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 <stddef.h> 12#include <libelf.h> 13#include <string.h> 14#include <stdlib.h> 15#include <unistd.h> 16#include <inttypes.h> 17#include <fcntl.h> 18#include <err.h> 19#ifdef HAVE_DWARF_SUPPORT 20#include <dwarf.h> 21#endif 22 23#include "genelf.h" 24#include "../util/jitdump.h" 25#include <linux/compiler.h> 26 27#ifndef NT_GNU_BUILD_ID 28#define NT_GNU_BUILD_ID 3 29#endif 30 31#define BUILD_ID_URANDOM /* different uuid for each run */ 32 33// FIXME, remove this and fix the deprecation warnings before its removed and 34// We'll break for good here... 35#pragma GCC diagnostic ignored "-Wdeprecated-declarations" 36 37#ifdef HAVE_LIBCRYPTO_SUPPORT 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 53typedef 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 60struct options { 61 char *output; 62 int fd; 63}; 64 65static 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 79static 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 85static 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 104static void 105gen_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 128static void 129gen_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 142static void 143gen_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 157static int 158jit_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 */ 244int 245jit_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_Phdr *phdr; 255 Elf_Shdr *shdr; 256 uint64_t eh_frame_base_offset; 257 char *strsym = NULL; 258 int symlen; 259 int retval = -1; 260 261 if (elf_version(EV_CURRENT) == EV_NONE) { 262 warnx("ELF initialization failed"); 263 return -1; 264 } 265 266 e = elf_begin(fd, ELF_C_WRITE, NULL); 267 if (!e) { 268 warnx("elf_begin failed"); 269 goto error; 270 } 271 272 /* 273 * setup ELF header 274 */ 275 ehdr = elf_newehdr(e); 276 if (!ehdr) { 277 warnx("cannot get ehdr"); 278 goto error; 279 } 280 281 ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN; 282 ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS; 283 ehdr->e_machine = GEN_ELF_ARCH; 284 ehdr->e_type = ET_DYN; 285 ehdr->e_entry = GEN_ELF_TEXT_OFFSET; 286 ehdr->e_version = EV_CURRENT; 287 ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */ 288 289 /* 290 * setup program header 291 */ 292 phdr = elf_newphdr(e, 1); 293 phdr[0].p_type = PT_LOAD; 294 phdr[0].p_offset = GEN_ELF_TEXT_OFFSET; 295 phdr[0].p_vaddr = GEN_ELF_TEXT_OFFSET; 296 phdr[0].p_paddr = GEN_ELF_TEXT_OFFSET; 297 phdr[0].p_filesz = csize; 298 phdr[0].p_memsz = csize; 299 phdr[0].p_flags = PF_X | PF_R; 300 phdr[0].p_align = 8; 301 302 /* 303 * setup text section 304 */ 305 scn = elf_newscn(e); 306 if (!scn) { 307 warnx("cannot create section"); 308 goto error; 309 } 310 311 d = elf_newdata(scn); 312 if (!d) { 313 warnx("cannot get new data"); 314 goto error; 315 } 316 317 d->d_align = 16; 318 d->d_off = 0LL; 319 d->d_buf = (void *)code; 320 d->d_type = ELF_T_BYTE; 321 d->d_size = csize; 322 d->d_version = EV_CURRENT; 323 324 shdr = elf_getshdr(scn); 325 if (!shdr) { 326 warnx("cannot get section header"); 327 goto error; 328 } 329 330 shdr->sh_name = 1; 331 shdr->sh_type = SHT_PROGBITS; 332 shdr->sh_addr = GEN_ELF_TEXT_OFFSET; 333 shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 334 shdr->sh_entsize = 0; 335 336 /* 337 * Setup .eh_frame_hdr and .eh_frame 338 */ 339 if (unwinding) { 340 eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize); 341 retval = jit_add_eh_frame_info(e, unwinding, 342 unwinding_header_size, unwinding_size, 343 eh_frame_base_offset); 344 if (retval) 345 goto error; 346 } 347 348 /* 349 * setup section headers string table 350 */ 351 scn = elf_newscn(e); 352 if (!scn) { 353 