/* * 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 #include #include #include #include #include #include #include #include #include #include #ifdef HAVE_LIBDEBUGINFOD #include #endif #include #include "bcc_elf.h" #include "bcc_proc.h" #include "bcc_syms.h" #define NT_STAPSDT 3 #define ELF_ST_TYPE(x) (((uint32_t) x) & 0xf) static int openelf_fd(int fd, Elf **elf_out) { if (elf_version(EV_CURRENT) == EV_NONE) return -1; *elf_out = elf_begin(fd, ELF_C_READ, 0); if (*elf_out == NULL) return -1; return 0; } static int openelf(const char *path, Elf **elf_out, int *fd_out) { *fd_out = open(path, O_RDONLY); if (*fd_out < 0) return -1; if (openelf_fd(*fd_out, elf_out) == -1) { close(*fd_out); return -1; } return 0; } static const char *parse_stapsdt_note(struct bcc_elf_usdt *probe, GElf_Shdr *probes_shdr, 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; } // Offset from start of file if (probe->semaphore && probes_shdr) probe->semaphore_offset = probe->semaphore - probes_shdr->sh_addr + probes_shdr->sh_offset; else probe->semaphore_offset = 0; 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, GElf_Shdr *probes_shdr, int elf_class, bcc_elf_probecb callback, const char *binpath, uint64_t first_inst_offset, 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, probes_shdr, desc, elf_class) == desc_end) { if (probe.pc < first_inst_offset) fprintf(stderr, "WARNING: invalid address 0x%lx for probe (%s,%s) in binary %s\n", probe.pc, probe.provider, probe.name, binpath); else callback(binpath, &probe, payload); } } } return 0; } static int listprobes(Elf *e, bcc_elf_probecb callback, const char *binpath, void *payload) { Elf_Scn *section = NULL; bool found_probes_shdr; size_t stridx; int elf_class = gelf_getclass(e); uint64_t first_inst_offset = 0; GElf_Shdr probes_shdr = {}; if (elf_getshdrstrndx(e, &stridx) != 0) return -1; // Get the offset to the first instruction while ((section = elf_nextscn(e, section)) != 0) { GElf_Shdr header; if (!gelf_getshdr(section, &header)) continue; // The elf file section layout is based on increasing virtual address, // getting the first section with SHF_EXECINSTR is enough. if (header.sh_flags & SHF_EXECINSTR) { first_inst_offset = header.sh_addr; break; } } found_probes_shdr = false; while ((section = elf_nextscn(e, section)) != 0) { if (!gelf_getshdr(section, &probes_shdr)) continue; char *name = elf_strptr(e, stridx, probes_shdr.sh_name); if (name && !strcmp(name, ".probes")) { found_probes_shdr = true; break; } } 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")) { GElf_Shdr *shdr_ptr = found_probes_shdr ? &probes_shdr : NULL; if (do_note_segment(section, shdr_ptr, elf_class, callback, binpath, first_inst_offset, 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 Elf_Scn * get_section(Elf *e, const char *section_name, GElf_Shdr *section_hdr, size_t *section_idx) { Elf_Scn *section = NULL; GElf_Shdr header; char *name; size_t stridx; if (elf_getshdrstrndx(e, &stridx) != 0) return NULL; size_t index; for (index = 1; (section = elf_nextscn(e, section)) != 0; index++) { if (!gelf_getshdr(section, &header)) continue; name = elf_strptr(e, stridx, header.sh_name); if (name && !strcmp(name, section_name)) { if (section_hdr) *section_hdr = header; if (section_idx) *section_idx = index; return section; } } return NULL; } static int list_in_scn(Elf *e, Elf_Scn *section, size_t stridx, size_t symsize, struct bcc_symbol_option *option, bcc_elf_symcb callback, bcc_elf_symcb_lazy callback_lazy, void *payload, bool debugfile) { Elf_Data *data = NULL; #if defined(__powerpc64__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ size_t opdidx = 0; Elf_Scn *opdsec = NULL; GElf_Shdr opdshdr = {}; Elf_Data *opddata = NULL; opdsec = get_section(e, ".opd", &opdshdr, &opdidx); if (opdsec && opdshdr.sh_type == SHT_PROGBITS) opddata = elf_getdata(opdsec, NULL); #endif 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; size_t name_len; if (!gelf_getsym(data, (int)i, &sym)) continue; if ((name = elf_strptr(e, stridx, sym.st_name)) == NULL) continue; if (name[0] == 0) continue; name_len = strlen(name); if (sym.st_value == 0) continue; uint32_t st_type = ELF_ST_TYPE(sym.st_info); if (!