xref: /freebsd/lib/libc/gen/nlist.c (revision 4f52dfbb8d6c4d446500c5b097e3806ec219fbd4)
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 #if defined(LIBC_SCCS) && !defined(lint)
33 static char sccsid[] = "@(#)nlist.c	8.1 (Berkeley) 6/4/93";
34 #endif /* LIBC_SCCS and not lint */
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
37 
38 #include "namespace.h"
39 #include <sys/param.h>
40 #include <sys/mman.h>
41 #include <sys/stat.h>
42 #include <sys/file.h>
43 #include <arpa/inet.h>
44 
45 #include <errno.h>
46 #include <a.out.h>
47 #include <stdio.h>
48 #include <string.h>
49 #include <unistd.h>
50 #include "un-namespace.h"
51 
52 /* i386 is the only current FreeBSD architecture that used a.out format. */
53 #ifdef __i386__
54 #define _NLIST_DO_AOUT
55 #endif
56 #define _NLIST_DO_ELF
57 
58 #ifdef _NLIST_DO_ELF
59 #include <machine/elf.h>
60 #include <elf-hints.h>
61 #endif
62 
63 int __fdnlist(int, struct nlist *);
64 int __aout_fdnlist(int, struct nlist *);
65 int __elf_fdnlist(int, struct nlist *);
66 int __elf_is_okay__(Elf_Ehdr *);
67 
68 int
69 nlist(const char *name, struct nlist *list)
70 {
71 	int fd, n;
72 
73 	fd = _open(name, O_RDONLY | O_CLOEXEC, 0);
74 	if (fd < 0)
75 		return (-1);
76 	n = __fdnlist(fd, list);
77 	(void)_close(fd);
78 	return (n);
79 }
80 
81 static struct nlist_handlers {
82 	int	(*fn)(int fd, struct nlist *list);
83 } nlist_fn[] = {
84 #ifdef _NLIST_DO_AOUT
85 	{ __aout_fdnlist },
86 #endif
87 #ifdef _NLIST_DO_ELF
88 	{ __elf_fdnlist },
89 #endif
90 };
91 
92 int
93 __fdnlist(int fd, struct nlist *list)
94 {
95 	int n = -1;
96 	unsigned int i;
97 
98 	for (i = 0; i < nitems(nlist_fn); i++) {
99 		n = (nlist_fn[i].fn)(fd, list);
100 		if (n != -1)
101 			break;
102 	}
103 	return (n);
104 }
105 
106 #define	ISLAST(p)	(p->n_un.n_name == 0 || p->n_un.n_name[0] == 0)
107 
108 #ifdef _NLIST_DO_AOUT
109 int
110 __aout_fdnlist(int fd, struct nlist *list)
111 {
112 	struct nlist *p, *symtab;
113 	caddr_t strtab, a_out_mmap;
114 	off_t stroff, symoff;
115 	u_long symsize;
116 	int nent;
117 	struct exec * exec;
118 	struct stat st;
119 
120 	/* check that file is at least as large as struct exec! */
121 	if ((_fstat(fd, &st) < 0) || (st.st_size < sizeof(struct exec)))
122 		return (-1);
123 
124 	/* Check for files too large to mmap. */
125 	if (st.st_size > SIZE_T_MAX) {
126 		errno = EFBIG;
127 		return (-1);
128 	}
129 
130 	/*
131 	 * Map the whole a.out file into our address space.
132 	 * We then find the string table withing this area.
133 	 * We do not just mmap the string table, as it probably
134 	 * does not start at a page boundary - we save ourselves a
135 	 * lot of nastiness by mmapping the whole file.
136 	 *
137 	 * This gives us an easy way to randomly access all the strings,
138 	 * without making the memory allocation permanent as with
139 	 * malloc/free (i.e., munmap will return it to the system).
140 	 */
141 	a_out_mmap = mmap(NULL, (size_t)st.st_size, PROT_READ, MAP_PRIVATE, fd, (off_t)0);
142 	if (a_out_mmap == MAP_FAILED)
143 		return (-1);
144 
145 	exec = (struct exec *)a_out_mmap;
146 	if (N_BADMAG(*exec)) {
147 		munmap(a_out_mmap, (size_t)st.st_size);
148 		return (-1);
149 	}
150 
151 	symoff = N_SYMOFF(*exec);
152 	symsize = exec->a_syms;
153 	stroff = symoff + symsize;
154 
155 	/* find the string table in our mmapped area */
156 	strtab = a_out_mmap + stroff;
157 	symtab = (struct nlist *)(a_out_mmap + symoff);
158 
159 	/*
160 	 * clean out any left-over information for all valid entries.
