xref: /openbsd/usr.sbin/installboot/i386_nlist.c (revision 3a50f0a9)
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