summary refs log tree commit diff
path: root/elf/readlib.c
blob: 8a66ffe9d443a544e14c536973c9ba9a505d113c (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
/* Copyright (C) 1999-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Andreas Jaeger <aj@suse.de>, 1999 and
		  Jakub Jelinek <jakub@redhat.com>, 1999.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published
   by the Free Software Foundation; version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <http://www.gnu.org/licenses/>.  */

/* The code in this file and in readelflib is a heavily simplified
   version of the readelf program that's part of the current binutils
   development version.  Besides the simplification, it has also been
   modified to read some other file formats.  */

#include <a.out.h>
#include <elf.h>
#include <error.h>
#include <libintl.h>
#include <link.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <gnu/lib-names.h>

#include <ldconfig.h>

#define Elf32_CLASS ELFCLASS32
#define Elf64_CLASS ELFCLASS64

struct known_names
{
  const char *soname;
  int flag;
};

static struct known_names interpreters[] =
{
  { "/lib/" LD_SO, FLAG_ELF_LIBC6 },
#ifdef SYSDEP_KNOWN_INTERPRETER_NAMES
  SYSDEP_KNOWN_INTERPRETER_NAMES
#endif
};

static struct known_names known_libs[] =
{
  { LIBC_SO, FLAG_ELF_LIBC6 },
  { LIBM_SO, FLAG_ELF_LIBC6 },
#ifdef SYSDEP_KNOWN_LIBRARY_NAMES
  SYSDEP_KNOWN_LIBRARY_NAMES
#endif
};


/* Check if string corresponds to a GDB Python file.  */
static bool
is_gdb_python_file (const char *name)
{
  size_t len = strlen (name);
  return len > 7 && strcmp (name + len - 7, "-gdb.py") == 0;
}

/* Returns 0 if everything is ok, != 0 in case of error.  */
int
process_file (const char *real_file_name, const char *file_name,
	      const char *lib, int *flag, unsigned int *osversion,
	      char **soname, int is_link, struct stat64 *stat_buf)
{
  FILE *file;
  struct stat64 statbuf;
  void *file_contents;
  int ret;
  ElfW(Ehdr) *elf_header;
  struct exec *aout_header;

  ret = 0;
  *flag = FLAG_ANY;
  *soname = NULL;

  file = fopen (real_file_name, "rb");
  if (file == NULL)
    {
      /* No error for stale symlink.  */
      if (is_link && strstr (file_name, ".so") != NULL)
	return 1;
      error (0, 0, _("Input file %s not found.\n"), file_name);
      return 1;
    }

  if (fstat64 (fileno (file), &statbuf) < 0)
    {
      error (0, 0, _("Cannot fstat file %s.\n"), file_name);
      fclose (file);
      return 1;
    }

  /* Check that the file is large enough so that we can access the
     information.  We're only checking the size of the headers here.  */
  if ((size_t) statbuf.st_size < sizeof (struct exec)
      || (size_t) statbuf.st_size < sizeof (ElfW(Ehdr)))
    {
      if (statbuf.st_size == 0)
	error (0, 0, _("File %s is empty, not checked."), file_name);
      else
	{
	  char buf[SELFMAG];
	  size_t n = MIN (statbuf.st_size, SELFMAG);
	  if (fread (buf, n, 1, file) == 1 && memcmp (buf, ELFMAG, n) == 0)
	    error (0, 0, _("File %s is too small, not checked."), file_name);
	}
      fclose (file);
      return 1;
    }

  file_contents = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED,
			fileno (file), 0);
  if (file_contents == MAP_FAILED)
    {
      error (0, 0, _("Cannot mmap file %s.\n"), file_name);
      fclose (file);
      return 1;
    }

  /* First check if this is an aout file.  */
  aout_header = (struct exec *) file_contents;
  if (N_MAGIC (*aout_header) == ZMAGIC
#ifdef QMAGIC			/* Linuxism.  */
      || N_MAGIC (*aout_header) == QMAGIC
#endif
      )
    {
      /* Aout files don't have a soname, just return the name
	 including the major number.  */
      char *copy, *major, *dot;
      copy = xstrdup (lib);
      major = strstr (copy, ".so.");
      if (major)
	{
	  dot = strstr (major + 4, ".");
	  if (dot)
	    *dot = '\0';
	}
      *soname = copy;
      *flag = FLAG_LIBC4;
      goto done;
    }

  elf_header = (ElfW(Ehdr) *) file_contents;
  if (memcmp (elf_header->e_ident, ELFMAG, SELFMAG) != 0)
    {
      /* The file is neither ELF nor aout.  Check if it's a linker
	 script, like libc.so - otherwise complain.  Only search the
	 beginning of the file.  */
      size_t len = MIN (statbuf.st_size, 512);
      if (memmem (file_contents, len, "GROUP", 5) == NULL
	  && memmem (file_contents, len, "GNU ld script", 13) == NULL
	  && !is_gdb_python_file (file_name))
	error (0, 0, _("%s is not an ELF file - it has the wrong magic bytes at the start.\n"),
	       file_name);
      ret = 1;
    }
  /* Libraries have to be shared object files.  */
  else if (elf_header->e_type != ET_DYN)
    ret = 1;
  else if (process_elf_file (file_name, lib, flag, osversion, soname,
			     file_contents, statbuf.st_size))
    ret = 1;

 done:
  /* Clean up allocated memory and resources.  */
  munmap (file_contents, statbuf.st_size);
  fclose (file);

  *stat_buf = statbuf;
  return ret;
}

/* Returns made up soname if lib doesn't have explicit DT_SONAME.  */

char *
implicit_soname (const char *lib, int flag)
{
  char *soname = xstrdup (lib);

  if ((flag & FLAG_TYPE_MASK) != FLAG_LIBC4)
    return soname;

  /* Aout files don't have a soname, just return the name
     including the major number.  */
  char *major = strstr (soname, ".so.");
  if (major)
    {
      char *dot = strstr (major + 4, ".");
      if (dot)
	*dot = '\0';
    }
  return soname;
}

/* Get architecture specific version of process_elf_file.  */
#include <readelflib.c>