| /* |
| * Copyright (c) 2016 GitHub, Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <sys/mman.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| #include <string.h> |
| #include <libgen.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <limits.h> |
| |
| #include <gelf.h> |
| #include "bcc_elf.h" |
| #define NT_STAPSDT 3 |
| |
| static int openelf(const char *path, Elf **elf_out, int *fd_out) { |
| if (elf_version(EV_CURRENT) == EV_NONE) |
| return -1; |
| |
| *fd_out = open(path, O_RDONLY); |
| if (*fd_out < 0) |
| return -1; |
| |
| *elf_out = elf_begin(*fd_out, ELF_C_READ, 0); |
| if (*elf_out == 0) { |
| close(*fd_out); |
| return -1; |
| } |
| |
| return 0; |
| } |
| |
| static const char *parse_stapsdt_note(struct bcc_elf_usdt *probe, |
| const char *desc, int elf_class) { |
| if (elf_class == ELFCLASS32) { |
| probe->pc = *((uint32_t *)(desc)); |
| probe->base_addr = *((uint32_t *)(desc + 4)); |
| probe->semaphore = *((uint32_t *)(desc + 8)); |
| desc = desc + 12; |
| } else { |
| probe->pc = *((uint64_t *)(desc)); |
| probe->base_addr = *((uint64_t *)(desc + 8)); |
| probe->semaphore = *((uint64_t *)(desc + 16)); |
| desc = desc + 24; |
| } |
| |
| probe->provider = desc; |
| desc += strlen(desc) + 1; |
| |
| probe->name = desc; |
| desc += strlen(desc) + 1; |
| |
| probe->arg_fmt = desc; |
| desc += strlen(desc) + 1; |
| |
| return desc; |
| } |
| |
| static int do_note_segment(Elf_Scn *section, int elf_class, |
| bcc_elf_probecb callback, const char *binpath, |
| void *payload) { |
| Elf_Data *data = NULL; |
| |
| while ((data = elf_getdata(section, data)) != 0) { |
| size_t offset = 0; |
| GElf_Nhdr hdr; |
| size_t name_off, desc_off; |
| |
| while ((offset = gelf_getnote(data, offset, &hdr, &name_off, &desc_off)) != |
| 0) { |
| const char *desc, *desc_end; |
| struct bcc_elf_usdt probe; |
| |
| if (hdr.n_type != NT_STAPSDT) |
| continue; |
| |
| if (hdr.n_namesz != 8) |
| continue; |
| |
| if (memcmp((const char *)data->d_buf + name_off, "stapsdt", 8) != 0) |
| continue; |
| |
| desc = (const char *)data->d_buf + desc_off; |
| desc_end = desc + hdr.n_descsz; |
| |
| if (parse_stapsdt_note(&probe, desc, elf_class) == desc_end) |
| callback(binpath, &probe, payload); |
| } |
| } |
| return 0; |
| } |
| |
| static int listprobes(Elf *e, bcc_elf_probecb callback, const char *binpath, |
| void *payload) { |
| Elf_Scn *section = NULL; |
| size_t stridx; |
| int elf_class = gelf_getclass(e); |
| |
| if (elf_getshdrstrndx(e, &stridx) != 0) |
| return -1; |
| |
| while ((section = elf_nextscn(e, section)) != 0) { |
| GElf_Shdr header; |
| char *name; |
| |
| if (!gelf_getshdr(section, &header)) |
| continue; |
| |
| if (header.sh_type != SHT_NOTE) |
| continue; |
| |
| name = elf_strptr(e, stridx, header.sh_name); |
| if (name && !strcmp(name, ".note.stapsdt")) { |
| if (do_note_segment(section, elf_class, callback, binpath, payload) < 0) |
| return -1; |
| } |
| } |
| |
| return 0; |
| } |
| |
| int bcc_elf_foreach_usdt(const char *path, bcc_elf_probecb callback, |
| void *payload) { |
| Elf *e; |
| int fd, res; |
| |
| if (openelf(path, &e, &fd) < 0) |
| return -1; |
| |
| res = listprobes(e, callback, path, payload); |
| elf_end(e); |
| close(fd); |
| |
| return res; |
| } |
| |
| static int list_in_scn(Elf *e, Elf_Scn *section, size_t stridx, size_t symsize, |
| bcc_elf_symcb callback, void *payload) { |
| Elf_Data *data = NULL; |
| |
| while ((data = elf_getdata(section, data)) != 0) { |
| size_t i, symcount = data->d_size / symsize; |
| |
| if (data->d_size % symsize) |
| return -1; |
| |
| for (i = 0; i < symcount; ++i) { |
| GElf_Sym sym; |
| const char *name; |
| |
| if (!gelf_getsym(data, (int)i, &sym)) |
| continue; |
| |
| if ((name = elf_strptr(e, stridx, sym.st_name)) == NULL) |
| continue; |
| |
| if (callback(name, sym.st_value, sym.st_size, sym.st_info, payload) < 0) |
| return 1; // signal termination to caller |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int listsymbols(Elf *e, bcc_elf_symcb callback, void *payload) { |
| Elf_Scn *section = NULL; |
| |
| while ((section = elf_nextscn(e, section)) != 0) { |
| GElf_Shdr header; |
| |
| if (!gelf_getshdr(section, &header)) |
| continue; |
| |
| if (header.sh_type != SHT_SYMTAB && header.sh_type != SHT_DYNSYM) |
| continue; |
| |
| int rc = list_in_scn(e, section, header.sh_link, header.sh_entsize, |
| callback, payload); |
| if (rc == 1) |
| break; // callback signaled termination |
| |
| if (rc < 0) |
| return rc; |
| } |
| |
| return 0; |
| } |
| |
| static Elf_Data * get_section_elf_data(Elf *e, const char *section_name) { |
| Elf_Scn *section = NULL; |
| GElf_Shdr header; |
