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
42ELFTC_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 */
49static void *
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
110resourceerror:
111	LIBELF_SET_ERROR(RESOURCE, 0);
112error:
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
123Elf *
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