1 /* $NetBSD: libelf_ehdr.c,v 1.5 2024/03/03 17:37:34 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2006,2008 Joseph Koshy
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #if HAVE_NBTOOL_CONFIG_H
30 # include "nbtool_config.h"
31 #endif
32
33 #include <sys/cdefs.h>
34
35 #include <assert.h>
36 #include <gelf.h>
37 #include <libelf.h>
38 #include <stdlib.h>
39
40 #include "_libelf.h"
41
42 __RCSID("$NetBSD: libelf_ehdr.c,v 1.5 2024/03/03 17:37:34 christos Exp $");
43 ELFTC_VCSID("Id: libelf_ehdr.c 3977 2022-05-01 06:45:34Z jkoshy");
44
45 /*
46 * Retrieve counts for sections, phdrs and the section string table index
47 * from section header #0 of the ELF object.
48 */
49 static int
_libelf_load_extended(Elf * e,int ec,uint64_t shoff,uint16_t phnum,uint16_t strndx)50 _libelf_load_extended(Elf *e, int ec, uint64_t shoff, uint16_t phnum,
51 uint16_t strndx)
52 {
53 size_t fsz;
54 Elf_Scn *scn;
55 uint32_t shtype;
56 _libelf_translator_function *xlator;
57
58 assert(STAILQ_EMPTY(&e->e_u.e_elf.e_scn));
59
60 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, 1);
61 assert(fsz > 0);
62
63 if (shoff + fsz < shoff) { /* Numeric overflow. */
64 LIBELF_SET_ERROR(HEADER, 0);
65 return (0);
66 }
67
68 if ((uint64_t) e->e_rawsize < shoff + fsz) {
69 LIBELF_SET_ERROR(HEADER, 0);
70 return (0);
71 }
72
73 if ((scn = _libelf_allocate_scn(e, (size_t) 0)) == NULL)
74 return (0);
75
76 if (shoff > SSIZE_MAX) {
77 LIBELF_SET_ERROR(HEADER, 0);
78 return (0);
79 }
80
81 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
82 _libelf_elfmachine(e));
83 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
84 (unsigned char *) e->e_rawfile + shoff, (size_t) 1,
85 e->e_byteorder != LIBELF_PRIVATE(byteorder));
86
87 #define GET_SHDR_MEMBER(M) ((ec == ELFCLASS32) ? scn->s_shdr.s_shdr32.M : \
88 scn->s_shdr.s_shdr64.M)
89
90 if (GET_SHDR_MEMBER(sh_size) > UINT_MAX) {
91 LIBELF_SET_ERROR(HEADER, 0);
92 return (0);
93 }
94
95 if ((shtype = GET_SHDR_MEMBER(sh_type)) != SHT_NULL) {
96 LIBELF_SET_ERROR(SECTION, 0);
97 return (0);
98 }
99
100 e->e_u.e_elf.e_nscn = (size_t) GET_SHDR_MEMBER(sh_size);
101 e->e_u.e_elf.e_nphdr = (phnum != PN_XNUM) ? phnum :
102 GET_SHDR_MEMBER(sh_info);
103 e->e_u.e_elf.e_strndx = (strndx != SHN_XINDEX) ? strndx :
104 GET_SHDR_MEMBER(sh_link);
105 #undef GET_SHDR_MEMBER
106
107 return (1);
108 }
109
110 #define EHDR_INIT(E,SZ) do { \
111 Elf##SZ##_Ehdr *eh = (E); \
112 eh->e_ident[EI_MAG0] = ELFMAG0; \
113 eh->e_ident[EI_MAG1] = ELFMAG1; \
114 eh->e_ident[EI_MAG2] = ELFMAG2; \
115 eh->e_ident[EI_MAG3] = ELFMAG3; \
116 eh->e_ident[EI_CLASS] = ELFCLASS##SZ; \
117 eh->e_ident[EI_DATA] = ELFDATANONE; \
118 eh->e_ident[EI_VERSION] = LIBELF_PRIVATE(version) & 0xFFU; \
119 eh->e_machine = EM_NONE; \
120 eh->e_type = ELF_K_NONE; \
121 eh->e_version = LIBELF_PRIVATE(version); \
122 } while (/* CONSTCOND */ 0)
123
124 void *
_libelf_ehdr(Elf * e,int ec,int allocate)125 _libelf_ehdr(Elf *e, int ec, int allocate)
