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,v 1.2 2019/03/19 02:31:35 jsg Exp $");
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	_libelf_translator_function *xlator;
55
56	assert(e != NULL);
57	assert(ehdr != NULL);
58	assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);
59
60#define	CHECK_EHDR(E,EH)	do {				\
61		uintmax_t rawsize = (uintmax_t) e->e_rawsize;	\
62		if (shoff > (uintmax_t) e->e_rawsize ||		\
63		    fsz != (EH)->e_shentsize ||			\
64		    shnum > SIZE_MAX / fsz ||			\
65		    fsz * shnum > 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	    _libelf_elfmachine(e));
89
90	swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
91	src = e->e_rawfile + shoff;
92
93	/*
94	 * If the file is using extended numbering then section #0
95	 * would have already been read in.
96	 */
97
98	i = 0;
99	if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
100		assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) ==
101		    STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next));
102
103		i = 1;
104		src += fsz;
105	}
106
107	for (; i < shnum; i++, src += fsz) {
108		if ((scn = _libelf_allocate_scn(e, i)) == NULL)
109			return (0);
110
111		(*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
112		    src, (size_t) 1, swapbytes);
113
114		if (ec == ELFCLASS32) {
115			scn->s_offset = scn->s_rawoff =
116			    scn->s_shdr.s_shdr32.sh_offset;
117			scn->s_size = scn->s_shdr.s_shdr32.sh_size;
118		} else {
119			scn->s_offset = scn->s_rawoff =
120			    scn->s_shdr.s_shdr64.sh_offset;
121			scn->s_size = scn->s_shdr.s_shdr64.sh_size;
122		}
123	}
124
125	e->e_flags |= LIBELF_F_SHDRS_LOADED;
126
127	return (1);
128}
129
130
131Elf_Scn *
132elf_getscn(Elf *e, size_t index)
133{
134	int ec;
135	void *ehdr;
136	Elf_Scn *s;
137
138	if (e == NULL || e->e_kind != ELF_K_ELF ||
139	    ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
140		LIBELF_SET_ERROR(ARGUMENT, 0);
141		return (NULL);
142	}
143
144	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
145		return (NULL);
146
147	if (e->e_cmd != ELF_C_WRITE &&
148	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
149	    _libelf_load_section_headers(e, ehdr) == 0)
150		return (NULL);
151
152	STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next)
153		if (s->s_ndx == index)
154			return (s);
155
156	LIBELF_SET_ERROR(ARGUMENT, 0);
157	return (NULL);
158}
159
160size_t
161elf_ndxscn(Elf_Scn *s)
162{
163	if (s == NULL) {
164		LIBELF_SET_ERROR(ARGUMENT, 0);
165		return (SHN_UNDEF);
166	}
167	return (s->s_ndx);
168}
169
170Elf_Scn *
171elf_newscn(Elf *e)
172{
173	int ec;
174	void *ehdr;
175	Elf_Scn *scn;
176
177	if (e == NULL || e->e_kind != ELF_K_ELF) {
178		LIBELF_SET_ERROR(ARGUMENT, 0);
179		return (NULL);
180	}
181
182	if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
183		LIBELF_SET_ERROR(CLASS, 0);
184		return (NULL);
185	}
186
187	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
188		return (NULL);
189
190	/*
191	 * The application may be asking for a new section descriptor
192	 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
193	 * need to bring in the existing section information before
194	 * appending a new one to the list.
195	 *
196	 * Per the ELF(3) API, an application is allowed to open a
197	 * file using ELF_C_READ, mess with its internal structure and
198	 * use elf_update(...,ELF_C_NULL) to compute its new layout.
199	 */
200	if (e->e_cmd != ELF_C_WRITE &&
201	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
202	    _libelf_load_section_headers(e, ehdr) == 0)
203		return (NULL);
204
205	if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
206		assert(e->e_u.e_elf.e_nscn == 0);
207		if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
208		    NULL)
209			return (NULL);
210		e->e_u.e_elf.e_nscn++;
211	}
212
213	assert(e->e_u.e_elf.e_nscn > 0);
214
215	if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
216		return (NULL);
217
218	e->e_u.e_elf.e_nscn++;
219
220	(void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
221
222	return (scn);
223}
224
225Elf_Scn *
226elf_nextscn(Elf *e, Elf_Scn *s)
227{
228	if (e == NULL || (e->e_kind != ELF_K_ELF) ||
229	    (s && s->s_elf != e)) {
230		LIBELF_SET_ERROR(ARGUMENT, 0);
231		return (NULL);
232	}
233
234	return (s == NULL ? elf_getscn(e, (size_t) 1) :
235	    STAILQ_NEXT(s, s_next));
236}
237