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 <sys/cdefs.h>
33__SCCSID("@(#)nlist.c	8.1 (Berkeley) 6/4/93");
34__FBSDID("$FreeBSD$");
35
36#include "namespace.h"
37#include <sys/param.h>
38#include <sys/mman.h>
39#include <sys/stat.h>
40#include <sys/file.h>
41#include <arpa/inet.h>
42
43#include <errno.h>
44#include <a.out.h>
45#include <stdio.h>
46#include <string.h>
47#include <unistd.h>
48#include "un-namespace.h"
49
50#include <machine/elf.h>
51#include <elf-hints.h>
52
53int __fdnlist(int, struct nlist *);
54int __elf_fdnlist(int, struct nlist *);
55int __elf_is_okay__(Elf_Ehdr *);
56
57int
58nlist(const char *name, struct nlist *list)
59{
60	int fd, n;
61
62	fd = _open(name, O_RDONLY | O_CLOEXEC, 0);
63	if (fd < 0)
64		return (-1);
65	n = __fdnlist(fd, list);
66	(void)_close(fd);
67	return (n);
68}
69
70static struct nlist_handlers {
71	int	(*fn)(int fd, struct nlist *list);
72} nlist_fn[] = {
73	{ __elf_fdnlist },
74};
75
76int
77__fdnlist(int fd, struct nlist *list)
78{
79	int n = -1;
80	unsigned int i;
81
82	for (i = 0; i < nitems(nlist_fn); i++) {
83		n = (nlist_fn[i].fn)(fd, list);
84		if (n != -1)
85			break;
86	}
87	return (n);
88}
89
90#define	ISLAST(p)	(p->n_un.n_name == 0 || p->n_un.n_name[0] == 0)
91
92static void elf_sym_to_nlist(struct nlist *, Elf_Sym *, Elf_Shdr *, int);
93
94/*
95 * __elf_is_okay__ - Determine if ehdr really
96 * is ELF and valid for the target platform.
97 *
98 * WARNING:  This is NOT an ELF ABI function and
99 * as such its use should be restricted.
100 */
101int
102__elf_is_okay__(Elf_Ehdr *ehdr)
103{
104	int retval = 0;
105	/*
106	 * We need to check magic, class size, endianess,
107	 * and version before we look at the rest of the
108	 * Elf_Ehdr structure.  These few elements are
109	 * represented in a machine independant fashion.
110	 */
111	if (IS_ELF(*ehdr) &&
112	    ehdr->e_ident[EI_CLASS] == ELF_TARG_CLASS &&
113	    ehdr->e_ident[EI_DATA] == ELF_TARG_DATA &&
114	    ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) {
115
116		/* Now check the machine dependant header */
117		if (ehdr->e_machine == ELF_TARG_MACH &&
118		    ehdr->e_version == ELF_TARG_VER)
119			retval = 1;
120	}
121	return retval;
122}
123
124int
125__elf_fdnlist(int fd, struct nlist *list)
126{
127	struct nlist *p;
128	Elf_Off symoff = 0, symstroff = 0;
129	Elf_Size symsize = 0, symstrsize = 0;
130	Elf_Ssize cc, i;
131	int nent = -1;
132	int errsave;
133	Elf_Sym sbuf[1024];
134	Elf_Sym *s;
135	Elf_Ehdr ehdr;
136	char *strtab = NULL;
137	Elf_Shdr *shdr = NULL;
138	Elf_Size shdr_size;
139	void *base;
140	struct stat st;
141
142	/* Make sure obj is OK */
143	if (lseek(fd, (off_t)0, SEEK_SET) == -1 ||
144	    _read(fd, &ehdr, sizeof(Elf_Ehdr)) != sizeof(Elf_Ehdr) ||
145	    !__elf_is_okay__(&ehdr) ||
146	    _fstat(fd, &st) < 0)
147		return (-1);
148
149	/* calculate section header table size */
150	shdr_size = ehdr.e_shentsize * ehdr.e_shnum;
151
152	/* Make sure it's not too big to mmap */
153	if (shdr_size > SIZE_T_MAX) {
154		errno = EFBIG;
155		return (-1);
156	}
157
158	/* mmap section header table */
159	base = mmap(NULL, (size_t)shdr_size, PROT_READ, MAP_PRIVATE, fd,
160	    (off_t)ehdr.e_shoff);
161	if (base == MAP_FAILED)
162		return (-1);
163	shdr = (Elf_Shdr *)base;
164
165	/*
166	 * Find the symbol table entry and it's corresponding
167	 * string table entry.	Version 1.1 of the ABI states
168	 * that there is only one symbol table but that this
169	 * could change in the future.
