1 /*	$NetBSD: libelf_open.c,v 1.2 2014/03/09 16:58:04 christos Exp $	*/
2 
3 /*-
4  * Copyright (c) 2006,2008-2011 Joseph Koshy
5  * 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  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #if HAVE_NBTOOL_CONFIG_H
30 # include "nbtool_config.h"
31 #endif
32 
33 #include <sys/types.h>
34 #include <sys/stat.h>
35 
36 #include <assert.h>
37 #include <errno.h>
38 #include <libelf.h>
39 #include <stdlib.h>
40 #include <unistd.h>
41 
42 #include "_libelf.h"
43 
44 #if	ELFTC_HAVE_MMAP
45 #include <sys/mman.h>
46 #endif
47 
48 __RCSID("$NetBSD: libelf_open.c,v 1.2 2014/03/09 16:58:04 christos Exp $");
49 ELFTC_VCSID("Id: libelf_open.c 2932 2013-03-30 01:26:04Z jkoshy ");
50 
51 #define	_LIBELF_INITSIZE	(64*1024)
52 
53 /*
54  * Read from a device file, pipe or socket.
55  */
56 static void *
_libelf_read_special_file(int fd,size_t * fsz)57 _libelf_read_special_file(int fd, size_t *fsz)
58 {
59 	ssize_t readsz;
60 	size_t bufsz, datasz;
61 	unsigned char *buf, *t;
62 
63 	datasz = 0;
64 	readsz = 0;
65 	bufsz = _LIBELF_INITSIZE;
66 	if ((buf = malloc(bufsz)) == NULL)
67 		goto resourceerror;
68 
69 	/*
70 	 * Read data from the file descriptor till we reach EOF, or
71 	 * till an error is encountered.
72 	 */
73 	do {
74 		/* Check if we need to expand the data buffer. */
75 		if (datasz == bufsz) {
76 			bufsz *= 2;
77 			if ((t = realloc(buf, bufsz)) == NULL)
78 				goto resourceerror;
79 			buf = t;
80 		}
81 
82 		do {
83 			readsz = bufsz - datasz;
84 			t = buf + datasz;
85 			if ((readsz = read(fd, t, readsz)) <= 0)
86 				break;
87 			datasz += readsz;
88 		} while (datasz < bufsz);
89 
90 	} while (readsz > 0);
91 
92 	if (readsz < 0) {
93 		LIBELF_SET_ERROR(IO, errno);
94 		goto error;
95 	}
96 
97 	assert(readsz == 0);
98 
99 	/*
100 	 * Free up extra buffer space.
101 	 */
102 	if (bufsz > datasz) {
103 		if (datasz > 0) {
104 			if ((t = realloc(buf, datasz)) == NULL)
105 				goto resourceerror;
106 			buf = t;
107 		} else {	/* Zero bytes read. */
108 			LIBELF_SET_ERROR(ARGUMENT, 0);
109 			free(buf);
110 			buf = NULL;
111 		}
112 	}
113 
114 	*fsz = datasz;
115 	return (buf);
116 
117 resourceerror:
118 	LIBELF_SET_ERROR(RESOURCE, 0);
119 error:
120 	if (buf != NULL)
121 		free(buf);
122 	return (NULL);
123 }
124 
125 /*
126  * Read the contents of the file referenced by the file descriptor
127  * 'fd'.
128  */
129 
130 Elf *
_libelf_open_object(int fd,Elf_Cmd c,int reporterror)131 _libelf_open_object(int fd, Elf_Cmd c, int reporterror)
132 {
133 	Elf *e;
134 	void *m;
135 	mode_t mode;
136 	size_t fsize;
137 	struct stat sb;
138 	unsigned int flags;
139 
140 	assert(c == ELF_C_READ || c == ELF_C_RDWR || c == ELF_C_WRITE);
141 
142 	if (fstat(fd, &sb) < 0) {
143 		LIBELF_SET_ERROR(IO, errno);
144 		return (NULL);
145 	}
146 
147 	mode = sb.st_mode;
148 	fsize = (size_t) sb.st_size;
149 
150 	/*
151 	 * Reject unsupported file types.
