libelf_xlate.c revision 260684 
1/*-
2 * Copyright (c) 2006,2008 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/cdefs.h>
28
29#include <assert.h>
30#include <libelf.h>
31
32#include "_libelf.h"
33
34ELFTC_VCSID("$Id: libelf_xlate.c 2225 2011-11-26 18:55:54Z jkoshy $");
35
36/*
37 * Translate to/from the file representation of ELF objects.
38 *
39 * Translation could potentially involve the following
40 * transformations:
41 *
42 * - an endianness conversion,
43 * - a change of layout, as the file representation of ELF objects
44 *   can differ from their in-memory representation.
45 * - a change in representation due to a layout version change.
46 */
47
48Elf_Data *
49_libelf_xlate(Elf_Data *dst, const Elf_Data *src, unsigned int encoding,
50    int elfclass, int direction)
51{
52	int byteswap;
53	size_t cnt, dsz, fsz, msz;
54	uintptr_t sb, se, db, de;
55
56	if (encoding == ELFDATANONE)
57		encoding = LIBELF_PRIVATE(byteorder);
58
59	if ((encoding != ELFDATA2LSB && encoding != ELFDATA2MSB) ||
60	    dst == NULL || src == NULL || dst == src)	{
61		LIBELF_SET_ERROR(ARGUMENT, 0);
62		return (NULL);
63	}
64
65	assert(elfclass == ELFCLASS32 || elfclass == ELFCLASS64);
66	assert(direction == ELF_TOFILE || direction == ELF_TOMEMORY);
67
68	if (dst->d_version != src->d_version) {
69		LIBELF_SET_ERROR(UNIMPL, 0);
70		return (NULL);
71	}
72
73	if  (src->d_buf == NULL || dst->d_buf == NULL) {
74		LIBELF_SET_ERROR(DATA, 0);
75		return (NULL);
76	}
77
78	if ((int) src->d_type < 0 || src->d_type >= ELF_T_NUM) {
79		LIBELF_SET_ERROR(DATA, 0);
80		return (NULL);
81	}
82
83	if ((fsz = (elfclass == ELFCLASS32 ? elf32_fsize : elf64_fsize)
84	    (src->d_type, (size_t) 1, src->d_version)) == 0)
85		return (NULL);
86
87	msz = _libelf_msize(src->d_type, elfclass, src->d_version);
88
89	assert(msz > 0);
90
91	if (src->d_size % (direction == ELF_TOMEMORY ? fsz : msz)) {
92		LIBELF_SET_ERROR(DATA, 0);
93		return (NULL);
94	}
95
96	/*
97	 * Determine the number of objects that need to be converted, and
98	 * the space required for the converted objects in the destination
99	 * buffer.
100	 */
101	if (direction == ELF_TOMEMORY) {
102		cnt = src->d_size / fsz;
103		dsz = cnt * msz;
104	} else {
105		cnt = src->d_size / msz;
106		dsz = cnt * fsz;
107	}
108
109	if (dst->d_size  <  dsz) {
110		LIBELF_SET_ERROR(DATA, 0);
111		return (NULL);
112	}
113
114	sb = (uintptr_t) src->d_buf;
115	se = sb + src->d_size;
116	db = (uintptr_t) dst->d_buf;
117	de = db + dst->d_size;
118
119	/*
120	 * Check for overlapping buffers.  Note that db == sb is
121	 * allowed.
122	 */
123	if (db != sb && de > sb && se > db) {
124		LIBELF_SET_ERROR(DATA, 0);
125		return (NULL);
126	}
127
128	if ((direction == ELF_TOMEMORY ? db : sb) %
129	    _libelf_malign(src->d_type, elfclass)) {
130		LIBELF_SET_ERROR(DATA, 0);
131		return (NULL);
132	}
133
134	dst->d_type = src->d_type;
135	dst->d_size = dsz;
136
137	byteswap = encoding != LIBELF_PRIVATE(byteorder);
138
139	if (src->d_size == 0 ||
140	    (db == sb && !byteswap && fsz == msz))
141		return (dst);	/* nothing more to do */
142
143	if (!(_libelf_get_translator(src->d_type, direction, elfclass))
144	    (dst->d_buf, dsz, src->d_buf, cnt, byteswap)) {
145		LIBELF_SET_ERROR(DATA, 0);
146		return (NULL);
147	}
148
149	return (dst);
150}
151