161 	 * Type and value defined to be 0 if not found; historical
162 	 * versions cleared other and desc as well.  Also figure out
163 	 * the largest string length so don't read any more of the
164 	 * string table than we have to.
165 	 *
166 	 * XXX clearing anything other than n_type and n_value violates
167 	 * the semantics given in the man page.
168 	 */
169 	nent = 0;
170 	for (p = list; !ISLAST(p); ++p) {
171 		p->n_type = 0;
172 		p->n_other = 0;
173 		p->n_desc = 0;
174 		p->n_value = 0;
175 		++nent;
176 	}
177 
178 	while (symsize > 0) {
179 		int soff;
180 
181 		symsize-= sizeof(struct nlist);
182 		soff = symtab->n_un.n_strx;
183 
184 
185 		if (soff != 0 && (symtab->n_type & N_STAB) == 0)
186 			for (p = list; !ISLAST(p); p++)
187 				if (!strcmp(&strtab[soff], p->n_un.n_name)) {
188 					p->n_value = symtab->n_value;
189 					p->n_type = symtab->n_type;
190 					p->n_desc = symtab->n_desc;
191 					p->n_other = symtab->n_other;
192 					if (--nent <= 0)
193 						break;
194 				}
195 		symtab++;
196 	}
197 	munmap(a_out_mmap, (size_t)st.st_size);
198 	return (nent);
199 }
200 #endif
201 
202 #ifdef _NLIST_DO_ELF
203 static void elf_sym_to_nlist(struct nlist *, Elf_Sym *, Elf_Shdr *, int);
204 
205 /*
206  * __elf_is_okay__ - Determine if ehdr really
207  * is ELF and valid for the target platform.
208  *
209  * WARNING:  This is NOT an ELF ABI function and
210  * as such its use should be restricted.
211  */
212 int
213 __elf_is_okay__(Elf_Ehdr *ehdr)
214 {
215 	int retval = 0;
216 	/*
217 	 * We need to check magic, class size, endianess,
218 	 * and version before we look at the rest of the
219 	 * Elf_Ehdr structure.  These few elements are
220 	 * represented in a machine independant fashion.
221 	 */
222 	if (IS_ELF(*ehdr) &&
223 	    ehdr->e_ident[EI_CLASS] == ELF_TARG_CLASS &&
224 	    ehdr->e_ident[EI_DATA] == ELF_TARG_DATA &&
225 	    ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) {
226 
227 		/* Now check the machine dependant header */
228 		if (ehdr->e_machine == ELF_TARG_MACH &&
229 		    ehdr->e_version == ELF_TARG_VER)
230 			retval = 1;
231 	}
232 	return retval;
233 }
234 
235 int
236 __elf_fdnlist(int fd, struct nlist *list)
237 {
238 	struct nlist *p;
239 	Elf_Off symoff = 0, symstroff = 0;
240 	Elf_Size symsize = 0, symstrsize = 0;
241 	Elf_Ssize cc, i;
242 	int nent = -1;
243 	int errsave;
244 	Elf_Sym sbuf[1024];
245 	Elf_Sym *s;
246 	Elf_Ehdr ehdr;
247 	char *strtab = NULL;
248 	Elf_Shdr *shdr = NULL;
249 	Elf_Size shdr_size;
250 	void *base;
251 	struct stat st;
252 
253 	/* Make sure obj is OK */
254 	if (lseek(fd, (off_t)0, SEEK_SET) == -1 ||
255 	    _read(fd, &ehdr, sizeof(Elf_Ehdr)) != sizeof(Elf_Ehdr) ||
256 	    !__elf_is_okay__(&ehdr) ||
257 	    _fstat(fd, &st) < 0)
258 		return (-1);
259 
260 	/* calculate section header table size */
261 	shdr_size = ehdr.e_shentsize * ehdr.e_shnum;
262 
263 	/* Make sure it's not too big to mmap */
264 	if (shdr_size > SIZE_T_MAX) {
265 		errno = EFBIG;
266 		return (-1);
267 	}
268 
269 	/* mmap section header table */
270 	base = mmap(NULL, (size_t)shdr_size, PROT_READ, MAP_PRIVATE, fd,
271 	    (off_t)ehdr.e_shoff);
272 	if (base == MAP_FAILED)
273 		return (-1);
274 	shdr = (Elf_Shdr *)base;
275 
276 	/*
277 	 * Find the symbol table entry and it's corresponding
278 	 * string table entry.	Version 1.1 of the ABI states
279 	 * that there is only one symbol table but that this
280 	 * could change in the future.
