1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * genelf.c 4 * Copyright (C) 2014, Google, Inc 5 * 6 * Contributed by: 7 * Stephane Eranian <eranian@gmail.com> 8 */ 9 10 #include <sys/types.h> 11 #include <stdio.h> 12 #include <getopt.h> 13 #include <stddef.h> 14 #include <libelf.h> 15 #include <string.h> 16 #include <stdlib.h> 17 #include <inttypes.h> 18 #include <limits.h> 19 #include <fcntl.h> 20 #include <err.h> 21 #ifdef HAVE_DWARF_SUPPORT 22 #include <dwarf.h> 23 #endif 24 25 #include "perf.h" 26 #include "genelf.h" 27 #include "../util/jitdump.h" 28 29 #ifndef NT_GNU_BUILD_ID 30 #define NT_GNU_BUILD_ID 3 31 #endif 32 33 #define JVMTI 34 35 #define BUILD_ID_URANDOM /* different uuid for each run */ 36 37 #ifdef HAVE_LIBCRYPTO 38 39 #define BUILD_ID_MD5 40 #undef BUILD_ID_SHA /* does not seem to work well when linked with Java */ 41 #undef BUILD_ID_URANDOM /* different uuid for each run */ 42 43 #ifdef BUILD_ID_SHA 44 #include <openssl/sha.h> 45 #endif 46 47 #ifdef BUILD_ID_MD5 48 #include <openssl/md5.h> 49 #endif 50 #endif 51 52 53 typedef struct { 54 unsigned int namesz; /* Size of entry's owner string */ 55 unsigned int descsz; /* Size of the note descriptor */ 56 unsigned int type; /* Interpretation of the descriptor */ 57 char name[0]; /* Start of the name+desc data */ 58 } Elf_Note; 59 60 struct options { 61 char *output; 62 int fd; 63 }; 64 65 static char shd_string_table[] = { 66 0, 67 '.', 't', 'e', 'x', 't', 0, /* 1 */ 68 '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */ 69 '.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */ 70 '.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */ 71 '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */ 72 '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */ 73 '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */ 74 '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */ 75 '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */ 76 '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */ 77 }; 78 79 static struct buildid_note { 80 Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */ 81 char name[4]; /* GNU\0 */ 82 char build_id[20]; 83 } bnote; 84 85 static Elf_Sym symtab[]={ 86 /* symbol 0 MUST be the undefined symbol */ 87 { .st_name = 0, /* index in sym_string table */ 88 .st_info = ELF_ST_TYPE(STT_NOTYPE), 89 .st_shndx = 0, /* for now */ 90 .st_value = 0x0, 91 .st_other = ELF_ST_VIS(STV_DEFAULT), 92 .st_size = 0, 93 }, 94 { .st_name = 1, /* index in sym_string table */ 95 .st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC), 96 .st_shndx = 1, 97 .st_value = 0, /* for now */ 98 .st_other = ELF_ST_VIS(STV_DEFAULT), 99 .st_size = 0, /* for now */ 100 } 101 }; 102 103 #ifdef BUILD_ID_URANDOM 104 static void 105 gen_build_id(struct buildid_note *note, 106 unsigned long load_addr __maybe_unused, 107 const void *code __maybe_unused, 108 size_t csize __maybe_unused) 109 { 110 int fd; 111 size_t sz = sizeof(note->build_id); 112 ssize_t sret; 113 114 fd = open("/dev/urandom", O_RDONLY); 115 if (fd == -1) 116 err(1, "cannot access /dev/urandom for buildid"); 117 118 sret = read(fd, note->build_id, sz); 119 120 close(fd); 121 122 if (sret != (ssize_t)sz) 123 