src/unexcw.c

   1 /* unexec() support for Cygwin;
   2    complete rewrite of xemacs Cygwin unexec() code
   3
   4    Copyright (C) 2004-2014 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 #include "lisp.h"
  24
  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 extern void report_sheap_usage (int);
  34
  35 extern int bss_sbrk_did_unexec;
  36
  37 extern int __malloc_initialized;
  38
  39 /* emacs symbols that indicate where bss and data end for emacs internals */
  40 extern char my_endbss[];
  41 extern char my_edata[];
  42
  43 /*
  44 ** header for Windows executable files
  45 */
  46 typedef struct
  47 {
  48   FILHDR file_header;
  49   PEAOUTHDR file_optional_header;
  50   SCNHDR section_header[32];
  51 } exe_header_t;
  52
  53 int debug_unexcw = 0;
  54
  55 /*
  56 ** Read the header from the executable into memory so we can more easily access it.
  57 */
  58 static exe_header_t *
  59 read_exe_header (int fd, exe_header_t * exe_header_buffer)
  60 {
  61   int i;
  62   int ret;
  63
  64   assert (fd >= 0);
  65   assert (exe_header_buffer != 0);
  66
  67   ret = lseek (fd, 0L, SEEK_SET);
  68   assert (ret != -1);
  69
  70   ret =
  71     read (fd, &exe_header_buffer->file_header,
  72           sizeof (exe_header_buffer->file_header));
  73   assert (ret == sizeof (exe_header_buffer->file_header));
  74
  75   assert (exe_header_buffer->file_header.e_magic == 0x5a4d);
  76   assert (exe_header_buffer->file_header.nt_signature == 0x4550);
  77 #ifdef __x86_64__
  78   assert (exe_header_buffer->file_header.f_magic == 0x8664);
  79 #else
  80   assert (exe_header_buffer->file_header.f_magic == 0x014c);
  81 #endif
  82   assert (exe_header_buffer->file_header.f_nscns > 0);
  83   assert (exe_header_buffer->file_header.f_nscns <=
  84           ARRAYELTS (exe_header_buffer->section_header));
  85   assert (exe_header_buffer->file_header.f_opthdr > 0);
  86
  87   ret =
  88     read (fd, &exe_header_buffer->file_optional_header,
  89           sizeof (exe_header_buffer->file_optional_header));
  90   assert (ret == sizeof (exe_header_buffer->file_optional_header));
  91
  92 #ifdef __x86_64__
  93   assert (exe_header_buffer->file_optional_header.magic == 0x020b);
  94 #else
  95   assert (exe_header_buffer->file_optional_header.magic == 0x010b);
  96 #endif
  97
  98   for (i = 0; i < exe_header_buffer->file_header.f_nscns; ++i)
  99     {
 100       ret =
 101         read (fd, &exe_header_buffer->section_header[i],
 102               sizeof (exe_header_buffer->section_header[i]));
 103       assert (ret == sizeof (exe_header_buffer->section_header[i]));
 104     }
 105
 106   return (exe_header_buffer);
 107 }
 108
 109 /*
 110 ** Fix the dumped emacs executable:
 111 **
 112 ** - copy .data section data of interest from running executable into
 113 **   output .exe file
 114 **
 115 ** - convert .bss section into an initialized data section (like
 116 **   .data) and copy .bss section data of interest from running
 117 **   executable into output .exe file
 118 */
 119 static void
 120 fixup_executable (int fd)
 121 {
 122   exe_header_t exe_header_buffer;
 123   exe_header_t *exe_header;
 124   int i;
 125   int ret;
 126   int found_data = 0;
 127   int found_bss = 0;
 128
 129   exe_header = read_exe_header (fd, &exe_header_buffer);
 130   assert (exe_header != 0);
 131
 132   assert (exe_header->file_header.f_nscns > 0);
 133   for (i = 0; i < exe_header->file_header.f_nscns; ++i)
 134     {
 135       unsigned long start_address =
 136         exe_header->section_header[i].s_vaddr +
 137         exe_header->file_optional_header.ImageBase;
 138       unsigned long end_address =
 139         exe_header->section_header[i].s_vaddr +
 140         exe_header->file_optional_header.ImageBase +
 141         exe_header->section_header[i].s_paddr;
 142       if (debug_unexcw)
 143         printf ("%8s start %#lx end %#lx\n",
 144                 exe_header->section_header[i].s_name,
 145                 start_address, end_address);
 146       if (my_edata >= (char *) start_address
 147           && my_edata < (char *) end_address)
 148         {
 149           /* data section */
 150           ret =
 151             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 152                    SEEK_SET);
 153           assert (ret != -1);
 154           ret =
 155             write (fd, (char *) start_address,
 156                    my_edata - (char *) start_address);
 157           assert (ret == my_edata - (char *) start_address);
 158           ++found_data;
 159           if (debug_unexcw)
 160             printf ("         .data, mem start %#lx mem length %d\n",
 161                     start_address, my_edata - (char *) start_address);
 162           if (debug_unexcw)
 163             printf ("         .data, file start %d file length %d\n",
 164                     (int) exe_header->section_header[i].s_scnptr,
 165                     (int) exe_header->section_header[i].s_paddr);
 166         }
 167       else if (my_endbss >= (char *) start_address
 168                && my_endbss < (char *) end_address)
 169         {
 170           /* bss section */
 171           ++found_bss;
 172           if (exe_header->section_header[i].s_flags & 0x00000080)
 173             {
 174               /* convert uninitialized data section to initialized data section */
 175               struct stat statbuf;
 176               ret = fstat (fd, &statbuf);
 177               assert (ret != -1);