(option->use_symbol_type & (1 << st_type))) continue; #ifdef __powerpc64__ #if defined(_CALL_ELF) && _CALL_ELF == 2 if (option->use_symbol_type & (1 << STT_PPC64_ELFV2_SYM_LEP)) { /* * The PowerPC 64-bit ELF v2 ABI says that the 3 most significant bits * in the st_other field of the symbol table specifies the number of * instructions between a function's Global Entry Point (GEP) and Local * Entry Point (LEP). */ switch (sym.st_other >> 5) { /* GEP and LEP are the same for 0 or 1, usage is reserved for 7 */ /* If 2, LEP is 1 instruction past the GEP */ case 2: sym.st_value += 4; break; /* If 3, LEP is 2 instructions past the GEP */ case 3: sym.st_value += 8; break; /* If 4, LEP is 4 instructions past the GEP */ case 4: sym.st_value += 16; break; /* If 5, LEP is 8 instructions past the GEP */ case 5: sym.st_value += 32; break; /* If 6, LEP is 16 instructions past the GEP */ case 6: sym.st_value += 64; break; } } #else if (opddata && sym.st_shndx == opdidx) { size_t offset = sym.st_value - opdshdr.sh_addr; /* Find the function descriptor */ uint64_t *descr = opddata->d_buf + offset; /* Read the actual entry point address from the descriptor */ sym.st_value = *descr; } #endif #endif int ret; if (option->lazy_symbolize) ret = callback_lazy(stridx, sym.st_name, name_len, sym.st_value, sym.st_size, debugfile, payload); else ret = callback(name, sym.st_value, sym.st_size, payload); if (ret < 0) return 1; // signal termination to caller } } return 0; } static int listsymbols(Elf *e, bcc_elf_symcb callback, bcc_elf_symcb_lazy callback_lazy, void *payload, struct bcc_symbol_option *option, bool debugfile) { 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, option, callback, callback_lazy, payload, debugfile); 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 = get_section(e, section_name, NULL, NULL); if (section) 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 || 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; size_t i = 0; for (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) { close(fd); 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; } // Check if two filenames point to the same file, including hard or soft links. static bool same_file(char *a, const char *b) { struct stat stat_a, stat_b; if (stat(a, &stat_a) || stat(b, &stat_b)) return false; if ((stat_a.st_dev == stat_b.st_dev) && (stat_a.st_ino == stat_b.st_ino)) return true; else return false; } static char *find_debug_via_debuglink(Elf *e, const char *binpath, int check_crc) { char fullpath[PATH_MAX]; char *tmppath; 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; tmppath = strdup(binpath); bindir = dirname(tmppath); // Search for the file in 'binpath', but ignore the file we find if it // matches the binary itself: the binary will always be probed later on, // and it might contain poorer symbols (e.g. stripped or partial symbols) // than the external debuginfo that might be available elsewhere. snprintf(fullpath, sizeof(fullpath),"%s/%s", bindir, name); if (same_file(fullpath, binpath) != true && access(fullpath, F_OK) != -1) { res = strdup(fullpath); goto DONE; } // Search for the file in 'binpath'/.debug snprintf(fullpath, sizeof(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' snprintf(fullpath, sizeof(fullpath), "/usr/lib/debug%s/%s", bindir, name); if (access(fullpath, F_OK) != -1) { res = strdup(fullpath); goto DONE; } DONE: free(tmppath); if (res && check_crc && !verify_checksum(res, crc)) { free(res); return NULL; } return res; } 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. snprintf(fullpath, sizeof(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 char *find_debug_via_symfs(Elf *e, const char* path) { char fullpath[PATH_MAX]; char buildid[128]; char symfs_buildid[128]; int check_build_id; char *symfs; Elf *symfs_e = NULL; int symfs_fd = -1; char *result = NULL; symfs = getenv("BCC_SYMFS"); if (!symfs || !