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508 lines
10 KiB
508 lines
10 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* genelf.c |
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* Copyright (C) 2014, Google, Inc |
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* |
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* Contributed by: |
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* Stephane Eranian <[email protected]> |
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*/ |
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#include <sys/types.h> |
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#include <stddef.h> |
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#include <libelf.h> |
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#include <string.h> |
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#include <stdlib.h> |
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#include <unistd.h> |
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#include <inttypes.h> |
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#include <fcntl.h> |
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#include <err.h> |
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#ifdef HAVE_DWARF_SUPPORT |
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#include <dwarf.h> |
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#endif |
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#include "genelf.h" |
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#include "../util/jitdump.h" |
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#include <linux/compiler.h> |
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#ifndef NT_GNU_BUILD_ID |
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#define NT_GNU_BUILD_ID 3 |
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#endif |
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#define BUILD_ID_URANDOM /* different uuid for each run */ |
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#ifdef HAVE_LIBCRYPTO |
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#define BUILD_ID_MD5 |
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#undef BUILD_ID_SHA /* does not seem to work well when linked with Java */ |
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#undef BUILD_ID_URANDOM /* different uuid for each run */ |
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#ifdef BUILD_ID_SHA |
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#include <openssl/sha.h> |
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#endif |
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#ifdef BUILD_ID_MD5 |
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#include <openssl/md5.h> |
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#endif |
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#endif |
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typedef struct { |
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unsigned int namesz; /* Size of entry's owner string */ |
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unsigned int descsz; /* Size of the note descriptor */ |
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unsigned int type; /* Interpretation of the descriptor */ |
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char name[0]; /* Start of the name+desc data */ |
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} Elf_Note; |
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struct options { |
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char *output; |
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int fd; |
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}; |
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static char shd_string_table[] = { |
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0, |
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'.', 't', 'e', 'x', 't', 0, /* 1 */ |
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'.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */ |
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'.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */ |
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'.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */ |
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'.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */ |
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'.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */ |
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'.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */ |
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'.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */ |
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'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */ |
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'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */ |
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}; |
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static struct buildid_note { |
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Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */ |
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char name[4]; /* GNU\0 */ |
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char build_id[20]; |
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} bnote; |
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static Elf_Sym symtab[]={ |
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/* symbol 0 MUST be the undefined symbol */ |
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{ .st_name = 0, /* index in sym_string table */ |
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.st_info = ELF_ST_TYPE(STT_NOTYPE), |
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.st_shndx = 0, /* for now */ |
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.st_value = 0x0, |
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.st_other = ELF_ST_VIS(STV_DEFAULT), |
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.st_size = 0, |
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}, |
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{ .st_name = 1, /* index in sym_string table */ |
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.st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC), |
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.st_shndx = 1, |
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.st_value = 0, /* for now */ |
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.st_other = ELF_ST_VIS(STV_DEFAULT), |
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.st_size = 0, /* for now */ |
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} |
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}; |
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#ifdef BUILD_ID_URANDOM |
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static void |
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gen_build_id(struct buildid_note *note, |
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unsigned long load_addr __maybe_unused, |
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const void *code __maybe_unused, |
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size_t csize __maybe_unused) |
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{ |
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int fd; |
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size_t sz = sizeof(note->build_id); |
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ssize_t sret; |
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fd = open("/dev/urandom", O_RDONLY); |
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if (fd == -1) |
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err(1, "cannot access /dev/urandom for buildid"); |
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sret = read(fd, note->build_id, sz); |
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close(fd); |
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if (sret != (ssize_t)sz) |
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memset(note->build_id, 0, sz); |
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} |
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#endif |
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#ifdef BUILD_ID_SHA |
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static void |
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gen_build_id(struct buildid_note *note, |
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unsigned long load_addr __maybe_unused, |
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const void *code, |
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size_t csize) |
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{ |
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if (sizeof(note->build_id) < SHA_DIGEST_LENGTH) |
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errx(1, "build_id too small for SHA1"); |
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SHA1(code, csize, (unsigned char *)note->build_id); |
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} |
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#endif |
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#ifdef BUILD_ID_MD5 |
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static void |
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gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize) |
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{ |
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MD5_CTX context; |
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if (sizeof(note->build_id) < 16) |
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errx(1, "build_id too small for MD5"); |
