genchecksum.c

/* Generate checksums of executables for PCH validation
   Copyright (C) 2005-2018 Free Software Foundation, Inc.

This file is part of GCC.

GCC 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; either version 3, or (at your option) any later
version.

GCC 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 GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "bconfig.h"
#include "system.h"
#include "md5.h"

static void
usage (void)
{
  fputs ("Usage: genchecksums <filename> ...\n", stderr);
}

/* Important: BLOCKSIZE must be a multiple of 64.  */
#define BLOCKSIZE 4096

static void
dosum (struct md5_ctx *ctx, const char *file)
{
  FILE *f;
  char buffer[BLOCKSIZE + 72];
  size_t sum;

  f = fopen (file, "rb");
  if (!f)
    {
      fprintf (stderr, "opening %s: %s\n", file, xstrerror (errno));
      exit (1);
    }

  /* Some executable formats have timestamps in the first 16 bytes, yuck.  */
  if (fseek (f, 16, SEEK_SET) != 0)
     {
      fprintf (stderr, "seeking in %s: %s\n", file, xstrerror (errno));
      exit (1);
    }

  /* Iterate over full file contents.  */
  while (1)
    {
      /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
	 computation function processes the whole buffer so that with the
	 next round of the loop another block can be read.  */
      size_t n;
      sum = 0;

      /* Read block.  Take care for partial reads.  */
      do
	{
	  n = fread (buffer + sum, 1, BLOCKSIZE - sum, f);

	  sum += n;
	}
      while (sum < BLOCKSIZE && n != 0);
      if (n == 0 && ferror (f))
        exit (1);

      /* If end of file is reached, end the loop.  */
      if (n == 0)
	break;

      /* Process buffer with BLOCKSIZE bytes.  Note that
			BLOCKSIZE % 64 == 0
       */
      md5_process_block (buffer, BLOCKSIZE, ctx);
    }

  /* Add the last bytes if necessary.  */
  if (sum > 0)
    md5_process_bytes (buffer, sum, ctx);

  if (fclose (f) != 0)
     {
      fprintf (stderr, "reading %s: %s\n", file, xstrerror (errno));
      exit (1);
    }
}

int
main (int argc, char ** argv)
{
  struct md5_ctx ctx;
  unsigned char result[16];
  int i;

  if (argc < 2)
    {
      usage ();
      return 1;
    }

  md5_init_ctx (&ctx);
  for (i = 1; i < argc; i++) 
    dosum (&ctx, argv[i]);
  md5_finish_ctx (&ctx, result);

  puts ("#include \"config.h\"");
  puts ("#include \"system.h\"");
  fputs ("EXPORTED_CONST unsigned char executable_checksum[16] = { ", stdout);
  for (i = 0; i < 16; i++)
    printf ("0x%02x%s", result[i], i == 15 ? " };\n" : ", ");

  return 0;
}