tools/perf/util/genelf.c

   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