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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * genelf.c4 * Copyright (C) 2014, Google, Inc5 *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_SUPPORT20#include <dwarf.h>21#endif22 23#include "genelf.h"24#include "../util/jitdump.h"25#include <linux/compiler.h>26 27#ifndef NT_GNU_BUILD_ID28#define NT_GNU_BUILD_ID 329#endif30 31#define BUILD_ID_URANDOM /* different uuid for each run */32 33#ifdef HAVE_LIBCRYPTO_SUPPORT34 35#define BUILD_ID_MD536#undef BUILD_ID_SHA /* does not seem to work well when linked with Java */37#undef BUILD_ID_URANDOM /* different uuid for each run */38 39#ifdef BUILD_ID_SHA40#include <openssl/sha.h>41#endif42 43#ifdef BUILD_ID_MD544#include <openssl/evp.h>45#include <openssl/md5.h>46#endif47#endif48 49 50typedef struct {51 unsigned int namesz; /* Size of entry's owner string */52 unsigned int descsz; /* Size of the note descriptor */53 unsigned int type; /* Interpretation of the descriptor */54 char name[0]; /* Start of the name+desc data */55} Elf_Note;56 57static char shd_string_table[] = {58 0,59 '.', 't', 'e', 'x', 't', 0, /* 1 */60 '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */61 '.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */62 '.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */63 '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */64 '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */65 '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */66 '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */67 '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */68 '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */69};70 71static struct buildid_note {72 Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */73 char name[4]; /* GNU\0 */74 char build_id[20];75} bnote;76 77static Elf_Sym symtab[]={78 /* symbol 0 MUST be the undefined symbol */79 { .st_name = 0, /* index in sym_string table */80 .st_info = ELF_ST_TYPE(STT_NOTYPE),81 .st_shndx = 0, /* for now */82 .st_value = 0x0,83 .st_other = ELF_ST_VIS(STV_DEFAULT),84 .st_size = 0,85 },86 { .st_name = 1, /* index in sym_string table */87 .st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC),88 .st_shndx = 1,89 .st_value = 0, /* for now */90 .st_other = ELF_ST_VIS(STV_DEFAULT),91 .st_size = 0, /* for now */92 }93};94 95#ifdef BUILD_ID_URANDOM96static void97gen_build_id(struct buildid_note *note,98 unsigned long load_addr __maybe_unused,99 const void *code __maybe_unused,100 size_t csize __maybe_unused)101{102 int fd;103 size_t sz = sizeof(note->build_id);104 ssize_t sret;105 106 fd = open("/dev/urandom", O_RDONLY);107 if (fd == -1)108 err(1, "cannot access /dev/urandom for buildid");109 110 sret = read(fd, note->build_id, sz);111 112 close(fd);113 114 if (sret != (ssize_t)sz)115 memset(note->build_id, 0, sz);116}117#endif118 119#ifdef BUILD_ID_SHA120static void121gen_build_id(struct buildid_note *note,122 unsigned long load_addr __maybe_unused,123 const void *code,124 size_t csize)125{126 if (sizeof(note->build_id) < SHA_DIGEST_LENGTH)127 errx(1, "build_id too small for SHA1");128 129 SHA1(code, csize, (unsigned char *)note->build_id);130}131#endif132 133#ifdef BUILD_ID_MD5134static void135gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize)136{137 EVP_MD_CTX *mdctx;138 139 if (sizeof(note->build_id) < 16)140 errx(1, "build_id too small for MD5");141 142 mdctx = EVP_MD_CTX_new();143 if (!mdctx)144 errx(2, "failed to create EVP_MD_CTX");145 146 EVP_DigestInit_ex(mdctx, EVP_md5(), NULL);147 EVP_DigestUpdate(mdctx, &load_addr, sizeof(load_addr));148 EVP_DigestUpdate(mdctx, code, csize);149 EVP_DigestFinal_ex(mdctx, (unsigned char *)note->build_id, NULL);150 EVP_MD_CTX_free(mdctx);151}152#endif153 154static int155jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size,156 uint64_t unwinding_size, uint64_t base_offset)157{158 Elf_Data *d;159 