1/*-
2 * Copyright (c) 2006,2008-2010 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/queue.h>
28
29#include <assert.h>
30#include <errno.h>
31#include <gelf.h>
32#include <libelf.h>
33#include <stddef.h>
34#include <stdint.h>
35#include <stdlib.h>
36
37#include "_libelf.h"
38
39ELFTC_VCSID("$Id: elf_scn.c 3177 2015-03-30 18:19:41Z emaste $");
40
41/*
42 * Load an ELF section table and create a list of Elf_Scn structures.
43 */
44int
45_libelf_load_section_headers(Elf *e, void *ehdr)
46{
47	Elf_Scn *scn;
48	uint64_t shoff;
49	Elf32_Ehdr *eh32;
50	Elf64_Ehdr *eh64;
51	int ec, swapbytes;
52	unsigned char *src;
53	size_t fsz, i, shnum;
54	int (*xlator)(unsigned char *_d, size_t _dsz, unsigned char *_s,
55	    size_t _c, int _swap);
56
57	assert(e != NULL);
58	assert(ehdr != NULL);
59	assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);
60
61#define	CHECK_EHDR(E,EH)	do {				\
62		if (shoff > e->e_rawsize ||			\
63		    fsz != (EH)->e_shentsize ||			\
64		    shnum > SIZE_MAX / fsz ||			\
65		    fsz * shnum > e->e_rawsize - shoff) {	\
66			LIBELF_SET_ERROR(HEADER, 0);		\
67			return (0);				\
68		}						\
69	} while (0)
70
71	ec = e->e_class;
72	fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
73	assert(fsz > 0);
74
75	shnum = e->e_u.e_elf.e_nscn;
76
77	if (ec == ELFCLASS32) {
78		eh32 = (Elf32_Ehdr *) ehdr;
79		shoff = (uint64_t) eh32->e_shoff;
80		CHECK_EHDR(e, eh32);
81	} else {
82		eh64 = (Elf64_Ehdr *) ehdr;
83		shoff = eh64->e_shoff;
84		CHECK_EHDR(e, eh64);
85	}
86
87	xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec);
88
89	swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
90	src = e->e_rawfile + shoff;
91
92	/*
93	 * If the file is using extended numbering then section #0
94	 * would have already been read in.
95	 */
96
97	i = 0;
98	if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
99		assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) ==
100		    STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next));
101
102		i = 1;
103		src += fsz;
104	}
105
106	for (; i < shnum; i++, src += fsz) {
107		if ((scn = _libelf_allocate_scn(e, i)) == NULL)
108			return (0);
109
110		(*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
111		    src, (size_t) 1, swapbytes);
112
113		if (ec == ELFCLASS32) {
114			scn->s_offset = scn->s_rawoff =
115			    scn->s_shdr.s_shdr32.sh_offset;
116			scn->s_size = scn->s_shdr.s_shdr32.sh_size;
117		} else {
118			scn->s_offset = scn->s_rawoff =
119			    scn->s_shdr.s_shdr64.sh_offset;
120			scn->s_size = scn->s_shdr.s_shdr64.sh_size;
121		}
122	}
123
124	e->e_flags |= LIBELF_F_SHDRS_LOADED;
125
126	return (1);
127}
128
129
130Elf_Scn *
131elf_getscn(Elf *e, size_t index)
132{
133	int ec;
134	void *ehdr;
135	Elf_Scn *s;
136
137	if (e == NULL || e->e_kind != ELF_K_ELF ||
138	    ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
139		LIBELF_SET_ERROR(ARGUMENT, 0);
140		return (NULL);
141	}
142
143	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
144		return (NULL);
145
146	if (e->e_cmd != ELF_C_WRITE &&
147	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
148	    _libelf_load_section_headers(e, ehdr) == 0)
149		return (NULL);
150
151	STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next)
152		if (s->s_ndx == index)
153			return (s);
154
155	LIBELF_SET_ERROR(ARGUMENT, 0);
156	return (NULL);
157}
158
159size_t
160elf_ndxscn(Elf_Scn *s)
161{
162	if (s == NULL) {
163		LIBELF_SET_ERROR(ARGUMENT, 0);
164		return (SHN_UNDEF);
165	}
166	return (s->s_ndx);
167}
168
169Elf_Scn *
170elf_newscn(Elf *e)
171{
172	int ec;
173	void *ehdr;
174	Elf_Scn *scn;
175
176	if (e == NULL || e->e_kind != ELF_K_ELF) {
177		LIBELF_SET_ERROR(ARGUMENT, 0);
178		return (NULL);
179	}
180
181	if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
182		LIBELF_SET_ERROR(CLASS, 0);
183		return (NULL);
184	}
185
186	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
187		return (NULL);
188
189	/*
190	 * The application may be asking for a new section descriptor
191	 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
192	 * need to bring in the existing section information before
193	 * appending a new one to the list.
194	 *
195	 * Per the ELF(3) API, an application is allowed to open a
196	 * file using ELF_C_READ, mess with its internal structure and
197	 * use elf_update(...,ELF_C_NULL) to compute its new layout.
198	 */
199	if (e->e_cmd != ELF_C_WRITE &&
200	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
201	    _libelf_load_section_headers(e, ehdr) == 0)
202		return (NULL);
203
204	if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
205		assert(e->e_u.e_elf.e_nscn == 0);
206		if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
207		    NULL)
208			return (NULL);
209		e->e_u.e_elf.e_nscn++;
210	}
211
212	assert(e->e_u.e_elf.e_nscn > 0);
213
214	if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
215		return (NULL);
216
217	e->e_u.e_elf.e_nscn++;
218
219	(void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
220
221	return (scn);
222}
223
224Elf_Scn *
225elf_nextscn(Elf *e, Elf_Scn *s)
226{
227	if (e == NULL || (e->e_kind != ELF_K_ELF) ||
228	    (s && s->s_elf != e)) {
229		LIBELF_SET_ERROR(ARGUMENT, 0);
230		return (NULL);
231	}
232
233	return (s == NULL ? elf_getscn(e, (size_t) 1) :
234	    STAILQ_NEXT(s, s_next));
235}
236