src/unexcw.c

   1 /* unexec() support for Cygwin;
   2    complete rewrite of xemacs Cygwin unexec() code
   3
   4    Copyright (C) 2004-2011 Free Software Foundation, Inc.
   5
   6 This file is part of GNU Emacs.
   7
   8 GNU Emacs is free software: you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or
  11 (at your option) any later version.
  12
  13 GNU Emacs is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "unexec.h"
  23
  24 #include <setjmp.h>
  25 #include <lisp.h>
  26 #include <stdio.h>
  27 #include <fcntl.h>
  28 #include <a.out.h>
  29 #include <unistd.h>
  30 #include <assert.h>
  31
  32 #define DOTEXE ".exe"
  33
  34 extern int bss_sbrk_did_unexec;
  35
  36 /* emacs symbols that indicate where bss and data end for emacs internals */
  37 extern char my_endbss[];
  38 extern char my_edata[];
  39
  40 /*
  41 ** header for Windows executable files
  42 */
  43 typedef struct
  44 {
  45   FILHDR file_header;
  46   PEAOUTHDR file_optional_header;
  47   SCNHDR section_header[32];
  48 } exe_header_t;
  49
  50 int debug_unexcw = 0;
  51
  52 /*
  53 ** Read the header from the executable into memory so we can more easily access it.
  54 */
  55 static exe_header_t *
  56 read_exe_header (int fd, exe_header_t * exe_header_buffer)
  57 {
  58   int i;
  59   int ret;
  60
  61   assert (fd >= 0);
  62   assert (exe_header_buffer != 0);
  63
  64   ret = lseek (fd, 0L, SEEK_SET);
  65   assert (ret != -1);
  66
  67   ret =
  68     read (fd, &exe_header_buffer->file_header,
  69           sizeof (exe_header_buffer->file_header));
  70   assert (ret == sizeof (exe_header_buffer->file_header));
  71
  72   assert (exe_header_buffer->file_header.e_magic == 0x5a4d);
  73   assert (exe_header_buffer->file_header.nt_signature == 0x4550);
  74   assert (exe_header_buffer->file_header.f_magic == 0x014c);
  75   assert (exe_header_buffer->file_header.f_nscns > 0);
  76   assert (exe_header_buffer->file_header.f_nscns <=
  77           sizeof (exe_header_buffer->section_header) /
  78           sizeof (exe_header_buffer->section_header[0]));
  79   assert (exe_header_buffer->file_header.f_opthdr > 0);
  80
  81   ret =
  82     read (fd, &exe_header_buffer->file_optional_header,
  83           sizeof (exe_header_buffer->file_optional_header));
  84   assert (ret == sizeof (exe_header_buffer->file_optional_header));
  85
  86   assert (exe_header_buffer->file_optional_header.magic == 0x010b);
  87
  88   for (i = 0; i < exe_header_buffer->file_header.f_nscns; ++i)
  89     {
  90       ret =
  91         read (fd, &exe_header_buffer->section_header[i],
  92               sizeof (exe_header_buffer->section_header[i]));
  93       assert (ret == sizeof (exe_header_buffer->section_header[i]));
  94     }
  95
  96   return (exe_header_buffer);
  97 }
  98
  99 /*
 100 ** Fix the dumped emacs executable:
 101 **
 102 ** - copy .data section data of interest from running executable into
 103 **   output .exe file
 104 **
 105 ** - convert .bss section into an initialized data section (like
 106 **   .data) and copy .bss section data of interest from running
 107 **   executable into output .exe file
 108 */
 109 static void
 110 fixup_executable (int fd)
 111 {
 112   exe_header_t exe_header_buffer;
 113   exe_header_t *exe_header;
 114   int i;
 115   int ret;
 116   int found_data = 0;
 117   int found_bss = 0;
 118
 119   exe_header = read_exe_header (fd, &exe_header_buffer);
 120   assert (exe_header != 0);
 121
 122   assert (exe_header->file_header.f_nscns > 0);
 123   for (i = 0; i < exe_header->file_header.f_nscns; ++i)
 124     {
 125       unsigned long start_address =
 126         exe_header->section_header[i].s_vaddr +
 127         exe_header->file_optional_header.ImageBase;
 128       unsigned long end_address =
 129         exe_header->section_header[i].s_vaddr +
 130         exe_header->file_optional_header.ImageBase +
 131         exe_header->section_header[i].s_paddr;
 132       if (debug_unexcw)
 133         printf ("%8s start 0x%08x end 0x%08x\n",
 134                 exe_header->section_header[i].s_name,
 135                 start_address, end_address);
 136       if (my_edata >= (char *) start_address
 137           && my_edata < (char *) end_address)
 138         {
 139           /* data section */
 140           ret =
 141             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 142                    SEEK_SET);
 143           assert (ret != -1);
 144           ret =
 145             write (fd, (char *) start_address,
 146                    my_edata - (char *) start_address);
 147           assert (ret == my_edata - (char *) start_address);
 148           ++found_data;
 149           if (debug_unexcw)
 150             printf ("         .data, mem start 0x%08x mem length %d\n",
 151                     start_address, my_edata - (char *) start_address);
 152           if (debug_unexcw)
 153             printf ("         .data, file start %d file length %d\n",
 154                     (int) exe_header->section_header[i].s_scnptr,
 155                     (int) exe_header->section_header[i].s_paddr);
 156         }
 157       else if (my_endbss >= (char *) start_address
 158                && my_endbss < (char *) end_address)