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MD5_Init(&context); |
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MD5_Update(&context, &load_addr, sizeof(load_addr)); |
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MD5_Update(&context, code, csize); |
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MD5_Final((unsigned char *)note->build_id, &context); |
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} |
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#endif |
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static int |
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jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size, |
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uint64_t unwinding_size, uint64_t base_offset) |
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{ |
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Elf_Data *d; |
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Elf_Scn *scn; |
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Elf_Shdr *shdr; |
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uint64_t unwinding_table_size = unwinding_size - unwinding_header_size; |
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/* |
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* setup eh_frame section |
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*/ |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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return -1; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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return -1; |
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} |
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d->d_align = 8; |
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d->d_off = 0LL; |
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d->d_buf = unwinding; |
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d->d_type = ELF_T_BYTE; |
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d->d_size = unwinding_table_size; |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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return -1; |
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} |
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shdr->sh_name = 104; |
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shdr->sh_type = SHT_PROGBITS; |
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shdr->sh_addr = base_offset; |
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shdr->sh_flags = SHF_ALLOC; |
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shdr->sh_entsize = 0; |
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/* |
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* setup eh_frame_hdr section |
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*/ |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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return -1; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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return -1; |
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} |
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d->d_align = 4; |
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d->d_off = 0LL; |
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d->d_buf = unwinding + unwinding_table_size; |
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d->d_type = ELF_T_BYTE; |
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d->d_size = unwinding_header_size; |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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return -1; |
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} |
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shdr->sh_name = 90; |
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shdr->sh_type = SHT_PROGBITS; |
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shdr->sh_addr = base_offset + unwinding_table_size; |
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shdr->sh_flags = SHF_ALLOC; |
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shdr->sh_entsize = 0; |
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return 0; |
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} |
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/* |
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* fd: file descriptor open for writing for the output file |
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* load_addr: code load address (could be zero, just used for buildid) |
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* sym: function name (for native code - used as the symbol) |
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* code: the native code |
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* csize: the code size in bytes |
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*/ |
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int |
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jit_write_elf(int fd, uint64_t load_addr, const char *sym, |
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const void *code, int csize, |
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void *debug __maybe_unused, int nr_debug_entries __maybe_unused, |
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void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size) |
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{ |
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Elf *e; |
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Elf_Data *d; |
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Elf_Scn *scn; |
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Elf_Ehdr *ehdr; |
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Elf_Shdr *shdr; |
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uint64_t eh_frame_base_offset; |
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char *strsym = NULL; |
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int symlen; |
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int retval = -1; |
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if (elf_version(EV_CURRENT) == EV_NONE) { |
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warnx("ELF initialization failed"); |
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return -1; |
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} |
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e = elf_begin(fd, ELF_C_WRITE, NULL); |
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if (!e) { |
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warnx("elf_begin failed"); |
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goto error; |
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} |
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/* |
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* setup ELF header |
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*/ |
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ehdr = elf_newehdr(e); |
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if (!ehdr) { |
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warnx("cannot get ehdr"); |
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goto error; |
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} |
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ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN; |
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ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS; |
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ehdr->e_machine = GEN_ELF_ARCH; |
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ehdr->e_type = ET_DYN; |
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ehdr->e_entry = GEN_ELF_TEXT_OFFSET; |
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ehdr->e_version = EV_CURRENT; |
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ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */ |
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/* |
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* setup text section |
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*/ |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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goto error; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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goto error; |
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} |
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d->d_align = 16; |
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d->d_off = 0LL; |
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d->d_buf = (void *)code; |
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d->d_type = ELF_T_BYTE; |
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d->d_size = csize; |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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goto error; |
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} |
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shdr->sh_name = 1; |
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shdr->sh_type = SHT_PROGBITS; |
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shdr->sh_addr = GEN_ELF_TEXT_OFFSET; |
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shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; |
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shdr->sh_entsize = 0; |
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/* |
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* Setup .eh_frame_hdr and .eh_frame |
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*/ |
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if (unwinding) { |
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eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize); |
