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