LXR linux/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#ifdef HAVE_DWARF_SUPPORT
  23#include <dwarf.h>
  24#endif
  25
  26#include "perf.h"
  27#include "genelf.h"
  28#include "../util/jitdump.h"
  29
  30#ifndef NT_GNU_BUILD_ID
  31#define NT_GNU_BUILD_ID 3
  32#endif
  33
  34#define JVMTI
  35
  36#define BUILD_ID_URANDOM /* different uuid for each run */
  37
  38#ifdef HAVE_LIBCRYPTO
  39
  40#define BUILD_ID_MD5
  41#undef BUILD_ID_SHA     /* does not seem to work well when linked with Java */
  42#undef BUILD_ID_URANDOM /* different uuid for each run */
  43
  44#ifdef BUILD_ID_SHA
  45#include <openssl/sha.h>
  46#endif
  47
  48#ifdef BUILD_ID_MD5
  49#include <openssl/md5.h>
  50#endif
  51#endif
  52
  53
  54typedef struct {
  55  unsigned int namesz;  /* Size of entry's owner string */
  56  unsigned int descsz;  /* Size of the note descriptor */
  57  unsigned int type;    /* Interpretation of the descriptor */
  58  char         name[0]; /* Start of the name+desc data */
  59} Elf_Note;
  60
  61struct options {
  62        char *output;
  63        int fd;
  64};
  65
  66static char shd_string_table[] = {
  67        0,
  68        '.', 't', 'e', 'x', 't', 0,                     /*  1 */
  69        '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /*  7 */
  70        '.', 's', 'y', 'm', 't', 'a', 'b', 0,           /* 17 */
  71        '.', 's', 't', 'r', 't', 'a', 'b', 0,           /* 25 */
  72        '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */
  73        '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */
  74        '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */
  75        '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */
  76        '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */
  77        '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */
  78};
  79
  80static struct buildid_note {
  81        Elf_Note desc;          /* descsz: size of build-id, must be multiple of 4 */
  82        char     name[4];       /* GNU\0 */
  83        char     build_id[20];
  84} bnote;
  85
  86static Elf_Sym symtab[]={
  87        /* symbol 0 MUST be the undefined symbol */
  88        { .st_name  = 0, /* index in sym_string table */
  89          .st_info  = ELF_ST_TYPE(STT_NOTYPE),
  90          .st_shndx = 0, /* for now */
  91          .st_value = 0x0,
  92          .st_other = ELF_ST_VIS(STV_DEFAULT),
  93          .st_size  = 0,
  94        },
  95        { .st_name  = 1, /* index in sym_string table */
  96          .st_info  = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC),
  97          .st_shndx = 1,
  98          .st_value = 0, /* for now */
  99          .st_other = ELF_ST_VIS(STV_DEFAULT),
 100          .st_size  = 0, /* for now */
 101        }
 102};
 103
 104#ifdef BUILD_ID_URANDOM
 105static void
 106gen_build_id(struct buildid_note *note,
 107             unsigned long load_addr __maybe_unused,
 108             const void *code __maybe_unused,
 109             size_t csize __maybe_unused)
 110{
 111        int fd;
 112        size_t sz = sizeof(note->build_id);
 113        ssize_t sret;
 114
 115        fd = open("/dev/urandom", O_RDONLY);
 116        if (fd == -1)
 117                err(1, "cannot access /dev/urandom for builid");
 118
 119        sret = read(fd, note->build_id, sz);
 120
 121        close(fd);
 122
 123        if (sret != (ssize_t)sz)
 124                memset(note->build_id, 0, sz);
 125}
 126#endif
 127
 128#ifdef BUILD_ID_SHA
 129static void
 130gen_build_id(struct buildid_note *note,
 131             unsigned long load_addr __maybe_unused,
 132             const void *code,
 133             size_t csize)
 134{
 135        if (sizeof(note->build_id) < SHA_DIGEST_LENGTH)
 136                errx(1, "build_id too small for SHA1");
 137
 138        SHA1(code, csize, (unsigned char *)note->build_id);
