xref: /netbsd-src/external/bsd/elftoolchain/dist/libelf/libelf_open.c (revision 5ac3bc719ce6e70593039505b491894133237d12)
1 /*	$NetBSD: libelf_open.c,v 1.5 2024/03/03 17:37:34 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/cdefs.h>
34 #include <sys/types.h>
35 #include <sys/stat.h>
36 
37 #include <assert.h>
38 #include <errno.h>
39 #include <libelf.h>
40 #include <stdlib.h>
41 #include <unistd.h>
42 
43 #include "_libelf.h"
44 
45 #if	ELFTC_HAVE_MMAP
46 #include <sys/mman.h>
47 #endif
48 
49 __RCSID("$NetBSD: libelf_open.c,v 1.5 2024/03/03 17:37:34 christos Exp $");
50 ELFTC_VCSID("Id: libelf_open.c 3977 2022-05-01 06:45:34Z jkoshy");
51 
52 #define	_LIBELF_INITSIZE	(64*1024)
53 
54 /*
55  * Read from a device file, pipe or socket.
56  */
57 static void *
_libelf_read_special_file(int fd,size_t * fsz)58 _libelf_read_special_file(int fd, size_t *fsz)
59 {
60 	ssize_t readsz;
61 	size_t bufsz, datasz;
62 	unsigned char *buf, *t;
63 
64 	datasz = 0;
65 	readsz = 0;
66 	bufsz = _LIBELF_INITSIZE;
67 	if ((buf = malloc(bufsz)) == NULL)
68 		goto resourceerror;
69 
70 	/*
71 	 * Read data from the file descriptor till we reach EOF, or
72 	 * till an error is encountered.
73 	 */
74 	do {
75 		/* Check if we need to expand the data buffer. */
76 		if (datasz == bufsz) {
77 			bufsz *= 2;
78 			if ((t = realloc(buf, bufsz)) == NULL)
79 				goto resourceerror;
80 			buf = t;
81 		}
82 
83 		do {
84 			assert(bufsz - datasz > 0);
85 			t = buf + datasz;
86 			if ((readsz = read(fd, t, bufsz - datasz)) <= 0)
87 				break;
88 			datasz += (size_t) readsz;
89 		} while (datasz < bufsz);
90 
91 	} while (readsz > 0);
92 
93 	if (readsz < 0) {
94 		LIBELF_SET_ERROR(IO, errno);
95 		goto error;
96 	}
97 
98 	assert(readsz == 0);
99 
100 	/*
101 	 * Free up extra buffer space.
102 	 */
103 	if (bufsz > datasz) {
104 		if (datasz > 0) {
105 			if ((t = realloc(buf, datasz)) == NULL)
106 				goto resourceerror;
107 			buf = t;
108 		} else {	/* Zero bytes read. */
109 			LIBELF_SET_ERROR(ARGUMENT, 0);
110 			free(buf);
111 			buf = NULL;
112 		}
113 	}
114 
115 	*fsz = datasz;
116 	return (buf);
117 
118 resourceerror:
119 	LIBELF_SET_ERROR(RESOURCE, 0);
120 error:
121 	if (buf != NULL)
122 		free(buf);
123 	return (NULL);
124 }
125 
126 /*
127  * Read the contents of the file referenced by the file descriptor
128  * 'fd'.
129  */
130 
131 Elf *
_libelf_open_object(int fd,Elf_Cmd c,int reporterror)132 _libelf_open_object(int fd, Elf_Cmd c, int reporterror)
133 {
134 	Elf *e;
135 	void *m;
136 	mode_t mode;
137 	size_t fsize;
138 	struct stat sb;
139 	unsigned int flags;
140 
141 	assert(c == ELF_C_READ || c == ELF_C_RDWR || c == ELF_C_WRITE);
142 
143 	if (fstat(fd, &sb) < 0) {
144 		LIBELF_SET_ERROR(IO, errno);
145 		return (NULL);
146 	}
147 
148 	mode = sb.st_mode;
149 	fsize = (size_t) sb.st_size;
150 
151 	/*
152 	 * Reject unsupported file types.
