objdiff.c

   1 /*  Copyright (C) 2008  Jeffrey Brian Arnold <jbarnold@mit.edu>
   2  *
   3  *  This program is free software; you can redistribute it and/or modify
   4  *  it under the terms of the GNU General Public License, version 2.
   5  *
   6  *  This program is distributed in the hope that it will be useful,
   7  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   8  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9  *  GNU General Public License for more details.
  10  *
  11  *  You should have received a copy of the GNU General Public License
  12  *  along with this program; if not, write to the Free Software
  13  *  Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
  14  *  02110-1301, USA.
  15  */
  16
  17 /*
  18  * "objdiff old.o new.o" prints two lists to STDOUT, one per line:
  19  * (1) the names of the ELF sections in new.o that either
  20  *     (a) do not appear in old.o, or
  21  *     (b) have different contents in old.o and new.o
  22  * (2) the names of the "entry point" ELF symbols in new.o
  23  *     corresponding to the ELF sections in list (1)
  24  *
  25  * Before printing these two lists, objdiff prints the number of bits
  26  * per address on the target architecture.
  27  */
  28
  29 #include "objcommon.h"
  30 #include "objdiff.h"
  31
  32 bfd *newbfd;
  33 struct asymbolp_vec new_syms, old_syms;
  34
  35 int main(int argc, char **argv)
  36 {
  37         bfd_init();
  38         bfd *oldbfd = bfd_openr(argv[1], NULL);
  39         assert(oldbfd != NULL);
  40         newbfd = bfd_openr(argv[2], NULL);
  41         assert(newbfd != NULL);
  42
  43         char **matching;
  44         assert(bfd_check_format_matches(oldbfd, bfd_object, &matching));
  45         assert(bfd_check_format_matches(newbfd, bfd_object, &matching));
  46
  47         get_syms(newbfd, &new_syms);
  48         get_syms(oldbfd, &old_syms);
  49
  50         printf("%d\n", bfd_arch_bits_per_address(oldbfd));
  51         foreach_nonmatching(oldbfd, newbfd, print_newbfd_section_name);
  52         printf("\n");
  53         foreach_nonmatching(oldbfd, newbfd, print_newbfd_entry_symbols);
  54         printf("\n");
  55
  56         assert(bfd_close(oldbfd));
  57         assert(bfd_close(newbfd));
  58         return EXIT_SUCCESS;
  59 }
  60
  61 void foreach_nonmatching(bfd *oldbfd, bfd *newbfd, section_fn s_fn)
  62 {
  63         asection *newp, *oldp;
  64         for (newp = newbfd->sections; newp != NULL; newp = newp->next) {
  65                 if (!starts_with(newp->name, ".text"))
  66                         continue;
  67                 oldp = bfd_get_section_by_name(oldbfd, newp->name);
  68                 if (oldp == NULL) {
  69                         if (s_fn == print_newbfd_section_name)
  70                                 s_fn(newp);
  71                         continue;
  72                 }
  73                 int newsize = bfd_get_section_size(newp);
  74                 int oldsize = bfd_get_section_size(oldp);
  75                 if (newsize == oldsize) {
  76                         void *newmem = malloc(newsize);
  77                         void *oldmem = malloc(oldsize);
  78                         assert(bfd_get_section_contents
  79                                (oldbfd, oldp, oldmem, 0, oldsize));
  80                         assert(bfd_get_section_contents
  81                                (newbfd, newp, newmem, 0, newsize));
  82                         if (memcmp(newmem, oldmem, newsize) == 0 &&
  83                             reloc_cmp(oldbfd, oldp, newbfd, newp) == 0)
  84                                 continue;
  85                 }
  86                 s_fn(newp);
  87         }
  88 }
  89
  90 /*
  91  * reloc_cmp checks to see whether the old section and the new section
  92  * reference different read-only data in their relocations -- if a hard-coded
  93  * string has been changed between the old file and the new file, reloc_cmp
  94  * will detect the difference.
  95  */
  96 int reloc_cmp(bfd *oldbfd, asection *oldp, bfd *newbfd, asection *newp)
  97 {
  98         int i;
  99         struct supersect *old_ss, *new_ss;
 100
 101         old_ss = fetch_supersect(oldbfd, oldp, &old_syms);
 102         new_ss = fetch_supersect(newbfd, newp, &new_syms);
 103
 104         if (old_ss->relocs.size != new_ss->relocs.size)
 105                 return -1;
 106
 107         for (i = 0; i < old_ss->relocs.size; i++) {
 108                 struct supersect *ro_old_ss, *ro_new_ss;
 109
 110                 asection *ro_oldp =
 111                     (*old_ss->relocs.data[i]->sym_ptr_ptr)->section;
 112                 asection *ro_newp =
 113                     (*new_ss->relocs.data[i]->sym_ptr_ptr)->section;
 114
 115                 ro_old_ss = fetch_supersect(oldbfd, ro_oldp, &old_syms);
 116                 ro_new_ss = fetch_supersect(newbfd, ro_newp, &new_syms);
 117
 118                 if (!starts_with(ro_old_ss->name, ".rodata"))
 119                         continue;
 120
 121                 if (strcmp(ro_old_ss->name, ro_new_ss->name) != 0)
 122                         return -1;
 123
 124                 int old_offset = *(int *)(old_ss->contents.data +
 125                                           old_ss->relocs.data[i]->address);
 126                 int new_offset = *(int *)(new_ss->contents.data +
 127                                           new_ss->relocs.data[i]->address);
 128
 129                 if (starts_with(ro_old_ss->name, ".rodata.str")) {
 130                         if (strcmp
 131                             (ro_old_ss->contents.data + old_offset,
 132                              ro_new_ss->contents.data + new_offset) != 0)
 133                                 return -1;
 134                         continue;
 135                 }
 136
 137                 if (ro_old_ss->contents.size != ro_new_ss->contents.size)
 138                         return -1;
 139
 140                 if (memcmp(ro_old_ss->contents.data, ro_new_ss->contents.data,
 141                            ro_old_ss->contents.size) != 0)
 142                         return -1;
 143         }
 144
 145         return 0;
 146 }
 147
 148 void print_newbfd_section_name(asection *sect)
 149 {
 150         printf("%s ", sect->name);
 151 }
 152
 153 void print_newbfd_entry_symbols(asection *sect)
 154 {
 155         asymbol **symp;
 156         for (symp = new_syms.data; symp < new_syms.data + new_syms.size;
 157              symp++) {
 158                 asymbol *sym = *symp;
 159                 if (strlen(sym->name) != 0 &&
 160                     !starts_with(sym->name, ".text") &&
 161                     strcmp(sym->section->name, sect->name) == 0)
 162                         printf("%s ", sym->name);
 163         }
 164 }