| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * genelf.c |
| * Copyright (C) 2014, Google, Inc |
| * |
| * Contributed by: |
| * Stephane Eranian <eranian@gmail.com> |
| */ |
| |
| #include <sys/types.h> |
| #include <stdio.h> |
| #include <getopt.h> |
| #include <stddef.h> |
| #include <libelf.h> |
| #include <string.h> |
| #include <stdlib.h> |
| #include <unistd.h> |
| #include <inttypes.h> |
| #include <limits.h> |
| #include <fcntl.h> |
| #include <err.h> |
| #ifdef HAVE_DWARF_SUPPORT |
| #include <dwarf.h> |
| #endif |
| |
| #include "genelf.h" |
| #include "../util/jitdump.h" |
| #include <linux/compiler.h> |
| |
| #ifndef NT_GNU_BUILD_ID |
| #define NT_GNU_BUILD_ID 3 |
| #endif |
| |
| #define JVMTI |
| |
| #define BUILD_ID_URANDOM /* different uuid for each run */ |
| |
| #ifdef HAVE_LIBCRYPTO |
| |
| #define BUILD_ID_MD5 |
| #undef BUILD_ID_SHA /* does not seem to work well when linked with Java */ |
| #undef BUILD_ID_URANDOM /* different uuid for each run */ |
| |
| #ifdef BUILD_ID_SHA |
| #include <openssl/sha.h> |
| #endif |
| |
| #ifdef BUILD_ID_MD5 |
| #include <openssl/md5.h> |
| #endif |
| #endif |
| |
| |
| typedef struct { |
| unsigned int namesz; /* Size of entry's owner string */ |
| unsigned int descsz; /* Size of the note descriptor */ |
| unsigned int type; /* Interpretation of the descriptor */ |
| char name[0]; /* Start of the name+desc data */ |
| } Elf_Note; |
| |
| struct options { |
| char *output; |
| int fd; |
| }; |
| |
| static char shd_string_table[] = { |
| 0, |
| '.', 't', 'e', 'x', 't', 0, /* 1 */ |
| '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */ |
| '.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */ |
| '.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */ |
| '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */ |
| '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */ |
| '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */ |
| '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */ |
| '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */ |
| '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */ |
| }; |
| |
| static struct buildid_note { |
| Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */ |
| char name[4]; /* GNU\0 */ |
| char build_id[20]; |
| } bnote; |
| |
| static Elf_Sym symtab[]={ |
| /* symbol 0 MUST be the undefined symbol */ |
| { .st_name = 0, /* index in sym_string table */ |
| .st_info = ELF_ST_TYPE(STT_NOTYPE), |
| .st_shndx = 0, /* for now */ |
| .st_value = 0x0, |
| .st_other = ELF_ST_VIS(STV_DEFAULT), |
| .st_size = 0, |
| }, |
| { .st_name = 1, /* index in sym_string table */ |
| .st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC), |
| .st_shndx = 1, |
| .st_value = 0, /* for now */ |
| .st_other = ELF_ST_VIS(STV_DEFAULT), |
| .st_size = 0, /* for now */ |
| } |
| }; |
| |
| #ifdef BUILD_ID_URANDOM |
| static void |
| gen_build_id(struct buildid_note *note, |
| unsigned long load_addr __maybe_unused, |
| const void *code __maybe_unused, |
| size_t csize __maybe_unused) |
| { |
| int fd; |
| size_t sz = sizeof(note->build_id); |
| ssize_t sret; |
| |
| fd = open("/dev/urandom", O_RDONLY); |
| if (fd == -1) |
| err(1, "cannot access /dev/urandom for buildid"); |
| |
| sret = read(fd, note->build_id, sz); |
| |
| close(fd); |
| |
| if (sret != (ssize_t)sz) |
| memset(note->build_id, 0, sz); |
| } |
| #endif |
| |
| #ifdef BUILD_ID_SHA |
| static void |
| gen_build_id(struct buildid_note *note, |
| unsigned long load_addr __maybe_unused, |
| const void *code, |
| size_t csize) |
| { |
| if (sizeof(note->build_id) < SHA_DIGEST_LENGTH) |
| errx(1, "build_id too small for SHA1"); |
| |
| SHA1(code, csize, (unsigned char *)note->build_id); |
| } |
| #endif |
| |
| #ifdef BUILD_ID_MD5 |
| static void |
| gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize) |
| { |
| MD5_CTX context; |
| |
| if (sizeof(note->build_id) < 16) |
| errx(1, "build_id too small for MD5"); |
| |
| MD5_Init(&context); |
| MD5_Update(&context, &load_addr, sizeof(load_addr)); |
