src/unexcw.c

   1 /* unexec() support for Cygwin;
   2    complete rewrite of xemacs Cygwin unexec() code
   3
   4    Copyright (C) 2004-2015 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           sizeof (exe_header_buffer->section_header) /
  85           sizeof (exe_header_buffer->section_header[0]));
  86   assert (exe_header_buffer->file_header.f_opthdr > 0);
  87
  88   ret =
  89     read (fd, &exe_header_buffer->file_optional_header,
  90           sizeof (exe_header_buffer->file_optional_header));
  91   assert (ret == sizeof (exe_header_buffer->file_optional_header));
  92
  93 #ifdef __x86_64__
  94   assert (exe_header_buffer->file_optional_header.magic == 0x020b);
  95 #else
  96   assert (exe_header_buffer->file_optional_header.magic == 0x010b);
  97 #endif
  98
  99   for (i = 0; i < exe_header_buffer->file_header.f_nscns; ++i)
 100     {
 101       ret =
 102         read (fd, &exe_header_buffer->section_header[i],
 103               sizeof (exe_header_buffer->section_header[i]));
 104       assert (ret == sizeof (exe_header_buffer->section_header[i]));
 105     }
 106
 107   return (exe_header_buffer);
 108 }
 109
 110 /*
 111 ** Fix the dumped emacs executable:
 112 **
 113 ** - copy .data section data of interest from running executable into
 114 **   output .exe file
 115 **
 116 ** - convert .bss section into an initialized data section (like
 117 **   .data) and copy .bss section data of interest from running
 118 **   executable into output .exe file
 119 */
 120 static void
 121 fixup_executable (int fd)
 122 {
 123   exe_header_t exe_header_buffer;
 124   exe_header_t *exe_header;
 125   int i;
 126   int ret;
 127   int found_data = 0;
 128   int found_bss = 0;
 129
 130   exe_header = read_exe_header (fd, &exe_header_buffer);
 131   assert (exe_header != 0);
 132
 133   assert (exe_header->file_header.f_nscns > 0);
 134   for (i = 0; i < exe_header->file_header.f_nscns; ++i)
 135     {
 136       unsigned long start_address =
 137         exe_header->section_header[i].s_vaddr +
 138         exe_header->file_optional_header.ImageBase;
 139       unsigned long end_address =
 140         exe_header->section_header[i].s_vaddr +
 141         exe_header->file_optional_header.ImageBase +
 142         exe_header->section_header[i].s_paddr;
 143       if (debug_unexcw)
 144         printf ("%8s start %#lx end %#lx\n",
 145                 exe_header->section_header[i].s_name,
 146                 start_address, end_address);
 147       if (my_edata >= (char *) start_address
 148           && my_edata < (char *) end_address)
 149         {
 150           /* data section */
 151           ret =
 152             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 153                    SEEK_SET);
 154           assert (ret != -1);
 155           ret =
 156             write (fd, (char *) start_address,
 157                    my_edata - (char *) start_address);
 158           assert (ret == my_edata - (char *) start_address);
 159           ++found_data;
 160           if (debug_unexcw)
 161             printf ("         .data, mem start %#lx mem length %d\n",
 162                     start_address, my_edata - (char *) start_address);
 163           if (debug_unexcw)
 164             printf ("         .data, file start %d file length %d\n",
 165                     (int) exe_header->section_header[i].s_scnptr,
 166                     (int) exe_header->section_header[i].s_paddr);
 167         }
 168       else if (my_endbss >= (char *) start_address
 169                && my_endbss < (char *) end_address)
 170         {
 171           /* bss section */
 172           ++found_bss;
 173           if (exe_header->section_header[i].s_flags & 0x00000080)
 174             {
 175               /* convert uninitialized data section to initialized data section */
 176               struct stat statbuf;
 177               ret = fstat (fd, &statbuf);
 178               assert (ret != -1);
 179
 180               exe_header->section_header[i].s_flags &= ~0x00000080;
 181               exe_header->section_header[i].s_flags |= 0x00000040;
 182
 183               exe_header->section_header[i].s_scnptr =
 184                 (statbuf.st_size +
 185                  exe_header->file_optional_header.FileAlignment) /
 186                 exe_header->file_optional_header.FileAlignment *
 187                 exe_header->file_optional_header.FileAlignment;
 188
 189               exe_header->section_header[i].s_size =
 190                 (exe_header->section_header[i].s_paddr +
 191                  exe_header->file_optional_header.FileAlignment) /
 192                 exe_header->file_optional_header.FileAlignment *
 193                 exe_header->file_optional_header.FileAlignment;
 194
 195               /* Make sure the generated bootstrap binary isn't
