1 /*-
2 * Copyright (c) 2010,2011 Kai Wang
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 <sys/param.h>
28 #include <sys/stat.h>
29 #include <ctype.h>
30 #include <err.h>
31 #include <gelf.h>
32 #include <stdio.h>
33 #include <stdlib.h>
34 #include <string.h>
35 #include <unistd.h>
36
37 #include "elfcopy.h"
38
39 ELFTC_VCSID("$Id: binary.c 3611 2018-04-16 21:35:18Z jkoshy $");
40
41 /*
42 * Convert ELF object to `binary'. Sections with SHF_ALLOC flag set
43 * are copied to the result binary. The relative offsets for each section
44 * are retained, so the result binary file might contain "holes".
45 */
46 void
create_binary(int ifd,int ofd)47 create_binary(int ifd, int ofd)
48 {
49 Elf *e;
50 Elf_Scn *scn;
51 Elf_Data *d;
52 GElf_Shdr sh;
53 off_t base, off;
54 int elferr;
55
56 if ((e = elf_begin(ifd, ELF_C_READ, NULL)) == NULL)
57 errx(EXIT_FAILURE, "elf_begin() failed: %s",
58 elf_errmsg(-1));
59
60 base = 0;
61 if (lseek(ofd, base, SEEK_SET) < 0)
62 err(EXIT_FAILURE, "lseek failed");
63
64 /*
65 * Find base offset in the first iteration.
66 */
67 base = -1;
68 scn = NULL;
69 while ((scn = elf_nextscn(e, scn)) != NULL) {
70 if (gelf_getshdr(scn, &sh) == NULL) {
71 warnx("gelf_getshdr failed: %s", elf_errmsg(-1));
72 (void) elf_errno();
73 continue;
74 }
75 if ((sh.sh_flags & SHF_ALLOC) == 0 ||
76 sh.sh_type == SHT_NOBITS ||
77 sh.sh_size == 0)
78 continue;
79 if (base == -1 || (off_t) sh.sh_offset < base)
80 base = sh.sh_offset;
81 }
82 elferr = elf_errno();
83 if (elferr != 0)
84 warnx("elf_nextscn failed: %s", elf_errmsg(elferr));
85
86 if (base == -1)
87 return;
88
89 /*
90 * Write out sections in the second iteration.
91 */
92 scn = NULL;
93 while ((scn = elf_nextscn(e, scn)) != NULL) {
94 if (gelf_getshdr(scn, &sh) == NULL) {
95 warnx("gelf_getshdr failed: %s", elf_errmsg(-1));
96 (void) elf_errno();
97 continue;
98 }
99 if ((sh.sh_flags & SHF_ALLOC) == 0 ||
100 sh.sh_type == SHT_NOBITS ||
101 sh.sh_size == 0)
102 continue;
103 (void) elf_errno();
104 if ((d = elf_rawdata(scn, NULL)) == NULL) {
105 elferr = elf_errno();
106 if (elferr != 0)
107 warnx("elf_rawdata failed: %s", elf_errmsg(-1));
108 continue;
109 }
110 if (d->d_buf == NULL || d->d_size == 0)
111 continue;
112
113 /* lseek to section offset relative to `base'. */
114 off = sh.sh_offset - base;
115 if (lseek(ofd, off, SEEK_SET) < 0)
116 err(EXIT_FAILURE, "lseek failed");
117
118 /* Write out section contents. */
119 if (write(ofd, d->d_buf, d->d_size) != (ssize_t) d->d_size)
120 err(EXIT_FAILURE, "write failed");
121 }
122 elferr = elf_errno();
123 if (elferr != 0)
124 warnx("elf_nextscn failed: %s", elf_errmsg(elferr));
125 }
126
127 #define _SYMBOL_NAMSZ 1024
128
129 /*
130 * Convert `binary' to ELF object. The input `binary' is converted to
131 * a relocatable (.o) file, a few symbols will also be created to make
132 * it easier to access the binary data in other compilation units.
133 */
134 void
create_elf_from_binary(struct elfcopy * ecp,int ifd,const char * ifn)135 create_elf_from_binary(struct elfcopy *ecp, int ifd, const char *ifn)
136 {
137 char name[_SYMBOL_NAMSZ];
138 struct section *sec, *sec_temp, *shtab;
139 struct stat sb;
140 GElf_Ehdr oeh;
141 GElf_Shdr sh;
142 void *content;
143 uint64_t off, data_start, data_end, data_size;
144 char *sym_basename, *p;
145
146 /* Reset internal section list. */
147 if (!TAILQ_EMPTY(&ecp->v_sec))
148 TAILQ_FOREACH_SAFE(sec, &ecp->v_sec, sec_list, sec_temp) {
149 TAILQ_REMOVE(&ecp->v_sec, sec, sec_list);
150 free(sec);
151 }
152
153 if (fstat(ifd, &sb) == -1)
154 err(EXIT_FAILURE, "fstat failed");
155
156 /* Read the input binary file to a internal buffer. */
157 if ((content = malloc(sb.st_size)) == NULL)
158 err(EXIT_FAILURE, "malloc failed");
159 if (read(ifd, content, sb.st_size) != sb.st_size)
160 err(EXIT_FAILURE, "read failed");
161
162 /*
163 * TODO: copy the input binary to output binary verbatim if -O is not
164 * specified.