 139}
 140#endif
 141
 142#ifdef BUILD_ID_MD5
 143static void
 144gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize)
 145{
 146        MD5_CTX context;
 147
 148        if (sizeof(note->build_id) < 16)
 149                errx(1, "build_id too small for MD5");
 150
 151        MD5_Init(&context);
 152        MD5_Update(&context, &load_addr, sizeof(load_addr));
 153        MD5_Update(&context, code, csize);
 154        MD5_Final((unsigned char *)note->build_id, &context);
 155}
 156#endif
 157
 158static int
 159jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size,
 160                      uint64_t unwinding_size, uint64_t base_offset)
 161{
 162        Elf_Data *d;
 163        Elf_Scn *scn;
 164        Elf_Shdr *shdr;
 165        uint64_t unwinding_table_size = unwinding_size - unwinding_header_size;
 166
 167        /*
 168         * setup eh_frame section
 169         */
 170        scn = elf_newscn(e);
 171        if (!scn) {
 172                warnx("cannot create section");
 173                return -1;
 174        }
 175
 176        d = elf_newdata(scn);
 177        if (!d) {
 178                warnx("cannot get new data");
 179                return -1;
 180        }
 181
 182        d->d_align = 8;
 183        d->d_off = 0LL;
 184        d->d_buf = unwinding;
 185        d->d_type = ELF_T_BYTE;
 186        d->d_size = unwinding_table_size;
 187        d->d_version = EV_CURRENT;
 188
 189        shdr = elf_getshdr(scn);
 190        if (!shdr) {
 191                warnx("cannot get section header");
 192                return -1;
 193        }
 194
 195        shdr->sh_name = 104;
 196        shdr->sh_type = SHT_PROGBITS;
 197        shdr->sh_addr = base_offset;
 198        shdr->sh_flags = SHF_ALLOC;
 199        shdr->sh_entsize = 0;
 200
 201        /*
 202         * setup eh_frame_hdr section
 203         */
 204        scn = elf_newscn(e);
 205        if (!scn) {
 206                warnx("cannot create section");
 207                return -1;
 208        }
 209
 210        d = elf_newdata(scn);
 211        if (!d) {
 212                warnx("cannot get new data");
 213                return -1;
 214        }
 215
 216        d->d_align = 4;
 217        d->d_off = 0LL;
 218        d->d_buf = unwinding + unwinding_table_size;
 219        d->d_type = ELF_T_BYTE;
 220        d->d_size = unwinding_header_size;
 221        d->d_version = EV_CURRENT;
 222
 223        shdr = elf_getshdr(scn);
 224        if (!shdr) {
 225                warnx("cannot get section header");
 226                return -1;
 227        }
 228
 229        shdr->sh_name = 90;
 230        shdr->sh_type = SHT_PROGBITS;
 231        shdr->sh_addr = base_offset + unwinding_table_size;
 232        shdr->sh_flags = SHF_ALLOC;
 233        shdr->sh_entsize = 0;
 234
 235        return 0;
 236}
 237
 238/*
 239 * fd: file descriptor open for writing for the output file
 240 * load_addr: code load address (could be zero, just used for buildid)
 241 * sym: function name (for native code - used as the symbol)
 242 * code: the native code
 243 * csize: the code size in bytes
 244 */
 245int
 246jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 247              const void *code, int csize,
 248              void *debug __maybe_unused, int nr_debug_entries __maybe_unused,
 249              void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size)
 250{
 251        Elf *e;
 252        Elf_Data *d;
 253        Elf_Scn *scn;
 254        Elf_Ehdr *ehdr;
 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 text section
 291         */
 292        scn = elf_newscn(e);
 293        if (!scn) {
 294                warnx("cannot create section");
 295                goto error;
 296        }
 297
 298        d = elf_newdata(scn);
 299        if (!d) {
 300                warnx("cannot get new data");
