1 /* Returns the build id if found in a NT_GNU_BUILD_ID note. 2 Copyright (C) 2014 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 #ifdef HAVE_CONFIG_H 30 # include <config.h> 31 #endif 32 33 #include "libdwelfP.h" 34 #include "libdwflP.h" 35 36 #define NO_VADDR ((GElf_Addr) -1l) 37 38 static int 39 check_notes (Elf_Data *data, GElf_Addr data_elfaddr, 40 const void **build_id_bits, GElf_Addr *build_id_elfaddr, 41 int *build_id_len) 42 { 43 size_t pos = 0; 44 GElf_Nhdr nhdr; 45 size_t name_pos; 46 size_t desc_pos; 47 while ((pos = gelf_getnote (data, pos, &nhdr, &name_pos, &desc_pos)) > 0) 48 if (nhdr.n_type == NT_GNU_BUILD_ID 49 && nhdr.n_namesz == sizeof "GNU" 50 && !memcmp (data->d_buf + name_pos, "GNU", sizeof "GNU")) 51 { 52 *build_id_bits = data->d_buf + desc_pos; 53 *build_id_elfaddr = (data_elfaddr == NO_VADDR 54 ? 0 : data_elfaddr + desc_pos); 55 *build_id_len = nhdr.n_descsz; 56 return 1; 57 } 58 return 0; 59 } 60 61 /* Defined here for reuse. The dwelf interface doesn't care about the 62 address of the note, but libdwfl does. */ 63 static int 64 find_elf_build_id (Dwfl_Module *mod, int e_type, Elf *elf, 65 const void **build_id_bits, GElf_Addr *build_id_elfaddr, 66 int *build_id_len) 67 { 68 size_t shstrndx = SHN_UNDEF; 69 int result = 0; 70 71 Elf_Scn *scn = elf_nextscn (elf, NULL); 72 73 if (scn == NULL) 74 { 75 /* No sections, have to look for phdrs. */ 76 size_t phnum; 77 if (unlikely (elf_getphdrnum (elf, &phnum) != 0)) 78 { 79 if (mod != NULL) 80 __libdwfl_seterrno (DWFL_E_LIBELF); 81 return -1; 82 } 83 for (size_t i = 0; result == 0 && i < phnum; ++i) 84 { 85 GElf_Phdr phdr_mem; 86 GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem); 87 if (likely (phdr != NULL) && phdr->p_type == PT_NOTE) 88 result = check_notes (elf_getdata_rawchunk (elf, 89 phdr->p_offset, 90 phdr->p_filesz, 91 ELF_T_NHDR), 92 phdr->p_vaddr, 93 build_id_bits, 94 build_id_elfaddr, 95 build_id_len); 96 } 97 } 98 else 99 do 100 { 101 GElf_Shdr shdr_mem; 102 GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem); 103 if (likely (shdr != NULL) && shdr->sh_type == SHT_NOTE) 104 { 105 /* Determine the right sh_addr in this module. */ 106 GElf_Addr vaddr = 0; 107 if (!(shdr->sh_flags & SHF_ALLOC)) 108 vaddr = NO_VADDR; 109 else if (mod == NULL || e_type != ET_REL) 110 vaddr = shdr->sh_addr; 111 else if (__libdwfl_relocate_value (mod, elf, &shstrndx, 112 elf_ndxscn (scn), &vaddr)) 113 vaddr = NO_VADDR; 114 result = check_notes (elf_getdata (scn, NULL), vaddr, 115 build_id_bits, 116 build_id_elfaddr, 117 build_id_len); 118 } 119 } 120 while (result == 0 && (scn = elf_nextscn (elf, scn)) != NULL); 121 122 return result; 123 } 124 125 int 126 internal_function 127 __libdwfl_find_elf_build_id (Dwfl_Module *mod, Elf *elf, 128 const void **build_id_bits, 129 GElf_Addr *build_id_elfaddr, int *build_id_len) 130 { 131 GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (elf, &ehdr_mem); 132 if (unlikely (ehdr == NULL)) 133 { 134 __libdwfl_seterrno (DWFL_E_LIBELF); 135 return -1; 136 } 137 // MOD->E_TYPE is zero here. 138 assert (ehdr->e_type != ET_REL || mod != NULL); 139 140 return find_elf_build_id (mod, ehdr->e_type, elf, 141 build_id_bits, build_id_elfaddr, build_id_len); 142 } 143 144 ssize_t 145 dwelf_elf_gnu_build_id (Elf *elf, const void **build_idp) 146 { 147 GElf_Addr build_id_elfaddr; 148 int build_id_len; 149 int result = find_elf_build_id (NULL, ET_NONE, elf, build_idp, 150 &build_id_elfaddr, &build_id_len); 151 if (result > 0) 152 return build_id_len; 153 154 return result; 155 } 156 INTDEF(dwelf_elf_gnu_build_id) 157
