1 /* $NetBSD: elf2aout.c,v 1.10 2000/03/13 23:22:50 soren Exp $ */ 2 3 /* 4 * Copyright (c) 1995 5 * Ted Lemon (hereinafter referred to as the author) 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 /* elf2aout.c 32 33 This program converts an elf executable to a NetBSD a.out executable. 34 The minimal symbol table is copied, but the debugging symbols and 35 other informational sections are not. */ 36 37 #include <sys/types.h> 38 #include <sys/exec_aout.h> 39 #include <sys/exec_elf.h> 40 41 #include <a.out.h> 42 #include <err.h> 43 #include <errno.h> 44 #include <fcntl.h> 45 #include <limits.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include <string.h> 49 #include <unistd.h> 50 51 52 struct sect { 53 unsigned long vaddr; 54 unsigned long len; 55 }; 56 57 void combine __P((struct sect *, struct sect *, int)); 58 int phcmp __P((const void *, const void *)); 59 char *saveRead __P((int file, off_t offset, off_t len, char *name)); 60 void copy __P((int, int, off_t, off_t)); 61 void translate_syms __P((int, int, off_t, off_t, off_t, off_t)); 62 63 int *symTypeTable; 64 65 int 66 main(int argc, char **argv) 67 { 68 Elf32_Ehdr ex; 69 Elf32_Phdr *ph; 70 Elf32_Shdr *sh; 71 char *shstrtab; 72 int strtabix, symtabix; 73 int i; 74 struct sect text, data, bss; 75 struct exec aex; 76 int infile, outfile; 77 unsigned long cur_vma = ULONG_MAX; 78 int symflag = 0; 79 80 strtabix = symtabix = 0; 81 text.len = data.len = bss.len = 0; 82 text.vaddr = data.vaddr = bss.vaddr = 0; 83 84 /* Check args... */ 85 if (argc < 3 || argc > 4) { 86 usage: 87 fprintf(stderr, 88 "usage: elf2aout <elf executable> <a.out executable> [-s]\n"); 89 exit(1); 90 } 91 if (argc == 4) { 92 if (strcmp(argv[3], "-s")) 93 goto usage; 94 symflag = 1; 95 } 96 /* Try the input file... */ 97 if ((infile = open(argv[1], O_RDONLY)) < 0) { 98 fprintf(stderr, "Can't open %s for read: %s\n", 99 argv[1], strerror(errno)); 100 exit(1); 101 } 102 /* Read the header, which is at the beginning of the file... */ 103 i = read(infile, &ex, sizeof ex); 104 if (i != sizeof ex) { 105 fprintf(stderr, "ex: %s: %s.\n", 106 argv[1], i ? strerror(errno) : "End of file reached"); 107 exit(1); 108 } 109 /* Read the program headers... */ 110 ph = (Elf32_Phdr *) saveRead(infile, ex.e_phoff, 111 ex.e_phnum * sizeof(Elf32_Phdr), "ph"); 112 /* Read the section headers... */ 113 sh = (Elf32_Shdr *) saveRead(infile, ex.e_shoff, 114 ex.e_shnum * sizeof(Elf32_Shdr), "sh"); 115 /* Read in the section string table. */ 116 shstrtab = saveRead(infile, sh[ex.e_shstrndx].sh_offset, 117 sh[ex.e_shstrndx].sh_size, "shstrtab"); 118 119 /* Find space for a table matching ELF section indices to a.out symbol 120 * types. */ 121 symTypeTable = (int *) malloc(ex.e_shnum * sizeof(int)); 122 if (!symTypeTable) { 123 fprintf(stderr, "symTypeTable: can't allocate.\n"); 124 exit(1); 125 } 126 memset(symTypeTable, 0, ex.e_shnum * sizeof(int)); 127 128 /* Look for the symbol table and string table... Also map section 129 * indices to symbol types for a.out */ 130 for (i = 0; i < ex.e_shnum; i++) { 131 char *name = shstrtab + sh[i].sh_name; 132 if (!strcmp(name, ".symtab")) 133 symtabix = i; 134 else 135 if (!strcmp(name, ".strtab")) 136 strtabix = i; 137 else 138 if (!strcmp(name, ".text") || !strcmp(name, ".rodata")) 139 symTypeTable[i] = N_TEXT; 140 else 141 if (!strcmp(name, ".data") || !strcmp(name, ".sdata") || 142 !strcmp(name, ".lit4") || !strcmp(name, ".lit8")) 143 symTypeTable[i] = N_DATA; 144 else 