1 /*-
2 * Copyright (c) 2006,2008-2011 Joseph Koshy
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/types.h>
28 #include <sys/stat.h>
29
30 #include <assert.h>
31 #include <errno.h>
32 #include <libelf.h>
33 #include <stdlib.h>
34 #include <unistd.h>
35
36 #include "_libelf.h"
37
38 #if ELFTC_HAVE_MMAP
39 #include <sys/mman.h>
40 #endif
41
42 ELFTC_VCSID("$Id: libelf_open.c 3007 2014-03-22 08:10:14Z jkoshy $");
43
44 #define _LIBELF_INITSIZE (64*1024)
45
46 /*
47 * Read from a device file, pipe or socket.
48 */
49 static void *
_libelf_read_special_file(int fd,size_t * fsz)50 _libelf_read_special_file(int fd, size_t *fsz)
51 {
52 ssize_t readsz;
53 size_t bufsz, datasz;
54 unsigned char *buf, *t;
55
56 datasz = 0;
57 readsz = 0;
58 bufsz = _LIBELF_INITSIZE;
59 if ((buf = malloc(bufsz)) == NULL)
60 goto resourceerror;
61
62 /*
63 * Read data from the file descriptor till we reach EOF, or
64 * till an error is encountered.
65 */
66 do {
67 /* Check if we need to expand the data buffer. */
68 if (datasz == bufsz) {
69 bufsz *= 2;
70 if ((t = realloc(buf, bufsz)) == NULL)
71 goto resourceerror;
72 buf = t;
73 }
74
75 do {
76 assert(bufsz - datasz > 0);
77 t = buf + datasz;
78 if ((readsz = read(fd, t, bufsz - datasz)) <= 0)
79 break;
80 datasz += (size_t) readsz;
81 } while (datasz < bufsz);
82
83 } while (readsz > 0);
84
85 if (readsz < 0) {
86 LIBELF_SET_ERROR(IO, errno);
87 goto error;
88 }
89
90 assert(readsz == 0);
91
92 /*
93 * Free up extra buffer space.
94 */
95 if (bufsz > datasz) {
96 if (datasz > 0) {
97 if ((t = realloc(buf, datasz)) == NULL)
98 goto resourceerror;
99 buf = t;
100 } else { /* Zero bytes read. */
101 LIBELF_SET_ERROR(ARGUMENT, 0);
102 free(buf);
103 buf = NULL;
104 }
105 }
106
107 *fsz = datasz;
108 return (buf);
109
110 resourceerror:
111 LIBELF_SET_ERROR(RESOURCE, 0);
112 error:
113 if (buf != NULL)
114 free(buf);
115 return (NULL);
116 }
117
118 /*
119 * Read the contents of the file referenced by the file descriptor
120 * 'fd'.
121 */
122
123 Elf *
_libelf_open_object(int fd,Elf_Cmd c,int reporterror)124 _libelf_open_object(int fd, Elf_Cmd c, int reporterror)
125 {
126 Elf *e;
127 void *m;
128 mode_t mode;
129 size_t fsize;
130 struct stat sb;
131 unsigned int flags;
132
133 assert(c == ELF_C_READ || c == ELF_C_RDWR || c == ELF_C_WRITE);
134
135 if (fstat(fd, &sb) < 0) {
136 LIBELF_SET_ERROR(IO, errno);
137 return (NULL);
138 }
139
140 mode = sb.st_mode;
141 fsize = (size_t) sb.st_size;
142
143 /*
144 * Reject unsupported file types.
145 */
146 if (!S_ISREG(mode) && !S_ISCHR(mode) && !S_ISFIFO(mode) &&
147 !S_ISSOCK(mode)) {
148 LIBELF_SET_ERROR(ARGUMENT, 0);
149 return (NULL);
150 }
151
152 /*
153 * For ELF_C_WRITE mode, allocate and return a descriptor.
154 */
155 if (c == ELF_C_WRITE) {
156 if ((e = _libelf_allocate_elf()) != NULL) {
157 _libelf_init_elf(e, ELF_K_ELF);
158 e->e_byteorder = LIBELF_PRIVATE(byteorder);
159 e->e_fd = fd;
160 e->e_cmd = c;
161 if (!S_ISREG(mode))
162 e->e_flags |= LIBELF_F_SPECIAL_FILE;
163 }
164
165 return (e);
166 }
167
168
169 /*
170 * ELF_C_READ and ELF_C_RDWR mode.
171 */
172 m = NULL;
173 flags = 0;
174 if (S_ISREG(mode)) {
175
176 /*
177 * Reject zero length files.
178 */
179 if (fsize == 0) {
180 LIBELF_SET_ERROR(ARGUMENT, 0);
181 return (NULL);
182 }
183
184 #if ELFTC_HAVE_MMAP
185 /*
186 * Always map regular files in with 'PROT_READ'
187 * permissions.
188 *
189 * For objects opened in ELF_C_RDWR mode, when
190 * elf_update(3) is called, we remove this mapping,
191 * write file data out using write(2), and map the new
192 * contents back.
193 */
194 m = mmap(NULL, fsize, PROT_READ, MAP_PRIVATE, fd, (off_t) 0);
195
196 if (m == MAP_FAILED)
197 m = NULL;
198 else
199 flags = LIBELF_F_RAWFILE_MMAP;
200 #endif
201
202 /*
203 * Fallback to a read() if the call to mmap() failed,
204 * or if mmap() is not available.
205 */
206 if (m == NULL) {
207 if ((m = malloc(fsize)) == NULL) {
208 LIBELF_SET_ERROR(RESOURCE, 0);
209 return (NULL);
210 }
211
212 if (read(fd, m, fsize) != (ssize_t) fsize) {
213 LIBELF_SET_ERROR(IO, errno);
214 free(m);
215 return (NULL);
216 }
217
218 flags = LIBELF_F_RAWFILE_MALLOC;
219 }
220 } else if ((m = _libelf_read_special_file(fd, &fsize)) != NULL)
221 flags = LIBELF_F_RAWFILE_MALLOC | LIBELF_F_SPECIAL_FILE;
222 else
223 return (NULL);
224
225 if ((e = _libelf_memory(m, fsize, reporterror)) == NULL) {
226 assert((flags & LIBELF_F_RAWFILE_MALLOC) ||
227 (flags & LIBELF_F_RAWFILE_MMAP));
228 if (flags & LIBELF_F_RAWFILE_MALLOC)
229 free(m);
230 #if ELFTC_HAVE_MMAP
231 else
232 (void) munmap(m, fsize);
233 #endif
234 return (NULL);
235 }
236
237 /* ar(1) archives aren't supported in RDWR mode. */
238 if (c == ELF_C_RDWR && e->e_kind == ELF_K_AR) {
239 (void) elf_end(e);
240 LIBELF_SET_ERROR(ARGUMENT, 0);
241 return (NULL);
242 }
243
244 e->e_flags |= flags;
245 e->e_fd = fd;
246 e->e_cmd = c;
247
248 return (e);
249 }
250