 301                goto error;
 302        }
 303
 304        d->d_align = 16;
 305        d->d_off = 0LL;
 306        d->d_buf = (void *)code;
 307        d->d_type = ELF_T_BYTE;
 308        d->d_size = csize;
 309        d->d_version = EV_CURRENT;
 310
 311        shdr = elf_getshdr(scn);
 312        if (!shdr) {
 313                warnx("cannot get section header");
 314                goto error;
 315        }
 316
 317        shdr->sh_name = 1;
 318        shdr->sh_type = SHT_PROGBITS;
 319        shdr->sh_addr = GEN_ELF_TEXT_OFFSET;
 320        shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
 321        shdr->sh_entsize = 0;
 322
 323        /*
 324         * Setup .eh_frame_hdr and .eh_frame
 325         */
 326        if (unwinding) {
 327                eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize);
 328                retval = jit_add_eh_frame_info(e, unwinding,
 329                                               unwinding_header_size, unwinding_size,
 330                                               eh_frame_base_offset);
 331                if (retval)
 332                        goto error;
 333        }
 334
 335        /*
 336         * setup section headers string table
 337         */
 338        scn = elf_newscn(e);
 339        if (!scn) {
 340                warnx("cannot create section");
 341                goto error;
 342        }
 343
 344        d = elf_newdata(scn);
 345        if (!d) {
 346                warnx("cannot get new data");
 347                goto error;
 348        }
 349
 350        d->d_align = 1;
 351        d->d_off = 0LL;
 352        d->d_buf = shd_string_table;
 353        d->d_type = ELF_T_BYTE;
 354        d->d_size = sizeof(shd_string_table);
 355        d->d_version = EV_CURRENT;
 356
 357        shdr = elf_getshdr(scn);
 358        if (!shdr) {
 359                warnx("cannot get section header");
 360                goto error;
 361        }
 362
 363        shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */
 364        shdr->sh_type = SHT_STRTAB;
 365        shdr->sh_flags = 0;
 366        shdr->sh_entsize = 0;
 367
 368        /*
 369         * setup symtab section
 370         */
 371        symtab[1].st_size  = csize;
 372        symtab[1].st_value = GEN_ELF_TEXT_OFFSET;
 373
 374        scn = elf_newscn(e);
 375        if (!scn) {
 376                warnx("cannot create section");
 377                goto error;
 378        }
 379
 380        d = elf_newdata(scn);
 381        if (!d) {
 382                warnx("cannot get new data");
 383                goto error;
 384        }
 385
 386        d->d_align = 8;
 387        d->d_off = 0LL;
 388        d->d_buf = symtab;
 389        d->d_type = ELF_T_SYM;
 390        d->d_size = sizeof(symtab);
 391        d->d_version = EV_CURRENT;
 392
 393        shdr = elf_getshdr(scn);
 394        if (!shdr) {
 395                warnx("cannot get section header");
 396                goto error;
 397        }
 398
 399        shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */
 400        shdr->sh_type = SHT_SYMTAB;
 401        shdr->sh_flags = 0;
 402        shdr->sh_entsize = sizeof(Elf_Sym);
 403        shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */
 404
 405        /*
 406         * setup symbols string table
 407         * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry
 408         */
 409        symlen = 2 + strlen(sym);
 410        strsym = calloc(1, symlen);
 411        if (!strsym) {
 412                warnx("cannot allocate strsym");
 413                goto error;
 414        }
 415        strcpy(strsym + 1, sym);
 416
 417        scn = elf_newscn(e);
 418        if (!scn) {
 419                warnx("cannot create section");
 420                goto error;
 421        }
 422
 423        d = elf_newdata(scn);
