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    /* Base address of shared object, taken from Dl_info::dli_fbase */
  50    const void *dli_fbase;
  51
  52    struct build_id_note *note;
  53 };
  54
  55 static int
  56 build_id_find_nhdr_callback(struct dl_phdr_info *info, size_t size, void *data_)
  57 {
  58    struct callback_data *data = data_;
  59
  60    if ((void *)info->dlpi_addr != data->dli_fbase)
  61       return 0;
  62
  63    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  64       if (info->dlpi_phdr[i].p_type != PT_NOTE)
  65          continue;
  66
  67       struct build_id_note *note = (void *)(info->dlpi_addr +
  68                                             info->dlpi_phdr[i].p_vaddr);
  69       ptrdiff_t len = info->dlpi_phdr[i].p_filesz;
  70
  71       while (len >= sizeof(struct build_id_note)) {
  72          if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
  73             note->nhdr.n_descsz != 0 &&
  74             note->nhdr.n_namesz == 4 &&
  75             memcmp(note->name, "GNU", 4) == 0) {
  76             data->note = note;
  77             return 1;
  78          }
  79
  80          size_t offset = sizeof(ElfW(Nhdr)) +
  81                          ALIGN(note->nhdr.n_namesz, 4) +
  82                          ALIGN(note->nhdr.n_descsz, 4);
  83          note = (struct build_id_note *)((char *)note + offset);
  84          len -= offset;
  85       }
  86    }
  87
  88    return 0;
  89 }
  90
  91 const struct build_id_note *
  92 build_id_find_nhdr_for_addr(const void *addr)
  93 {
  94    Dl_info info;
  95
  96    if (!dladdr(addr, &info))
  97       return NULL;
  98
  99    if (!info.dli_fbase)
 100       return NULL;
 101
 102    struct callback_data data = {
 103       .dli_fbase = info.dli_fbase,
 104       .note = NULL,
 105    };
 106
 107    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
 108       return NULL;
 109
 110    return data.note;
 111 }
 112
 113 unsigned
 114 build_id_length(const struct build_id_note *note)
 115 {
 116    return note->nhdr.n_descsz;
 117 }
 118
 119 const uint8_t *
 120 build_id_data(const struct build_id_note *note)
 121 {
 122    return note->build_id;
 123 }
 124
 125 #endif