1 /* Create an ELF file with all the DT_* flags set.
2 Copyright (C) 2011, 2016 Red Hat, Inc.
3 This file is part of elfutils.
4 Written by Marek Polacek <mpolacek@redhat.com>, 2011.
5
6 This file is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
10
11 elfutils is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18
19 #ifdef HAVE_CONFIG_H
20 # include <config.h>
21 #endif
22
23 #include ELFUTILS_HEADER(dwelf)
24 #include <elf.h>
25 #include <gelf.h>
26 #include <fcntl.h>
27 #include <libelf.h>
28 #include <stdio.h>
29 #include <stdio_ext.h>
30 #include <stdint.h>
31 #include <stdbool.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <unistd.h>
35 #include "system.h"
36
37
38 int
main(void)39 main (void)
40 {
41 static const char fname[] = "testfile-alldts";
42 Dwelf_Strtab *shst;
43 Dwelf_Strent *dynscn;
44 Dwelf_Strent *shstrtabse;
45 const Elf32_Sword dtflags[] =
46 {
47 DT_NULL, DT_NEEDED, DT_PLTRELSZ, DT_PLTGOT,
48 DT_HASH, DT_STRTAB, DT_SYMTAB, DT_RELA,
49 DT_RELASZ, DT_RELAENT, DT_STRSZ, DT_SYMENT,
50 DT_INIT, DT_FINI, DT_SONAME, DT_RPATH,
51 DT_SYMBOLIC, DT_REL, DT_RELSZ, DT_RELENT,
52 DT_PLTREL, DT_DEBUG, DT_TEXTREL, DT_JMPREL,
53 DT_BIND_NOW, DT_INIT_ARRAY, DT_FINI_ARRAY,
54 DT_INIT_ARRAYSZ, DT_FINI_ARRAYSZ, DT_RUNPATH,
55 DT_FLAGS, DT_ENCODING, DT_PREINIT_ARRAY,
56 DT_PREINIT_ARRAYSZ, DT_VERSYM, DT_GNU_PRELINKED,
57 DT_GNU_CONFLICTSZ, DT_GNU_LIBLISTSZ, DT_CHECKSUM,
58 DT_PLTPADSZ, DT_MOVEENT, DT_MOVESZ, DT_FEATURE_1,
59 DT_POSFLAG_1, DT_SYMINSZ, DT_SYMINENT, DT_GNU_HASH,
60 DT_TLSDESC_PLT, DT_TLSDESC_GOT, DT_GNU_CONFLICT,
61 DT_GNU_LIBLIST, DT_CONFIG, DT_DEPAUDIT, DT_AUDIT,
62 DT_PLTPAD, DT_MOVETAB, DT_SYMINFO, DT_RELACOUNT,
63 DT_RELCOUNT, DT_FLAGS_1, DT_VERDEF, DT_VERDEFNUM,
64 DT_VERNEED, DT_VERNEEDNUM, DT_AUXILIARY, DT_FILTER
65 };
66 const int ndtflags = sizeof (dtflags) / sizeof (dtflags[0]);
67
68 /* We use no threads here which can interfere with handling a stream. */
69 (void) __fsetlocking (stdout, FSETLOCKING_BYCALLER);
70
71 /* Open the file. */
72 int fd = open (fname, O_RDWR | O_CREAT | O_TRUNC, DEFFILEMODE);
73 if (fd == -1)
74 {
75 printf ("cannot open `%s': %m\n", fname);
76 return 1;
77 }
78
79 /* Tell the library which version are we expecting. */
80 elf_version (EV_CURRENT);
81
82 /* Create an ELF descriptor. */
83 Elf *elf = elf_begin (fd, ELF_C_WRITE, NULL);
84 if (elf == NULL)
85 {
86 printf ("cannot create ELF descriptor: %s\n", elf_errmsg (-1));
87 return 1;
88 }
89
90 /* Create an ELF header. */
91 Elf32_Ehdr *ehdr = elf32_newehdr (elf);
92 if (ehdr == NULL)
93 {
94 printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
95 return 1;
96 }
97
98 ehdr->e_ident[0] = 42;
99 ehdr->e_ident[5] = 1;
100 ehdr->e_ident[6] = 2;
101 ehdr->e_type = ET_EXEC;
102 ehdr->e_machine = EM_386;
103 ehdr->e_version = 1;
104 ehdr->e_ehsize = 1;
105 ehdr->e_shnum = 3;
106
107 elf_flagehdr (elf, ELF_C_SET, ELF_F_DIRTY);
108
109 /* Create the program headers. */
110 Elf32_Phdr *phdr = elf32_newphdr (elf, 2);
111 if (phdr == NULL)
112 {
113 printf ("cannot create program headers: %s\n", elf_errmsg (-1));
114 return 1;
115 }
116
117 phdr[0].p_type = PT_PHDR;
118 phdr[1].p_type = PT_DYNAMIC;
119
120 elf_flagphdr (elf, ELF_C_SET, ELF_F_DIRTY);
121 shst = dwelf_strtab_init (true);
122
123 /* Create the .dynamic section. */
124 Elf_Scn *scn = elf_newscn (elf);
125 if (scn == NULL)
126 {
127 printf ("cannot create DYNAMIC section: %s\n", elf_errmsg (-1));
128 return 1;
129 }
130
131 Elf32_Shdr *shdr = elf32_getshdr (scn);
132 if (shdr == NULL)
133 {
134 printf ("cannot get header for DYNAMIC section: %s\n", elf_errmsg (-1));
135 return 1;
136 }
137
138 dynscn = dwelf_strtab_add (shst, ".dynamic");
139
140 /* We'll need to know the section offset. But this will be set up