 424        if (!d) {
 425                warnx("cannot get new data");
 426                goto error;
 427        }
 428
 429        d->d_align = 1;
 430        d->d_off = 0LL;
 431        d->d_buf = strsym;
 432        d->d_type = ELF_T_BYTE;
 433        d->d_size = symlen;
 434        d->d_version = EV_CURRENT;
 435
 436        shdr = elf_getshdr(scn);
 437        if (!shdr) {
 438                warnx("cannot get section header");
 439                goto error;
 440        }
 441
 442        shdr->sh_name = 25; /* offset in shd_string_table */
 443        shdr->sh_type = SHT_STRTAB;
 444        shdr->sh_flags = 0;
 445        shdr->sh_entsize = 0;
 446
 447        /*
 448         * setup build-id section
 449         */
 450        scn = elf_newscn(e);
 451        if (!scn) {
 452                warnx("cannot create section");
 453                goto error;
 454        }
 455
 456        d = elf_newdata(scn);
 457        if (!d) {
 458                warnx("cannot get new data");
 459                goto error;
 460        }
 461
 462        /*
 463         * build-id generation
 464         */
 465        gen_build_id(&bnote, load_addr, code, csize);
 466        bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */
 467        bnote.desc.descsz = sizeof(bnote.build_id);
 468        bnote.desc.type   = NT_GNU_BUILD_ID;
 469        strcpy(bnote.name, "GNU");
 470
 471        d->d_align = 4;
 472        d->d_off = 0LL;
 473        d->d_buf = &bnote;
 474        d->d_type = ELF_T_BYTE;
 475        d->d_size = sizeof(bnote);
 476        d->d_version = EV_CURRENT;
 477
 478        shdr = elf_getshdr(scn);
 479        if (!shdr) {
 480                warnx("cannot get section header");
 481                goto error;
 482        }
 483
 484        shdr->sh_name = 33; /* offset in shd_string_table */
 485        shdr->sh_type = SHT_NOTE;
 486        shdr->sh_addr = 0x0;
 487        shdr->sh_flags = SHF_ALLOC;
 488        shdr->sh_size = sizeof(bnote);
 489        shdr->sh_entsize = 0;
 490
 491#ifdef HAVE_DWARF_SUPPORT
 492        if (debug && nr_debug_entries) {
 493                retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
 494                if (retval)
 495                        goto error;
 496        } else
 497#endif
 498        {
 499                if (elf_update(e, ELF_C_WRITE) < 0) {
 500                        warnx("elf_update 4 failed");
 501                        goto error;
 502                }
 503        }
 504
 505        retval = 0;
 506error:
 507        (void)elf_end(e);
 508
 509        free(strsym);
 510
 511
 512        return retval;
 513}
 514
 515#ifndef JVMTI
 516
 517static unsigned char x86_code[] = {
 518    0xBB, 0x2A, 0x00, 0x00, 0x00, /* movl $42, %ebx */
 519    0xB8, 0x01, 0x00, 0x00, 0x00, /* movl $1, %eax */
 520    0xCD, 0x80            /* int $0x80 */
 521};
 522
 523static struct options options;
 524
 525int main(int argc, char **argv)
 526{
 527        int c, fd, ret;
 528
 529        while ((c = getopt(argc, argv, "o:h")) != -1) {
 530                switch (c) {
 531                case 'o':
 532                        options.output = optarg;
 533                        break;
 534                case 'h':
 535                        printf("Usage: genelf -o output_file [-h]\n");
 536                        return 0;
 537                default:
 538                        errx(1, "unknown option");
 539                }
 540        }
 541
 542        fd = open(options.output, O_CREAT|O_TRUNC|O_RDWR, 0666);
 543        if (fd == -1)
 544                err(1, "cannot create file %s", options.output);
 545
 546        ret = jit_write_elf(fd, "main", x86_code, sizeof(x86_code));
 547        close(fd);
 548
 549        if (ret != 0)
 550                unlink(options.output);
 551
 552        return ret;
 553}
 554#endif
 555