memset(note->build_id, 0, sz); 124 } 125 #endif 126 127 #ifdef BUILD_ID_SHA 128 static void 129 gen_build_id(struct buildid_note *note, 130 unsigned long load_addr __maybe_unused, 131 const void *code, 132 size_t csize) 133 { 134 if (sizeof(note->build_id) < SHA_DIGEST_LENGTH) 135 errx(1, "build_id too small for SHA1"); 136 137 SHA1(code, csize, (unsigned char *)note->build_id); 138 } 139 #endif 140 141 #ifdef BUILD_ID_MD5 142 static void 143 gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize) 144 { 145 MD5_CTX context; 146 147 if (sizeof(note->build_id) < 16) 148 errx(1, "build_id too small for MD5"); 149 150 MD5_Init(&context); 151 MD5_Update(&context, &load_addr, sizeof(load_addr)); 152 MD5_Update(&context, code, csize); 153 MD5_Final((unsigned char *)note->build_id, &context); 154 } 155 #endif 156 157 static int 158 jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size, 159 uint64_t unwinding_size, uint64_t base_offset) 160 { 161 Elf_Data *d; 162 Elf_Scn *scn; 163 Elf_Shdr *shdr; 164 uint64_t unwinding_table_size = unwinding_size - unwinding_header_size; 165 166 /* 167 * setup eh_frame section 168 */ 169 scn = elf_newscn(e); 170 if (!scn) { 171 warnx("cannot create section"); 172 return -1; 173 } 174 175 d = elf_newdata(scn); 176 if (!d) { 177 warnx("cannot get new data"); 178 return -1; 179 } 180 181 d->d_align = 8; 182 d->d_off = 0LL; 183 d->d_buf = unwinding; 184 d->d_type = ELF_T_BYTE; 185 d->d_size = unwinding_table_size; 186 d->d_version = EV_CURRENT; 187 188 shdr = elf_getshdr(scn); 189 if (!shdr) { 190 warnx("cannot get section header"); 191 return -1; 192 } 193 194 shdr->sh_name = 104; 195 shdr->sh_type = SHT_PROGBITS; 196 shdr->sh_addr = base_offset; 197 shdr->sh_flags = SHF_ALLOC; 198 shdr->sh_entsize = 0; 199 200 /* 201 * setup eh_frame_hdr section 202 */ 203 scn = elf_newscn(e); 204 if (!scn) { 205 warnx("cannot create section"); 206 return -1; 207 } 208 209 d = elf_newdata(scn); 210 if (!d) { 211 warnx("cannot get new data"); 212 return -1; 213 } 214 215 d->d_align = 4; 216 d->d_off = 0LL; 217 d->d_buf = unwinding + unwinding_table_size; 218 d->d_type = ELF_T_BYTE; 219 d->d_size = unwinding_header_size; 220 d->d_version = EV_CURRENT; 221 222 shdr = elf_getshdr(scn); 223 if (!shdr) { 224 warnx("cannot get section header"); 225 return -1; 226 } 227 228 shdr->sh_name = 90; 229 shdr->sh_type = SHT_PROGBITS; 230 shdr->sh_addr = base_offset + unwinding_table_size; 231 shdr->sh_flags = SHF_ALLOC; 232 shdr->sh_entsize = 0; 233 234 return 0; 235 } 236 237 /* 238 * fd: file descriptor open for writing for the output file 239 * load_addr: code load address (could be zero, just used for buildid) 240 * sym: function name (for native code - used as the symbol) 241 * code: the native code 242 * csize: the code size in bytes 243 */ 244 int 245 jit_write_elf(int fd, uint64_t load_addr, const char *sym, 246 const void *code, int csize, 247 void *debug __maybe_unused, int nr_debug_entries __maybe_unused, 248 void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size) 249 { 250 Elf *e; 251 Elf_Data *d; 252 Elf_Scn *scn; 253 Elf_Ehdr *ehdr; 254 Elf_Shdr *shdr; 255 uint64_t eh_frame_base_offset; 256 char *strsym = NULL; 257 int symlen; 