src/util/build_id.c

   1 /*
   2  * Copyright © 2016 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #ifdef HAVE_DL_ITERATE_PHDR
  25 #include <link.h>
  26 #include <stddef.h>
  27 #include <string.h>
  28
  29 #include "build_id.h"
  30
  31 #ifndef NT_GNU_BUILD_ID
  32 #define NT_GNU_BUILD_ID 3
  33 #endif
  34
  35 #ifndef ElfW
  36 #define ElfW(type) Elf_##type
  37 #endif
  38
  39 #define ALIGN(val, align)      (((val) + (align) - 1) & ~((align) - 1))
  40
  41 struct build_id_note {
  42    ElfW(Nhdr) nhdr;
  43
  44    char name[4]; /* Note name for build-id is "GNU\0" */
  45    uint8_t build_id[0];
  46 };
  47
  48 struct callback_data {
  49    const char *filename;
  50    struct build_id_note *note;
  51 };
  52
  53 static int
  54 build_id_find_nhdr_callback(struct dl_phdr_info *info, size_t size, void *data_)
  55 {
  56    struct callback_data *data = data_;
  57
  58    char *ptr = strstr(info->dlpi_name, data->filename);
  59    if (ptr == NULL || ptr[strlen(data->filename)] != '\0')
  60       return 0;
  61
  62    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  63       if (info->dlpi_phdr[i].p_type != PT_NOTE)
  64          continue;
  65
  66       struct build_id_note *note = (void *)(info->dlpi_addr +
  67                                             info->dlpi_phdr[i].p_vaddr);
  68       ptrdiff_t len = info->dlpi_phdr[i].p_filesz;
  69
  70       while (len >= sizeof(struct build_id_note)) {
  71          if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
  72             note->nhdr.n_descsz != 0 &&
  73             note->nhdr.n_namesz == 4 &&
  74             memcmp(note->name, "GNU", 4) == 0) {
  75             data->note = note;
  76             return 1;
  77          }
  78
  79          size_t offset = sizeof(ElfW(Nhdr)) +
  80                          ALIGN(note->nhdr.n_namesz, 4) +
  81                          ALIGN(note->nhdr.n_descsz, 4);
  82          note = (struct build_id_note *)((char *)note + offset);
  83          len -= offset;
  84       }
  85    }
  86
  87    return 0;
  88 }
  89
  90 const struct build_id_note *
  91 build_id_find_nhdr(const char *filename)
  92 {
  93    struct callback_data data = {
  94       .filename = filename,
  95       .note = NULL,
  96    };
  97
  98    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
  99       return NULL;
 100
 101    return data.note;
 102 }
 103
 104 unsigned
 105 build_id_length(const struct build_id_note *note)
 106 {
 107    return note->nhdr.n_descsz;
 108 }
 109
 110 const uint8_t *
 111 build_id_data(const struct build_id_note *note)
 112 {
 113    return note->build_id;
 114 }
 115
 116 #endif