src/unexcw.c

   1 /* unexec() support for Cygwin;
   2    complete rewrite of xemacs Cygwin unexec() code
   3
   4    Copyright (C) 2004-2016 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 (at
  11 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 #include "lisp.h"
  24 #include <string.h>
  25 #include <stdio.h>
  26 #include <fcntl.h>
  27 #include <a.out.h>
  28 #include <unistd.h>
  29 #include <assert.h>
  30
  31 #define DOTEXE ".exe"
  32
  33 /*
  34 ** header for Windows executable files
  35 */
  36 typedef struct
  37 {
  38   FILHDR file_header;
  39   PEAOUTHDR file_optional_header;
  40   SCNHDR section_header[32];
  41 } exe_header_t;
  42
  43 int debug_unexcw = 0;
  44
  45 /*
  46 ** Read the header from the executable into memory so we can more easily access it.
  47 */
  48 static exe_header_t *
  49 read_exe_header (int fd, exe_header_t * exe_header_buffer)
  50 {
  51   int i;
  52   int ret;
  53
  54   assert (fd >= 0);
  55   assert (exe_header_buffer != 0);
  56
  57   ret = lseek (fd, 0L, SEEK_SET);
  58   assert (ret != -1);
  59
  60   ret =
  61     read (fd, &exe_header_buffer->file_header,
  62           sizeof (exe_header_buffer->file_header));
  63   assert (ret == sizeof (exe_header_buffer->file_header));
  64
  65   assert (exe_header_buffer->file_header.e_magic == 0x5a4d);
  66   assert (exe_header_buffer->file_header.nt_signature == 0x4550);
  67 #ifdef __x86_64__
  68   assert (exe_header_buffer->file_header.f_magic == 0x8664);
  69 #else
  70   assert (exe_header_buffer->file_header.f_magic == 0x014c);
  71 #endif
  72   assert (exe_header_buffer->file_header.f_nscns > 0);
  73   assert (exe_header_buffer->file_header.f_nscns <=
  74           ARRAYELTS (exe_header_buffer->section_header));
  75   assert (exe_header_buffer->file_header.f_opthdr > 0);
  76
  77   ret =
  78     read (fd, &exe_header_buffer->file_optional_header,
  79           sizeof (exe_header_buffer->file_optional_header));
  80   assert (ret == sizeof (exe_header_buffer->file_optional_header));
  81
  82 #ifdef __x86_64__
  83   assert (exe_header_buffer->file_optional_header.magic == 0x020b);
  84 #else
  85   assert (exe_header_buffer->file_optional_header.magic == 0x010b);
  86 #endif
  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 %#lx end %#lx\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 %#lx mem length %td\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               /* Make sure the generated bootstrap binary isn't
 185                * sparse.  NT doesn't use a file cache for sparse
 186                * executables, so if we bootstrap Emacs using a sparse
 187                * bootstrap-emacs.exe, bootstrap takes about twenty
 188                * times longer than it would otherwise.  */
 189
 190               ret = posix_fallocate (fd,
 191                                      ( exe_header->section_header[i].s_scnptr +
 192                                        exe_header->section_header[i].s_size ),
 193                                      1);
 194
 195               assert (ret != -1);
 196
 197               ret =
 198                 lseek (fd,
 199                        (long) (exe_header->section_header[i].s_scnptr +
 200                                exe_header->section_header[i].s_size - 1),
 201                        SEEK_SET);
 202               assert (ret != -1);
 203               ret = write (fd, "", 1);
 204               assert (ret == 1);
 205
 206               ret =
 207                 lseek (fd,
 208                        (long) ((char *) &exe_header->section_header[i] -
 209                                (char *) exe_header), SEEK_SET);
 210               assert (ret != -1);
 211               ret =
 212                 write (fd, &exe_header->section_header[i],
 213                        sizeof (exe_header->section_header[i]));
 214               assert (ret == sizeof (exe_header->section_header[i]));
 215               if (debug_unexcw)
 216                 printf ("         seek to %ld, write %zu\n",
 217                         (long) ((char *) &exe_header->section_header[i] -
 218                                 (char *) exe_header),
 219                         sizeof (exe_header->section_header[i]));
 220             }
 221           /* write initialized data section */
 222           ret =
 223             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 224                    SEEK_SET);
 225           assert (ret != -1);
 226           ret =
 227             write (fd, (char *) start_address,
 228                    my_endbss - (char *) start_address);
 229           assert (ret == (my_endbss - (char *) start_address));
 230           if (debug_unexcw)
 231             printf ("         .bss, mem start %#lx mem length %td\n",
 232                     start_address, my_endbss - (char *) start_address);
 233           if (debug_unexcw)
 234             printf ("         .bss, file start %d file length %d\n",
 235                     (int) exe_header->section_header[i].s_scnptr,
 236                     (int) exe_header->section_header[i].s_paddr);
 237         }
 238     }
 239   assert (found_bss == 1);
 240   assert (found_data == 1);
 241 }
 242
 243 /*
 244 ** Windows likes .exe suffixes on executables.
 245 */
 246 static char *
 247 add_exe_suffix_if_necessary (const char *name, char *modified)
 248 {
 249   int i = strlen (name);
 250   if (i <= (sizeof (DOTEXE) - 1))
 251     {
 252       sprintf (modified, "%s%s", name, DOTEXE);
 253     }
 254   else if (!strcasecmp (name + i - (sizeof (DOTEXE) - 1), DOTEXE))
 255     {
 256       strcpy (modified, name);
 257     }
 258   else
 259     {
 260       sprintf (modified, "%s%s", name, DOTEXE);
 261     }
 262   return (modified);
 263 }
 264
 265 void
 266 unexec (const char *outfile, const char *infile)
 267 {
 268   char infile_buffer[FILENAME_MAX];
 269   char outfile_buffer[FILENAME_MAX];
 270   int fd_in;
 271   int fd_out;
 272   int ret;
 273   int ret2;
 274
 275   infile = add_exe_suffix_if_necessary (infile, infile_buffer);
 276   outfile = add_exe_suffix_if_necessary (outfile, outfile_buffer);
 277
 278   fd_in = emacs_open (infile, O_RDONLY, 0);
 279   assert (fd_in >= 0);
 280   fd_out = emacs_open (outfile, O_RDWR | O_TRUNC | O_CREAT, 0755);
 281   assert (fd_out >= 0);
 282   for (;;)
 283     {
 284       char buffer[4096];
 285       ret = read (fd_in, buffer, sizeof (buffer));
 286       if (ret == 0)
 287         {
 288           /* eof */
 289           break;
 290         }
 291       assert (ret > 0);
 292       /* data */
 293       ret2 = write (fd_out, buffer, ret);
 294       assert (ret2 == ret);
 295     }
 296   ret = emacs_close (fd_in);
 297   assert (ret == 0);
 298
 299   fixup_executable (fd_out);
 300
 301   ret = emacs_close (fd_out);
 302   assert (ret == 0);
 303 }