258 int retval = -1; 259 260 if (elf_version(EV_CURRENT) == EV_NONE) { 261 warnx("ELF initialization failed"); 262 return -1; 263 } 264 265 e = elf_begin(fd, ELF_C_WRITE, NULL); 266 if (!e) { 267 warnx("elf_begin failed"); 268 goto error; 269 } 270 271 /* 272 * setup ELF header 273 */ 274 ehdr = elf_newehdr(e); 275 if (!ehdr) { 276 warnx("cannot get ehdr"); 277 goto error; 278 } 279 280 ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN; 281 ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS; 282 ehdr->e_machine = GEN_ELF_ARCH; 283 ehdr->e_type = ET_DYN; 284 ehdr->e_entry = GEN_ELF_TEXT_OFFSET; 285 ehdr->e_version = EV_CURRENT; 286 ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */ 287 288 /* 289 * setup text section 290 */ 291 scn = elf_newscn(e); 292 if (!scn) { 293 warnx("cannot create section"); 294 goto error; 295 } 296 297 d = elf_newdata(scn); 298 if (!d) { 299 warnx("cannot get new data"); 300 goto error; 301 } 302 303 d->d_align = 16; 304 d->d_off = 0LL; 305 d->d_buf = (void *)code; 306 d->d_type = ELF_T_BYTE; 307 d->d_size = csize; 308 d->d_version = EV_CURRENT; 309 310 shdr = elf_getshdr(scn); 311 if (!shdr) { 312 warnx("cannot get section header"); 313 goto error; 314 } 315 316 shdr->sh_name = 1; 317 shdr->sh_type = SHT_PROGBITS; 318 shdr->sh_addr = GEN_ELF_TEXT_OFFSET; 319 shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 320 shdr->sh_entsize = 0; 321 322 /* 323 * Setup .eh_frame_hdr and .eh_frame 324 */ 325 if (unwinding) { 326 eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize); 327 retval = jit_add_eh_frame_info(e, unwinding, 328 unwinding_header_size, unwinding_size, 329 eh_frame_base_offset); 330 if (retval) 331 goto error; 332 } 333 334 /* 335 * setup section headers string table 336 */ 337 scn = elf_newscn(e); 338 if (!scn) { 339 warnx("cannot create section"); 340 goto error; 341 } 342 343 d = elf_newdata(scn); 344 if (!d) { 345 warnx("cannot get new data"); 346 goto error; 347 } 348 349 d->d_align = 1; 350 d->d_off = 0LL; 351 d->d_buf = shd_string_table; 352 d->d_type = ELF_T_BYTE; 353 d->d_size = sizeof(shd_string_table); 354 d->d_version = EV_CURRENT; 355 356 shdr = elf_getshdr(scn); 357 if (!shdr) { 358 warnx("cannot get section header"); 359 goto error; 360 } 361 362 shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */ 363 shdr->sh_type = SHT_STRTAB; 364 shdr->sh_flags = 0; 365 shdr->sh_entsize = 0; 366 367 /* 368 * setup symtab section 369 */ 370 symtab[1].st_size = csize; 371 symtab[1].st_value = GEN_ELF_TEXT_OFFSET; 372 373 scn = elf_newscn(e); 374 if (!scn) { 375 warnx("cannot create section"); 376 goto error; 377 } 378 379 d = elf_newdata(scn); 380 if (!d) { 381 warnx("cannot get new data"); 382 goto error; 383 } 384 385 d->d_align = 8; 386 d->d_off = 0LL; 387 d->d_buf = symtab; 388 d->d_type = ELF_T_SYM; 389 d->d_size = sizeof(symtab); 390 d->d_version = EV_CURRENT; 391 392 shdr = elf_getshdr(scn); 393 if (!shdr) { 394 warnx("cannot get section header"); 395 goto error; 396 } 397 398 shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */ 399 shdr->sh_type = SHT_SYMTAB; 400 shdr->sh_flags = 0; 401 shdr->sh_entsize = sizeof(Elf_Sym); 402 shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */ 