src/unexcw.c

   1 /* unexec() support for Cygwin;
   2    complete rewrite of xemacs Cygwin unexec() code
   3
   4    Copyright (C) 2004-2018 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 <https://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "unexec.h"
  23 #include "lisp.h"
  24 #include <stdio.h>
  25 #include <fcntl.h>
  26 #include <a.out.h>
  27 #include <unistd.h>
  28 #include <assert.h>
  29
  30 #define DOTEXE ".exe"
  31
  32 /*
  33 ** header for Windows executable files
  34 */
  35 typedef struct
  36 {
  37   FILHDR file_header;
  38   PEAOUTHDR file_optional_header;
  39   SCNHDR section_header[32];
  40 } exe_header_t;
  41
  42 int debug_unexcw = 0;
  43
  44 /*
  45 ** Read the header from the executable into memory so we can more easily access it.
  46 */
  47 static exe_header_t *
  48 read_exe_header (int fd, exe_header_t * exe_header_buffer)
  49 {
  50   int i;
  51   int ret;
  52
  53   assert (fd >= 0);
  54   assert (exe_header_buffer != 0);
  55
  56   ret = lseek (fd, 0L, SEEK_SET);
  57   assert (ret != -1);
  58
  59   ret =
  60     read (fd, &exe_header_buffer->file_header,
  61           sizeof (exe_header_buffer->file_header));
  62   assert (ret == sizeof (exe_header_buffer->file_header));
  63
  64   assert (exe_header_buffer->file_header.e_magic == 0x5a4d);
  65   assert (exe_header_buffer->file_header.nt_signature == 0x4550);
  66 #ifdef __x86_64__
  67   assert (exe_header_buffer->file_header.f_magic == 0x8664);
  68 #else
  69   assert (exe_header_buffer->file_header.f_magic == 0x014c);
  70 #endif
  71   assert (exe_header_buffer->file_header.f_nscns > 0);
  72   assert (exe_header_buffer->file_header.f_nscns <=
  73           ARRAYELTS (exe_header_buffer->section_header));
  74   assert (exe_header_buffer->file_header.f_opthdr > 0);
  75
  76   ret =
  77     read (fd, &exe_header_buffer->file_optional_header,
  78           sizeof (exe_header_buffer->file_optional_header));
  79   assert (ret == sizeof (exe_header_buffer->file_optional_header));
  80
  81 #ifdef __x86_64__
  82   assert (exe_header_buffer->file_optional_header.magic == 0x020b);
  83 #else
  84   assert (exe_header_buffer->file_optional_header.magic == 0x010b);
  85 #endif
  86
  87   for (i = 0; i < exe_header_buffer->file_header.f_nscns; ++i)
  88     {
  89       ret =
  90         read (fd, &exe_header_buffer->section_header[i],
  91               sizeof (exe_header_buffer->section_header[i]));
  92       assert (ret == sizeof (exe_header_buffer->section_header[i]));
  93     }
  94
  95   return (exe_header_buffer);
  96 }
  97
  98 /*
  99 ** Fix the dumped emacs executable:
 100 **
 101 ** - copy .data section data of interest from running executable into
 102 **   output .exe file
 103 **
 104 ** - convert .bss section into an initialized data section (like
 105 **   .data) and copy .bss section data of interest from running
 106 **   executable into output .exe file
 107 */
 108 static void
 109 fixup_executable (int fd)
 110 {
 111   exe_header_t exe_header_buffer;
 112   exe_header_t *exe_header;
 113   int i;
 114   int ret;
 115   int found_data = 0;
 116   int found_bss = 0;
 117
 118   exe_header = read_exe_header (fd, &exe_header_buffer);
 119   assert (exe_header != 0);
 120
 121   assert (exe_header->file_header.f_nscns > 0);
 122   for (i = 0; i < exe_header->file_header.f_nscns; ++i)
 123     {
 124       unsigned long start_address =
 125         exe_header->section_header[i].s_vaddr +
 126         exe_header->file_optional_header.ImageBase;
 127       unsigned long end_address =
 128         exe_header->section_header[i].s_vaddr +
 129         exe_header->file_optional_header.ImageBase +
 130         exe_header->section_header[i].s_paddr;
 131       if (debug_unexcw)
 132         printf ("%8s start %#lx end %#lx\n",
 133                 exe_header->section_header[i].s_name,
 134                 start_address, end_address);
 135       if (my_edata >= (char *) start_address
 136           && my_edata < (char *) end_address)
 137         {
 138           /* data section */
 139           ret =
 140             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 141                    SEEK_SET);
 142           assert (ret != -1);
 143           ret =
 144             write (fd, (char *) start_address,
 145                    my_edata - (char *) start_address);
 146           assert (ret == my_edata - (char *) start_address);
 147           ++found_data;
 148           if (debug_unexcw)
 149             printf ("         .data, mem start %#lx mem length %td\n",
 150                     start_address, my_edata - (char *) start_address);
 151           if (debug_unexcw)
 152             printf ("         .data, file start %d file length %d\n",
 153                     (int) exe_header->section_header[i].s_scnptr,
 154                     (int) exe_header->section_header[i].s_paddr);
 155         }
 156       else if (my_endbss >= (char *) start_address
 157                && my_endbss < (char *) end_address)
 158         {
 159           /* bss section */
 160           ++found_bss;
 161           if (exe_header->section_header[i].s_flags & 0x00000080)
 162             {
 163               /* convert uninitialized data section to initialized data section */
 164               struct stat statbuf;
