dwfl_build_id_find_elf.c revision de2ed97f33139af5c7a0811e4ec66fc896a13cf2
1/* Find an ELF file for a module from its build ID. 2 Copyright (C) 2007-2010 Red Hat, Inc. 3 This file is part of elfutils. 4 5 This file is free software; you can redistribute it and/or modify 6 it under the terms of either 7 8 * the GNU Lesser General Public License as published by the Free 9 Software Foundation; either version 3 of the License, or (at 10 your option) any later version 11 12 or 13 14 * the GNU General Public License as published by the Free 15 Software Foundation; either version 2 of the License, or (at 16 your option) any later version 17 18 or both in parallel, as here. 19 20 elfutils is distributed in the hope that it will be useful, but 21 WITHOUT ANY WARRANTY; without even the implied warranty of 22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 23 General Public License for more details. 24 25 You should have received copies of the GNU General Public License and 26 the GNU Lesser General Public License along with this program. If 27 not, see <http://www.gnu.org/licenses/>. */ 28 29#include "libdwflP.h" 30#include <inttypes.h> 31#include <fcntl.h> 32#include <unistd.h> 33 34 35int 36internal_function 37__libdwfl_open_by_build_id (Dwfl_Module *mod, bool debug, char **file_name) 38{ 39 /* If *FILE_NAME was primed into the module, leave it there 40 as the fallback when we have nothing to offer. */ 41 errno = 0; 42 if (mod->build_id_len <= 0) 43 return -1; 44 45 const size_t id_len = mod->build_id_len; 46 const uint8_t *id = mod->build_id_bits; 47 48 /* Search debuginfo_path directories' .build-id/ subdirectories. */ 49 50 char id_name[sizeof "/.build-id/" + 1 + id_len * 2 + sizeof ".debug" - 1]; 51 strcpy (id_name, "/.build-id/"); 52 int n = snprintf (&id_name[sizeof "/.build-id/" - 1], 53 4, "%02" PRIx8 "/", (uint8_t) id[0]); 54 assert (n == 3); 55 for (size_t i = 1; i < id_len; ++i) 56 { 57 n = snprintf (&id_name[sizeof "/.build-id/" - 1 + 3 + (i - 1) * 2], 58 3, "%02" PRIx8, (uint8_t) id[i]); 59 assert (n == 2); 60 } 61 if (debug) 62 strcpy (&id_name[sizeof "/.build-id/" - 1 + 3 + (id_len - 1) * 2], 63 ".debug"); 64 65 const Dwfl_Callbacks *const cb = mod->dwfl->callbacks; 66 char *path = strdupa ((cb->debuginfo_path ? *cb->debuginfo_path : NULL) 67 ?: DEFAULT_DEBUGINFO_PATH); 68 69 int fd = -1; 70 char *dir; 71 while (fd < 0 && (dir = strsep (&path, ":")) != NULL) 72 { 73 if (dir[0] == '+' || dir[0] == '-') 74 ++dir; 75 76 /* Only absolute directory names are useful to us. */ 77 if (dir[0] != '/') 78 continue; 79 80 size_t dirlen = strlen (dir); 81 char *name = malloc (dirlen + sizeof id_name); 82 if (unlikely (name == NULL)) 83 break; 84 memcpy (mempcpy (name, dir, dirlen), id_name, sizeof id_name); 85 86 fd = TEMP_FAILURE_RETRY (open64 (name, O_RDONLY)); 87 if (fd >= 0) 88 { 89 if (*file_name != NULL) 90 free (*file_name); 91 *file_name = canonicalize_file_name (name); 92 if (*file_name == NULL) 93 { 94 *file_name = name; 95 name = NULL; 96 } 97 } 98 free (name); 99 } 100 101 /* If we simply found nothing, clear errno. If we had some other error 102 with the file, report that. Possibly this should treat other errors 103 like ENOENT too. But ignoring all errors could mask some that should 104 be reported. */ 105 if (fd < 0 && errno == ENOENT) 106 errno = 0; 107 108 return fd; 109} 110 111int 112dwfl_build_id_find_elf (Dwfl_Module *mod, 113 void **userdata __attribute__ ((unused)), 114 const char *modname __attribute__ ((unused)), 115 Dwarf_Addr base __attribute__ ((unused)), 116 char **file_name, Elf **elfp) 117{ 118 *elfp = NULL; 119 int fd = __libdwfl_open_by_build_id (mod, false, file_name); 120 if (fd >= 0) 121 { 122 Dwfl_Error error = __libdw_open_file (&fd, elfp, true, false); 123 if (error != DWFL_E_NOERROR) 124 __libdwfl_seterrno (error); 125 else if (__libdwfl_find_build_id (mod, false, *elfp) == 2) 126 { 127 /* This is a backdoor signal to short-circuit the ID refresh. */ 128 mod->main.valid = true; 129 return fd; 130 } 131 else 132 { 133 /* This file does not contain the ID it should! */ 134 elf_end (*elfp); 135 *elfp = NULL; 136 close (fd); 137 fd = -1; 138 } 139 free (*file_name); 140 *file_name = NULL; 141 } 142 else if (errno == 0 && mod->build_id_len > 0) 143 /* Setting this with no file yet loaded is a marker that 144 the build ID is authoritative even if we also know a 145 putative *FILE_NAME. */ 146 mod->main.valid = true; 147 148 return fd; 149} 150INTDEF (dwfl_build_id_find_elf) 151