170	 */
171	for (i = 0; i < ehdr.e_shnum; i++) {
172		if (shdr[i].sh_type == SHT_SYMTAB) {
173			symoff = shdr[i].sh_offset;
174			symsize = shdr[i].sh_size;
175			symstroff = shdr[shdr[i].sh_link].sh_offset;
176			symstrsize = shdr[shdr[i].sh_link].sh_size;
177			break;
178		}
179	}
180
181	/* Check for files too large to mmap. */
182	if (symstrsize > SIZE_T_MAX) {
183		errno = EFBIG;
184		goto done;
185	}
186	/*
187	 * Map string table into our address space.  This gives us
188	 * an easy way to randomly access all the strings, without
189	 * making the memory allocation permanent as with malloc/free
190	 * (i.e., munmap will return it to the system).
191	 */
192	base = mmap(NULL, (size_t)symstrsize, PROT_READ, MAP_PRIVATE, fd,
193	    (off_t)symstroff);
194	if (base == MAP_FAILED)
195		goto done;
196	strtab = (char *)base;
197
198	/*
199	 * clean out any left-over information for all valid entries.
200	 * Type and value defined to be 0 if not found; historical
201	 * versions cleared other and desc as well.  Also figure out
202	 * the largest string length so don't read any more of the
203	 * string table than we have to.
204	 *
205	 * XXX clearing anything other than n_type and n_value violates
206	 * the semantics given in the man page.
207	 */
208	nent = 0;
209	for (p = list; !ISLAST(p); ++p) {
210		p->n_type = 0;
211		p->n_other = 0;
212		p->n_desc = 0;
213		p->n_value = 0;
214		++nent;
215	}
216
217	/* Don't process any further if object is stripped. */
218	if (symoff == 0)
219		goto done;
220
221	if (lseek(fd, (off_t) symoff, SEEK_SET) == -1) {
222		nent = -1;
223		goto done;
224	}
225
226	while (symsize > 0 && nent > 0) {
227		cc = MIN(symsize, sizeof(sbuf));
228		if (_read(fd, sbuf, cc) != cc)
229			break;
230		symsize -= cc;
231		for (s = sbuf; cc > 0 && nent > 0; ++s, cc -= sizeof(*s)) {
232			char *name;
233			struct nlist *p;
234
235			name = strtab + s->st_name;
236			if (name[0] == '\0')
237				continue;
238			for (p = list; !ISLAST(p); p++) {
239				if ((p->n_un.n_name[0] == '_' &&
240				    strcmp(name, p->n_un.n_name+1) == 0)
241				    || strcmp(name, p->n_un.n_name) == 0) {
242					elf_sym_to_nlist(p, s, shdr,
243					    ehdr.e_shnum);
244					if (--nent <= 0)
245						break;
246				}
247			}
248		}
249	}
250  done:
251	errsave = errno;
252	if (strtab != NULL)
253		munmap(strtab, symstrsize);
254	if (shdr != NULL)
255		munmap(shdr, shdr_size);
256	errno = errsave;
257	return (nent);
258}
259
260/*
261 * Convert an Elf_Sym into an nlist structure.  This fills in only the
262 * n_value and n_type members.
263 */
264static void
265elf_sym_to_nlist(struct nlist *nl, Elf_Sym *s, Elf_Shdr *shdr, int shnum)
266{
267	nl->n_value = s->st_value;
268
269	switch (s->st_shndx) {
270	case SHN_UNDEF:
271	case SHN_COMMON:
272		nl->n_type = N_UNDF;
273		break;
274	case SHN_ABS:
275		nl->n_type = ELF_ST_TYPE(s->st_info) == STT_FILE ?
276		    N_FN : N_ABS;
277		break;
278	default:
279		if (s->st_shndx >= shnum)
280			nl->n_type = N_UNDF;
281		else {
282			Elf_Shdr *sh = shdr + s->st_shndx;
283
284			nl->n_type = sh->sh_type == SHT_PROGBITS ?
285			    (sh->sh_flags & SHF_WRITE ? N_DATA : N_TEXT) :
286			    (sh->sh_type == SHT_NOBITS ? N_BSS : N_UNDF);
287		}
288		break;
289	}
290
291	if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
292	    ELF_ST_BIND(s->st_info) == STB_WEAK)
293		nl->n_type |= N_EXT;
294}
295