281 	 */
282 	for (i = 0; i < ehdr.e_shnum; i++) {
283 		if (shdr[i].sh_type == SHT_SYMTAB) {
284 			symoff = shdr[i].sh_offset;
285 			symsize = shdr[i].sh_size;
286 			symstroff = shdr[shdr[i].sh_link].sh_offset;
287 			symstrsize = shdr[shdr[i].sh_link].sh_size;
288 			break;
289 		}
290 	}
291 
292 	/* Check for files too large to mmap. */
293 	if (symstrsize > SIZE_T_MAX) {
294 		errno = EFBIG;
295 		goto done;
296 	}
297 	/*
298 	 * Map string table into our address space.  This gives us
299 	 * an easy way to randomly access all the strings, without
300 	 * making the memory allocation permanent as with malloc/free
301 	 * (i.e., munmap will return it to the system).
302 	 */
303 	base = mmap(NULL, (size_t)symstrsize, PROT_READ, MAP_PRIVATE, fd,
304 	    (off_t)symstroff);
305 	if (base == MAP_FAILED)
306 		goto done;
307 	strtab = (char *)base;
308 
309 	/*
310 	 * clean out any left-over information for all valid entries.
311 	 * Type and value defined to be 0 if not found; historical
312 	 * versions cleared other and desc as well.  Also figure out
313 	 * the largest string length so don't read any more of the
314 	 * string table than we have to.
315 	 *
316 	 * XXX clearing anything other than n_type and n_value violates
317 	 * the semantics given in the man page.
318 	 */
319 	nent = 0;
320 	for (p = list; !ISLAST(p); ++p) {
321 		p->n_type = 0;
322 		p->n_other = 0;
323 		p->n_desc = 0;
324 		p->n_value = 0;
325 		++nent;
326 	}
327 
328 	/* Don't process any further if object is stripped. */
329 	if (symoff == 0)
330 		goto done;
331 
332 	if (lseek(fd, (off_t) symoff, SEEK_SET) == -1) {
333 		nent = -1;
334 		goto done;
335 	}
336 
337 	while (symsize > 0 && nent > 0) {
338 		cc = MIN(symsize, sizeof(sbuf));
339 		if (_read(fd, sbuf, cc) != cc)
340 			break;
341 		symsize -= cc;
342 		for (s = sbuf; cc > 0 && nent > 0; ++s, cc -= sizeof(*s)) {
343 			char *name;
344 			struct nlist *p;
345 
346 			name = strtab + s->st_name;
347 			if (name[0] == '\0')
348 				continue;
349 			for (p = list; !ISLAST(p); p++) {
350 				if ((p->n_un.n_name[0] == '_' &&
351 				    strcmp(name, p->n_un.n_name+1) == 0)
352 				    || strcmp(name, p->n_un.n_name) == 0) {
353 					elf_sym_to_nlist(p, s, shdr,
354 					    ehdr.e_shnum);
355 					if (--nent <= 0)
356 						break;
357 				}
358 			}
359 		}
360 	}
361   done:
362 	errsave = errno;
363 	if (strtab != NULL)
364 		munmap(strtab, symstrsize);
365 	if (shdr != NULL)
366 		munmap(shdr, shdr_size);
367 	errno = errsave;
368 	return (nent);
369 }
370 
371 /*
372  * Convert an Elf_Sym into an nlist structure.  This fills in only the
373  * n_value and n_type members.
374  */
375 static void
376 elf_sym_to_nlist(struct nlist *nl, Elf_Sym *s, Elf_Shdr *shdr, int shnum)
377 {
378 	nl->n_value = s->st_value;
379 
380 	switch (s->st_shndx) {
381 	case SHN_UNDEF:
382 	case SHN_COMMON:
383 		nl->n_type = N_UNDF;
384 		break;
385 	case SHN_ABS:
386 		nl->n_type = ELF_ST_TYPE(s->st_info) == STT_FILE ?
387 		    N_FN : N_ABS;
388 		break;
389 	default:
390 		if (s->st_shndx >= shnum)
391 			nl->n_type = N_UNDF;
392 		else {
393 			Elf_Shdr *sh = shdr + s->st_shndx;
394 
395 			nl->n_type = sh->sh_type == SHT_PROGBITS ?
396 			    (sh->sh_flags & SHF_WRITE ? N_DATA : N_TEXT) :
397 			    (sh->sh_type == SHT_NOBITS ? N_BSS : N_UNDF);
398 		}
399 		break;
400 	}
401 
402 	if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
403 	    ELF_ST_BIND(s->st_info) == STB_WEAK)
404 		nl->n_type |= N_EXT;
405 }
406 #endif /* _NLIST_DO_ELF */
407