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
39 ELFTC_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 */
44 int
_libelf_load_section_headers(Elf * e,void * ehdr)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
131 Elf_Scn *
elf_getscn(Elf * e,size_t index)132 elf_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
160 size_t
elf_ndxscn(Elf_Scn * s)161 elf_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
170 Elf_Scn *
elf_newscn(Elf * e)171 elf_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
225 Elf_Scn *
elf_nextscn(Elf * e,Elf_Scn * s)226 elf_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