165 */
166
167 /* Create EHDR for output .o file. */
168 if (gelf_newehdr(ecp->eout, ecp->oec) == NULL)
169 errx(EXIT_FAILURE, "gelf_newehdr failed: %s",
170 elf_errmsg(-1));
171 if (gelf_getehdr(ecp->eout, &oeh) == NULL)
172 errx(EXIT_FAILURE, "gelf_getehdr() failed: %s",
173 elf_errmsg(-1));
174
175 /* Initialise e_ident fields. */
176 oeh.e_ident[EI_CLASS] = ecp->oec;
177 oeh.e_ident[EI_DATA] = ecp->oed;
178 /*
179 * TODO: Set OSABI according to the OS platform where elfcopy(1)
180 * was build. (probably)
181 */
182 oeh.e_ident[EI_OSABI] = ELFOSABI_NONE;
183 oeh.e_machine = ecp->oem;
184 oeh.e_type = ET_REL;
185 oeh.e_entry = 0;
186
187 ecp->flags |= RELOCATABLE;
188
189 /* Create .shstrtab section */
190 init_shstrtab(ecp);
191 ecp->shstrtab->off = 0;
192
193 /*
194 * Create `.data' section which contains the binary data. The
195 * section is inserted immediately after EHDR.
196 */
197 off = gelf_fsize(ecp->eout, ELF_T_EHDR, 1, EV_CURRENT);
198 if (off == 0)
199 errx(EXIT_FAILURE, "gelf_fsize() failed: %s", elf_errmsg(-1));
200 (void) create_external_section(ecp, ".data", NULL, content, sb.st_size,
201 off, SHT_PROGBITS, ELF_T_BYTE, SHF_ALLOC | SHF_WRITE, 1, 0, 1);
202
203 /* Insert .shstrtab after .data section. */
204 if ((ecp->shstrtab->os = elf_newscn(ecp->eout)) == NULL)
205 errx(EXIT_FAILURE, "elf_newscn failed: %s",
206 elf_errmsg(-1));
207 insert_to_sec_list(ecp, ecp->shstrtab, 1);
208
209 /* Insert section header table here. */
210 shtab = insert_shtab(ecp, 1);
211
212 /* Count in .symtab and .strtab section headers. */
213 shtab->sz += gelf_fsize(ecp->eout, ELF_T_SHDR, 2, EV_CURRENT);
214
215 if ((sym_basename = strdup(ifn)) == NULL)
216 err(1, "strdup");
217 for (p = sym_basename; *p != '\0'; p++)
218 if (!isalnum(*p & 0xFF))
219 *p = '_';
220 #define _GEN_SYMNAME(S) do { \
221 snprintf(name, sizeof(name), "%s%s%s", "_binary_", sym_basename, S); \
222 } while (0)
223
224 /*
225 * Create symbol table.
226 */
227 create_external_symtab(ecp);
228 data_start = 0;
229 data_end = data_start + sb.st_size;
230 data_size = sb.st_size;
231 _GEN_SYMNAME("_start");
232 add_to_symtab(ecp, name, data_start, 0, 1,
233 ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE), 0, 1);
234 _GEN_SYMNAME("_end");
235 add_to_symtab(ecp, name, data_end, 0, 1,
236 ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE), 0, 1);
237 _GEN_SYMNAME("_size");
238 add_to_symtab(ecp, name, data_size, 0, SHN_ABS,
239 ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE), 0, 1);
240 finalize_external_symtab(ecp);
241 create_symtab_data(ecp);
242 #undef _GEN_SYMNAME
243 free(sym_basename);
244
245 /*
246 * Write the underlying ehdr. Note that it should be called
247 * before elf_setshstrndx() since it will overwrite e->e_shstrndx.
248 */
249 if (gelf_update_ehdr(ecp->eout, &oeh) == 0)
250 errx(EXIT_FAILURE, "gelf_update_ehdr() failed: %s",
251 elf_errmsg(-1));
252
253 /* Update sh_name pointer for each section header entry. */
254 ecp->flags |= SYMTAB_EXIST;
255 update_shdr(ecp, 0);
256
257 /* Properly set sh_link field of .symtab section. */
258 if (gelf_getshdr(ecp->symtab->os, &sh) == NULL)
259 errx(EXIT_FAILURE, "692 gelf_getshdr() failed: %s",
260 elf_errmsg(-1));
261 sh.sh_link = elf_ndxscn(ecp->strtab->os);
262 if (!gelf_update_shdr(ecp->symtab->os, &sh))
263 errx(EXIT_FAILURE, "gelf_update_shdr() failed: %s",
264 elf_errmsg(-1));
265
266 /* Renew oeh to get the updated e_shstrndx. */
267 if (gelf_getehdr(ecp->eout, &oeh) == NULL)
268 errx(EXIT_FAILURE, "gelf_getehdr() failed: %s",
269 elf_errmsg(-1));
270
271 /* Resync section offsets. */
272 resync_sections(ecp);
273
274 /* Store SHDR offset in EHDR. */
275 oeh.e_shoff = shtab->off;
276
277 /* Update ehdr since we modified e_shoff. */
278 if (gelf_update_ehdr(ecp->eout, &oeh) == 0)
279 errx(EXIT_FAILURE, "gelf_update_ehdr() failed: %s",
280 elf_errmsg(-1));
281
282 /* Write out the output elf object. */
283 if (elf_update(ecp->eout, ELF_C_WRITE) < 0)
284 errx(EXIT_FAILURE, "elf_update() failed: %s",
285 elf_errmsg(-1));
286
287 /* Release allocated resource. */
288 free(content);
289 free_elf(ecp);
290 }
291