Elf_Scn *scn;160 Elf_Shdr *shdr;161 uint64_t unwinding_table_size = unwinding_size - unwinding_header_size;162 163 /*164 * setup eh_frame section165 */166 scn = elf_newscn(e);167 if (!scn) {168 warnx("cannot create section");169 return -1;170 }171 172 d = elf_newdata(scn);173 if (!d) {174 warnx("cannot get new data");175 return -1;176 }177 178 d->d_align = 8;179 d->d_off = 0LL;180 d->d_buf = unwinding;181 d->d_type = ELF_T_BYTE;182 d->d_size = unwinding_table_size;183 d->d_version = EV_CURRENT;184 185 shdr = elf_getshdr(scn);186 if (!shdr) {187 warnx("cannot get section header");188 return -1;189 }190 191 shdr->sh_name = 104;192 shdr->sh_type = SHT_PROGBITS;193 shdr->sh_addr = base_offset;194 shdr->sh_flags = SHF_ALLOC;195 shdr->sh_entsize = 0;196 197 /*198 * setup eh_frame_hdr section199 */200 scn = elf_newscn(e);201 if (!scn) {202 warnx("cannot create section");203 return -1;204 }205 206 d = elf_newdata(scn);207 if (!d) {208 warnx("cannot get new data");209 return -1;210 }211 212 d->d_align = 4;213 d->d_off = 0LL;214 d->d_buf = unwinding + unwinding_table_size;215 d->d_type = ELF_T_BYTE;216 d->d_size = unwinding_header_size;217 d->d_version = EV_CURRENT;218 219 shdr = elf_getshdr(scn);220 if (!shdr) {221 warnx("cannot get section header");222 return -1;223 }224 225 shdr->sh_name = 90;226 shdr->sh_type = SHT_PROGBITS;227 shdr->sh_addr = base_offset + unwinding_table_size;228 shdr->sh_flags = SHF_ALLOC;229 shdr->sh_entsize = 0;230 231 return 0;232}233 234/*235 * fd: file descriptor open for writing for the output file236 * load_addr: code load address (could be zero, just used for buildid)237 * sym: function name (for native code - used as the symbol)238 * code: the native code239 * csize: the code size in bytes240 */241int242jit_write_elf(int fd, uint64_t load_addr, const char *sym,243 const void *code, int csize,244 void *debug __maybe_unused, int nr_debug_entries __maybe_unused,245 void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size)246{247 Elf *e;248 Elf_Data *d;249 Elf_Scn *scn;250 Elf_Ehdr *ehdr;251 Elf_Phdr *phdr;252 Elf_Shdr *shdr;253 uint64_t eh_frame_base_offset;254 char *strsym = NULL;255 int symlen;256 int retval = -1;257 258 if (elf_version(EV_CURRENT) == EV_NONE) {259 warnx("ELF initialization failed");260 return -1;261 }262 263 e = elf_begin(fd, ELF_C_WRITE, NULL);264 if (!e) {265 warnx("elf_begin failed");266 goto error;267 }268 269 /*270 * setup ELF header271 */272 ehdr = elf_newehdr(e);273 if (!ehdr) {274 warnx("cannot get ehdr");275 goto error;276 }277 278 ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN;279 ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS;280 ehdr->e_machine = GEN_ELF_ARCH;281 ehdr->e_type = ET_DYN;282 ehdr->e_entry = GEN_ELF_TEXT_OFFSET;283 ehdr->e_version = EV_CURRENT;284 ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */285 286 /*287 * setup program header288 */289 phdr = elf_newphdr(e, 1);290 phdr[0].p_type = PT_LOAD;291 phdr[0].p_offset = GEN_ELF_TEXT_OFFSET;292 phdr[0].p_vaddr = GEN_ELF_TEXT_OFFSET;293 phdr[0].p_paddr = GEN_ELF_TEXT_OFFSET;294 phdr[0].p_filesz = csize;295 phdr[0].p_memsz = csize;296 phdr[0].p_flags = PF_X | PF_R;297 phdr[0].p_align = 8;298 299 /*300 * setup text section301 */302 scn = elf_newscn(e);303 if (!scn) {304 warnx("cannot create section");305 goto error;306 }307 308 d = elf_newdata(scn);309 if (!d) {310 warnx("cannot get new data");311 goto error;312 }313 314 d->d_align = 16;315 d->d_off = 0LL;316 d->d_buf = (void *)code;317 d->d_type = ELF_T_BYTE;318 d->d_size = csize;319 d->d_version = EV_CURRENT;320 321 shdr = elf_getshdr(scn);322 if (!shdr) {323 warnx("cannot get section header");324 goto error;325 }326 327 shdr->sh_name = 1;328 shdr->sh_type = SHT_PROGBITS;329 shdr->sh_addr = GEN_ELF_TEXT_OFFSET;330 shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;331 shdr->sh_entsize = 0;332 333 /*334 * Setup .eh_frame_hdr and .eh_frame335 */336 if (unwinding) {337 eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize);338 retval = jit_add_eh_frame_info(e, unwinding,339 unwinding_header_size, unwinding_size,340 eh_frame_base_offset);341 if (retval)342 goto error;343 retval = -1;344 }345 346 /*347 * setup section headers string table348 */349 scn = elf_newscn(e);350 if (!scn) {351 warnx("cannot create section");352 goto error;353 }354 355 d = elf_newdata(scn);356 if (!d) {357 warnx("cannot get new data");358 goto error;359 }360 361 d->d_align = 1;362 d->d_off = 0LL;363 d->d_buf = shd_string_table;364 d->d_type = ELF_T_BYTE;365 d->d_size = sizeof(shd_string_table);366 d->d_version = EV_CURRENT;367 368 shdr = elf_getshdr(scn);369 if (!shdr) {370 warnx("cannot get section header");371 goto error;372 }373 374 shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */375 shdr->sh_type = SHT_STRTAB;376 shdr->sh_flags = 0;377 shdr->sh_entsize = 0;378 379 /*380 * setup symtab section381 */382 symtab[1].st_size = csize;383 symtab[1].st_value = GEN_ELF_TEXT_OFFSET;384 385 scn = elf_newscn(e);386 if (!scn) {387 warnx("cannot create section");388 goto error;389 }390 391 d = elf_newdata(scn);392 if (!d) {393 warnx("cannot get new data");394 goto error;395 }396 397 d->d_align = 8;398 d->d_off = 0LL;399 d->d_buf = symtab;400 d->d_type = ELF_T_SYM;401 d->d_size = sizeof(symtab);402 d->d_version = EV_CURRENT;403 404 shdr = elf_getshdr(scn);405 if (!shdr) {406 warnx("cannot get section header");407 goto error;408 }409 410 shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */411 shdr->sh_type = SHT_SYMTAB;412 shdr->sh_flags = 0;413 shdr->sh_entsize = sizeof(Elf_Sym);414 shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */415 416 /*417 * setup symbols string table418 * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry419 */420 symlen = 2 + strlen(sym);421 strsym = calloc(1, symlen);422 if (!strsym) {423 warnx("cannot allocate strsym");424 goto error;425 }426 strcpy(strsym + 1, sym);427 428 scn = elf_newscn(e);429 if (!scn) {430 warnx("cannot create section");431 goto error;432 }433 434 d = elf_newdata(scn);435 if (!d) {436 warnx("cannot get new data");437 goto error;438 }439 440 d->d_align = 1;441 d->d_off = 0LL;442 d->d_buf = strsym;443 d->d_type = ELF_T_BYTE;444 d->d_size = symlen;445 d->d_version = EV_CURRENT;446 447 shdr = elf_getshdr(scn);448 if (!shdr) {449 warnx("cannot get section header");450 goto error;451 }452 453 shdr->sh_name = 25; /* offset in shd_string_table */454 shdr->sh_type = SHT_STRTAB;455 shdr->sh_flags = 0;456 shdr->sh_entsize = 0;457 458 /*459 * setup build-id section460 */461 scn = elf_newscn(e);462 if (!scn) {463 warnx("cannot create section");464 goto error;465 }466 467 d = elf_newdata(scn);468 if (!d) {469 warnx("cannot get new data");470 goto error;471 }472 473 /*474 * build-id generation475 */476 gen_build_id(&bnote, load_addr, code, csize);477 bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */478 bnote.desc.descsz = sizeof(bnote.build_id);479 bnote.desc.type = NT_GNU_BUILD_ID;480 strcpy(bnote.name, "GNU");481 482 d->d_align = 4;483 d->d_off = 0LL;484 d->d_buf = &bnote;485 d->d_type = ELF_T_BYTE;486 d->d_size = sizeof(bnote);487 d->d_version = EV_CURRENT;488 489 shdr = elf_getshdr(scn);490 if (!shdr) {491 warnx("cannot get section header");492 goto error;493 }494 495 shdr->sh_name = 33; /* offset in shd_string_table */496 shdr->sh_type = SHT_NOTE;497 shdr->sh_addr = 0x0;498 shdr->sh_flags = SHF_ALLOC;499 shdr->sh_size = sizeof(bnote);500 shdr->sh_entsize = 0;501 502#ifdef HAVE_DWARF_SUPPORT503 if (debug && nr_debug_entries) {504 retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);505 if (retval)506 goto error;507 } else508#endif509 {510 if (elf_update(e, ELF_C_WRITE) < 0) {511 warnx("elf_update 4 failed");512 goto error;513 }514 }515 516 retval = 0;517error:518 (void)elf_end(e);519 520 free(strsym);521 522 523 return retval;524}525