 178
 179               exe_header->section_header[i].s_flags &= ~0x00000080;
 180               exe_header->section_header[i].s_flags |= 0x00000040;
 181
 182               exe_header->section_header[i].s_scnptr =
 183                 (statbuf.st_size +
 184                  exe_header->file_optional_header.FileAlignment) /
 185                 exe_header->file_optional_header.FileAlignment *
 186                 exe_header->file_optional_header.FileAlignment;
 187
 188               exe_header->section_header[i].s_size =
 189                 (exe_header->section_header[i].s_paddr +
 190                  exe_header->file_optional_header.FileAlignment) /
 191                 exe_header->file_optional_header.FileAlignment *
 192                 exe_header->file_optional_header.FileAlignment;
 193
 194               /* Make sure the generated bootstrap binary isn't
 195                * sparse.  NT doesn't use a file cache for sparse
 196                * executables, so if we bootstrap Emacs using a sparse
 197                * bootstrap-emacs.exe, bootstrap takes about twenty
 198                * times longer than it would otherwise.  */
 199
 200               ret = posix_fallocate (fd,
 201                                      ( exe_header->section_header[i].s_scnptr +
 202                                        exe_header->section_header[i].s_size ),
 203                                      1);
 204
 205               assert (ret != -1);
 206
 207               ret =
 208                 lseek (fd,
 209                        (long) (exe_header->section_header[i].s_scnptr +
 210                                exe_header->section_header[i].s_size - 1),
 211                        SEEK_SET);
 212               assert (ret != -1);
 213               ret = write (fd, "", 1);
 214               assert (ret == 1);
 215
 216               ret =
 217                 lseek (fd,
 218                        (long) ((char *) &exe_header->section_header[i] -
 219                                (char *) exe_header), SEEK_SET);
 220               assert (ret != -1);
 221               ret =
 222                 write (fd, &exe_header->section_header[i],
 223                        sizeof (exe_header->section_header[i]));
 224               assert (ret == sizeof (exe_header->section_header[i]));
 225               if (debug_unexcw)
 226                 printf ("         seek to %ld, write %d\n",
 227                         (long) ((char *) &exe_header->section_header[i] -
 228                                 (char *) exe_header),
 229                         sizeof (exe_header->section_header[i]));
 230             }
 231           /* write initialized data section */
 232           ret =
 233             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 234                    SEEK_SET);
 235           assert (ret != -1);
 236           /* force the dumped emacs to reinitialize malloc */
 237           __malloc_initialized = 0;
 238           ret =
 239             write (fd, (char *) start_address,
 240                    my_endbss - (char *) start_address);
 241           __malloc_initialized = 1;
 242           assert (ret == (my_endbss - (char *) start_address));
 243           if (debug_unexcw)
 244             printf ("         .bss, mem start %#lx mem length %d\n",
 245                     start_address, my_endbss - (char *) start_address);
 246           if (debug_unexcw)
 247             printf ("         .bss, file start %d file length %d\n",
 248                     (int) exe_header->section_header[i].s_scnptr,
 249                     (int) exe_header->section_header[i].s_paddr);
 250         }
 251     }
 252   assert (found_bss == 1);
 253   assert (found_data == 1);
 254 }
 255
 256 /*
 257 ** Windows likes .exe suffixes on executables.
 258 */
 259 static char *
 260 add_exe_suffix_if_necessary (const char *name, char *modified)
 261 {
 262   int i = strlen (name);
 263   if (i <= (sizeof (DOTEXE) - 1))
 264     {
 265       sprintf (modified, "%s%s", name, DOTEXE);
 266     }
 267   else if (!strcasecmp (name + i - (sizeof (DOTEXE) - 1), DOTEXE))
 268     {
 269       strcpy (modified, name);
 270     }
 271   else
 272     {
 273       sprintf (modified, "%s%s", name, DOTEXE);
 274     }
 275   return (modified);
 276 }
 277
 278 void
 279 unexec (const char *outfile, const char *infile)
 280 {
 281   char infile_buffer[FILENAME_MAX];
 282   char outfile_buffer[FILENAME_MAX];
 283   int fd_in;
 284   int fd_out;
 285   int ret;
 286   int ret2;
 287
 288   report_sheap_usage (1);
 289
 290   infile = add_exe_suffix_if_necessary (infile, infile_buffer);
 291   outfile = add_exe_suffix_if_necessary (outfile, outfile_buffer);
 292
 293   fd_in = emacs_open (infile, O_RDONLY | O_BINARY, 0);
 294   assert (fd_in >= 0);
 295   fd_out = emacs_open (outfile, O_RDWR | O_TRUNC | O_CREAT | O_BINARY, 0755);
 296   assert (fd_out >= 0);
 297   for (;;)
 298     {
 299       char buffer[4096];
 300       ret = read (fd_in, buffer, sizeof (buffer));
 301       if (ret == 0)
 302         {
 303           /* eof */
 304           break;
 305         }
 306       assert (ret > 0);
 307       /* data */
 308       ret2 = write (fd_out, buffer, ret);
 309       assert (ret2 == ret);
 310     }
 311   ret = emacs_close (fd_in);
 312   assert (ret == 0);
 313
 314   bss_sbrk_did_unexec = 1;
 315   fixup_executable (fd_out);
 316   bss_sbrk_did_unexec = 0;
 317
 318   ret = emacs_close (fd_out);
 319   assert (ret == 0);
 320 }