1 /*-
2 * Copyright (c) 2006,2008 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 <assert.h>
28 #include <gelf.h>
29 #include <libelf.h>
30 #include <stdlib.h>
31
32 #include "_libelf.h"
33
34 ELFTC_VCSID("$Id: libelf_ehdr.c 3732 2019-04-22 11:08:38Z jkoshy $");
35
36 /*
37 * Retrieve counts for sections, phdrs and the section string table index
38 * from section header #0 of the ELF object.
39 */
40 static int
_libelf_load_extended(Elf * e,int ec,uint64_t shoff,uint16_t phnum,uint16_t strndx)41 _libelf_load_extended(Elf *e, int ec, uint64_t shoff, uint16_t phnum,
42 uint16_t strndx)
43 {
44 size_t fsz;
45 Elf_Scn *scn;
46 uint32_t shtype;
47 _libelf_translator_function *xlator;
48
49 assert(RB_EMPTY(&e->e_u.e_elf.e_scn));
50
51 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, 1);
52 assert(fsz > 0);
53
54 if (shoff + fsz < shoff) { /* Numeric overflow. */
55 LIBELF_SET_ERROR(HEADER, 0);
56 return (0);
57 }
58
59 if ((uint64_t) e->e_rawsize < shoff + fsz) {
60 LIBELF_SET_ERROR(HEADER, 0);
61 return (0);
62 }
63
64 if ((scn = _libelf_allocate_scn(e, (size_t) 0)) == NULL)
65 return (0);
66
67 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
68 _libelf_elfmachine(e));
69 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
70 (unsigned char *) e->e_rawfile + shoff, (size_t) 1,
71 e->e_byteorder != LIBELF_PRIVATE(byteorder));
72
73 #define GET_SHDR_MEMBER(M) ((ec == ELFCLASS32) ? scn->s_shdr.s_shdr32.M : \
74 scn->s_shdr.s_shdr64.M)
75
76 if ((shtype = GET_SHDR_MEMBER(sh_type)) != SHT_NULL) {
77 LIBELF_SET_ERROR(SECTION, 0);
78 return (0);
79 }
80
81 e->e_u.e_elf.e_nscn = (size_t) GET_SHDR_MEMBER(sh_size);
82 e->e_u.e_elf.e_nphdr = (phnum != PN_XNUM) ? phnum :
83 GET_SHDR_MEMBER(sh_info);
84 e->e_u.e_elf.e_strndx = (strndx != SHN_XINDEX) ? strndx :
85 GET_SHDR_MEMBER(sh_link);
86 #undef GET_SHDR_MEMBER
87
88 return (1);
89 }
90
91 #define EHDR_INIT(E,SZ) do { \
92 Elf##SZ##_Ehdr *eh = (E); \
93 eh->e_ident[EI_MAG0] = ELFMAG0; \
94 eh->e_ident[EI_MAG1] = ELFMAG1; \
95 eh->e_ident[EI_MAG2] = ELFMAG2; \
96 eh->e_ident[EI_MAG3] = ELFMAG3; \
97 eh->e_ident[EI_CLASS] = ELFCLASS##SZ; \
98 eh->e_ident[EI_DATA] = ELFDATANONE; \
99 eh->e_ident[EI_VERSION] = LIBELF_PRIVATE(version) & 0xFFU; \
100 eh->e_machine = EM_NONE; \
101 eh->e_type = ELF_K_NONE; \
102 eh->e_version = LIBELF_PRIVATE(version); \
103 } while (0)
104
105 void *
_libelf_ehdr(Elf * e,int ec,int allocate)106 _libelf_ehdr(Elf *e, int ec, int allocate)
107 {
108 void *ehdr;
109 size_t fsz, msz;
110 uint16_t phnum, shnum, strndx;
111 uint64_t shoff;
112 int (*xlator)(unsigned char *_d, size_t _dsz, unsigned char *_s,
113 size_t _c, int _swap);
114
