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 3712 2019-03-16 22:23:34Z jkoshy $");
40
41static int
42elfscn_cmp(struct _Elf_Scn *s1, struct _Elf_Scn *s2)
43{
44
45	if (s1->s_ndx < s2->s_ndx)
46		return (-1);
47	if (s1->s_ndx > s2->s_ndx)
48		return (1);
49	return (0);
50}
51
52RB_GENERATE(scntree, _Elf_Scn, s_tree, elfscn_cmp);
53
54/*
55 * Load an ELF section table and create a list of Elf_Scn structures.
56 */
57int
58_libelf_load_section_headers(Elf *e, void *ehdr)
59{
60	Elf_Scn *scn;
61	uint64_t shoff;
62	Elf32_Ehdr *eh32;
63	Elf64_Ehdr *eh64;
64	int ec, swapbytes;
65	unsigned char *src;
66	size_t fsz, i, shnum;
67	_libelf_translator_function *xlator;
68
69	assert(e != NULL);
70	assert(ehdr != NULL);
71	assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);
72
73#define	CHECK_EHDR(E,EH)	do {				\
74		uintmax_t rawsize = (uintmax_t) e->e_rawsize;	\
75		if (shoff > (uintmax_t) e->e_rawsize ||		\
76		    fsz != (EH)->e_shentsize ||			\
77		    shnum > SIZE_MAX / fsz ||			\
78		    fsz * shnum > rawsize - shoff) {		\
79			LIBELF_SET_ERROR(HEADER, 0);		\
80			return (0);				\
81		}						\
82	} while (0)
83
84	ec = e->e_class;
85	fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
86	assert(fsz > 0);
87
88	shnum = e->e_u.e_elf.e_nscn;
89
90	if (ec == ELFCLASS32) {
91		eh32 = (Elf32_Ehdr *) ehdr;
92		shoff = (uint64_t) eh32->e_shoff;
93		CHECK_EHDR(e, eh32);
94	} else {
95		eh64 = (Elf64_Ehdr *) ehdr;
96		shoff = eh64->e_shoff;
97		CHECK_EHDR(e, eh64);
98	}
99
100	xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
101	    _libelf_elfmachine(e));
102
103	swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
104	src = e->e_rawfile + shoff;
105
106	/*
107	 * If the file is using extended numbering then section #0
108	 * would have already been read in.
109	 */
110
111	i = 0;
112	if (!RB_EMPTY(&e->e_u.e_elf.e_scn)) {
113		assert(RB_MIN(scntree, &e->e_u.e_elf.e_scn) ==
114		    RB_MAX(scntree, &e->e_u.e_elf.e_scn));
115
116		i = 1;
117		src += fsz;
118	}
119
120	for (; i < shnum; i++, src += fsz) {
121		if ((scn = _libelf_allocate_scn(e, i)) == NULL)
122			return (0);
123
124		(*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
125		    src, (size_t) 1, swapbytes);
126
127		if (ec == ELFCLASS32) {
128			scn->s_offset = scn->s_rawoff =
129			    scn->s_shdr.s_shdr32.sh_offset;
130			scn->s_size = scn->s_shdr.s_shdr32.sh_size;
131		} else {
132			scn->s_offset = scn->s_rawoff =
133			    scn->s_shdr.s_shdr64.sh_offset;
134			scn->s_size = scn->s_shdr.s_shdr64.sh_size;
135		}
136	}
137
138	e->e_flags |= LIBELF_F_SHDRS_LOADED;
139
140	return (1);
141}
142
143
144Elf_Scn *
145elf_getscn(Elf *e, size_t index)
146{
147	int ec;
148	void *ehdr;
149	Elf_Scn *s;
150
151	if (e == NULL || e->e_kind != ELF_K_ELF ||
152	    ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
153		LIBELF_SET_ERROR(ARGUMENT, 0);
154		return (NULL);
155	}
156
157	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
158		return (NULL);
159
160	if (e->e_cmd != ELF_C_WRITE &&
161	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
162	    _libelf_load_section_headers(e, ehdr) == 0)
163		return (NULL);
164
165	for (s = RB_ROOT(&e->e_u.e_elf.e_scn); s != NULL;) {
166		if (s->s_ndx == index)
167			return (s);
168
169		if (s->s_ndx < index)
170			s = RB_RIGHT(s, s_tree);
171		else
172			s = RB_LEFT(s, s_tree);
173	}
174
175	LIBELF_SET_ERROR(ARGUMENT, 0);
176	return (NULL);
177}
178
179size_t
180elf_ndxscn(Elf_Scn *s)
181{
182	if (s == NULL) {
183		LIBELF_SET_ERROR(ARGUMENT, 0);
184		return (SHN_UNDEF);
185	}
186	return (s->s_ndx);
187}
188
189Elf_Scn *
190elf_newscn(Elf *e)
191{
192	int ec;
193	void *ehdr;
194	Elf_Scn *scn;
195
196	if (e == NULL || e->e_kind != ELF_K_ELF) {
197		LIBELF_SET_ERROR(ARGUMENT, 0);
198		return (NULL);
199	}
200
201	if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
202		LIBELF_SET_ERROR(CLASS, 0);
203		return (NULL);
204	}
205
206	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
207		return (NULL);
208
209	/*
210	 * The application may be asking for a new section descriptor
211	 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
212	 * need to bring in the existing section information before
213	 * appending a new one to the list.
214	 *
215	 * Per the ELF(3) API, an application is allowed to open a
216	 * file using ELF_C_READ, mess with its internal structure and
217	 * use elf_update(...,ELF_C_NULL) to compute its new layout.
218	 */
219	if (e->e_cmd != ELF_C_WRITE &&
220	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
221	    _libelf_load_section_headers(e, ehdr) == 0)
222		return (NULL);
223
224	if (RB_EMPTY(&e->e_u.e_elf.e_scn)) {
225		assert(e->e_u.e_elf.e_nscn == 0);
226		if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
227		    NULL)
228			return (NULL);
229		e->e_u.e_elf.e_nscn++;
230	}
231
232	assert(e->e_u.e_elf.e_nscn > 0);
233
234	if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
235		return (NULL);
236
237	e->e_u.e_elf.e_nscn++;
238
239	(void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
240
241	return (scn);
242}
243
244Elf_Scn *
245elf_nextscn(Elf *e, Elf_Scn *s)
246{
247	if (e == NULL || (e->e_kind != ELF_K_ELF) ||
248	    (s && s->s_elf != e)) {
249		LIBELF_SET_ERROR(ARGUMENT, 0);
250		return (NULL);
251	}
252
253	return (s == NULL ? elf_getscn(e, (size_t) 1) :
254	    RB_NEXT(scntree, &e->e_u.e_elf.e_scn, s));
255}
256