| MD5_Update(&context, code, csize); |
| MD5_Final((unsigned char *)note->build_id, &context); |
| } |
| #endif |
| |
| static int |
| jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size, |
| uint64_t unwinding_size, uint64_t base_offset) |
| { |
| Elf_Data *d; |
| Elf_Scn *scn; |
| Elf_Shdr *shdr; |
| uint64_t unwinding_table_size = unwinding_size - unwinding_header_size; |
| |
| /* |
| * setup eh_frame section |
| */ |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| return -1; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| return -1; |
| } |
| |
| d->d_align = 8; |
| d->d_off = 0LL; |
| d->d_buf = unwinding; |
| d->d_type = ELF_T_BYTE; |
| d->d_size = unwinding_table_size; |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| return -1; |
| } |
| |
| shdr->sh_name = 104; |
| shdr->sh_type = SHT_PROGBITS; |
| shdr->sh_addr = base_offset; |
| shdr->sh_flags = SHF_ALLOC; |
| shdr->sh_entsize = 0; |
| |
| /* |
| * setup eh_frame_hdr section |
| */ |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| return -1; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| return -1; |
| } |
| |
| d->d_align = 4; |
| d->d_off = 0LL; |
| d->d_buf = unwinding + unwinding_table_size; |
| d->d_type = ELF_T_BYTE; |
| d->d_size = unwinding_header_size; |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| return -1; |
| } |
| |
| shdr->sh_name = 90; |
| shdr->sh_type = SHT_PROGBITS; |
| shdr->sh_addr = base_offset + unwinding_table_size; |
| shdr->sh_flags = SHF_ALLOC; |
| shdr->sh_entsize = 0; |
| |
| return 0; |
| } |
| |
| /* |
| * fd: file descriptor open for writing for the output file |
| * load_addr: code load address (could be zero, just used for buildid) |
| * sym: function name (for native code - used as the symbol) |
| * code: the native code |
| * csize: the code size in bytes |
| */ |
| int |
| jit_write_elf(int fd, uint64_t load_addr, const char *sym, |
| const void *code, int csize, |
| void *debug __maybe_unused, int nr_debug_entries __maybe_unused, |
| void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size) |
| { |
| Elf *e; |
| Elf_Data *d; |
| Elf_Scn *scn; |
| Elf_Ehdr *ehdr; |
| Elf_Shdr *shdr; |
| uint64_t eh_frame_base_offset; |
| char *strsym = NULL; |
| int symlen; |
| int retval = -1; |
| |
| if (elf_version(EV_CURRENT) == EV_NONE) { |
| warnx("ELF initialization failed"); |
| return -1; |
| } |
| |
| e = elf_begin(fd, ELF_C_WRITE, NULL); |
| if (!e) { |
| warnx("elf_begin failed"); |
| goto error; |
| } |
| |
| /* |
| * setup ELF header |
| */ |
| ehdr = elf_newehdr(e); |
| if (!ehdr) { |
| warnx("cannot get ehdr"); |
| goto error; |
| } |
| |
| ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN; |
| ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS; |
| ehdr->e_machine = GEN_ELF_ARCH; |
| ehdr->e_type = ET_DYN; |
| ehdr->e_entry = GEN_ELF_TEXT_OFFSET; |
| ehdr->e_version = EV_CURRENT; |
| ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */ |
| |
| /* |
| * setup text section |
| */ |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| goto error; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| goto error; |
| } |
| |
| d->d_align = 16; |
| d->d_off = 0LL; |
| d->d_buf = (void *)code; |
| d->d_type = ELF_T_BYTE; |
| d->d_size = csize; |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| goto error; |
| } |
| |
| shdr->sh_name = 1; |
| shdr->sh_type = SHT_PROGBITS; |
| shdr->sh_addr = GEN_ELF_TEXT_OFFSET; |
| shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; |
| shdr->sh_entsize = 0; |
| |
| /* |
| * Setup .eh_frame_hdr and .eh_frame |
| */ |
| if (unwinding) { |
| eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize); |
| retval = jit_add_eh_frame_info(e, unwinding, |
| unwinding_header_size, unwinding_size, |
| eh_frame_base_offset); |
| if (retval) |
| goto error; |
| } |
| |
| /* |
| * setup section headers string table |
| */ |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| goto error; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| goto error; |
| } |
| |
| d->d_align = 1; |
| d->d_off = 0LL; |
