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      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 
     38 /* Defined here for reuse. The dwelf interface doesn't care about the
     39    address of the note, but libdwfl does.  */
     40 static int
     41 find_elf_build_id (Dwfl_Module *mod, int e_type, Elf *elf,
     42 		   const void **build_id_bits, GElf_Addr *build_id_elfaddr,
     43 		   int *build_id_len)
     44 {
     45   int check_notes (Elf_Data *data, GElf_Addr data_elfaddr)
     46   {
     47     size_t pos = 0;
     48     GElf_Nhdr nhdr;
     49     size_t name_pos;
     50     size_t desc_pos;
     51     while ((pos = gelf_getnote (data, pos, &nhdr, &name_pos, &desc_pos)) > 0)
     52       if (nhdr.n_type == NT_GNU_BUILD_ID
     53 	  && nhdr.n_namesz == sizeof "GNU" && !memcmp (data->d_buf + name_pos,
     54 						       "GNU", sizeof "GNU"))
     55 	{
     56 	  *build_id_bits = data->d_buf + desc_pos;
     57 	  *build_id_elfaddr = (data_elfaddr == NO_VADDR
     58 			       ? 0 : data_elfaddr + desc_pos);
     59 	  *build_id_len = nhdr.n_descsz;
     60 	  return 1;
     61 	}
     62     return 0;
     63   }
     64 
     65   size_t shstrndx = SHN_UNDEF;
     66   int result = 0;
     67 
     68   Elf_Scn *scn = elf_nextscn (elf, NULL);
     69 
     70   if (scn == NULL)
     71     {
     72       /* No sections, have to look for phdrs.  */
     73       size_t phnum;
     74       if (unlikely (elf_getphdrnum (elf, &phnum) != 0))
     75 	{
     76 	  if (mod != NULL)
     77 	    __libdwfl_seterrno (DWFL_E_LIBELF);
     78 	  return -1;
     79 	}
     80       for (size_t i = 0; result == 0 && i < phnum; ++i)
     81 	{
     82 	  GElf_Phdr phdr_mem;
     83 	  GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem);
     84 	  if (likely (phdr != NULL) && phdr->p_type == PT_NOTE)
     85 	    result = check_notes (elf_getdata_rawchunk (elf,
     86 							phdr->p_offset,
     87 							phdr->p_filesz,
     88 							ELF_T_NHDR),
     89 				  phdr->p_vaddr);
     90 	}
     91     }
     92   else
     93     do
     94       {
     95 	GElf_Shdr shdr_mem;
     96 	GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
     97 	if (likely (shdr != NULL) && shdr->sh_type == SHT_NOTE)
     98 	  {
     99 	    /* Determine the right sh_addr in this module.  */
    100 	    GElf_Addr vaddr = 0;
    101 	    if (!(shdr->sh_flags & SHF_ALLOC))
    102 	      vaddr = NO_VADDR;
    103 	    else if (mod == NULL || e_type != ET_REL)
    104 	      vaddr = shdr->sh_addr;
    105 	    else if (__libdwfl_relocate_value (mod, elf, &shstrndx,
    106 					       elf_ndxscn (scn), &vaddr))
    107 	      vaddr = NO_VADDR;
    108 	    result = check_notes (elf_getdata (scn, NULL), vaddr);
    109 	  }
    110       }
    111     while (result == 0 && (scn = elf_nextscn (elf, scn)) != NULL);
    112 
    113   return result;
    114 }
    115 
    116 int
    117 internal_function
    118 __libdwfl_find_elf_build_id (Dwfl_Module *mod, Elf *elf,
    119 			     const void **build_id_bits,
    120 			     GElf_Addr *build_id_elfaddr, int *build_id_len)
    121 {
    122   GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (elf, &ehdr_mem);
    123   if (unlikely (ehdr == NULL))
    124     {
    125       __libdwfl_seterrno (DWFL_E_LIBELF);
    126       return -1;
    127     }
    128   // MOD->E_TYPE is zero here.
    129   assert (ehdr->e_type != ET_REL || mod != NULL);
    130 
    131   return find_elf_build_id (mod, ehdr->e_type, elf,
    132 			    build_id_bits, build_id_elfaddr, build_id_len);
    133 }
    134 
    135 ssize_t
    136 dwelf_elf_gnu_build_id (Elf *elf, const void **build_idp)
    137 {
    138   GElf_Addr build_id_elfaddr;
    139   int build_id_len;
    140   int result = find_elf_build_id (NULL, ET_NONE, elf, build_idp,
    141 				  &build_id_elfaddr, &build_id_len);
    142   if (result > 0)
    143     return build_id_len;
    144 
    145   return result;
    146 }
    147 INTDEF(dwelf_elf_gnu_build_id)
    148