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