| d->d_buf = shd_string_table; |
| d->d_type = ELF_T_BYTE; |
| d->d_size = sizeof(shd_string_table); |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| goto error; |
| } |
| |
| shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */ |
| shdr->sh_type = SHT_STRTAB; |
| shdr->sh_flags = 0; |
| shdr->sh_entsize = 0; |
| |
| /* |
| * setup symtab section |
| */ |
| symtab[1].st_size = csize; |
| symtab[1].st_value = GEN_ELF_TEXT_OFFSET; |
| |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| goto error; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| goto error; |
| } |
| |
| d->d_align = 8; |
| d->d_off = 0LL; |
| d->d_buf = symtab; |
| d->d_type = ELF_T_SYM; |
| d->d_size = sizeof(symtab); |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| goto error; |
| } |
| |
| shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */ |
| shdr->sh_type = SHT_SYMTAB; |
| shdr->sh_flags = 0; |
| shdr->sh_entsize = sizeof(Elf_Sym); |
| shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */ |
| |
| /* |
| * setup symbols string table |
| * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry |
| */ |
| symlen = 2 + strlen(sym); |
| strsym = calloc(1, symlen); |
| if (!strsym) { |
| warnx("cannot allocate strsym"); |
| goto error; |
| } |
| strcpy(strsym + 1, sym); |
| |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| goto error; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| goto error; |
| } |
| |
| d->d_align = 1; |
| d->d_off = 0LL; |
| d->d_buf = strsym; |
| d->d_type = ELF_T_BYTE; |
| d->d_size = symlen; |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| goto error; |
| } |
| |
| shdr->sh_name = 25; /* offset in shd_string_table */ |
| shdr->sh_type = SHT_STRTAB; |
| shdr->sh_flags = 0; |
| shdr->sh_entsize = 0; |
| |
| /* |
| * setup build-id section |
| */ |
| scn = elf_newscn(e); |
| if (!scn) { |
| warnx("cannot create section"); |
| goto error; |
| } |
| |
| d = elf_newdata(scn); |
| if (!d) { |
| warnx("cannot get new data"); |
| goto error; |
| } |
| |
| /* |
| * build-id generation |
| */ |
| gen_build_id(&bnote, load_addr, code, csize); |
| bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */ |
| bnote.desc.descsz = sizeof(bnote.build_id); |
| bnote.desc.type = NT_GNU_BUILD_ID; |
| strcpy(bnote.name, "GNU"); |
| |
| d->d_align = 4; |
| d->d_off = 0LL; |
| d->d_buf = &bnote; |
| d->d_type = ELF_T_BYTE; |
| d->d_size = sizeof(bnote); |
| d->d_version = EV_CURRENT; |
| |
| shdr = elf_getshdr(scn); |
| if (!shdr) { |
| warnx("cannot get section header"); |
| goto error; |
| } |
| |
| shdr->sh_name = 33; /* offset in shd_string_table */ |
| shdr->sh_type = SHT_NOTE; |
| shdr->sh_addr = 0x0; |
| shdr->sh_flags = SHF_ALLOC; |
| shdr->sh_size = sizeof(bnote); |
| shdr->sh_entsize = 0; |
| |
| #ifdef HAVE_DWARF_SUPPORT |
| if (debug && nr_debug_entries) { |
| retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries); |
| if (retval) |
| goto error; |
| } else |
| #endif |
| { |
| if (elf_update(e, ELF_C_WRITE) < 0) { |
| warnx("elf_update 4 failed"); |
| goto error; |
| } |
| } |
| |
| retval = 0; |
| error: |
| (void)elf_end(e); |
| |
| free(strsym); |
| |
| |
| return retval; |
| } |
| |
| #ifndef JVMTI |
| |
| static unsigned char x86_code[] = { |
| 0xBB, 0x2A, 0x00, 0x00, 0x00, /* movl $42, %ebx */ |
| 0xB8, 0x01, 0x00, 0x00, 0x00, /* movl $1, %eax */ |
| 0xCD, 0x80 /* int $0x80 */ |
| }; |
| |
| static struct options options; |
| |
| int main(int argc, char **argv) |
| { |
| int c, fd, ret; |
| |
| while ((c = getopt(argc, argv, "o:h")) != -1) { |
| switch (c) { |
| case 'o': |
| options.output = optarg; |
| break; |
| case 'h': |
| printf("Usage: genelf -o output_file [-h]\n"); |
| return 0; |
| default: |
| errx(1, "unknown option"); |
| } |
| } |
| |
| fd = open(options.output, O_CREAT|O_TRUNC|O_RDWR, 0666); |
| if (fd == -1) |
| err(1, "cannot create file %s", options.output); |
| |
| ret = jit_write_elf(fd, "main", x86_code, sizeof(x86_code)); |
| close(fd); |
| |
| if (ret != 0) |
| unlink(options.output); |
| |
| return ret; |
| } |
| #endif |