126 {
127 void *ehdr;
128 size_t fsz, msz;
129 uint16_t phnum, shnum, strndx;
130 uint64_t shoff;
131 int (*xlator)(unsigned char *_d, size_t _dsz, unsigned char *_s,
132 size_t _c, int _swap);
133
134 assert(ec == ELFCLASS32 || ec == ELFCLASS64);
135
136 if (e == NULL || e->e_kind != ELF_K_ELF) {
137 LIBELF_SET_ERROR(ARGUMENT, 0);
138 return (NULL);
139 }
140
141 if (e->e_class != ELFCLASSNONE && e->e_class != ec) {
142 LIBELF_SET_ERROR(CLASS, 0);
143 return (NULL);
144 }
145
146 if (e->e_version != EV_CURRENT) {
147 LIBELF_SET_ERROR(VERSION, 0);
148 return (NULL);
149 }
150
151 if (e->e_class == ELFCLASSNONE)
152 e->e_class = ec;
153
154 if (ec == ELFCLASS32)
155 ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr32;
156 else
157 ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr64;
158
159 if (ehdr != NULL) /* already have a translated ehdr */
160 return (ehdr);
161
162 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
163 assert(fsz > 0);
164
165 if (e->e_cmd != ELF_C_WRITE && e->e_rawsize < (off_t) fsz) {
166 LIBELF_SET_ERROR(HEADER, 0);
167 return (NULL);
168 }
169
170 if ((msz = _libelf_msize(ELF_T_EHDR, ec, EV_CURRENT)) == 0)
171 return (NULL);
172
173 if ((ehdr = calloc((size_t) 1, msz)) == NULL) {
174 LIBELF_SET_ERROR(RESOURCE, 0);
175 return (NULL);
176 }
177
178 if (ec == ELFCLASS32) {
179 e->e_u.e_elf.e_ehdr.e_ehdr32 = ehdr;
180 EHDR_INIT(ehdr,32);
181 } else {
182 e->e_u.e_elf.e_ehdr.e_ehdr64 = ehdr;
183 EHDR_INIT(ehdr,64);
184 }
185
186 if (allocate)
187 e->e_flags |= ELF_F_DIRTY;
188
189 if (e->e_cmd == ELF_C_WRITE)
190 return (ehdr);
191
192 xlator = _libelf_get_translator(ELF_T_EHDR, ELF_TOMEMORY, ec,
193 _libelf_elfmachine(e));
194 (*xlator)((unsigned char*) ehdr, msz, e->e_rawfile, (size_t) 1,
195 e->e_byteorder != LIBELF_PRIVATE(byteorder));
196
197 if (ec == ELFCLASS32) {
198 phnum = ((Elf32_Ehdr *) ehdr)->e_phnum;
199 shnum = ((Elf32_Ehdr *) ehdr)->e_shnum;
200 shoff = ((Elf32_Ehdr *) ehdr)->e_shoff;
201 strndx = ((Elf32_Ehdr *) ehdr)->e_shstrndx;
202 } else {
203 phnum = ((Elf64_Ehdr *) ehdr)->e_phnum;
204 shnum = ((Elf64_Ehdr *) ehdr)->e_shnum;
205 shoff = ((Elf64_Ehdr *) ehdr)->e_shoff;
206 strndx = ((Elf64_Ehdr *) ehdr)->e_shstrndx;
207 }
208
209 if (shnum >= SHN_LORESERVE ||
210 (shoff == 0LL && (shnum != 0 || phnum == PN_XNUM ||
211 strndx == SHN_XINDEX))) {
212 LIBELF_SET_ERROR(HEADER, 0);
213 return (NULL);
214 }
215
216 /*
217 * If extended numbering is being used, read the correct
218 * number of sections and program header entries.
219 */
220 if ((shnum == 0 && shoff != 0) || phnum == PN_XNUM || strndx == SHN_XINDEX) {
221 if (_libelf_load_extended(e, ec, shoff, phnum, strndx) == 0)
222 return (NULL);
223 } else {
224 /* not using extended numbering */
225 e->e_u.e_elf.e_nphdr = phnum;
226 e->e_u.e_elf.e_nscn = shnum;
227 e->e_u.e_elf.e_strndx = strndx;
228 }
229
230 return (ehdr);
231 }
232