153 	 */
154 	if (!S_ISREG(mode) && !S_ISCHR(mode) && !S_ISFIFO(mode) &&
155 	    !S_ISSOCK(mode)) {
156 		LIBELF_SET_ERROR(ARGUMENT, 0);
157 		return (NULL);
158 	}
159 
160 	/*
161 	 * For ELF_C_WRITE mode, allocate and return a descriptor.
162 	 */
163 	if (c == ELF_C_WRITE) {
164 		if ((e = _libelf_allocate_elf()) != NULL) {
165 			_libelf_init_elf(e, ELF_K_ELF);
166 			e->e_byteorder = LIBELF_PRIVATE(byteorder);
167 			e->e_fd = fd;
168 			e->e_cmd = c;
169 			if (!S_ISREG(mode))
170 				e->e_flags |= LIBELF_F_SPECIAL_FILE;
171 		}
172 
173 		return (e);
174 	}
175 
176 
177 	/*
178 	 * ELF_C_READ and ELF_C_RDWR mode.
179 	 */
180 	m = NULL;
181 	flags = 0;
182 	if (S_ISREG(mode)) {
183 
184 		/*
185 		 * Reject zero length files.
186 		 */
187 		if (fsize == 0) {
188 			LIBELF_SET_ERROR(ARGUMENT, 0);
189 			return (NULL);
190 		}
191 
192 #if	ELFTC_HAVE_MMAP
193 		/*
194 		 * Always map regular files in with 'PROT_READ'
195 		 * permissions.
196 		 *
197 		 * For objects opened in ELF_C_RDWR mode, when
198 		 * elf_update(3) is called, we remove this mapping,
199 		 * write file data out using write(2), and map the new
200 		 * contents back.
201 		 */
202 		m = mmap(NULL, fsize, PROT_READ, MAP_PRIVATE, fd, (off_t) 0);
203 
204 		if (m == MAP_FAILED)
205 			m = NULL;
206 		else
207 			flags = LIBELF_F_RAWFILE_MMAP;
208 #endif
209 
210 		/*
211 		 * Fallback to a read() if the call to mmap() failed,
212 		 * or if mmap() is not available.
213 		 */
214 		if (m == NULL) {
215 			if ((m = malloc(fsize)) == NULL) {
216 				LIBELF_SET_ERROR(RESOURCE, 0);
217 				return (NULL);
218 			}
219 
220 			if (read(fd, m, fsize) != (ssize_t) fsize) {
221 				LIBELF_SET_ERROR(IO, errno);
222 				free(m);
223 				return (NULL);
224 			}
225 
226 			flags = LIBELF_F_RAWFILE_MALLOC;
227 		}
228 	} else if ((m = _libelf_read_special_file(fd, &fsize)) != NULL)
229 		flags = LIBELF_F_RAWFILE_MALLOC | LIBELF_F_SPECIAL_FILE;
230 	else
231 		return (NULL);
232 
233 	if ((e = _libelf_memory(m, fsize, reporterror)) == NULL) {
234 		assert((flags & LIBELF_F_RAWFILE_MALLOC) ||
235 		    (flags & LIBELF_F_RAWFILE_MMAP));
236 		if (flags & LIBELF_F_RAWFILE_MALLOC)
237 			free(m);
238 #if	ELFTC_HAVE_MMAP
239 		else
240 			(void) munmap(m, fsize);
241 #endif
242 		return (NULL);
243 	}
244 
245 	/* ar(1) archives aren't supported in RDWR mode. */
246 	if (c == ELF_C_RDWR && e->e_kind == ELF_K_AR) {
247 		(void) elf_end(e);
248 		LIBELF_SET_ERROR(ARGUMENT, 0);
249 		return (NULL);
250 	}
251 
252 	e->e_flags |= flags;
253 	e->e_fd = fd;
254 	e->e_cmd = c;
255 
256 	return (e);
257 }
258