*symfs) goto out; check_build_id = find_buildid(e, buildid); int ns_prefix_length = 0; sscanf(path, "/proc/%*u/root/%n", &ns_prefix_length); path += ns_prefix_length; snprintf(fullpath, sizeof(fullpath), "%s/%s", symfs, path); if (access(fullpath, F_OK) == -1) goto out; if (openelf(fullpath, &symfs_e, &symfs_fd) < 0) { symfs_e = NULL; symfs_fd = -1; goto out; } if (check_build_id) { if (!find_buildid(symfs_e, symfs_buildid)) goto out; if (strncmp(buildid, symfs_buildid, sizeof(buildid))) goto out; } result = strdup(fullpath); out: if (symfs_e) { elf_end(symfs_e); } if (symfs_fd != -1) { close(symfs_fd); } return result; } #ifdef HAVE_LIBDEBUGINFOD static char *find_debug_via_debuginfod(Elf *e){ char buildid[128]; char *debugpath = NULL; int fd = -1; if (!find_buildid(e, buildid)) return NULL; debuginfod_client *client = debuginfod_begin(); if (!client) return NULL; // In case of an error, the function returns a negative error code and // debugpath stays NULL. fd = debuginfod_find_debuginfo(client, (const unsigned char *) buildid, 0, &debugpath); if (fd >= 0) close(fd); debuginfod_end(client); return debugpath; } #endif static char *find_debug_file(Elf* e, const char* path, int check_crc) { char *debug_file = NULL; // If there is a separate debuginfo file, try to locate and read it, first // using symfs, then using the build-id section, finally using the debuglink // section. These rules are what perf and gdb follow. // See: // - https://github.com/torvalds/linux/blob/v5.2/tools/perf/Documentation/perf-report.txt#L325 // - https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html debug_file = find_debug_via_symfs(e, path); if (!debug_file) debug_file = find_debug_via_buildid(e); if (!debug_file) debug_file = find_debug_via_debuglink(e, path, check_crc); #ifdef HAVE_LIBDEBUGINFOD if (!debug_file) debug_file = find_debug_via_debuginfod(e); #endif return debug_file; } static int foreach_sym_core(const char *path, bcc_elf_symcb callback, bcc_elf_symcb_lazy callback_lazy, struct bcc_symbol_option *option, void *payload, int is_debug_file) { Elf *e; int fd, res; char *debug_file; if (!option) return -1; if (openelf(path, &e, &fd) < 0) return -1; if (option->use_debug_file && !is_debug_file) { // The is_debug_file argument helps avoid infinitely resolving debuginfo // files for debuginfo files and so on. debug_file = find_debug_file(e, path, option->check_debug_file_crc); if (debug_file) { foreach_sym_core(debug_file, callback, callback_lazy, option, payload, 1); free(debug_file); } } res = listsymbols(e, callback, callback_lazy, payload, option, is_debug_file); elf_end(e); close(fd); return res; } int bcc_elf_foreach_sym(const char *path, bcc_elf_symcb callback, void *option, void *payload) { struct bcc_symbol_option *o = option; o->lazy_symbolize = 0; return foreach_sym_core(path, callback, NULL, o, payload, 0); } int bcc_elf_foreach_sym_lazy(const char *path, bcc_elf_symcb_lazy callback, void *option, void *payload) { struct bcc_symbol_option *o = option; o->lazy_symbolize = 1; return foreach_sym_core(path, NULL, callback, o, payload, 0); } int bcc_elf_get_text_scn_info(const char *path, uint64_t *addr, uint64_t *offset) { Elf *e = NULL; int fd = -1, err; Elf_Scn *section = NULL; GElf_Shdr header; size_t stridx; char *name; if ((err = openelf(path, &e, &fd)) < 0 || (err = elf_getshdrstrndx(e, &stridx)) < 0) goto exit; err = -1; 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, ".text")) { *addr = (uint64_t)header.sh_addr; *offset = (uint64_t)header.sh_offset; err = 0; break; } } exit: if (e) elf_end(e); if (fd >= 0) close(fd); return err; } int bcc_elf_foreach_load_section(const char *path, bcc_elf_load_sectioncb callback, void *payload) { Elf *e = NULL; int fd = -1, err = -1, res; size_t nhdrs, i; if (openelf(path, &e, &fd) < 0) goto exit; if (elf_getphdrnum(e, &nhdrs) != 0) goto exit; GElf_Phdr header; for (i = 0; i < nhdrs; i++) { if (!gelf_getphdr(e, (int)i, &header)) continue; if (header.p_type != PT_LOAD || !