145 if (!strcmp(name, ".bss") || !strcmp(name, ".sbss")) 146 symTypeTable[i] = N_BSS; 147 } 148 149 /* Figure out if we can cram the program header into an a.out 150 * header... Basically, we can't handle anything but loadable 151 * segments, but we can ignore some kinds of segments. We can't 152 * handle holes in the address space, and we handle start addresses 153 * other than 0x1000 by hoping that the loader will know where to load 154 * - a.out doesn't have an explicit load address. Segments may be 155 * out of order, so we sort them first. */ 156 qsort(ph, ex.e_phnum, sizeof(Elf32_Phdr), phcmp); 157 for (i = 0; i < ex.e_phnum; i++) { 158 /* Section types we can ignore... */ 159 if (ph[i].p_type == PT_NULL || ph[i].p_type == PT_NOTE || 160 ph[i].p_type == PT_PHDR || ph[i].p_type == PT_MIPS_REGINFO) 161 continue; 162 /* Section types we can't handle... */ 163 else 164 if (ph[i].p_type != PT_LOAD) 165 errx(1, "Program header %d type %d can't be converted.", i, ph[i].p_type); 166 /* Writable (data) segment? */ 167 if (ph[i].p_flags & PF_W) { 168 struct sect ndata, nbss; 169 170 ndata.vaddr = ph[i].p_vaddr; 171 ndata.len = ph[i].p_filesz; 172 nbss.vaddr = ph[i].p_vaddr + ph[i].p_filesz; 173 nbss.len = ph[i].p_memsz - ph[i].p_filesz; 174 175 combine(&data, &ndata, 0); 176 combine(&bss, &nbss, 1); 177 } else { 178 struct sect ntxt; 179 180 ntxt.vaddr = ph[i].p_vaddr; 181 ntxt.len = ph[i].p_filesz; 182 183 combine(&text, &ntxt, 0); 184 } 185 /* Remember the lowest segment start address. */ 186 if (ph[i].p_vaddr < cur_vma) 187 cur_vma = ph[i].p_vaddr; 188 } 189 190 /* Sections must be in order to be converted... */ 191 if (text.vaddr > data.vaddr || data.vaddr > bss.vaddr || 192 text.vaddr + text.len > data.vaddr || data.vaddr + data.len > bss.vaddr) { 193 fprintf(stderr, "Sections ordering prevents a.out conversion.\n"); 194 exit(1); 195 } 196 /* If there's a data section but no text section, then the loader 197 * combined everything into one section. That needs to be the text 198 * section, so just make the data section zero length following text. */ 199 if (data.len && !text.len) { 200 text = data; 201 data.vaddr = text.vaddr + text.len; 202 data.len = 0; 203 } 204 /* If there is a gap between text and data, we'll fill it when we copy 205 * the data, so update the length of the text segment as represented 206 * in a.out to reflect that, since a.out doesn't allow gaps in the 207 * program address space. */ 208 if (text.vaddr + text.len < data.vaddr) 209 text.len = data.vaddr - text.vaddr; 210 211 /* We now have enough information to cons up an a.out header... */ 212 aex.a_midmag = htonl((symflag << 26) | (MID_PMAX << 16) | OMAGIC); 213 if (ex.e_machine == EM_PPC) 214 aex.a_midmag = htonl((symflag << 26) | (MID_POWERPC << 16) 215 | OMAGIC); 216 217 aex.a_text = text.len; 218 aex.a_data = data.len; 219 aex.a_bss = bss.len; 220 aex.a_entry = ex.e_entry; 221 aex.a_syms = (sizeof(struct nlist) * 222 (symtabix != -1 223 ? sh[symtabix].sh_size / sizeof(Elf32_Sym) : 0)); 224 aex.a_trsize = 0; 225 aex.a_drsize = 0; 226 227 /* Make the output file... */ 228 if ((outfile = open(argv[2], O_WRONLY | O_CREAT, 0777)) < 0) { 229 fprintf(stderr, "Unable to create %s: %s\n", argv[2], strerror(errno)); 230 exit(1); 231 } 232 /* Truncate file... */ 233 if (ftruncate(outfile, 0)) { 234 warn("ftruncate %s", argv[2]); 235 } 236 /* Write the header... */ 237 i = write(outfile, &aex, sizeof aex); 238 if (i != sizeof aex) { 239 perror("aex: write"); 