1 /* Create an ELF file with all the DT_* flags set.
2    Copyright (C) 2011 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(ebl)
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 
36 
37 int
38 main (void)
39 {
40   static const char fname[] = "testfile-alldts";
41   struct Ebl_Strtab *shst;
42   struct Ebl_Strent *dynscn;
43   struct Ebl_Strent *shstrtabse;
44   const Elf32_Sword dtflags[] =
45     {
46       DT_NULL, DT_NEEDED, DT_PLTRELSZ, DT_PLTGOT,
47       DT_HASH, DT_STRTAB, DT_SYMTAB, DT_RELA,
48       DT_RELASZ, DT_RELAENT, DT_STRSZ, DT_SYMENT,
49       DT_INIT, DT_FINI, DT_SONAME, DT_RPATH,
50       DT_SYMBOLIC, DT_REL, DT_RELSZ, DT_RELENT,
51       DT_PLTREL, DT_DEBUG, DT_TEXTREL, DT_JMPREL,
52       DT_BIND_NOW, DT_INIT_ARRAY, DT_FINI_ARRAY,
53       DT_INIT_ARRAYSZ, DT_FINI_ARRAYSZ, DT_RUNPATH,
54       DT_FLAGS, DT_ENCODING, DT_PREINIT_ARRAY,
55       DT_PREINIT_ARRAYSZ, DT_VERSYM, DT_GNU_PRELINKED,
56       DT_GNU_CONFLICTSZ, DT_GNU_LIBLISTSZ, DT_CHECKSUM,
57       DT_PLTPADSZ, DT_MOVEENT, DT_MOVESZ, DT_FEATURE_1,
58       DT_POSFLAG_1, DT_SYMINSZ, DT_SYMINENT, DT_GNU_HASH,
59       DT_TLSDESC_PLT, DT_TLSDESC_GOT, DT_GNU_CONFLICT,
60       DT_GNU_LIBLIST, DT_CONFIG, DT_DEPAUDIT, DT_AUDIT,
61       DT_PLTPAD, DT_MOVETAB, DT_SYMINFO, DT_RELACOUNT,
62       DT_RELCOUNT, DT_FLAGS_1, DT_VERDEF, DT_VERDEFNUM,
63       DT_VERNEED, DT_VERNEEDNUM, DT_AUXILIARY, DT_FILTER
64     };
65   const int ndtflags = sizeof (dtflags) / sizeof (dtflags[0]);
66 
67   /* We use no threads here which can interfere with handling a stream.  */
68   (void) __fsetlocking (stdout, FSETLOCKING_BYCALLER);
69 
70   /* Open the file.  */
71   int fd = open (fname, O_RDWR | O_CREAT | O_TRUNC, 0666);
72   if (fd == -1)
73     {
74       printf ("cannot open `%s': %m\n", fname);
75       return 1;
76     }
77 
78   /* Tell the library which version are we expecting.  */
79   elf_version (EV_CURRENT);
80 
81   /* Create an ELF descriptor.  */
82   Elf *elf = elf_begin (fd, ELF_C_WRITE, NULL);
83   if (elf == NULL)
84     {
85       printf ("cannot create ELF descriptor: %s\n", elf_errmsg (-1));
86       return 1;
87     }
88 
89   /* Create an ELF header.  */
90   Elf32_Ehdr *ehdr = elf32_newehdr (elf);
91   if (ehdr == NULL)
92     {
93       printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
94       return 1;
95     }
96 
97   ehdr->e_ident[0] = 42;
98   ehdr->e_ident[5] = 1;
99   ehdr->e_ident[6] = 2;
100   ehdr->e_type = ET_EXEC;
101   ehdr->e_machine = EM_386;
102   ehdr->e_version = 1;
103   ehdr->e_ehsize = 1;
104   ehdr->e_shnum = 3;
105 
106   elf_flagehdr (elf, ELF_C_SET, ELF_F_DIRTY);
107 
108   /* Create the program headers.  */
109   Elf32_Phdr *phdr = elf32_newphdr (elf, 2);
110   if (phdr == NULL)
111     {
112       printf ("cannot create program headers: %s\n", elf_errmsg (-1));
113       return 1;
114     }
115 
116   phdr[0].p_type = PT_PHDR;
117   phdr[1].p_type = PT_DYNAMIC;
118 
119   elf_flagphdr (elf, ELF_C_SET, ELF_F_DIRTY);
120   shst = ebl_strtabinit (true);
121 
122   /* Create the .dynamic section.  */
123   Elf_Scn *scn = elf_newscn (elf);
124   if (scn == NULL)
125     {
126       printf ("cannot create DYNAMIC section: %s\n", elf_errmsg (-1));
127       return 1;
128     }
129 
130   Elf32_Shdr *shdr = elf32_getshdr (scn);
131   if (shdr == NULL)
132     {
133       printf ("cannot get header for DYNAMIC section: %s\n", elf_errmsg (-1));
134       return 1;
135     }
136 
137   dynscn = ebl_strtabadd (shst, ".dynamic", 0);
138 
139   /* We'll need to know the section offset.  But this will be set up
140      by elf_update later, so for now just store the address.  */
141   const Elf32_Off *const dynscn_offset = &shdr->sh_offset;
142   shdr->sh_type = SHT_DYNAMIC;
143   shdr->sh_flags = SHF_ALLOC | SHF_WRITE;
144   shdr->sh_link = SHN_UNDEF;