(header.p_flags & PF_X)) continue; res = callback(header.p_vaddr, header.p_memsz, header.p_offset, payload); if (res < 0) { err = 1; goto exit; } } err = 0; exit: if (e) elf_end(e); if (fd >= 0) close(fd); return err; } int bcc_elf_get_type(const char *path) { Elf *e; GElf_Ehdr hdr; int fd; void* res = NULL; if (openelf(path, &e, &fd) < 0) return -1; res = (void*)gelf_getehdr(e, &hdr); elf_end(e); close(fd); if (!res) return -1; else return hdr.e_type; } int bcc_elf_is_exe(const char *path) { return (bcc_elf_get_type(path) != -1) && (access(path, X_OK) == 0); } int bcc_elf_is_shared_obj(const char *path) { return bcc_elf_get_type(path) == ET_DYN; } int bcc_elf_is_vdso(const char *name) { return strcmp(name, "[vdso]") == 0; } // -2: Failed // -1: Not initialized // >0: Initialized static int vdso_image_fd = -1; static int find_vdso(struct mod_info *info, int enter_ns, void *payload) { int fd; char tmpfile[128]; if (!bcc_elf_is_vdso(info->name)) return 0; uint64_t sz = info->end_addr - info->start_addr; void *image = malloc(sz); if (!image) goto on_error; memcpy(image, (void *)info->start_addr, sz); snprintf(tmpfile, sizeof(tmpfile), "/tmp/bcc_%d_vdso_image_XXXXXX", getpid()); fd = mkostemp(tmpfile, O_CLOEXEC); if (fd < 0) { fprintf(stderr, "Unable to create temp file: %s\n", strerror(errno)); goto on_error; } // Unlink the file to avoid leaking if (unlink(tmpfile) == -1) fprintf(stderr, "Unlink %s failed: %s\n", tmpfile, strerror(errno)); if (write(fd, image, sz) == -1) { fprintf(stderr, "Failed to write to vDSO image: %s\n", strerror(errno)); close(fd); goto on_error; } vdso_image_fd = fd; on_error: if (image) free(image); // Always stop the iteration return -1; } int bcc_elf_foreach_vdso_sym(bcc_elf_symcb callback, void *payload) { Elf *elf; static struct bcc_symbol_option default_option = { .use_debug_file = 0, .check_debug_file_crc = 0, .use_symbol_type = (1 << STT_FUNC) | (1 << STT_GNU_IFUNC) }; if (vdso_image_fd == -1) { vdso_image_fd = -2; bcc_procutils_each_module(getpid(), &find_vdso, NULL); } if (vdso_image_fd == -2) return -1; if (openelf_fd(vdso_image_fd, &elf) == -1) return -1; return listsymbols(elf, callback, NULL, payload, &default_option, 0); } // return value: 0 : success // < 0 : error and no bcc lib found // > 0 : error and bcc lib found static int bcc_free_memory_with_file(const char *path) { unsigned long sym_addr = 0, sym_shndx; Elf_Scn *section = NULL; int fd = -1, err; GElf_Shdr header; Elf *e = NULL; if ((err = openelf(path, &e, &fd)) < 0) goto exit; // get symbol address of "bcc_free_memory", which // will be used to calculate runtime .text address // range, esp. for shared libraries. err = -1; while ((section = elf_nextscn(e, section)) != 0) { Elf_Data *data = NULL; size_t symsize; if (!gelf_getshdr(section, &header)) continue; if (header.sh_type != SHT_SYMTAB && header.sh_type != SHT_DYNSYM) continue; /* iterate all symbols */ symsize = header.sh_entsize; while ((data = elf_getdata(section, data)) != 0) { size_t i, symcount = data->d_size / symsize; for (i = 0; i < symcount; ++i) { GElf_Sym sym; if (!gelf_getsym(data, (int)i, &sym)) continue; if (GELF_ST_TYPE(sym.st_info) != STT_FUNC) continue; const char *name; if ((name = elf_strptr(e, header.sh_link, sym.st_name)) == NULL) continue; if (strcmp(name, "bcc_free_memory") == 0) { sym_addr = sym.st_value; sym_shndx = sym.st_shndx; break; } } } } // Didn't find bcc_free_memory in the ELF file. if (sym_addr == 0) goto exit; int sh_idx = 0; section = NULL; err = 1; while ((section = elf_nextscn(e, section)) != 0) { sh_idx++; if (!gelf_getshdr(section, &header)) continue; if (sh_idx == sym_shndx) { unsigned long saddr, saddr_n, eaddr; long page_size = sysconf(_SC_PAGESIZE); saddr = (unsigned long)bcc_free_memory - sym_addr + header.sh_addr; eaddr = saddr + header.sh_size; // adjust saddr and eaddr, start addr needs to be page aligned saddr_n = (saddr + page_size - 1) & ~(page_size - 1); eaddr -= saddr_n - saddr; if (madvise((void *)saddr_n, eaddr - saddr_n, MADV_DONTNEED)) { fprintf(stderr, "madvise failed, saddr %lx, eaddr %lx\n", saddr, eaddr); goto exit; } err = 0; break; } } exit: if (e) elf_end(e); if (fd >= 0) close(fd); return err; } // Free bcc mmemory // // The main purpose of this function is to free llvm/clang text memory // through madvise MADV_DONTNEED. // // bcc could be linked statically or dynamically into the application. // If it is static linking, there is no easy way to know which region // inside .text section belongs to llvm/clang, so the whole .text section // is freed. Otherwise, the process map is searched to find libbcc.so // library and the whole .text section for that shared library is // freed. // // Note that the text memory used by bcc (mainly llvm/clang) is reclaimable // in the kernel as it is file backed. But the reclaim process // may take some time if no memory pressure. So this API is mostly // used for application who needs to immediately lowers its RssFile // metric right after loading BPF program. int bcc_free_memory() { int err; // First try whether bcc is statically linked or not err = bcc_free_memory_with_file("/proc/self/exe"); if (err >= 0) return -err; // Not statically linked, let us find the libbcc.so FILE *maps = fopen("/proc/self/maps", "r"); if (!maps) return -1; char *line = NULL; size_t size; while (getline(&line, &size, maps) > 0) { char *libbcc = strstr(line, "libbcc.so"); if (!libbcc) continue; // Parse the line and get the full libbcc.so path unsigned long addr_start, addr_end, offset, inode; int path_start = 0, path_end = 0; unsigned int devmajor, devminor; char perms[8]; if (sscanf(line, "%lx-%lx %7s %lx %x:%x %lu %n%*[^\n]%n", &addr_start, &addr_end, perms, &offset, &devmajor, &devminor, &inode, &path_start, &path_end) < 7) break; // Free the text in the bcc dynamic library. char libbcc_path[4096]; memcpy(libbcc_path, line + path_start, path_end - path_start); libbcc_path[path_end - path_start] = '\0'; err = bcc_free_memory_with_file(libbcc_path); err = (err <= 0) ? err : -err; } fclose(maps); free(line); return err; } int bcc_elf_get_buildid(const char *path, char *buildid) { Elf *e; int fd; if (openelf(path, &e, &fd) < 0) return -1; if (!find_buildid(e, buildid)) return -1; return 0; } int bcc_elf_symbol_str(const char *path, size_t section_idx, size_t str_table_idx, char *out, size_t len, int debugfile) { Elf *e = NULL, *d = NULL; int fd = -1, dfd = -1, err = 0; const char *name; char *debug_file = NULL; if (!out) return -1; if (openelf(path, &e, &fd) < 0) return -1; if (debugfile) { debug_file = find_debug_file(e, path, 0); if (!debug_file) { err = -1; goto exit; } if (openelf(debug_file, &d, &dfd) < 0) { err = -1; goto exit; } if ((name = elf_strptr(d, section_idx, str_table_idx)) == NULL) { err = -1; goto exit; } } else { if ((name = elf_strptr(e, section_idx, str_table_idx)) == NULL) { err = -1; goto exit; } } strncpy(out, name, len); exit: if (debug_file) free(debug_file); if (e) elf_end(e); if (d) elf_end(d); if (fd >= 0) close(fd); if (dfd >= 0) close(dfd); return err; } #if 0 #include 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