240 exit(1); 241 } 242 /* Copy the loadable sections. Zero-fill any gaps less than 64k; 243 * complain about any zero-filling, and die if we're asked to 244 * zero-fill more than 64k. */ 245 for (i = 0; i < ex.e_phnum; i++) { 246 /* Unprocessable sections were handled above, so just verify 247 * that the section can be loaded before copying. */ 248 if (ph[i].p_type == PT_LOAD && ph[i].p_filesz) { 249 if (cur_vma != ph[i].p_vaddr) { 250 unsigned long gap = ph[i].p_vaddr - cur_vma; 251 char obuf[1024]; 252 if (gap > 65536) 253 errx(1, 254 "Intersegment gap (%ld bytes) too large.", (long) gap); 255 #ifdef DEBUG 256 warnx("Warning: %ld byte intersegment gap.", 257 (long)gap); 258 #endif 259 memset(obuf, 0, sizeof obuf); 260 while (gap) { 261 int count = write(outfile, obuf, (gap > sizeof obuf 262 ? sizeof obuf : gap)); 263 if (count < 0) { 264 fprintf(stderr, "Error writing gap: %s\n", 265 strerror(errno)); 266 exit(1); 267 } 268 gap -= count; 269 } 270 } 271 copy(outfile, infile, ph[i].p_offset, ph[i].p_filesz); 272 cur_vma = ph[i].p_vaddr + ph[i].p_filesz; 273 } 274 } 275 276 /* Copy and translate the symbol table... */ 277 translate_syms(outfile, infile, 278 sh[symtabix].sh_offset, sh[symtabix].sh_size, 279 sh[strtabix].sh_offset, sh[strtabix].sh_size); 280 281 /* Looks like we won... */ 282 exit(0); 283 } 284 /* translate_syms (out, in, offset, size) 285 286 Read the ELF symbol table from in at offset; translate it into a.out 287 nlist format and write it to out. */ 288 289 void 290 translate_syms(out, in, symoff, symsize, stroff, strsize) 291 int out, in; 292 off_t symoff, symsize; 293 off_t stroff, strsize; 294 { 295 #define SYMS_PER_PASS 64 296 Elf32_Sym inbuf[64]; 297 struct nlist outbuf[64]; 298 int i, remaining, cur; 299 char *oldstrings; 300 char *newstrings, *nsp; 301 int newstringsize; 302 303 /* Zero the unused fields in the output buffer.. */ 304 memset(outbuf, 0, sizeof outbuf); 305 306 /* Find number of symbols to process... */ 307 remaining = symsize / sizeof(Elf32_Sym); 308 309 /* Suck in the old string table... */ 310 oldstrings = saveRead(in, stroff, strsize, "string table"); 311 312 /* Allocate space for the new one. XXX We make the wild assumption 313 * that no two symbol table entries will point at the same place in 314 * the string table - if that assumption is bad, this could easily 315 * blow up. */ 316 newstringsize = strsize + remaining; 317 newstrings = (char *) malloc(newstringsize); 318 if (!newstrings) { 319 fprintf(stderr, "No memory for new string table!\n"); 320 exit(1); 321 } 322 /* Initialize the table pointer... */ 323 nsp = newstrings; 324 325 /* Go the start of the ELF symbol table... */ 326 if (lseek(in, symoff, SEEK_SET) < 0) { 327 perror("translate_syms: lseek"); 328 exit(1); 329 } 330 /* Translate and copy symbols... */ 331 while (remaining) { 332 cur = remaining; 333 if (cur > SYMS_PER_PASS) 334 cur = SYMS_PER_PASS; 335 remaining -= cur; 336 if ((i = read(in, inbuf, cur * sizeof(Elf32_Sym))) 337 != cur * sizeof(Elf32_Sym)) { 338 if (i < 0) 339 perror("translate_syms"); 340 else 341 fprintf(stderr, "translate_syms: premature end of file.