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 <dlfcn.h>
  26 #include <link.h>
  27 #include <stddef.h>
  28 #include <string.h>
  29
  30 #include "build_id.h"
  31 #include "macros.h"
  32
  33 #ifndef NT_GNU_BUILD_ID
  34 #define NT_GNU_BUILD_ID 3
  35 #endif
  36
  37 #ifndef ElfW
  38 #define ElfW(type) Elf_##type
  39 #endif
  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    /* Calculate address where shared object is mapped into the process space.
  61     * (Using the base address and the virtual address of the first LOAD segment)
  62     */
  63    void *map_start = NULL;
  64    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  65       if (info->dlpi_phdr[i].p_type == PT_LOAD) {
  66          map_start = (void *)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
  67          break;
  68       }
  69    }
  70
  71    if (map_start != data->dli_fbase)
  72       return 0;
  73
  74    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
  75       if (info->dlpi_phdr[i].p_type != PT_NOTE)
  76          continue;
  77
  78       struct build_id_note *note = (void *)(info->dlpi_addr +
  79                                             info->dlpi_phdr[i].p_vaddr);
  80       ptrdiff_t len = info->dlpi_phdr[i].p_filesz;
  81
  82       while (len >= sizeof(struct build_id_note)) {
  83          if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
  84             note->nhdr.n_descsz != 0 &&
  85             note->nhdr.n_namesz == 4 &&
  86             memcmp(note->name, "GNU", 4) == 0) {
  87             data->note = note;
  88             return 1;
  89          }
  90
  91          size_t offset = sizeof(ElfW(Nhdr)) +
  92                          ALIGN_POT(note->nhdr.n_namesz, 4) +
  93                          ALIGN_POT(note->nhdr.n_descsz, 4);
  94          note = (struct build_id_note *)((char *)note + offset);
  95          len -= offset;
  96       }
  97    }
  98
  99    return 0;
 100 }
 101
 102 const struct build_id_note *
 103 build_id_find_nhdr_for_addr(const void *addr)
 104 {
 105    Dl_info info;
 106
 107    if (!dladdr(addr, &info))
 108       return NULL;
 109
 110    if (!info.dli_fbase)
 111       return NULL;
 112
 113    struct callback_data data = {
 114       .dli_fbase = info.dli_fbase,
 115       .note = NULL,
 116    };
 117
 118    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
 119       return NULL;
 120
 121    return data.note;
 122 }
 123
 124 unsigned
 125 build_id_length(const struct build_id_note *note)
 126 {
 127    return note->nhdr.n_descsz;
 128 }
 129
 130 const uint8_t *
 131 build_id_data(const struct build_id_note *note)
 132 {
 133    return note->build_id;
 134 }
 135
 136 #endif