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_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 DT_NULL
66 };
67 const int ndtflags = sizeof (dtflags) / sizeof (dtflags[0]);
68
69 /* We use no threads here which can interfere with handling a stream. */
70 (void) __fsetlocking (stdout, FSETLOCKING_BYCALLER);
71
72 /* Open the file. */
73 int fd = open (fname, O_RDWR | O_CREAT | O_TRUNC, DEFFILEMODE);
74 if (fd == -1)
75 {
76 printf ("cannot open `%s': %m\n", fname);
77 return 1;
78 }
79
80 /* Tell the library which version are we expecting. */
81 elf_version (EV_CURRENT);
82
83 /* Create an ELF descriptor. */
84 Elf *elf = elf_begin (fd, ELF_C_WRITE, NULL);
85 if (elf == NULL)
86 {
87 printf ("cannot create ELF descriptor: %s\n", elf_errmsg (-1));
88 return 1;
89 }
90
91 /* Create an ELF header. */
92 Elf32_Ehdr *ehdr = elf32_newehdr (elf);
93 if (ehdr == NULL)
94 {
95 printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
96 return 1;
97 }
98
99 ehdr->e_ident[0] = 42;
100 ehdr->e_ident[5] = 1;
101 ehdr->e_ident[6] = 2;
102 ehdr->e_type = ET_EXEC;
103 ehdr->e_machine = EM_386;
104 ehdr->e_version = 1;
105 ehdr->e_ehsize = 1;
106 ehdr->e_shnum = 3;
107
108 elf_flagehdr (elf, ELF_C_SET, ELF_F_DIRTY);
109
110 /* Create the program headers. */
111 Elf32_Phdr *phdr = elf32_newphdr (elf, 2);
112 if (phdr == NULL)
113 {
114 printf ("cannot create program headers: %s\n", elf_errmsg (-1));
115 return 1;
116 }
117
118 phdr[0].p_type = PT_PHDR;
119 phdr[1].p_type = PT_DYNAMIC;
120
121 elf_flagphdr (elf, ELF_C_SET, ELF_F_DIRTY);
122 shst = dwelf_strtab_init (true);
123
124 /* Create the .dynamic section. */
125 Elf_Scn *scn = elf_newscn (elf);
126 if (scn == NULL)
127 {
128 printf ("cannot create DYNAMIC section: %s\n", elf_errmsg (-1));
129 return 1;
130 }
131
132 Elf32_Shdr *shdr = elf32_getshdr (scn);
133 if (shdr == NULL)
134 {
135 printf ("cannot get header for DYNAMIC section: %s\n", elf_errmsg (-1));
136 return 1;
137 }
138
139 dynscn = dwelf_strtab_add (shst, ".dynamic");
140
141 /* We'll need to know the section offset. But this will be set up
142 by elf_update later, so for now just store the address. */
143 const Elf32_Off *const dynscn_offset = &shdr->sh_offset;
144 shdr->sh_type = SHT_DYNAMIC;
145 shdr->sh_flags = SHF_ALLOC | SHF_WRITE;
146 shdr->sh_link = SHN_UNDEF;
147 shdr->sh_info = SHN_UNDEF;
148 /* This section will start here. */
149 shdr->sh_addr = 0x1a0;
150
151 /* Create new section data. */
152 Elf_Data *data = elf_newdata (scn);
153 if (data == NULL)
154 {
155 printf ("cannot create data for DYNAMIC section: %s\n", elf_errmsg (-1));
156 return 1;
157 }
158
159 /* Allocate memory for all the .dynamic entries. */
160 Elf32_Dyn *dyn = malloc (ndtflags * sizeof (Elf32_Dyn));
161 if (dyn == NULL)
162 {
163 printf ("malloc failed: %m\n");
164 return 1;
165 }
166
167 /* Now write all the DT_* flags. */
168 for (int i = 0; i < ndtflags; ++i)