\n"); 342 exit(1); 343 } 344 /* Do the translation... */ 345 for (i = 0; i < cur; i++) { 346 int binding, type; 347 348 /* Copy the symbol into the new table, but prepend an 349 * underscore. */ 350 *nsp = '_'; 351 strcpy(nsp + 1, oldstrings + inbuf[i].st_name); 352 outbuf[i].n_un.n_strx = nsp - newstrings + 4; 353 nsp += strlen(nsp) + 1; 354 355 type = ELF32_ST_TYPE(inbuf[i].st_info); 356 binding = ELF32_ST_BIND(inbuf[i].st_info); 357 358 /* Convert ELF symbol type/section/etc info into a.out 359 * type info. */ 360 if (type == STT_FILE) 361 outbuf[i].n_type = N_FN; 362 else 363 if (inbuf[i].st_shndx == SHN_UNDEF) 364 outbuf[i].n_type = N_UNDF; 365 else 366 if (inbuf[i].st_shndx == SHN_ABS) 367 outbuf[i].n_type = N_ABS; 368 else 369 if (inbuf[i].st_shndx == SHN_COMMON || 370 inbuf[i].st_shndx == SHN_MIPS_ACOMMON) 371 outbuf[i].n_type = N_COMM; 372 else 373 outbuf[i].n_type = symTypeTable[inbuf[i].st_shndx]; 374 if (binding == STB_GLOBAL) 375 outbuf[i].n_type |= N_EXT; 376 /* Symbol values in executables should be compatible. */ 377 outbuf[i].n_value = inbuf[i].st_value; 378 } 379 /* Write out the symbols... */ 380 if ((i = write(out, outbuf, cur * sizeof(struct nlist))) 381 != cur * sizeof(struct nlist)) { 382 fprintf(stderr, "translate_syms: write: %s\n", strerror(errno)); 383 exit(1); 384 } 385 } 386 /* Write out the string table length... */ 387 if (write(out, &newstringsize, sizeof newstringsize) 388 != sizeof newstringsize) { 389 fprintf(stderr, 390 "translate_syms: newstringsize: %s\n", strerror(errno)); 391 exit(1); 392 } 393 /* Write out the string table... */ 394 if (write(out, newstrings, newstringsize) != newstringsize) { 395 fprintf(stderr, "translate_syms: newstrings: %s\n", strerror(errno)); 396 exit(1); 397 } 398 } 399 400 void 401 copy(out, in, offset, size) 402 int out, in; 403 off_t offset, size; 404 { 405 char ibuf[4096]; 406 int remaining, cur, count; 407 408 /* Go the the start of the ELF symbol table... */ 409 if (lseek(in, offset, SEEK_SET) < 0) { 410 perror("copy: lseek"); 411 exit(1); 412 } 413 remaining = size; 414 while (remaining) { 415 cur = remaining; 416 if (cur > sizeof ibuf) 417 cur = sizeof ibuf; 418 remaining -= cur; 419 if ((count = read(in, ibuf, cur)) != cur) { 420 fprintf(stderr, "copy: read: %s\n", 421 count ? strerror(errno) : "premature end of file"); 422 exit(1); 423 } 424 if ((count = write(out, ibuf, cur)) != cur) { 425 perror("copy: write"); 426 exit(1); 427 } 428 } 429 } 430 /* Combine two segments, which must be contiguous. If pad is true, it's 431 okay for there to be padding between. */ 432 void 433 combine(base, new, pad) 434 struct sect *base, *new; 435 int pad; 436 { 437 if (!base->len) 438 *base = *new; 439 else 440 if (new->len) { 441 if (base->vaddr + base->len != new->vaddr) { 442 if (pad) 443 base->len = new->vaddr - base->vaddr; 444 else { 445 fprintf(stderr, 446 "Non-contiguous data can't be converted.\n"); 447 exit(1); 448 } 449 } 450 base->len += new->len; 451 } 452 } 453 454 int 455 phcmp(vh1, vh2) 456 const void *vh1, *vh2; 457 { 458 Elf32_Phdr *h1, *h2; 459 h1 = (Elf32_Phdr *) vh1; 460 h2 = (Elf32_Phdr *) vh2; 461 462 if (h1->p_vaddr > h2->p_vaddr) 463 return 1; 464 else 465 if (h1->p_vaddr < h2->p_vaddr) 466 return -1; 467 else 468 return 0; 469 } 470 471 char * 472 saveRead(int file, off_t offset, off_t len, char *name) 473 { 474 char *tmp; 475 int count; 476 off_t off; 477 if ((off = lseek(file, offset, SEEK_SET)) < 0) { 478 fprintf(stderr, "%s: fseek: %s\n", name, strerror(errno)); 479 exit(1); 480 } 481 if (!(tmp = (char *) malloc(len))) 482 errx(1, "%s: Can't allocate %ld bytes.", name, (long)len); 483 count = read(file, tmp, len); 484 if (count != len) { 485 fprintf(stderr, "%s: read: %s.\n", 486 name, count ? strerror(errno) : "End of file reached"); 487 exit(1); 488 } 489 return tmp; 490 } 491