1 /* 2 * genelf.c 3 * Copyright (C) 2014, Google, Inc 4 * 5 * Contributed by: 6 * Stephane Eranian <eranian@gmail.com> 7 * 8 * Released under the GPL v2. (and only v2, not any later version) 9 */ 10 11 #include <sys/types.h> 12 #include <stdio.h> 13 #include <getopt.h> 14 #include <stddef.h> 15 #include <libelf.h> 16 #include <string.h> 17 #include <stdlib.h> 18 #include <inttypes.h> 19 #include <limits.h> 20 #include <fcntl.h> 21 #include <err.h> 22 #include <dwarf.h> 23 24 #include "perf.h" 25 #include "genelf.h" 26 #include "../util/jitdump.h" 27 28 #define JVMTI 29 30 #define BUILD_ID_URANDOM /* different uuid for each run */ 31 32 #ifdef HAVE_LIBCRYPTO 33 34 #define BUILD_ID_MD5 35 #undef BUILD_ID_SHA /* does not seem to work well when linked with Java */ 36 #undef BUILD_ID_URANDOM /* different uuid for each run */ 37 38 #ifdef BUILD_ID_SHA 39 #include <openssl/sha.h> 40 #endif 41 42 #ifdef BUILD_ID_MD5 43 #include <openssl/md5.h> 44 #endif 45 #endif 46 47 48 typedef struct { 49 unsigned int namesz; /* Size of entry's owner string */ 50 unsigned int descsz; /* Size of the note descriptor */ 51 unsigned int type; /* Interpretation of the descriptor */ 52 char name[0]; /* Start of the name+desc data */ 53 } Elf_Note; 54 55 struct options { 56 char *output; 57 int fd; 58 }; 59 60 static char shd_string_table[] = { 61 0, 62 '.', 't', 'e', 'x', 't', 0, /* 1 */ 63 '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */ 64 '.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */ 65 '.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */ 66 '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */ 67 '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */ 68 '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */ 69 '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */ 70 }; 71 72 static struct buildid_note { 73 Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */ 74 char name[4]; /* GNU\0 */ 75 char build_id[20]; 76 } bnote; 77 78 static Elf_Sym symtab[]={ 79 /* symbol 0 MUST be the undefined symbol */ 80 { .st_name = 0, /* index in sym_string table */ 81 .st_info = ELF_ST_TYPE(STT_NOTYPE), 82 .st_shndx = 0, /* for now */ 83 .st_value = 0x0, 84 .st_other = ELF_ST_VIS(STV_DEFAULT), 85 .st_size = 0, 86 }, 87 { .st_name = 1, /* index in sym_string table */ 88 .st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC), 89 .st_shndx = 1, 90 .st_value = 0, /* for now */ 91 .st_other = ELF_ST_VIS(STV_DEFAULT), 92 .st_size = 0, /* for now */ 93 } 94 }; 95 96 #ifdef BUILD_ID_URANDOM 97 static void 98 gen_build_id(struct buildid_note *note, 99 unsigned long load_addr __maybe_unused, 100 const void *code __maybe_unused, 101 size_t csize __maybe_unused) 102 { 103 int fd; 104 size_t sz = sizeof(note->build_id); 105 ssize_t sret; 106 107 fd = open("/dev/urandom", O_RDONLY); 108 if (fd == -1) 109 err(1, "cannot access /dev/urandom for builid"); 110 111 sret = read(fd, note->build_id, sz); 112 113 close(fd); 114 115 if (sret != (ssize_t)sz) 116 memset(note->build_id, 0, sz); 117 } 118 #endif 119 120 #ifdef BUILD_ID_SHA 121 static void 122 gen_build_id(struct buildid_note *note, 123 unsigned long load_addr __maybe_unused, 124 const void *code, 125 size_t csize) 126 { 127 if (sizeof(note->build_id) < SHA_DIGEST_LENGTH) 128 errx(1, "build_id too small for SHA1"); 129 130 SHA1(code, csize, (unsigned char *)note->build_id); 131 } 132 #endif 133 134 #ifdef BUILD_ID_MD5 135 static void 136 gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize) 