 159         {
 160           /* bss section */
 161           ++found_bss;
 162           if (exe_header->section_header[i].s_flags & 0x00000080)
 163             {
 164               /* convert uninitialized data section to initialized data section */
 165               struct stat statbuf;
 166               ret = fstat (fd, &statbuf);
 167               assert (ret != -1);
 168
 169               exe_header->section_header[i].s_flags &= ~0x00000080;
 170               exe_header->section_header[i].s_flags |= 0x00000040;
 171
 172               exe_header->section_header[i].s_scnptr =
 173                 (statbuf.st_size +
 174                  exe_header->file_optional_header.FileAlignment) /
 175                 exe_header->file_optional_header.FileAlignment *
 176                 exe_header->file_optional_header.FileAlignment;
 177
 178               exe_header->section_header[i].s_size =
 179                 (exe_header->section_header[i].s_paddr +
 180                  exe_header->file_optional_header.FileAlignment) /
 181                 exe_header->file_optional_header.FileAlignment *
 182                 exe_header->file_optional_header.FileAlignment;
 183
 184               ret =
 185                 lseek (fd,
 186                        (long) (exe_header->section_header[i].s_scnptr +
 187                                exe_header->section_header[i].s_size - 1),
 188                        SEEK_SET);
 189               assert (ret != -1);
 190               ret = write (fd, "", 1);
 191               assert (ret == 1);
 192
 193               ret =
 194                 lseek (fd,
 195                        (long) ((char *) &exe_header->section_header[i] -
 196                                (char *) exe_header), SEEK_SET);
 197               assert (ret != -1);
 198               ret =
 199                 write (fd, &exe_header->section_header[i],
 200                        sizeof (exe_header->section_header[i]));
 201               assert (ret == sizeof (exe_header->section_header[i]));
 202               if (debug_unexcw)
 203                 printf ("         seek to %ld, write %d\n",
 204                         (long) ((char *) &exe_header->section_header[i] -
 205                                 (char *) exe_header),
 206                         sizeof (exe_header->section_header[i]));
 207             }
 208           /* write initialized data section */
 209           ret =
 210             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 211                    SEEK_SET);
 212           assert (ret != -1);
 213           ret =
 214             write (fd, (char *) start_address,
 215                    my_endbss - (char *) start_address);
 216           assert (ret == (my_endbss - (char *) start_address));
 217           if (debug_unexcw)
 218             printf ("         .bss, mem start 0x%08x mem length %d\n",
 219                     start_address, my_endbss - (char *) start_address);
 220           if (debug_unexcw)
 221             printf ("         .bss, file start %d file length %d\n",
 222                     (int) exe_header->section_header[i].s_scnptr,
 223                     (int) exe_header->section_header[i].s_paddr);
 224         }
 225     }
 226   assert (found_bss == 1);
 227   assert (found_data == 1);
 228 }
 229
 230 /*
 231 ** Windows likes .exe suffixes on executables.
 232 */
 233 static char *
 234 add_exe_suffix_if_necessary (const char *name, char *modified)
 235 {
 236   int i = strlen (name);
 237   if (i <= (sizeof (DOTEXE) - 1))
 238     {
 239       sprintf (modified, "%s%s", name, DOTEXE);
 240     }
 241   else if (!strcasecmp (name + i - (sizeof (DOTEXE) - 1), DOTEXE))
 242     {
 243       strcpy (modified, name);
 244     }
 245   else
 246     {
 247       sprintf (modified, "%s%s", name, DOTEXE);
 248     }
 249   return (modified);
 250 }
 251
 252 void
 253 unexec (const char *outfile, const char *infile)
 254 {
 255   char infile_buffer[FILENAME_MAX];
 256   char outfile_buffer[FILENAME_MAX];
 257   int fd_in;
 258   int fd_out;
 259   int ret;
 260   int ret2;
 261
 262   if (bss_sbrk_did_unexec)
 263     {
 264       /* can only dump once */
 265       printf ("You can only dump Emacs once on this platform.\n");
 266       return;
 267     }
 268
 269   report_sheap_usage (1);
 270
 271   infile = add_exe_suffix_if_necessary (infile, infile_buffer);
 272   outfile = add_exe_suffix_if_necessary (outfile, outfile_buffer);
 273
 274   fd_in = open (infile, O_RDONLY | O_BINARY);
 275   assert (fd_in >= 0);
 276   fd_out = open (outfile, O_RDWR | O_TRUNC | O_CREAT | O_BINARY, 0755);
 277   assert (fd_out >= 0);
 278   for (;;)
 279     {
 280       char buffer[4096];
 281       ret = read (fd_in, buffer, sizeof (buffer));
 282       if (ret == 0)
 283         {
 284           /* eof */
 285           break;
 286         }
 287       assert (ret > 0);
 288       /* data */
 289       ret2 = write (fd_out, buffer, ret);
 290       assert (ret2 == ret);
 291     }
 292   ret = close (fd_in);
 293   assert (ret == 0);
 294
 295   bss_sbrk_did_unexec = 1;
 296   fixup_executable (fd_out);
 297   bss_sbrk_did_unexec = 0;
 298
 299   ret = close (fd_out);
 300   assert (ret == 0);
 301 }