 196                * sparse.  NT doesn't use a file cache for sparse
 197                * executables, so if we bootstrap Emacs using a sparse
 198                * bootstrap-emacs.exe, bootstrap takes about twenty
 199                * times longer than it would otherwise.  */
 200
 201               ret = posix_fallocate (fd,
 202                                      ( exe_header->section_header[i].s_scnptr +
 203                                        exe_header->section_header[i].s_size ),
 204                                      1);
 205
 206               assert (ret != -1);
 207
 208               ret =
 209                 lseek (fd,
 210                        (long) (exe_header->section_header[i].s_scnptr +
 211                                exe_header->section_header[i].s_size - 1),
 212                        SEEK_SET);
 213               assert (ret != -1);
 214               ret = write (fd, "", 1);
 215               assert (ret == 1);
 216
 217               ret =
 218                 lseek (fd,
 219                        (long) ((char *) &exe_header->section_header[i] -
 220                                (char *) exe_header), SEEK_SET);
 221               assert (ret != -1);
 222               ret =
 223                 write (fd, &exe_header->section_header[i],
 224                        sizeof (exe_header->section_header[i]));
 225               assert (ret == sizeof (exe_header->section_header[i]));
 226               if (debug_unexcw)
 227                 printf ("         seek to %ld, write %d\n",
 228                         (long) ((char *) &exe_header->section_header[i] -
 229                                 (char *) exe_header),
 230                         sizeof (exe_header->section_header[i]));
 231             }
 232           /* write initialized data section */
 233           ret =
 234             lseek (fd, (long) (exe_header->section_header[i].s_scnptr),
 235                    SEEK_SET);
 236           assert (ret != -1);
 237           /* force the dumped emacs to reinitialize malloc */
 238           __malloc_initialized = 0;
 239           ret =
 240             write (fd, (char *) start_address,
 241                    my_endbss - (char *) start_address);
 242           __malloc_initialized = 1;
 243           assert (ret == (my_endbss - (char *) start_address));
 244           if (debug_unexcw)
 245             printf ("         .bss, mem start %#lx mem length %d\n",
 246                     start_address, my_endbss - (char *) start_address);
 247           if (debug_unexcw)
 248             printf ("         .bss, file start %d file length %d\n",
 249                     (int) exe_header->section_header[i].s_scnptr,
 250                     (int) exe_header->section_header[i].s_paddr);
 251         }
 252     }
 253   assert (found_bss == 1);
 254   assert (found_data == 1);
 255 }
 256
 257 /*
 258 ** Windows likes .exe suffixes on executables.
 259 */
 260 static char *
 261 add_exe_suffix_if_necessary (const char *name, char *modified)
 262 {
 263   int i = strlen (name);
 264   if (i <= (sizeof (DOTEXE) - 1))
 265     {
 266       sprintf (modified, "%s%s", name, DOTEXE);
 267     }
 268   else if (!strcasecmp (name + i - (sizeof (DOTEXE) - 1), DOTEXE))
 269     {
 270       strcpy (modified, name);
 271     }
 272   else
 273     {
 274       sprintf (modified, "%s%s", name, DOTEXE);
 275     }
 276   return (modified);
 277 }
 278
 279 void
 280 unexec (const char *outfile, const char *infile)
 281 {
 282   char infile_buffer[FILENAME_MAX];
 283   char outfile_buffer[FILENAME_MAX];
 284   int fd_in;
 285   int fd_out;
 286   int ret;
 287   int ret2;
 288
 289   if (bss_sbrk_did_unexec)
 290     {
 291       /* can only dump once */
 292       printf ("You can only dump Emacs once on this platform.\n");
 293       return;
 294     }
 295
 296   report_sheap_usage (1);
 297
 298   infile = add_exe_suffix_if_necessary (infile, infile_buffer);
 299   outfile = add_exe_suffix_if_necessary (outfile, outfile_buffer);
 300
 301   fd_in = emacs_open (infile, O_RDONLY | O_BINARY, 0);
 302   assert (fd_in >= 0);
 303   fd_out = emacs_open (outfile, O_RDWR | O_TRUNC | O_CREAT | O_BINARY, 0755);
 304   assert (fd_out >= 0);
 305   for (;;)
 306     {
 307       char buffer[4096];
 308       ret = read (fd_in, buffer, sizeof (buffer));
 309       if (ret == 0)
 310         {
 311           /* eof */
 312           break;
 313         }
 314       assert (ret > 0);
 315       /* data */
 316       ret2 = write (fd_out, buffer, ret);
 317       assert (ret2 == ret);
 318     }
 319   ret = emacs_close (fd_in);
 320   assert (ret == 0);
 321
 322   bss_sbrk_did_unexec = 1;
 323   fixup_executable (fd_out);
 324   bss_sbrk_did_unexec = 0;
 325
 326   ret = emacs_close (fd_out);
 327   assert (ret == 0);
 328 }