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    /* The first object visited by callback is the main program.
  59     * Android's libc returns a NULL pointer for the first executable.
  60     */
  61    if (info->dlpi_name == NULL)
  62       return 0;
  63
  64    char *ptr = strstr(info->dlpi_name, data->filename);
  65    if (ptr == NULL || ptr[strlen(data->filename)] != '\0')
  66       return 0;
  67
  68    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  69       if (info->dlpi_phdr[i].p_type != PT_NOTE)
  70          continue;
  71
  72       struct build_id_note *note = (void *)(info->dlpi_addr +
  73                                             info->dlpi_phdr[i].p_vaddr);
  74       ptrdiff_t len = info->dlpi_phdr[i].p_filesz;
  75
  76       while (len >= sizeof(struct build_id_note)) {
  77          if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
  78             note->nhdr.n_descsz != 0 &&
  79             note->nhdr.n_namesz == 4 &&
  80             memcmp(note->name, "GNU", 4) == 0) {
  81             data->note = note;
  82             return 1;
  83          }
  84
  85          size_t offset = sizeof(ElfW(Nhdr)) +
  86                          ALIGN(note->nhdr.n_namesz, 4) +
  87                          ALIGN(note->nhdr.n_descsz, 4);
  88          note = (struct build_id_note *)((char *)note + offset);
  89          len -= offset;
  90       }
  91    }
  92
  93    return 0;
  94 }
  95
  96 const struct build_id_note *
  97 build_id_find_nhdr(const char *filename)
  98 {
  99    struct callback_data data = {
 100       .filename = filename,
 101       .note = NULL,
 102    };
 103
 104    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
 105       return NULL;
 106
 107    return data.note;
 108 }
 109
 110 unsigned
 111 build_id_length(const struct build_id_note *note)
 112 {
 113    return note->nhdr.n_descsz;
 114 }
 115
 116 const uint8_t *
 117 build_id_data(const struct build_id_note *note)
 118 {
 119    return note->build_id;
 120 }
 121
 122 #endif