof(Elf_Ehdr), (off_t)0) != sizeof(Elf_Ehdr) ||
112 !__elf_is_okay__(&ehdr) || fstat(fd, &st) == -1)
113 return (-1);
114
115 /* calculate section header table size */
116 shdr_size = ehdr.e_shentsize * ehdr.e_shnum;
117
118 /* Make sure it's not too big to mmap */
119 if (SIZE_MAX - ehdr.e_shoff < shdr_size ||
120 (S_ISREG(st.st_mode) && ehdr.e_shoff + shdr_size > st.st_size)) {
121 errno = EFBIG;
122 return (-1);
123 }
124
125 /* mmap section header table */
126 shdr = (Elf_Shdr *)mmap(NULL, (size_t)shdr_size, PROT_READ,
127 MAP_SHARED|MAP_FILE, fd, (off_t) ehdr.e_shoff);
128 if (shdr == MAP_FAILED) {
129 usemalloc = 1;
130 if ((shdr = malloc(shdr_size)) == NULL)
131 return (-1);
132
133 if (pread(fd, shdr, shdr_size, (off_t)ehdr.e_shoff) !=
134 shdr_size) {
135 free(shdr);
136 return (-1);
137 }
138 }
139
140 /*
141 * Find the symbol table entry and its corresponding
142 * string table entry. Version 1.1 of the ABI states
143 * that there is only one symbol table but that this
144 * could change in the future.
145 */
146 for (i = 0; i < ehdr.e_shnum; i++) {
147 if (shdr[i].sh_type == SHT_SYMTAB) {
148 if (shdr[i].sh_link >= ehdr.e_shnum)
149 continue;
150 symoff = shdr[i].sh_offset;
151 symsize = shdr[i].sh_size;
152 symstroff = shdr[shdr[i].sh_link].sh_offset;
153 symstrsize = shdr[shdr[i].sh_link].sh_size;
154 break;
155 }
156 }
157
158 /* Flush the section header table */
159 if (usemalloc)
160 free(shdr);
161 else
162 munmap((caddr_t)shdr, shdr_size);
163
164 /*
165 * clean out any left-over information for all valid entries.
166 * Type and value defined to be 0 if not found; historical
167 * versions cleared other and desc as well. Also figure out
168 * the largest string length so don't read any more of the
169 * string table than we have to.
170 *
171 * XXX clearing anything other than n_type and n_value violates
172 * the semantics given in the man page.
173 */
174 nent = 0;
175 for (p = list; !ISLAST(p); ++p) {
176 p->n_type = 0;
177 p->n_other = 0;
178 p->n_desc = 0;
179 p->n_value = 0;
180 ++nent;
181 }
182
183 /* Don't process any further if object is stripped. */
184 /* ELFism - dunno if stripped by looking at header */
185 if (symoff == 0)
186 return nent;
187
188 /* Check for files too large to mmap. */
189 if (SIZE_MAX - symstrsize < symstroff ||
190 (S_ISREG(st.st_mode) && symstrsize + symstroff > st.st_size)) {
191 errno = EFBIG;
192 return (-1);
193 }
194
195 /*
196 * Map string table into our address space. This gives us
197 * an easy way to randomly access all the strings, without
198 * making the memory allocation permanent as with malloc/free
199 * (i.e., munmap will return it to the system).
200 */
201 if (usemalloc) {
202 if ((strtab = malloc(symstrsize)) == NULL)
203 return (-1);
204 if (pread(fd, strtab, symstrsize, (off_t)symstroff) !=
205 symstrsize) {
206 free(strtab);
207 return (-1);
208 }
209 } else {
210 strtab = mmap(NULL, (size_t)symstrsize, PROT_READ,
211 MAP_SHARED|MAP_FILE, fd, (off_t) symstroff);
212 if (strtab == MAP_FAILED)
213 return (-1);
214 }
215
216 while (symsize >= sizeof(Elf_Sym)) {
217 cc = MINIMUM(symsize, sizeof(sbuf));
218 if (pread(fd, sbuf, cc, (off_t)symoff) != cc)
219 break;
220 symsize -= cc;
221 symoff += cc;
222 for (s = sbuf; cc > 0; ++s, cc -= sizeof(*s)) {
223 Elf_Word soff = s->st_name;
224
225 if (soff == 0 || soff >= symstrsize)
226 continue;
227 left = symstrsize - soff;
228
229 for (p = list; !ISLAST(p); p++) {
230 char *sym;
231
232 /*
233 * First we check for the symbol as it was
234 * provided by the user. If that fails
235 * and the first char is an '_', skip over
236 * the '_' and try again.
237 * XXX - What do we do when the user really
238 * wants '_foo' and there are symbols
239 * for both 'foo' and '_foo' in the
240 * table and 'foo' is first?
241 */
242 sym = p->n_name;
243 len = strlen(sym);
244
245 if ((len >= left ||
246 strcmp(&strtab[soff], sym) != 0) &&
247 (sym[0] != '_' || len - 1 >= left ||
248 strcmp(&strtab[soff], sym + 1) != 0))
249 continue;
250
251 p->n_value = s->st_value;
252
253 /* XXX - type conversion */
254 /* is pretty rude. */
255 switch(ELF_ST_TYPE(s->st_info)) {
256 case STT_NOTYPE:
257 switch (s->st_shndx) {
258 case SHN_UNDEF:
259 p->n_type = N_UNDF;
260 break;
261 case SHN_ABS:
262 p->n_type = N_ABS;
263 break;
264 case SHN_COMMON:
265 p->n_type = N_COMM;
266 break;
267 default:
268 p->n_type = N_COMM | N_EXT;
269 break;
270 }
271 break;
272 case STT_OBJECT:
273 p->n_type = N_DATA;
274 break;
275 case STT_FUNC:
276 p->n_type = N_TEXT;
277 break;
278 case STT_FILE:
279 p->n_type = N_FN;
280 break;
281 }
282 if (ELF_ST_BIND(s->st_info) == STB_LOCAL)
283 p->n_type = N_EXT;
284 p->n_desc = 0;
285 p->n_other = 0;
286 if (--nent <= 0)
287 break;
288 }
289 }
290 }
291 if (usemalloc)
292 free(strtab);
293 else
294 munmap(strtab, symstrsize);
295 return (nent);
296 }
297
298 int
nlist_elf32(const char * name,struct nlist * list)299 nlist_elf32(const char *name, struct nlist *list)
300 {
301 int fd, n;
302
303 fd = open(name, O_RDONLY);
304 if (fd == -1)
305 return (-1);
306 n = __elf_fdnlist(fd, list);
307 close(fd);
308
309 return (n);
310 }
311