libelf_xlate.c revision 280932 
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 <assert.h>
28#include <libelf.h>
29
30#include "_libelf.h"
31
32ELFTC_VCSID("$Id: libelf_xlate.c 3174 2015-03-27 17:13:41Z emaste $");
33
34/*
35 * Translate to/from the file representation of ELF objects.
36 *
37 * Translation could potentially involve the following
38 * transformations:
39 *
40 * - an endianness conversion,
41 * - a change of layout, as the file representation of ELF objects
42 *   can differ from their in-memory representation.
43 * - a change in representation due to a layout version change.
44 */
45
46Elf_Data *
47_libelf_xlate(Elf_Data *dst, const Elf_Data *src, unsigned int encoding,
48    int elfclass, int direction)
49{
50	int byteswap;
51	size_t cnt, dsz, fsz, msz;
52	uintptr_t sb, se, db, de;
53
54	if (encoding == ELFDATANONE)
55		encoding = LIBELF_PRIVATE(byteorder);
56
57	if ((encoding != ELFDATA2LSB && encoding != ELFDATA2MSB) ||
58	    dst == NULL || src == NULL || dst == src)	{
59		LIBELF_SET_ERROR(ARGUMENT, 0);
60		return (NULL);
61	}
62
63	assert(elfclass == ELFCLASS32 || elfclass == ELFCLASS64);
64	assert(direction == ELF_TOFILE || direction == ELF_TOMEMORY);
65
66	if (dst->d_version != src->d_version) {
67		LIBELF_SET_ERROR(UNIMPL, 0);
68		return (NULL);
69	}
70
71	if  (src->d_buf == NULL || dst->d_buf == NULL) {
72		LIBELF_SET_ERROR(DATA, 0);
73		return (NULL);
74	}
75
76	if ((int) src->d_type < 0 || src->d_type >= ELF_T_NUM) {
77		LIBELF_SET_ERROR(DATA, 0);
78		return (NULL);
79	}
80
81	if ((fsz = (elfclass == ELFCLASS32 ? elf32_fsize : elf64_fsize)
82	    (src->d_type, (size_t) 1, src->d_version)) == 0)
83		return (NULL);
84
85	msz = _libelf_msize(src->d_type, elfclass, src->d_version);
86
87	assert(msz > 0);
88
89	if (src->d_size % (direction == ELF_TOMEMORY ? fsz : msz)) {
90		LIBELF_SET_ERROR(DATA, 0);
91		return (NULL);
92	}
93
94	/*
95	 * Determine the number of objects that need to be converted, and
96	 * the space required for the converted objects in the destination
97	 * buffer.
98	 */
99	if (direction == ELF_TOMEMORY) {
100		cnt = (size_t) src->d_size / fsz;
101		dsz = cnt * msz;
102	} else {
103		cnt = (size_t) src->d_size / msz;
104		dsz = cnt * fsz;
105	}
106
107	if (dst->d_size  <  dsz) {
108		LIBELF_SET_ERROR(DATA, 0);
109		return (NULL);
110	}
111
112	sb = (uintptr_t) src->d_buf;
113	se = sb + (size_t) src->d_size;
114	db = (uintptr_t) dst->d_buf;
115	de = db + (size_t) dst->d_size;
116
117	/*
118	 * Check for overlapping buffers.  Note that db == sb is
119	 * allowed.
120	 */
121	if (db != sb && de > sb && se > db) {
122		LIBELF_SET_ERROR(DATA, 0);
123		return (NULL);
124	}
125
126	if ((direction == ELF_TOMEMORY ? db : sb) %
127	    _libelf_malign(src->d_type, elfclass)) {
128		LIBELF_SET_ERROR(DATA, 0);
129		return (NULL);
130	}
131
132	dst->d_type = src->d_type;
133	dst->d_size = dsz;
134
135	byteswap = encoding != LIBELF_PRIVATE(byteorder);
136
137	if (src->d_size == 0 ||
138	    (db == sb && !byteswap && fsz == msz))
139		return (dst);	/* nothing more to do */
140
141	if (!(_libelf_get_translator(src->d_type, direction, elfclass))
142	    (dst->d_buf, dsz, src->d_buf, cnt, byteswap)) {
143		LIBELF_SET_ERROR(DATA, 0);
144		return (NULL);
145	}
146
147	return (dst);
148}
149