152 	 */
153 	if (!S_ISREG(mode) && !S_ISCHR(mode) && !S_ISFIFO(mode) &&
154 	    !S_ISSOCK(mode)) {
155 		LIBELF_SET_ERROR(ARGUMENT, 0);
156 		return (NULL);
157 	}
158 
159 	/*
160 	 * For ELF_C_WRITE mode, allocate and return a descriptor.
161 	 */
162 	if (c == ELF_C_WRITE) {
163 		if ((e = _libelf_allocate_elf()) != NULL) {
164 			_libelf_init_elf(e, ELF_K_ELF);
165 			e->e_byteorder = _libelf_host_byteorder();
166 			e->e_fd = fd;
167 			e->e_cmd = c;
168 			if (!S_ISREG(mode))
169 				e->e_flags |= LIBELF_F_SPECIAL_FILE;
170 		}
171 
172 		return (e);
173 	}
174 
175 
176 	/*
177 	 * ELF_C_READ and ELF_C_RDWR mode.
178 	 */
179 	m = NULL;
180 	flags = 0;
181 	if (S_ISREG(mode)) {
182 
183 		/*
184 		 * Reject zero length files.
185 		 */
186 		if (fsize == 0) {
187 			LIBELF_SET_ERROR(ARGUMENT, 0);
188 			return (NULL);
189 		}
190 
191 #if	ELFTC_HAVE_MMAP
192 		/*
193 		 * Always map regular files in with 'PROT_READ'
194 		 * permissions.
195 		 *
196 		 * For objects opened in ELF_C_RDWR mode, when
197 		 * elf_update(3) is called, we remove this mapping,
198 		 * write file data out using write(2), and map the new
199 		 * contents back.
200 		 */
201 		m = mmap(NULL, fsize, PROT_READ, MAP_PRIVATE, fd, (off_t) 0);
202 
203 		if (m == MAP_FAILED)
204 			m = NULL;
205 		else
206 			flags = LIBELF_F_RAWFILE_MMAP;
207 #endif
208 
209 		/*
210 		 * Fallback to a read() if the call to mmap() failed,
211 		 * or if mmap() is not available.
212 		 */
213 		if (m == NULL) {
214 			if ((m = malloc(fsize)) == NULL) {
215 				LIBELF_SET_ERROR(RESOURCE, 0);
216 				return (NULL);
217 			}
218 
219 			if (read(fd, m, fsize) != (ssize_t) fsize) {
220 				LIBELF_SET_ERROR(IO, errno);
221 				free(m);
222 				return (NULL);
223 			}
224 
225 			flags = LIBELF_F_RAWFILE_MALLOC;
226 		}
227 	} else if ((m = _libelf_read_special_file(fd, &fsize)) != NULL)
228 		flags = LIBELF_F_RAWFILE_MALLOC | LIBELF_F_SPECIAL_FILE;
229 	else
230 		return (NULL);
231 
232 	if ((e = _libelf_memory(m, fsize, reporterror)) == NULL) {
233 		assert((flags & LIBELF_F_RAWFILE_MALLOC) ||
234 		    (flags & LIBELF_F_RAWFILE_MMAP));
235 		if (flags & LIBELF_F_RAWFILE_MALLOC)
236 			free(m);
237 #if	ELFTC_HAVE_MMAP
238 		else
239 			(void) munmap(m, fsize);
240 #endif
241 		return (NULL);
242 	}
243 
244 	/* ar(1) archives aren't supported in RDWR mode. */
245 	if (c == ELF_C_RDWR && e->e_kind == ELF_K_AR) {
246 		(void) elf_end(e);
247 		LIBELF_SET_ERROR(ARGUMENT, 0);
248 		return (NULL);
249 	}
250 
251 	e->e_flags |= flags;
252 	e->e_fd = fd;
253 	e->e_cmd = c;
254 
255 	return (e);
256 }
257