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retval = jit_add_eh_frame_info(e, unwinding, |
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unwinding_header_size, unwinding_size, |
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eh_frame_base_offset); |
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if (retval) |
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goto error; |
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} |
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/* |
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* setup section headers string table |
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*/ |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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goto error; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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goto error; |
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} |
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d->d_align = 1; |
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d->d_off = 0LL; |
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d->d_buf = shd_string_table; |
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d->d_type = ELF_T_BYTE; |
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d->d_size = sizeof(shd_string_table); |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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goto error; |
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} |
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shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */ |
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shdr->sh_type = SHT_STRTAB; |
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shdr->sh_flags = 0; |
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shdr->sh_entsize = 0; |
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/* |
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* setup symtab section |
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*/ |
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symtab[1].st_size = csize; |
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symtab[1].st_value = GEN_ELF_TEXT_OFFSET; |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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goto error; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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goto error; |
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} |
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d->d_align = 8; |
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d->d_off = 0LL; |
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d->d_buf = symtab; |
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d->d_type = ELF_T_SYM; |
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d->d_size = sizeof(symtab); |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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goto error; |
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} |
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shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */ |
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shdr->sh_type = SHT_SYMTAB; |
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shdr->sh_flags = 0; |
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shdr->sh_entsize = sizeof(Elf_Sym); |
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shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */ |
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/* |
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* setup symbols string table |
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* 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry |
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*/ |
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symlen = 2 + strlen(sym); |
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strsym = calloc(1, symlen); |
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if (!strsym) { |
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warnx("cannot allocate strsym"); |
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goto error; |
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} |
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strcpy(strsym + 1, sym); |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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goto error; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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goto error; |
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} |
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d->d_align = 1; |
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d->d_off = 0LL; |
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d->d_buf = strsym; |
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d->d_type = ELF_T_BYTE; |
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d->d_size = symlen; |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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goto error; |
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} |
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shdr->sh_name = 25; /* offset in shd_string_table */ |
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shdr->sh_type = SHT_STRTAB; |
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shdr->sh_flags = 0; |
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shdr->sh_entsize = 0; |
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/* |
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* setup build-id section |
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*/ |
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scn = elf_newscn(e); |
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if (!scn) { |
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warnx("cannot create section"); |
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goto error; |
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} |
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d = elf_newdata(scn); |
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if (!d) { |
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warnx("cannot get new data"); |
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goto error; |
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} |
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/* |
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* build-id generation |
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*/ |
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gen_build_id(&bnote, load_addr, code, csize); |
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bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */ |
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bnote.desc.descsz = sizeof(bnote.build_id); |
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bnote.desc.type = NT_GNU_BUILD_ID; |
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strcpy(bnote.name, "GNU"); |
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d->d_align = 4; |
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d->d_off = 0LL; |
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d->d_buf = &bnote; |
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d->d_type = ELF_T_BYTE; |
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d->d_size = sizeof(bnote); |
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d->d_version = EV_CURRENT; |
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shdr = elf_getshdr(scn); |
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if (!shdr) { |
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warnx("cannot get section header"); |
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goto error; |
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} |
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shdr->sh_name = 33; /* offset in shd_string_table */ |
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shdr->sh_type = SHT_NOTE; |
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shdr->sh_addr = 0x0; |
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shdr->sh_flags = SHF_ALLOC; |
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shdr->sh_size = sizeof(bnote); |
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shdr->sh_entsize = 0; |
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#ifdef HAVE_DWARF_SUPPORT |
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if (debug && nr_debug_entries) { |
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retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries); |
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if (retval) |
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goto error; |
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} else |
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#endif |
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{ |
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if (elf_update(e, ELF_C_WRITE) < 0) { |
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warnx("elf_update 4 failed"); |
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goto error; |
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} |
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} |
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retval = 0; |
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error: |
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(void)elf_end(e); |
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free(strsym); |
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return retval; |
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}
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