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 3632 2018-10-10 21:12:43Z jkoshy $");
40
41 static int
elfscn_cmp(struct _Elf_Scn * s1,struct _Elf_Scn * s2)42 elfscn_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
52 RB_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 */
57 int
_libelf_load_section_headers(Elf * e,void * ehdr)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 if (shoff > e->e_rawsize || \
75 fsz != (EH)->e_shentsize || \
76 shnum > SIZE_MAX / fsz || \
77 fsz * shnum > e->e_rawsize - shoff) { \
78 LIBELF_SET_ERROR(HEADER, 0); \
79 return (0); \
80 } \
81 } while (0)
82
83 ec = e->e_class;
84 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
85 assert(fsz > 0);
86
87 shnum = e->e_u.e_elf.e_nscn;
88
89 if (ec == ELFCLASS32) {
90 eh32 = (Elf32_Ehdr *) ehdr;
91 shoff = (uint64_t) eh32->e_shoff;
92 CHECK_EHDR(e, eh32);
93 } else {
94 eh64 = (Elf64_Ehdr *) ehdr;
95 shoff = eh64->e_shoff;
96 CHECK_EHDR(e, eh64);
97 }
98
99 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
100 _libelf_elfmachine(e));
101
102 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
103 src = e->e_rawfile + shoff;
104
105 /*
106 * If the file is using extended numbering then section #0
107 * would have already been read in.
108 */
109
110 i = 0;
111 if (!RB_EMPTY(&e->e_u.e_elf.e_scn)) {
112 assert(RB_MIN(scntree, &e->e_u.e_elf.e_scn) ==
113 RB_MAX(scntree, &e->e_u.e_elf.e_scn));
114
115 i = 1;
116 src += fsz;
117 }
118
119 for (; i < shnum; i++, src += fsz) {
120 if ((scn = _libelf_allocate_scn(e, i)) == NULL)
121 return (0);
122
123 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
124 src, (size_t) 1, swapbytes);
125
126 if (ec == ELFCLASS32) {
127 scn->s_offset = scn->s_rawoff =
128 scn->s_shdr.s_shdr32.sh_offset;
129 scn->s_size = scn->s_shdr.s_shdr32.sh_size;
130 } else {
131 scn->s_offset = scn->s_rawoff =
132 scn->s_shdr.s_shdr64.sh_offset;
133 scn->s_size = scn->s_shdr.s_shdr64.sh_size;
134 }
135 }
136
137 e->e_flags |= LIBELF_F_SHDRS_LOADED;
138
139 return (1);
140 }
141
142
143 Elf_Scn *
elf_getscn(Elf * e,size_t index)144 elf_getscn(Elf *e, size_t index)
145 {
146 int ec;
147 void *ehdr;
148 Elf_Scn *s;
149
150 if (e == NULL || e->e_kind != ELF_K_ELF ||
151 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
152 LIBELF_SET_ERROR(ARGUMENT, 0);
153 return (NULL);
154 }
155
156 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
157 return (NULL);
158
159 if (e->e_cmd != ELF_C_WRITE &&
160 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
161 _libelf_load_section_headers(e, ehdr) == 0)
162 return (NULL);
163
164 for (s = RB_ROOT(&e->e_u.e_elf.e_scn); s != NULL;) {
165 if (s->s_ndx == index)
166 return (s);
167
168 if (s->s_ndx < index)
169 s = RB_RIGHT(s, s_tree);
170 else
171 s = RB_LEFT(s, s_tree);
172 }
173
174 LIBELF_SET_ERROR(ARGUMENT, 0);
175 return (NULL);
176 }
177
178 size_t
elf_ndxscn(Elf_Scn * s)179 elf_ndxscn(Elf_Scn *s)
180 {
181 if (s == NULL) {
182 LIBELF_SET_ERROR(ARGUMENT, 0);
183 return (SHN_UNDEF);
184 }
185 return (s->s_ndx);
186 }
187
188 Elf_Scn *
elf_newscn(Elf * e)189 elf_newscn(Elf *e)
190 {
191 int ec;
192 void *ehdr;
193 Elf_Scn *scn;
194
195 if (e == NULL || e->e_kind != ELF_K_ELF) {
196 LIBELF_SET_ERROR(ARGUMENT, 0);
197 return (NULL);
198 }
199
200 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
201 LIBELF_SET_ERROR(CLASS, 0);
202 return (NULL);
203 }
204
205 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
206 return (NULL);
207
208 /*
209 * The application may be asking for a new section descriptor
210 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We
211 * need to bring in the existing section information before
212 * appending a new one to the list.
213 *
214 * Per the ELF(3) API, an application is allowed to open a
215 * file using ELF_C_READ, mess with its internal structure and
216 * use elf_update(...,ELF_C_NULL) to compute its new layout.
217 */
218 if (e->e_cmd != ELF_C_WRITE &&
219 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
220 _libelf_load_section_headers(e, ehdr) == 0)
221 return (NULL);
222
223 if (RB_EMPTY(&e->e_u.e_elf.e_scn)) {
224 assert(e->e_u.e_elf.e_nscn == 0);
225 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
226 NULL)
227 return (NULL);
228 e->e_u.e_elf.e_nscn++;
229 }
230
231 assert(e->e_u.e_elf.e_nscn > 0);
232
233 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
234 return (NULL);
235
236 e->e_u.e_elf.e_nscn++;
237
238 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
239
240 return (scn);
241 }
242
243 Elf_Scn *
elf_nextscn(Elf * e,Elf_Scn * s)244 elf_nextscn(Elf *e, Elf_Scn *s)
245 {
246 if (e == NULL || (e->e_kind != ELF_K_ELF) ||
247 (s && s->s_elf != e)) {
248 LIBELF_SET_ERROR(ARGUMENT, 0);
249 return (NULL);
250 }
251
252 return (s == NULL ? elf_getscn(e, (size_t) 1) :
253 RB_NEXT(scntree, &e->e_u.e_elf.e_scn, s));
254 }
255