403 404 /* 405 * setup symbols string table 406 * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry 407 */ 408 symlen = 2 + strlen(sym); 409 strsym = calloc(1, symlen); 410 if (!strsym) { 411 warnx("cannot allocate strsym"); 412 goto error; 413 } 414 strcpy(strsym + 1, sym); 415 416 scn = elf_newscn(e); 417 if (!scn) { 418 warnx("cannot create section"); 419 goto error; 420 } 421 422 d = elf_newdata(scn); 423 if (!d) { 424 warnx("cannot get new data"); 425 goto error; 426 } 427 428 d->d_align = 1; 429 d->d_off = 0LL; 430 d->d_buf = strsym; 431 d->d_type = ELF_T_BYTE; 432 d->d_size = symlen; 433 d->d_version = EV_CURRENT; 434 435 shdr = elf_getshdr(scn); 436 if (!shdr) { 437 warnx("cannot get section header"); 438 goto error; 439 } 440 441 shdr->sh_name = 25; /* offset in shd_string_table */ 442 shdr->sh_type = SHT_STRTAB; 443 shdr->sh_flags = 0; 444 shdr->sh_entsize = 0; 445 446 /* 447 * setup build-id section 448 */ 449 scn = elf_newscn(e); 450 if (!scn) { 451 warnx("cannot create section"); 452 goto error; 453 } 454 455 d = elf_newdata(scn); 456 if (!d) { 457 warnx("cannot get new data"); 458 goto error; 459 } 460 461 /* 462 * build-id generation 463 */ 464 gen_build_id(&bnote, load_addr, code, csize); 465 bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */ 466 bnote.desc.descsz = sizeof(bnote.build_id); 467 bnote.desc.type = NT_GNU_BUILD_ID; 468 strcpy(bnote.name, "GNU"); 469 470 d->d_align = 4; 471 d->d_off = 0LL; 472 d->d_buf = &bnote; 473 d->d_type = ELF_T_BYTE; 474 d->d_size = sizeof(bnote); 475 d->d_version = EV_CURRENT; 476 477 shdr = elf_getshdr(scn); 478 if (!shdr) { 479 warnx("cannot get section header"); 480 goto error; 481 } 482 483 shdr->sh_name = 33; /* offset in shd_string_table */ 484 shdr->sh_type = SHT_NOTE; 485 shdr->sh_addr = 0x0; 486 shdr->sh_flags = SHF_ALLOC; 487 shdr->sh_size = sizeof(bnote); 488 shdr->sh_entsize = 0; 489 490 #ifdef HAVE_DWARF_SUPPORT 491 if (debug && nr_debug_entries) { 492 retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries); 493 if (retval) 494 goto error; 495 } else 496 #endif 497 { 498 if (elf_update(e, ELF_C_WRITE) < 0) { 499 warnx("elf_update 4 failed"); 500 goto error; 501 } 502 } 503 504 retval = 0; 505 error: 506 (void)elf_end(e); 507 508 free(strsym); 509 510 511 return retval; 512 } 513 514 #ifndef JVMTI 515 516 static unsigned char x86_code[] = { 517 0xBB, 0x2A, 0x00, 0x00, 0x00, /* movl $42, %ebx */ 518 0xB8, 0x01, 0x00, 0x00, 0x00, /* movl $1, %eax */ 519 0xCD, 0x80 /* int $0x80 */ 520 }; 521 522 static struct options options; 523 524 int main(int argc, char **argv) 525 { 526 int c, fd, ret; 527 528 while ((c = getopt(argc, argv, "o:h")) != -1) { 529 switch (c) { 530 case 'o': 531 options.output = optarg; 532 break; 533 case 'h': 534 printf("Usage: genelf -o output_file [-h]\n"); 535 return 0; 536 default: 537 errx(1, "unknown option"); 538 } 539 } 540 541 fd = open(options.output, O_CREAT|O_TRUNC|O_RDWR, 0666); 542 if (fd == -1) 543 err(1, "cannot create file %s", options.output); 544 545 ret = jit_write_elf(fd, "main", x86_code, sizeof(x86_code)); 546 close(fd); 547 548 if (ret != 0) 549 unlink(options.output); 550 551 return ret; 552 } 553 #endif 554