elf/check-localplt.c

   1 /* Show local PLT use in DSOs.
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contribute by Ulrich Drepper <drepper@redhat.com>. 2006.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <byteswap.h>
  21 #include <elf.h>
  22 #include <endian.h>
  23 #include <fcntl.h>
  24 #include <stdint.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29
  30
  31 #ifdef BITS
  32
  33 # define AB(name) _AB (name, BITS)
  34 # define _AB(name, bits) __AB (name, bits)
  35 # define __AB(name, bits) name##bits
  36 # define E(name) _E (name, BITS)
  37 # define _E(name, bits) __E (name, bits)
  38 # define __E(name, bits) Elf##bits##_##name
  39 # define EE(name) _EE (name, BITS)
  40 # define _EE(name, bits) __EE (name, bits)
  41 # define __EE(name, bits) ELF##bits##_##name
  42 # define SWAP(val) \
  43   ({ __typeof (val) __res;                                                    \
  44      if (((ehdr.e_ident[EI_DATA] == ELFDATA2MSB                               \
  45            && BYTE_ORDER == LITTLE_ENDIAN)                                    \
  46           || (ehdr.e_ident[EI_DATA] == ELFDATA2LSB                            \
  47               && BYTE_ORDER == BIG_ENDIAN))                                   \
  48          && sizeof (val) != 1)                                                \
  49        {                                                                      \
  50          if (sizeof (val) == 2)                                               \
  51            __res = bswap_16 (val);                                            \
  52          else if (sizeof (val) == 4)                                          \
  53            __res = bswap_32 (val);                                            \
  54          else                                                                 \
  55            __res = bswap_64 (val);                                            \
  56        }                                                                      \
  57      else                                                                     \
  58        __res = (val);                                                         \
  59      __res; })
  60
  61
  62 static int
  63 AB(handle_file) (const char *fname, int fd)
  64 {
  65   E(Ehdr) ehdr;
  66
  67   if (pread (fd, &ehdr, sizeof (ehdr), 0) != sizeof (ehdr))
  68     {
  69     read_error:
  70       printf ("%s: read error: %m\n", fname);
  71       return 1;
  72     }
  73
  74   const size_t phnum = SWAP (ehdr.e_phnum);
  75   const size_t phentsize = SWAP (ehdr.e_phentsize);
  76
  77   /* Read the program header.  */
  78   E(Phdr) *phdr = alloca (phentsize * phnum);
  79   if (pread (fd, phdr, phentsize * phnum, SWAP (ehdr.e_phoff))
  80       != phentsize * phnum)
  81     goto read_error;
  82
  83   /* Search for the PT_DYNAMIC entry.  */
  84   size_t cnt;
  85   E(Phdr) *dynphdr = NULL;
  86   for (cnt = 0; cnt < phnum; ++cnt)
  87     if (SWAP (phdr[cnt].p_type) == PT_DYNAMIC)
  88       {
  89         dynphdr = &phdr[cnt];
  90         break;
  91       }
  92
  93   if (dynphdr == NULL)
  94     {
  95       printf ("%s: no DYNAMIC segment found\n", fname);
  96       return 1;
  97     }
  98
  99   /* Read the dynamic segment.  */
 100   size_t pmemsz = SWAP(dynphdr->p_memsz);
 101   E(Dyn) *dyn = alloca (pmemsz);
 102   if (pread64 (fd, dyn, pmemsz, SWAP(dynphdr->p_offset)) != pmemsz)
 103     goto read_error;
 104
 105   /* Search for an DT_PLTREL, DT_JMPREL, DT_PLTRELSZ, DT_STRTAB,
 106      DT_STRSZ, and DT_SYMTAB entries.  */
 107   size_t pltrel_idx = SIZE_MAX;
 108   size_t jmprel_idx = SIZE_MAX;
 109   size_t pltrelsz_idx = SIZE_MAX;
 110   size_t strtab_idx = SIZE_MAX;
 111   size_t strsz_idx = SIZE_MAX;
 112   size_t symtab_idx = SIZE_MAX;
 113   for (cnt = 0; (cnt + 1) * sizeof (E(Dyn)) - 1 < pmemsz; ++cnt)
 114     {
 115       unsigned int tag = SWAP (dyn[cnt].d_tag);
 116
 117       if (tag == DT_NULL)
 118         /* We reached the end.  */
 119         break;
 120
 121       if (tag == DT_PLTREL)
 122         pltrel_idx = cnt;
 123       else if (tag == DT_JMPREL)
 124         jmprel_idx = cnt;
 125       else if (tag == DT_PLTRELSZ)
 126         pltrelsz_idx = cnt;
 127       else if (tag == DT_STRTAB)
 128         strtab_idx = cnt;
 129       else if (tag == DT_STRSZ)
 130         strsz_idx = cnt;
 131       else if (tag == DT_SYMTAB)
 132         symtab_idx = cnt;
 133     }
 134
 135   if (pltrel_idx == SIZE_MAX || jmprel_idx == SIZE_MAX
 136       || pltrelsz_idx == SIZE_MAX || strtab_idx == SIZE_MAX
 137       || strsz_idx == SIZE_MAX || symtab_idx == SIZE_MAX)
 138     {
 139       puts ("not all PLT information found");
 140       return 1;
 141     }
 142
 143   E(Xword) relsz = SWAP (dyn[pltrelsz_idx].d_un.d_val);
 144