137 { 138 MD5_CTX context; 139 140 if (sizeof(note->build_id) < 16) 141 errx(1, "build_id too small for MD5"); 142 143 MD5_Init(&context); 144 MD5_Update(&context, &load_addr, sizeof(load_addr)); 145 MD5_Update(&context, code, csize); 146 MD5_Final((unsigned char *)note->build_id, &context); 147 } 148 #endif 149 150 /* 151 * fd: file descriptor open for writing for the output file 152 * load_addr: code load address (could be zero, just used for buildid) 153 * sym: function name (for native code - used as the symbol) 154 * code: the native code 155 * csize: the code size in bytes 156 */ 157 int 158 jit_write_elf(int fd, uint64_t load_addr, const char *sym, 159 const void *code, int csize, 160 void *debug, int nr_debug_entries) 161 { 162 Elf *e; 163 Elf_Data *d; 164 Elf_Scn *scn; 165 Elf_Ehdr *ehdr; 166 Elf_Shdr *shdr; 167 char *strsym = NULL; 168 int symlen; 169 int retval = -1; 170 171 if (elf_version(EV_CURRENT) == EV_NONE) { 172 warnx("ELF initialization failed"); 173 return -1; 174 } 175 176 e = elf_begin(fd, ELF_C_WRITE, NULL); 177 if (!e) { 178 warnx("elf_begin failed"); 179 goto error; 180 } 181 182 /* 183 * setup ELF header 184 */ 185 ehdr = elf_newehdr(e); 186 if (!ehdr) { 187 warnx("cannot get ehdr"); 188 goto error; 189 } 190 191 ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN; 192 ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS; 193 ehdr->e_machine = GEN_ELF_ARCH; 194 ehdr->e_type = ET_DYN; 195 ehdr->e_entry = GEN_ELF_TEXT_OFFSET; 196 ehdr->e_version = EV_CURRENT; 197 ehdr->e_shstrndx= 2; /* shdr index for section name */ 198 199 /* 200 * setup text section 201 */ 202 scn = elf_newscn(e); 203 if (!scn) { 204 warnx("cannot create section"); 205 goto error; 206 } 207 208 d = elf_newdata(scn); 209 if (!d) { 210 warnx("cannot get new data"); 211 goto error; 212 } 213 214 d->d_align = 16; 215 d->d_off = 0LL; 216 d->d_buf = (void *)code; 217 d->d_type = ELF_T_BYTE; 218 d->d_size = csize; 219 d->d_version = EV_CURRENT; 220 221 shdr = elf_getshdr(scn); 222 if (!shdr) { 223 warnx("cannot get section header"); 224 goto error; 225 } 226 227 shdr->sh_name = 1; 228 shdr->sh_type = SHT_PROGBITS; 229 shdr->sh_addr = GEN_ELF_TEXT_OFFSET; 230 shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 231 shdr->sh_entsize = 0; 232 233 /* 234 * setup section headers string table 235 */ 236 scn = elf_newscn(e); 237 if (!scn) { 238 warnx("cannot create section"); 239 goto error; 240 } 241 242 d = elf_newdata(scn); 243 if (!d) { 244 warnx("cannot get new data"); 245 goto error; 246 } 247 248 d->d_align = 1; 249 d->d_off = 0LL; 250 d->d_buf = shd_string_table; 251 d->d_type = ELF_T_BYTE; 252 d->d_size = sizeof(shd_string_table); 253 d->d_version = EV_CURRENT; 254 255 shdr = elf_getshdr(scn); 256 if (!shdr) { 257 warnx("cannot get section header"); 258 goto error; 259 } 260 261 shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */ 262 shdr->sh_type = SHT_STRTAB; 263 shdr->sh_flags = 0; 264 shdr->sh_entsize = 0; 265 266 /* 267 * setup symtab section 268 */ 269 symtab[1].st_size = csize; 270 symtab[1].st_value = GEN_ELF_TEXT_OFFSET; 271 272 scn = elf_newscn(e); 273 if (!scn) { 274 warnx("cannot create section"); 275 goto error; 276 } 277 278 d = elf_newdata(scn); 279 if (!d) { 280 warnx("cannot get new data"); 281 goto error; 282 } 283 284 d->d_align = 8; 285 d->d_off = 0LL; 286 d->d_buf = symtab; 287 d->d_type = ELF_T_SYM; 288 d->d_size = sizeof(symtab); 289 d->d_version = EV_CURRENT; 