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1 /* Get note information at the supplied offset.
2    Copyright (C) 2007, 2014, 2015, 2018 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 <assert.h>
34 #include <gelf.h>
35 #include <string.h>
36 
37 #include "libelfP.h"
38 
39 size_t
gelf_getnote(Elf_Data * data,size_t offset,GElf_Nhdr * result,size_t * name_offset,size_t * desc_offset)40 gelf_getnote (Elf_Data *data, size_t offset, GElf_Nhdr *result,
41 	      size_t *name_offset, size_t *desc_offset)
42 {
43   if (data == NULL)
44     return 0;
45 
46   if (unlikely (data->d_type != ELF_T_NHDR && data->d_type != ELF_T_NHDR8))
47     {
48       __libelf_seterrno (ELF_E_INVALID_HANDLE);
49       return 0;
50     }
51 
52   /* It's easy to handle this type.  It has the same size for 32 and
53      64 bit objects.  */
54   assert (sizeof (GElf_Nhdr) == sizeof (Elf32_Nhdr));
55   assert (sizeof (GElf_Nhdr) == sizeof (Elf64_Nhdr));
56 
57   rwlock_rdlock (((Elf_Data_Scn *) data)->s->elf->lock);
58 
59   /* The data is already in the correct form.  Just make sure the
60      offset is OK.  */
61   if (unlikely (offset > data->d_size
62 		|| data->d_size - offset < sizeof (GElf_Nhdr)))
63     {
64       __libelf_seterrno (ELF_E_OFFSET_RANGE);
65       offset = 0;
66     }
67   else
68     {
69       const GElf_Nhdr *n = data->d_buf + offset;
70       offset += sizeof *n;
71 
72       if (offset > data->d_size)
73 	offset = 0;
74       else
75 	{
76 	  /* This is slightly tricky, offset is guaranteed to be 4
77 	     byte aligned, which is what we need for the name_offset.
78 	     And normally desc_offset is also 4 byte aligned, but not
79 	     for GNU Property notes, then it should be 8.  So align
80 	     the offset, after adding the namesz, and include padding
81 	     in descsz to get to the end.  */
82 	  *name_offset = offset;
83 	  if (n->n_namesz > data->d_size
84 	      || offset > data->d_size - n->n_namesz)
85 	    offset = 0;
86 	  else
87 	    {
88 	      offset += n->n_namesz;
89 	      /* Include padding.  Check below for overflow.  */
90 	      GElf_Word descsz = (data->d_type == ELF_T_NHDR8
91 				  ? NOTE_ALIGN8 (n->n_descsz)
92 				  : NOTE_ALIGN4 (n->n_descsz));
93 
94 	      if (data->d_type == ELF_T_NHDR8)
95 		offset = NOTE_ALIGN8 (offset);
96 	      else
97 		offset = NOTE_ALIGN4 (offset);
98 
99 	      if (unlikely (offset > data->d_size
100 			    || data->d_size - offset < descsz
101 			    || (descsz == 0 && n->n_descsz != 0)))
102 		offset = 0;
103 	      else
104 		{
105 		  *desc_offset = offset;
106 		  offset += descsz;
107 		  *result = *n;
108 		}
109 	    }
110 	}
111     }
112 
113   rwlock_unlock (((Elf_Data_Scn *) data)->s->elf->lock);
114 
115   return offset;
116 }
117