warnx("cannot create section"); 354 goto error; 355 } 356 357 d = elf_newdata(scn); 358 if (!d) { 359 warnx("cannot get new data"); 360 goto error; 361 } 362 363 d->d_align = 1; 364 d->d_off = 0LL; 365 d->d_buf = shd_string_table; 366 d->d_type = ELF_T_BYTE; 367 d->d_size = sizeof(shd_string_table); 368 d->d_version = EV_CURRENT; 369 370 shdr = elf_getshdr(scn); 371 if (!shdr) { 372 warnx("cannot get section header"); 373 goto error; 374 } 375 376 shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */ 377 shdr->sh_type = SHT_STRTAB; 378 shdr->sh_flags = 0; 379 shdr->sh_entsize = 0; 380 381 /* 382 * setup symtab section 383 */ 384 symtab[1].st_size = csize; 385 symtab[1].st_value = GEN_ELF_TEXT_OFFSET; 386 387 scn = elf_newscn(e); 388 if (!scn) { 389 warnx("cannot create section"); 390 goto error; 391 } 392 393 d = elf_newdata(scn); 394 if (!d) { 395 warnx("cannot get new data"); 396 goto error; 397 } 398 399 d->d_align = 8; 400 d->d_off = 0LL; 401 d->d_buf = symtab; 402 d->d_type = ELF_T_SYM; 403 d->d_size = sizeof(symtab); 404 d->d_version = EV_CURRENT; 405 406 shdr = elf_getshdr(scn); 407 if (!shdr) { 408 warnx("cannot get section header"); 409 goto error; 410 } 411 412 shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */ 413 shdr->sh_type = SHT_SYMTAB; 414 shdr->sh_flags = 0; 415 shdr->sh_entsize = sizeof(Elf_Sym); 416 shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */ 417 418 /* 419 * setup symbols string table 420 * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry 421 */ 422 symlen = 2 + strlen(sym); 423 strsym = calloc(1, symlen); 424 if (!strsym) { 425 warnx("cannot allocate strsym"); 426 goto error; 427 } 428 strcpy(strsym + 1, sym); 429 430 scn = elf_newscn(e); 431 if (!scn) { 432 warnx("cannot create section"); 433 goto error; 434 } 435 436 d = elf_newdata(scn); 437 if (!d) { 438 warnx("cannot get new data"); 439 goto error; 440 } 441 442 d->d_align = 1; 443 d->d_off = 0LL; 444 d->d_buf = strsym; 445 d->d_type = ELF_T_BYTE; 446 d->d_size = symlen; 447 d->d_version = EV_CURRENT; 448 449 shdr = elf_getshdr(scn); 450 if (!shdr) { 451 warnx("cannot get section header"); 452 goto error; 453 } 454 455 shdr->sh_name = 25; /* offset in shd_string_table */ 456 shdr->sh_type = SHT_STRTAB; 457 shdr->sh_flags = 0; 458 shdr->sh_entsize = 0; 459 460 /* 461 * setup build-id section 462 */ 463 scn = elf_newscn(e); 464 if (!scn) { 465 warnx("cannot create section"); 466 goto error; 467 } 468 469 d = elf_newdata(scn); 470 if (!d) { 471 warnx("cannot get new data"); 472 goto error; 473 } 474 475 /* 476 * build-id generation 477 */ 478 gen_build_id(&bnote, load_addr, code, csize); 479 bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */ 480 bnote.desc.descsz = sizeof(bnote.build_id); 481 bnote.desc.type = NT_GNU_BUILD_ID; 482 strcpy(bnote.name, "GNU"); 483 484 d->d_align = 4; 485 d->d_off = 0LL; 486 d->d_buf = &bnote; 487 d->d_type = ELF_T_BYTE; 488 d->d_size = sizeof(bnote); 489 d->d_version = EV_CURRENT; 490 491 shdr = elf_getshdr(scn); 492 if (!shdr) { 493 warnx("cannot get section header"); 494 goto error; 495 } 496 497 shdr->sh_name = 33; /* offset in shd_string_table */ 498 shdr->sh_type = SHT_NOTE; 499 shdr->sh_addr = 0x0; 500 shdr->sh_flags = SHF_ALLOC; 501 shdr->sh_size = sizeof(bnote); 502 shdr->sh_entsize = 0; 503 504#ifdef HAVE_DWARF_SUPPORT 505 if (debug && nr_debug_entries) { 506 retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries); 507 if (retval) 508 goto error; 509 } else 510#endif 511 { 512 if (elf_update(e, ELF_C_WRITE) < 0) { 513 warnx("elf_update 4 failed"); 514 goto error; 515 } 516 } 517 518 retval = 0; 519error: 520 (void)elf_end(e); 521 522 free(strsym); 523 524 525 return retval; 526} 527