169 {
170 dyn[i].d_tag = dtflags[i];
171 dyn[i].d_un.d_val = 0xdeadbeef;
172 }
173
174 /* Set the pointer to allocated memory. */
175 data->d_buf = dyn;
176 data->d_type = ELF_T_DYN;
177 data->d_version = EV_CURRENT;
178 data->d_size = ndtflags * sizeof (Elf32_Dyn);
179 data->d_align = 0x8;
180
181 /* Create .shstrtab section. */
182 scn = elf_newscn (elf);
183 if (scn == NULL)
184 {
185 printf ("cannot create SHSTRTAB section: %s\n", elf_errmsg (-1));
186 return 1;
187 }
188
189 shdr = elf32_getshdr (scn);
190 if (shdr == NULL)
191 {
192 printf ("cannot get header for SHSTRTAB section: %s\n", elf_errmsg (-1));
193 return 1;
194 }
195
196 shstrtabse = dwelf_strtab_add (shst, ".shstrtab");
197
198 shdr->sh_type = SHT_STRTAB;
199 shdr->sh_flags = 0;
200 shdr->sh_addr = 0;
201 shdr->sh_link = SHN_UNDEF;
202 shdr->sh_info = SHN_UNDEF;
203 shdr->sh_entsize = 1;
204
205 /* We have to store the section index in the ELF header. */
206 ehdr->e_shstrndx = elf_ndxscn (scn);
207
208 data = elf_newdata (scn);
209 if (data == NULL)
210 {
211 printf ("cannot create data SHSTRTAB section: %s\n", elf_errmsg (-1));
212 return 1;
213 }
214
215 /* No more sections, finalize the section header string table. */
216 dwelf_strtab_finalize (shst, data);
217
218 elf32_getshdr (elf_getscn (elf, 1))->sh_name = dwelf_strent_off (dynscn);
219 shdr->sh_name = dwelf_strent_off (shstrtabse);
220
221 /* Let the library compute the internal structure information. */
222 if (elf_update (elf, ELF_C_NULL) < 0)
223 {
224 printf ("failure in elf_update(NULL): %s\n", elf_errmsg (-1));
225 return 1;
226 }
227
228 ehdr = elf32_getehdr (elf);
229
230 phdr[0].p_offset = ehdr->e_phoff;
231 phdr[0].p_vaddr = ehdr->e_phoff;
232 phdr[0].p_paddr = ehdr->e_phoff;
233 phdr[0].p_flags = PF_R | PF_X;
234 phdr[0].p_filesz = ehdr->e_phnum * elf32_fsize (ELF_T_PHDR, 1, EV_CURRENT);
235 phdr[0].p_memsz = ehdr->e_phnum * elf32_fsize (ELF_T_PHDR, 1, EV_CURRENT);
236 phdr[0].p_align = sizeof (Elf32_Word);
237
238 phdr[1].p_flags = PF_W | PF_R;
239 phdr[1].p_offset = *dynscn_offset;
240 /* Set up the start of this segment to equal start address of the
241 .dynamic section. */
242 phdr[1].p_vaddr = 0x1a0;
243 phdr[1].p_paddr = 0x1a0;
244 phdr[1].p_align = 2 * sizeof (Elf32_Word);
245 phdr[1].p_filesz = ndtflags * sizeof (Elf32_Dyn);
246 phdr[1].p_memsz = ndtflags * sizeof (Elf32_Dyn);
247
248 /* Write out the file. */
249 if (elf_update (elf, ELF_C_WRITE) < 0)
250 {
251 printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
252 return 1;
253 }
254
255 /* We don't need the string table anymore. */
256 dwelf_strtab_free (shst);
257
258 /* And the data allocated in the .shstrtab section. */
259 free (data->d_buf);
260
261 /* And the dynamic entries. */
262 free (dyn);
263
264 /* All done. */
265 if (elf_end (elf) != 0)
266 {
267 printf ("failure in elf_end: %s\n", elf_errmsg (-1));
268 return 1;
269 }
270
271 return 0;
272 }
273