 165               ret = fstat (fd, &statbuf);
 166               assert (ret != -1);
 167
 168               exe_header->section_header[i].s_flags &= ~0x00000080;
 169               exe_header->section_header[i].s_flags |= 0x00000040;
 170
 171               exe_header->section_header[i].s_scnptr =
 172                 (statbuf.st_size +
 173                  exe_header->file_optional_header.FileAlignment) /
 174                 exe_header->file_optional_header.FileAlignment *
 175                 exe_header->file_optional_header.FileAlignment;
 176
 177               exe_header->section_header[i].s_size =
 178                 (exe_header->section_header[i].s_paddr +
 179                  exe_header->file_optional_header.FileAlignment) /
 180                 exe_header->file_optional_header.FileAlignment *
 181                 exe_header->file_optional_header.FileAlignment;
 182
 183               /* Make sure the generated bootstrap binary isn't
 184                * sparse.  NT doesn't use a file cache for sparse
 185                * executables, so if we bootstrap Emacs using a sparse
 186                * bootstrap-emacs.exe, bootstrap takes about twenty
 187                * times longer than it would otherwise.  */
 188
 189               ret = posix_fallocate (fd,
 190                                      ( exe_header->section_header[i].s_scnptr +
 191                                        exe_header->section_header[i].s_size ),
 192                                      1);
 193
 194               assert (ret != -1);
 195
 196               ret =
 197                 lseek (fd,
 198                        (long) (exe_header->section_header[i].s_scnptr +
 199                                exe_header->section_header[i].s_size - 1),
 200                        SEEK_SET);
 201               assert (ret != -1);
 202               ret = write (fd, "", 1);
 203               assert (ret == 1);
 204
 205               ret =
 206                 lseek (fd,
 207                        (long) ((char *) &exe_header->section_header[i] -
 208                                (char *) exe_header), SEEK_SET);
 209               assert (ret != -1);
 210               ret =
 211                 write (fd, &exe_header->section_header[i],
 212                        sizeof (exe_header->section_header[i]));
 213               assert (ret == sizeof (exe_header->section_header[i]));
 214               if (debug_unexcw)
 215                 printf ("         seek to %ld, write %zu\n",
 216                         (long) ((char *) &exe_header->section_header[i] -
 217                                 (char *) exe_header),
 218                         sizeof (exe_header->section_header[i]));
 219             }
 220           /* write initialized data section */
 221           ret =
 222             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 223                    SEEK_SET);
 224           assert (ret != -1);
 225           ret =
 226             write (fd, (char *) start_address,
 227                    my_endbss - (char *) start_address);
 228           assert (ret == (my_endbss - (char *) start_address));
 229           if (debug_unexcw)
 230             printf ("         .bss, mem start %#lx mem length %td\n",
 231                     start_address, my_endbss - (char *) start_address);
 232           if (debug_unexcw)
 233             printf ("         .bss, file start %d file length %d\n",
 234                     (int) exe_header->section_header[i].s_scnptr,
 235                     (int) exe_header->section_header[i].s_paddr);
 236         }
 237     }
 238   assert (found_bss == 1);
 239   assert (found_data == 1);
 240 }
 241
 242 /*
 243 ** Windows likes .exe suffixes on executables.
 244 */
 245 static char *
 246 add_exe_suffix_if_necessary (const char *name, char *modified)
 247 {
 248   int i = strlen (name);
 249   if (i <= (sizeof (DOTEXE) - 1))
 250     {
 251       sprintf (modified, "%s%s", name, DOTEXE);
 252     }
 253   else if (!strcasecmp (name + i - (sizeof (DOTEXE) - 1), DOTEXE))
 254     {
 255       strcpy (modified, name);
 256     }
 257   else
 258     {
 259       sprintf (modified, "%s%s", name, DOTEXE);
 260     }
 261   return (modified);
 262 }
 263
 264 void
 265 unexec (const char *outfile, const char *infile)
 266 {
 267   char infile_buffer[FILENAME_MAX];
 268   char outfile_buffer[FILENAME_MAX];
 269   int fd_in;
 270   int fd_out;
 271   int ret;
 272   int ret2;
 273
 274   infile = add_exe_suffix_if_necessary (infile, infile_buffer);
 275   outfile = add_exe_suffix_if_necessary (outfile, outfile_buffer);
 276
 277   fd_in = emacs_open (infile, O_RDONLY, 0);
 278   assert (fd_in >= 0);
 279   fd_out = emacs_open (outfile, O_RDWR | O_TRUNC | O_CREAT, 0755);
 280   assert (fd_out >= 0);
 281   for (;;)
 282     {
 283       char buffer[4096];
 284       ret = read (fd_in, buffer, sizeof (buffer));
 285       if (ret == 0)
 286         {
 287           /* eof */
 288           break;
 289         }
 290       assert (ret > 0);
 291       /* data */
 292       ret2 = write (fd_out, buffer, ret);
 293       assert (ret2 == ret);
 294     }
 295   ret = emacs_close (fd_in);
 296   assert (ret == 0);
 297
 298   fixup_executable (fd_out);
 299
 300   ret = emacs_close (fd_out);
 301   assert (ret == 0);
 302 }