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