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 asymbol **new_sympp, **old_sympp;
  34 int new_symcount, old_symcount;
  35
  36 int
  37 main(int argc, char **argv)
  38 {
  39         bfd_init();
  40         bfd *oldbfd = bfd_openr(argv[1], NULL);
  41         assert(oldbfd != NULL);
  42         newbfd = bfd_openr(argv[2], NULL);
  43         assert(newbfd != NULL);
  44
  45         char **matching;
  46         assert(bfd_check_format_matches(oldbfd, bfd_object, &matching));
  47         assert(bfd_check_format_matches(newbfd, bfd_object, &matching));
  48
  49         new_symcount = get_syms(newbfd, &new_sympp);
  50         old_symcount = get_syms(oldbfd, &old_sympp);
  51
  52         printf("%d\n", bfd_arch_bits_per_address(oldbfd));
  53         foreach_nonmatching(oldbfd, newbfd, print_newbfd_section_name);
  54         printf("\n");
  55         foreach_nonmatching(oldbfd, newbfd, print_newbfd_entry_symbols);
  56         printf("\n");
  57
  58         assert(bfd_close(oldbfd));
  59         assert(bfd_close(newbfd));
  60         printf("ksplice: success\n");
  61         return(EXIT_SUCCESS);
  62 }
  63
  64 void
  65 foreach_nonmatching(bfd * oldbfd, bfd * newbfd, section_fn s_fn)
  66 {
  67         asection *newp, *oldp;
  68         for (newp = newbfd->sections; newp != NULL; newp = newp->next) {
  69                 if (!starts_with(newp->name, ".text"))
  70                         continue;
  71                 oldp = bfd_get_section_by_name(oldbfd, newp->name);
  72                 if (oldp == NULL) {
  73                         if (s_fn == print_newbfd_section_name)
  74                                 s_fn(newp);
  75                         continue;
  76                 }
  77                 int newsize = bfd_get_section_size(newp);
  78                 int oldsize = bfd_get_section_size(oldp);
  79                 if (newsize == oldsize) {
  80                         void *newmem = malloc(newsize);
  81                         void *oldmem = malloc(oldsize);
  82                         assert(bfd_get_section_contents
  83                                (oldbfd, oldp, oldmem, 0, oldsize));
  84                         assert(bfd_get_section_contents
  85                                (newbfd, newp, newmem, 0, newsize));
  86                         if (memcmp(newmem, oldmem, newsize) == 0 &&
  87                             reloc_cmp(oldbfd, oldp, newbfd, newp) == 0)
  88                                 continue;
  89                 }
  90                 s_fn(newp);
  91         }
  92 }
  93
  94 /*
  95  * reloc_cmp checks to see whether the old section and the new section
  96  * reference different read-only data in their relocations -- if a hard-coded
  97  * string has been changed between the old file and the new file, reloc_cmp
  98  * will detect the difference.
  99  */
 100 int
 101 reloc_cmp(bfd * oldbfd, asection * oldp, bfd * newbfd, asection * newp)
 102 {
 103         int i;
 104         struct supersect *old_ss, *new_ss;
 105
 106         old_ss = fetch_supersect(oldbfd, oldp, old_sympp);
 107         new_ss = fetch_supersect(newbfd, newp, new_sympp);
 108
 109         if (old_ss->num_relocs != new_ss->num_relocs)
 110                 return -1;
 111
 112         for (i = 0; i < old_ss->num_relocs; i++) {
 113                 struct supersect *ro_old_ss, *ro_new_ss;
 114
 115                 asection *ro_oldp = (*old_ss->relocs[i]->sym_ptr_ptr)->section;
 116                 asection *ro_newp = (*new_ss->relocs[i]->sym_ptr_ptr)->section;
 117
 118                 ro_old_ss = fetch_supersect(oldbfd, ro_oldp, old_sympp);
 119                 ro_new_ss = fetch_supersect(newbfd, ro_newp, new_sympp);
 120
 121                 if (!starts_with(ro_old_ss->name, ".rodata"))
 122                         continue;
 123
 124                 if (strcmp(ro_old_ss->name, ro_new_ss->name) != 0)
 125                         return -1;
 126
 127                 int old_offset =
 128                     *(int *) (old_ss->contents + old_ss->relocs[i]->address);
 129                 int new_offset =
 130                     *(int *) (new_ss->contents + new_ss->relocs[i]->address);
 131
 132                 if (starts_with(ro_old_ss->name, ".rodata.str")) {
 133                         if (strcmp
 134                             (ro_old_ss->contents + old_offset,
 135                              ro_new_ss->contents + new_offset) != 0)
 136                                 return -1;
 137                         continue;
 138                 }
 139
 140                 if (ro_old_ss->contents_size != ro_new_ss->contents_size)
 141                         return -1;
 142
 143                 if (memcmp(ro_old_ss->contents,
 144                            ro_new_ss->contents, ro_old_ss->contents_size) != 0)
 145                         return -1;
 146         }
 147
 148         return 0;
 149 }
 150
 151 void
 152 print_newbfd_section_name(asection * sect)
 153 {
 154         printf("%s ", sect->name);
 155 }
 156
 157 void
 158 print_newbfd_entry_symbols(asection * sect)
 159 {
 160         int i;
 161         for (i = 0; i < new_symcount; i++) {
 162                 if (strlen(new_sympp[i]->name) != 0 &&
 163                     !starts_with(new_sympp[i]->name, ".text") &&
 164                     strcmp(new_sympp[i]->section->name, sect->name) == 0) {
 165                         printf("%s ", new_sympp[i]->name);
 166                 }
 167         }
 168 }