| char *name; |
| |
| size_t stridx; |
| if (elf_getshdrstrndx(e, &stridx) != 0) |
| return NULL; |
| |
| while ((section = elf_nextscn(e, section)) != 0) { |
| if (!gelf_getshdr(section, &header)) |
| continue; |
| |
| name = elf_strptr(e, stridx, header.sh_name); |
| if (name && !strcmp(name, section_name)) { |
| return elf_getdata(section, NULL); |
| } |
| } |
| |
| return NULL; |
| } |
| |
| static int find_debuglink(Elf *e, char **debug_file, unsigned int *crc) { |
| Elf_Data *data = NULL; |
| |
| *debug_file = NULL; |
| *crc = 0; |
| |
| data = get_section_elf_data(e, ".gnu_debuglink"); |
| if (!data || data->d_size <= 5) |
| return 0; |
| |
| *debug_file = (char *)data->d_buf; |
| *crc = *(unsigned int*)((char *)data->d_buf + data->d_size - 4); |
| |
| return *debug_file ? 1 : 0; |
| } |
| |
| static int find_buildid(Elf *e, char *buildid) { |
| Elf_Data *data = get_section_elf_data(e, ".note.gnu.build-id"); |
| if (data->d_size <= 16 || strcmp((char *)data->d_buf + 12, "GNU")) |
| return 0; |
| |
| char *buf = (char *)data->d_buf + 16; |
| size_t length = data->d_size - 16; |
| for (size_t i = 0; i < length; ++i) { |
| sprintf(buildid + (i * 2), "%02hhx", buf[i]); |
| } |
| |
| return 1; |
| } |
| |
| // The CRC algorithm used by GNU debuglink. Taken from: |
| // https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html |
| static unsigned int gnu_debuglink_crc32(unsigned int crc, |
| char *buf, size_t len) { |
| static const unsigned int crc32_table[256] = |
| { |
| 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, |
| 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, |
| 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, |
| 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, |
| 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, |
| 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, |
| 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, |
| 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, |
| 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, |
| 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, |
| 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, |
| 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, |
| 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, |
| 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, |
| 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, |
| 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, |
| 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, |
| 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, |
| 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, |
| 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, |
| 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, |
| 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, |
| 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, |
| 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, |
| 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, |
| 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, |
| 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, |
| 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, |
| 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, |
| 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, |
| 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, |
| 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, |
| 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, |
| 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, |
| 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, |
| 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, |
| 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, |
| 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, |
| 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, |
| 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, |
| 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, |
| 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242, |
| 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, |
| 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, |
| 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278, |
| 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, |
| 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, |
| 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, |
| 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, |
| 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, |
| 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, |
| 0x2d02ef8d |
| }; |
| char *end; |
| |
| crc = ~crc & 0xffffffff; |
| for (end = buf + len; buf < end; ++buf) |
| crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8); |
| return ~crc & 0xffffffff; |
| } |
| |
| static int verify_checksum(const char *file, unsigned int crc) { |
| struct stat st; |
| int fd; |
| void *buf; |
| unsigned int actual; |
| |
| fd = open(file, O_RDONLY); |
| if (fd < 0) |
| return 0; |
| |
| if (fstat(fd, &st) < 0) |
| return 0; |
| |
| buf = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0); |
| if (!buf) { |
| close(fd); |
| return 0; |
| } |
| |
| actual = gnu_debuglink_crc32(0, buf, st.st_size); |
| |
| munmap(buf, st.st_size); |
| close(fd); |
| return actual == crc; |
| } |
| |
| static char *find_debug_via_debuglink(Elf *e, const char *binpath) { |
| char fullpath[PATH_MAX]; |
| char *bindir = NULL; |
| char *res = NULL; |
| unsigned int crc; |
| char *name; // the name of the debuginfo file |
| |
| if (!find_debuglink(e, &name, &crc)) |
| return NULL; |
| |
| bindir = strdup(binpath); |
| bindir = dirname(bindir); |
| |
| // Search for the file in 'binpath' |
| sprintf(fullpath, "%s/%s", bindir, name); |
| if (access(fullpath, F_OK) != -1) { |
| res = strdup(fullpath); |
| goto DONE; |
| } |
| |
| // Search for the file in 'binpath'/.debug |
| sprintf(fullpath, "%s/.debug/%s", bindir, name); |
| if (access(fullpath, F_OK) != -1) { |
| res = strdup(fullpath); |
| goto DONE; |
| } |
| |
| // Search for the file in the global debug directory /usr/lib/debug/'binpath' |
| sprintf(fullpath, "/usr/lib/debug%s/%s", bindir, name); |
| if (access(fullpath, F_OK) != -1) { |
| res = strdup(fullpath); |
| goto DONE; |
| } |
| |
| DONE: |
| free(bindir); |
| if (verify_checksum(res, crc)) |
| return res; |
| return NULL; |
| } |
| |
| static char *find_debug_via_buildid(Elf *e) { |
| char fullpath[PATH_MAX]; |
| char buildid[128]; // currently 40 seems to be default, let's be safe |
| |
| if (!find_buildid(e, buildid)) |
| return NULL; |
| |
| // Search for the file in the global debug directory with a sub-path: |
| // mm/nnnnnn...nnnn.debug |
| // Where mm are the first two characters of the buildid, and nnnn are the |
| // rest of the build id, followed by .debug. |
| sprintf(fullpath, "/usr/lib/debug/.build-id/%c%c/%s.debug", |
| buildid[0], buildid[1], buildid + 2); |
| if (access(fullpath, F_OK) != -1) { |
| return strdup(fullpath); |
| } |
| |
| return NULL; |
| } |
| |
| static int foreach_sym_core(const char *path, bcc_elf_symcb callback, |
| void *payload, int is_debug_file) { |
| Elf *e; |
| int fd, res; |
| char *debug_file; |
| |
| if (openelf(path, &e, &fd) < 0) |
| return -1; |
| |
| // If there is a separate debuginfo file, try to locate and read it, first |
| // using the build-id section, then using the debuglink section. These are |
| // also the rules that GDB folows. |
| // See: https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html |
| if (!is_debug_file) { |
| // The is_debug_file argument helps avoid infinitely resolving debuginfo |
| // files for debuginfo files and so on. |
| debug_file = find_debug_via_buildid(e); |
| if (!debug_file) |
| debug_file = find_debug_via_debuglink(e, path); |
| if (debug_file) { |
| foreach_sym_core(debug_file, callback, payload, 1); |
| free(debug_file); |
| } |
| } |
| |
| res = listsymbols(e, callback, payload); |
| elf_end(e); |
| close(fd); |
| return res; |
| } |
| |
| int bcc_elf_foreach_sym(const char *path, bcc_elf_symcb callback, |
| void *payload) { |
| return foreach_sym_core(path, callback, payload, 0); |
| } |
| |
| static int loadaddr(Elf *e, uint64_t *addr) { |
| size_t phnum, i; |
| |
| if (elf_getphdrnum(e, &phnum) != 0) |
| return -1; |
| |
| for (i = 0; i < phnum; ++i) { |
| GElf_Phdr header; |
| |
| if (!gelf_getphdr(e, (int)i, &header)) |
| continue; |
| |
| if (header.p_type != PT_LOAD) |
| continue; |
| |
| *addr = (uint64_t)header.p_vaddr; |
| return 0; |
| } |
| |
| return -1; |
| } |
| |
| int bcc_elf_loadaddr(const char *path, uint64_t *address) { |
| Elf *e; |
| int fd, res; |
| |
| if (openelf(path, &e, &fd) < 0) |
| return -1; |
| |
| res = loadaddr(e, address); |
| elf_end(e); |
| close(fd); |
| |
| return res; |
| } |
| |
| int bcc_elf_is_shared_obj(const char *path) { |
| Elf *e; |
| GElf_Ehdr hdr; |
| int fd, res = -1; |
| |
| if (openelf(path, &e, &fd) < 0) |
| return -1; |
| |
| if (gelf_getehdr(e, &hdr)) |
| res = (hdr.e_type == ET_DYN); |
| |
| elf_end(e); |
| close(fd); |
| |
| return res; |
| } |
| |
| #if 0 |
| #include <stdio.h> |
| |
| int main(int argc, char *argv[]) |
| { |
| uint64_t addr; |
| if (bcc_elf_findsym(argv[1], argv[2], -1, STT_FUNC, &addr) < 0) |
| return -1; |
| |
| printf("%s: %p\n", argv[2], (void *)addr); |
| return 0; |
| } |
| #endif |