 145   void *relmem = NULL;
 146   char *strtab = NULL;
 147   E(Xword) symtab_offset = 0;
 148
 149   /* Find the offset of DT_JMPREL and load the data.  */
 150   for (cnt = 0; cnt < phnum; ++cnt)
 151     if (SWAP (phdr[cnt].p_type) == PT_LOAD)
 152       {
 153         E(Addr) vaddr = SWAP (phdr[cnt].p_vaddr);
 154         E(Xword) memsz = SWAP (phdr[cnt].p_memsz);
 155
 156         if (vaddr <= SWAP (dyn[jmprel_idx].d_un.d_val)
 157             && vaddr + memsz >= SWAP (dyn[jmprel_idx].d_un.d_val) + relsz)
 158           {
 159             relmem = alloca (SWAP (dyn[pltrelsz_idx].d_un.d_val));
 160             if (pread64 (fd, relmem, relsz,
 161                          SWAP (phdr[cnt].p_offset)
 162                          + SWAP (dyn[jmprel_idx].d_un.d_val) - vaddr)
 163                 != relsz)
 164               {
 165                 puts ("cannot read JMPREL");
 166                 return 1;
 167               }
 168           }
 169
 170         if (vaddr <= SWAP (dyn[symtab_idx].d_un.d_val)
 171             && vaddr + memsz > SWAP (dyn[symtab_idx].d_un.d_val))
 172           symtab_offset = (SWAP (phdr[cnt].p_offset)
 173                            + SWAP (dyn[symtab_idx].d_un.d_val) - vaddr);
 174
 175         if (vaddr <= SWAP (dyn[strtab_idx].d_un.d_val)
 176             && vaddr + memsz >= (SWAP (dyn[strtab_idx].d_un.d_val)
 177                                  + SWAP(dyn[strsz_idx].d_un.d_val)))
 178           {
 179             strtab = alloca (SWAP(dyn[strsz_idx].d_un.d_val));
 180             if (pread64 (fd, strtab, SWAP(dyn[strsz_idx].d_un.d_val),
 181                          SWAP (phdr[cnt].p_offset)
 182                          + SWAP (dyn[strtab_idx].d_un.d_val) - vaddr)
 183                 != SWAP(dyn[strsz_idx].d_un.d_val))
 184               {
 185                 puts ("cannot read STRTAB");
 186                 return 1;
 187               }
 188           }
 189       }
 190
 191   if (relmem == NULL || strtab == NULL || symtab_offset == 0)
 192     {
 193       puts ("couldn't load PLT data");
 194       return 1;
 195     }
 196
 197   if (SWAP (dyn[pltrel_idx].d_un.d_val) == DT_RELA)
 198     for (E(Rela) *rela = relmem; (char *) rela - (char *) relmem < relsz;
 199          ++rela)
 200       {
 201         E(Sym) sym;
 202
 203         if (pread64 (fd, &sym, sizeof (sym),
 204                      symtab_offset
 205                      + EE(R_SYM) (SWAP (rela->r_info)) * sizeof (sym))
 206             != sizeof (sym))
 207           {
 208             puts ("cannot read symbol");
 209             return 1;
 210           }
 211
 212         if (sym.st_value != 0)
 213           /* This symbol is locally defined.  */
 214           printf ("%s: %s\n", basename (fname), strtab + SWAP (sym.st_name));
 215       }
 216   else
 217     for (E(Rel) *rel = relmem; (char *) rel - (char *) relmem < relsz; ++rel)
 218       {
 219         E(Sym) sym;
 220
 221         if (pread64 (fd, &sym, sizeof (sym),
 222                      symtab_offset
 223                      + EE(R_SYM) (SWAP (rel->r_info)) * sizeof (sym))
 224             != sizeof (sym))
 225           {
 226             puts ("cannot read symbol");
 227             return 1;
 228           }
 229
 230         if (sym.st_value != 0)
 231           /* This symbol is locally defined.  */
 232           printf ("%s: %s\n", basename (fname), strtab + SWAP (sym.st_name));
 233       }
 234
 235   return 0;
 236 }
 237
 238 # undef BITS
 239 #else
 240
 241 # define BITS 32
 242 # include "check-localplt.c"
 243
 244 # define BITS 64
 245 # include "check-localplt.c"
 246
 247
 248 static int
 249 handle_file (const char *fname)
 250 {
 251   int fd = open (fname, O_RDONLY);
 252   if (fd == -1)
 253     {
 254       printf ("cannot open %s: %m\n", fname);
 255       return 1;
 256     }
 257
 258   /* Read was is supposed to be the ELF header.  Read the initial
 259      bytes to determine whether this is a 32 or 64 bit file.  */
 260   char ident[EI_NIDENT];
 261   if (read (fd, ident, EI_NIDENT) != EI_NIDENT)
 262     {
 263       printf ("%s: read error: %m\n", fname);
 264       close (fd);
 265       return 1;
 266     }
 267
 268   if (memcmp (&ident[EI_MAG0], ELFMAG, SELFMAG) != 0)
 269     {
 270       printf ("%s: not an ELF file\n", fname);
 271       close (fd);
 272       return 1;
 273     }
 274
 275   int result;
 276   if (ident[EI_CLASS] == ELFCLASS64)
 277     result = handle_file64 (fname, fd);
 278   else
 279     result = handle_file32 (fname, fd);
 280
 281   close (fd);
 282
 283   return result;
 284 }
 285
 286
 287 int
 288 main (int argc, char *argv[])
 289 {
 290   int cnt;
 291   int result = 0;
 292
 293   for (cnt = 1; cnt < argc; ++cnt)
 294     result |= handle_file (argv[cnt]);
 295
 296   return result;
 297 }
 298 #endif