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
38static int
39check_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.  */
63static int
64find_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
125int
126internal_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
144ssize_t
145dwelf_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}
156INTDEF(dwelf_elf_gnu_build_id)
157