290 291 shdr = elf_getshdr(scn); 292 if (!shdr) { 293 warnx("cannot get section header"); 294 goto error; 295 } 296 297 shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */ 298 shdr->sh_type = SHT_SYMTAB; 299 shdr->sh_flags = 0; 300 shdr->sh_entsize = sizeof(Elf_Sym); 301 shdr->sh_link = 4; /* index of .strtab section */ 302 303 /* 304 * setup symbols string table 305 * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry 306 */ 307 symlen = 2 + strlen(sym); 308 strsym = calloc(1, symlen); 309 if (!strsym) { 310 warnx("cannot allocate strsym"); 311 goto error; 312 } 313 strcpy(strsym + 1, sym); 314 315 scn = elf_newscn(e); 316 if (!scn) { 317 warnx("cannot create section"); 318 goto error; 319 } 320 321 d = elf_newdata(scn); 322 if (!d) { 323 warnx("cannot get new data"); 324 goto error; 325 } 326 327 d->d_align = 1; 328 d->d_off = 0LL; 329 d->d_buf = strsym; 330 d->d_type = ELF_T_BYTE; 331 d->d_size = symlen; 332 d->d_version = EV_CURRENT; 333 334 shdr = elf_getshdr(scn); 335 if (!shdr) { 336 warnx("cannot get section header"); 337 goto error; 338 } 339 340 shdr->sh_name = 25; /* offset in shd_string_table */ 341 shdr->sh_type = SHT_STRTAB; 342 shdr->sh_flags = 0; 343 shdr->sh_entsize = 0; 344 345 /* 346 * setup build-id section 347 */ 348 scn = elf_newscn(e); 349 if (!scn) { 350 warnx("cannot create section"); 351 goto error; 352 } 353 354 d = elf_newdata(scn); 355 if (!d) { 356 warnx("cannot get new data"); 357 goto error; 358 } 359 360 /* 361 * build-id generation 362 */ 363 gen_build_id(&bnote, load_addr, code, csize); 364 bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */ 365 bnote.desc.descsz = sizeof(bnote.build_id); 366 bnote.desc.type = NT_GNU_BUILD_ID; 367 strcpy(bnote.name, "GNU"); 368 369 d->d_align = 4; 370 d->d_off = 0LL; 371 d->d_buf = &bnote; 372 d->d_type = ELF_T_BYTE; 373 d->d_size = sizeof(bnote); 374 d->d_version = EV_CURRENT; 375 376 shdr = elf_getshdr(scn); 377 if (!shdr) { 378 warnx("cannot get section header"); 379 goto error; 380 } 381 382 shdr->sh_name = 33; /* offset in shd_string_table */ 383 shdr->sh_type = SHT_NOTE; 384 shdr->sh_addr = 0x0; 385 shdr->sh_flags = SHF_ALLOC; 386 shdr->sh_size = sizeof(bnote); 387 shdr->sh_entsize = 0; 388 389 if (debug && nr_debug_entries) { 390 retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries); 391 if (retval) 392 goto error; 393 } else { 394 if (elf_update(e, ELF_C_WRITE) < 0) { 395 warnx("elf_update 4 failed"); 396 goto error; 397 } 398 } 399 400 retval = 0; 401 error: 402 (void)elf_end(e); 403 404 free(strsym); 405 406 407 return retval; 408 } 409 410 #ifndef JVMTI 411 412 static unsigned char x86_code[] = { 413 0xBB, 0x2A, 0x00, 0x00, 0x00, /* movl $42, %ebx */ 414 0xB8, 0x01, 0x00, 0x00, 0x00, /* movl $1, %eax */ 415 0xCD, 0x80 /* int $0x80 */ 416 }; 417 418 static struct options options; 419 420 int main(int argc, char **argv) 421 { 422 int c, fd, ret; 423 424 while ((c = getopt(argc, argv, "o:h")) != -1) { 425 switch (c) { 426 case 'o': 427 options.output = optarg; 428 break; 429 case 'h': 430 printf("Usage: genelf -o output_file [-h]\n"); 431 return 0; 432 default: 433 errx(1, "unknown option"); 434 } 435 } 436 437 fd = open(options.output, O_CREAT|O_TRUNC|O_RDWR, 0666); 438 if (fd == -1) 439 err(1, "cannot create file %s", options.output); 440 441 ret = jit_write_elf(fd, "main", x86_code, sizeof(x86_code)); 442 close(fd); 443 444 if (ret != 0) 445 unlink(options.output); 446 447 return ret; 448 } 449 #endif 450