145   shdr->sh_info = SHN_UNDEF;
146   /* This section will start here.  */
147   shdr->sh_addr = 0x1a0;
148 
149   /* Create new section data.  */
150   Elf_Data *data = elf_newdata (scn);
151   if (data == NULL)
152     {
153       printf ("cannot create data for DYNAMIC section: %s\n", elf_errmsg (-1));
154       return 1;
155     }
156 
157   /* Allocate memory for all the .dynamic entries.  */
158   Elf32_Dyn *dyn = malloc (ndtflags * sizeof (Elf32_Dyn));
159   if (dyn == NULL)
160     {
161       printf ("malloc failed: %m\n");
162       return 1;
163     }
164 
165   /* Now write all the DT_* flags.  */
166   for (int i = 0; i < ndtflags; ++i)
167     {
168       dyn[i].d_tag = dtflags[i];
169       dyn[i].d_un.d_val = 0xdeadbeef;
170     }
171 
172   /* Set the pointer to allocated memory.  */
173   data->d_buf = dyn;
174   data->d_type = ELF_T_DYN;
175   data->d_version = EV_CURRENT;
176   data->d_size = ndtflags * sizeof (Elf32_Dyn);
177   data->d_align = 0x8;
178 
179   /* Create .shstrtab section.  */
180   scn = elf_newscn (elf);
181   if (scn == NULL)
182     {
183       printf ("cannot create SHSTRTAB section: %s\n", elf_errmsg (-1));
184       return 1;
185     }
186 
187   shdr = elf32_getshdr (scn);
188   if (shdr == NULL)
189     {
190       printf ("cannot get header for SHSTRTAB section: %s\n", elf_errmsg (-1));
191       return 1;
192     }
193 
194   shstrtabse = ebl_strtabadd (shst, ".shstrtab", 0);
195 
196   shdr->sh_type = SHT_STRTAB;
197   shdr->sh_flags = 0;
198   shdr->sh_addr = 0;
199   shdr->sh_link = SHN_UNDEF;
200   shdr->sh_info = SHN_UNDEF;
201   shdr->sh_entsize = 1;
202 
203   /* We have to store the section index in the ELF header.  */
204   ehdr->e_shstrndx = elf_ndxscn (scn);
205 
206   data = elf_newdata (scn);
207   if (data == NULL)
208     {
209       printf ("cannot create data SHSTRTAB section: %s\n", elf_errmsg (-1));
210       return 1;
211     }
212 
213   /* No more sections, finalize the section header string table.  */
214   ebl_strtabfinalize (shst, data);
215 
216   elf32_getshdr (elf_getscn (elf, 1))->sh_name = ebl_strtaboffset (dynscn);
217   shdr->sh_name = ebl_strtaboffset (shstrtabse);
218 
219   /* Let the library compute the internal structure information.  */
220   if (elf_update (elf, ELF_C_NULL) < 0)
221     {
222       printf ("failure in elf_update(NULL): %s\n", elf_errmsg (-1));
223       return 1;
224     }
225 
226   ehdr = elf32_getehdr (elf);
227 
228   phdr[0].p_offset = ehdr->e_phoff;
229   phdr[0].p_vaddr = ehdr->e_phoff;
230   phdr[0].p_paddr = ehdr->e_phoff;
231   phdr[0].p_flags = PF_R | PF_X;
232   phdr[0].p_filesz = ehdr->e_phnum * elf32_fsize (ELF_T_PHDR, 1, EV_CURRENT);
233   phdr[0].p_memsz = ehdr->e_phnum * elf32_fsize (ELF_T_PHDR, 1, EV_CURRENT);
234   phdr[0].p_align = sizeof (Elf32_Word);
235 
236   phdr[1].p_flags = PF_W | PF_R;
237   phdr[1].p_offset = *dynscn_offset;
238   /* Set up the start of this segment to equal start address of the
239      .dynamic section.  */
240   phdr[1].p_vaddr = 0x1a0;
241   phdr[1].p_paddr = 0x1a0;
242   phdr[1].p_align = 2 * sizeof (Elf32_Word);
243   phdr[1].p_filesz = ndtflags * sizeof (Elf32_Dyn);
244   phdr[1].p_memsz = ndtflags * sizeof (Elf32_Dyn);
245 
246   /* Write out the file.  */
247   if (elf_update (elf, ELF_C_WRITE) < 0)
248     {
249       printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
250       return 1;
251     }
252 
253   /* We don't need the string table anymore.  */
254   ebl_strtabfree (shst);
255 
256   /* And the data allocated in the .shstrtab section.  */
257   free (data->d_buf);
258 
259   /* And the dynamic entries.  */
260   free (dyn);
261 
262   /* All done.  */
263   if (elf_end (elf) != 0)
264     {
265       printf ("failure in elf_end: %s\n", elf_errmsg (-1));
266       return 1;
267     }
268 
269   return 0;
270 }
271