115 assert(ec == ELFCLASS32 || ec == ELFCLASS64);
116
117 if (e == NULL || e->e_kind != ELF_K_ELF) {
118 LIBELF_SET_ERROR(ARGUMENT, 0);
119 return (NULL);
120 }
121
122 if (e->e_class != ELFCLASSNONE && e->e_class != ec) {
123 LIBELF_SET_ERROR(CLASS, 0);
124 return (NULL);
125 }
126
127 if (e->e_version != EV_CURRENT) {
128 LIBELF_SET_ERROR(VERSION, 0);
129 return (NULL);
130 }
131
132 if (e->e_class == ELFCLASSNONE)
133 e->e_class = ec;
134
135 if (ec == ELFCLASS32)
136 ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr32;
137 else
138 ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr64;
139
140 if (ehdr != NULL) /* already have a translated ehdr */
141 return (ehdr);
142
143 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
144 assert(fsz > 0);
145
146 if (e->e_cmd != ELF_C_WRITE && e->e_rawsize < (off_t) fsz) {
147 LIBELF_SET_ERROR(HEADER, 0);
148 return (NULL);
149 }
150
151 if ((msz = _libelf_msize(ELF_T_EHDR, ec, EV_CURRENT)) == 0)
152 return (NULL);
153
154 if ((ehdr = calloc((size_t) 1, msz)) == NULL) {
155 LIBELF_SET_ERROR(RESOURCE, 0);
156 return (NULL);
157 }
158
159 if (ec == ELFCLASS32) {
160 e->e_u.e_elf.e_ehdr.e_ehdr32 = ehdr;
161 EHDR_INIT(ehdr,32);
162 } else {
163 e->e_u.e_elf.e_ehdr.e_ehdr64 = ehdr;
164 EHDR_INIT(ehdr,64);
165 }
166
167 if (allocate)
168 e->e_flags |= ELF_F_DIRTY;
169
170 if (e->e_cmd == ELF_C_WRITE)
171 return (ehdr);
172
173 xlator = _libelf_get_translator(ELF_T_EHDR, ELF_TOMEMORY, ec,
174 _libelf_elfmachine(e));
175 (*xlator)((unsigned char*) ehdr, msz, e->e_rawfile, (size_t) 1,
176 e->e_byteorder != LIBELF_PRIVATE(byteorder));
177
178 if (ec == ELFCLASS32) {
179 phnum = ((Elf32_Ehdr *) ehdr)->e_phnum;
180 shnum = ((Elf32_Ehdr *) ehdr)->e_shnum;
181 shoff = ((Elf32_Ehdr *) ehdr)->e_shoff;
182 strndx = ((Elf32_Ehdr *) ehdr)->e_shstrndx;
183 } else {
184 phnum = ((Elf64_Ehdr *) ehdr)->e_phnum;
185 shnum = ((Elf64_Ehdr *) ehdr)->e_shnum;
186 shoff = ((Elf64_Ehdr *) ehdr)->e_shoff;
187 strndx = ((Elf64_Ehdr *) ehdr)->e_shstrndx;
188 }
189
190 if (shnum >= SHN_LORESERVE ||
191 (shoff == 0LL && (shnum != 0 || phnum == PN_XNUM ||
192 strndx == SHN_XINDEX))) {
193 LIBELF_SET_ERROR(HEADER, 0);
194 return (NULL);
195 }
196
197 /*
198 * If extended numbering is being used, read the correct
199 * number of sections and program header entries.
200 */
201 if ((shnum == 0 && shoff != 0) || phnum == PN_XNUM || strndx == SHN_XINDEX) {
202 if (_libelf_load_extended(e, ec, shoff, phnum, strndx) == 0)
203 return (NULL);
204 } else {
205 /* not using extended numbering */
206 e->e_u.e_elf.e_nphdr = phnum;
207 e->e_u.e_elf.e_nscn = shnum;
208 e->e_u.e_elf.e_strndx = strndx;
209 }
210
211 return (ehdr);
212 }
213