141 by elf_update later, so for now just store the address. */
142 const Elf32_Off *const dynscn_offset = &shdr->sh_offset;
143 shdr->sh_type = SHT_DYNAMIC;
144 shdr->sh_flags = SHF_ALLOC | SHF_WRITE;
145 shdr->sh_link = SHN_UNDEF;
146 shdr->sh_info = SHN_UNDEF;
147 /* This section will start here. */
148 shdr->sh_addr = 0x1a0;
149
150 /* Create new section data. */
151 Elf_Data *data = elf_newdata (scn);
152 if (data == NULL)
153 {
154 printf ("cannot create data for DYNAMIC section: %s\n", elf_errmsg (-1));
155 return 1;
156 }
157
158 /* Allocate memory for all the .dynamic entries. */
159 Elf32_Dyn *dyn = malloc (ndtflags * sizeof (Elf32_Dyn));
160 if (dyn == NULL)
161 {
162 printf ("malloc failed: %m\n");
163 return 1;
164 }
165
166 /* Now write all the DT_* flags. */
167 for (int i = 0; i < ndtflags; ++i)
168 {
169 dyn[i].d_tag = dtflags[i];
170 dyn[i].d_un.d_val = 0xdeadbeef;
171 }
172
173 /* Set the pointer to allocated memory. */
174 data->d_buf = dyn;
175 data->d_type = ELF_T_DYN;
176 data->d_version = EV_CURRENT;
177 data->d_size = ndtflags * sizeof (Elf32_Dyn);
178 data->d_align = 0x8;
179
180 /* Create .shstrtab section. */
181 scn = elf_newscn (elf);
182 if (scn == NULL)
183 {
184 printf ("cannot create SHSTRTAB section: %s\n", elf_errmsg (-1));
185 return 1;
186 }
187
188 shdr = elf32_getshdr (scn);
189 if (shdr == NULL)
190 {
191 printf ("cannot get header for SHSTRTAB section: %s\n", elf_errmsg (-1));
192 return 1;
193 }
194
195 shstrtabse = dwelf_strtab_add (shst, ".shstrtab");
196
197 shdr->sh_type = SHT_STRTAB;
198 shdr->sh_flags = 0;
199 shdr->sh_addr = 0;
200 shdr->sh_link = SHN_UNDEF;
201 shdr->sh_info = SHN_UNDEF;
202 shdr->sh_entsize = 1;
203
204 /* We have to store the section index in the ELF header. */
205 ehdr->e_shstrndx = elf_ndxscn (scn);
206
207 data = elf_newdata (scn);
208 if (data == NULL)
209 {
210 printf ("cannot create data SHSTRTAB section: %s\n", elf_errmsg (-1));
211 return 1;
212 }
213
214 /* No more sections, finalize the section header string table. */
215 dwelf_strtab_finalize (shst, data);
216
217 elf32_getshdr (elf_getscn (elf, 1))->sh_name = dwelf_strent_off (dynscn);
218 shdr->sh_name = dwelf_strent_off (shstrtabse);
219
220 /* Let the library compute the internal structure information. */
221 if (elf_update (elf, ELF_C_NULL) < 0)
222 {
223 printf ("failure in elf_update(NULL): %s\n", elf_errmsg (-1));
224 return 1;
225 }
226
227 ehdr = elf32_getehdr (elf);
228
229 phdr[0].p_offset = ehdr->e_phoff;
230 phdr[0].p_vaddr = ehdr->e_phoff;
231 phdr[0].p_paddr = ehdr->e_phoff;
232 phdr[0].p_flags = PF_R | PF_X;
233 phdr[0].p_filesz = ehdr->e_phnum * elf32_fsize (ELF_T_PHDR, 1, EV_CURRENT);
234 phdr[0].p_memsz = ehdr->e_phnum * elf32_fsize (ELF_T_PHDR, 1, EV_CURRENT);
235 phdr[0].p_align = sizeof (Elf32_Word);
236
237 phdr[1].p_flags = PF_W | PF_R;
238 phdr[1].p_offset = *dynscn_offset;
239 /* Set up the start of this segment to equal start address of the
240 .dynamic section. */
241 phdr[1].p_vaddr = 0x1a0;
242 phdr[1].p_paddr = 0x1a0;
243 phdr[1].p_align = 2 * sizeof (Elf32_Word);
244 phdr[1].p_filesz = ndtflags * sizeof (Elf32_Dyn);
245 phdr[1].p_memsz = ndtflags * sizeof (Elf32_Dyn);
246
247 /* Write out the file. */
248 if (elf_update (elf, ELF_C_WRITE) < 0)
249 {
250 printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
251 return 1;
252 }
253
254 /* We don't need the string table anymore. */
255 dwelf_strtab_free (shst);
256
257 /* And the data allocated in the .shstrtab section. */
258 free (data->d_buf);
259
260 /* And the dynamic entries. */
261 free (dyn);
262
263 /* All done. */
264 if (elf_end (elf) != 0)
265 {
266 printf ("failure in elf_end: %s\n", elf_errmsg (-1));
267 return 1;
268 }
269
270 return 0;
271 }
272