src/unexcoff.c

   1 /* Copyright (C) 1985-1988, 1992-1994, 2001-2012  Free Software Foundation, Inc.
   2
   3 This file is part of GNU Emacs.
   4
   5 GNU Emacs is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation, either version 3 of the License, or
   8 (at your option) any later version.
   9
  10 GNU Emacs is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18
  19 /*
  20  * unexcoff.c - Convert a running program into an a.out or COFF file.
  21  *
  22  * ==================================================================
  23  * Note: This file is currently used only by the MSDOS (a.k.a. DJGPP)
  24  * build of Emacs.  If you are not interested in the MSDOS build, you
  25  * are looking at the wrong version of unexec!
  26  * ==================================================================
  27  *
  28  * Author:      Spencer W. Thomas
  29  *              Computer Science Dept.
  30  *              University of Utah
  31  * Date:        Tue Mar  2 1982
  32  * Originally under the name unexec.c.
  33  * Modified heavily since then.
  34  *
  35  * Synopsis:
  36  *      unexec (const char *new_name, const char *old_name);
  37  *
  38  * Takes a snapshot of the program and makes an a.out format file in the
  39  * file named by the string argument new_name.
  40  * If a_name is non-NULL, the symbol table will be taken from the given file.
  41  * On some machines, an existing a_name file is required.
  42  *
  43  * If you make improvements I'd like to get them too.
  44  * harpo!utah-cs!thomas, thomas@Utah-20
  45  *
  46  */
  47
  48 /* Modified to support SysVr3 shared libraries by James Van Artsdalen
  49  * of Dell Computer Corporation.  james@bigtex.cactus.org.
  50  */
  51
  52 #include <config.h>
  53 #include "unexec.h"
  54
  55 #define PERROR(file) report_error (file, new)
  56
  57 #ifndef CANNOT_DUMP  /* all rest of file!  */
  58
  59 #ifdef HAVE_COFF_H
  60 #include <coff.h>
  61 #ifdef MSDOS
  62 #include <fcntl.h>  /* for O_RDONLY, O_RDWR */
  63 #include <crt0.h>   /* for _crt0_startup_flags and its bits */
  64 #include <sys/exceptn.h>
  65 static int save_djgpp_startup_flags;
  66 #define filehdr external_filehdr
  67 #define scnhdr external_scnhdr
  68 #define syment external_syment
  69 #define auxent external_auxent
  70 #define n_numaux e_numaux
  71 #define n_type e_type
  72 struct aouthdr
  73 {
  74   unsigned short        magic;  /* type of file                         */
  75   unsigned short        vstamp; /* version stamp                        */
  76   unsigned long         tsize;  /* text size in bytes, padded to FW bdry*/
  77   unsigned long         dsize;  /* initialized data "  "                */
  78   unsigned long         bsize;  /* uninitialized data "   "             */
  79   unsigned long         entry;  /* entry pt.                            */
  80   unsigned long         text_start;/* base of text used for this file */
  81   unsigned long         data_start;/* base of data used for this file */
  82 };
  83 #endif /* not MSDOS */
  84 #else  /* not HAVE_COFF_H */
  85 #include <a.out.h>
  86 #endif /* not HAVE_COFF_H */
  87
  88 /* Define getpagesize if the system does not.
  89    Note that this may depend on symbols defined in a.out.h.  */
  90 #include "getpagesize.h"
  91
  92 #ifndef makedev                 /* Try to detect types.h already loaded */
  93 #include <sys/types.h>
  94 #endif /* makedev */
  95 #include <stdio.h>
  96 #include <sys/stat.h>
  97 #include <errno.h>
  98
  99 #include <sys/file.h>
 100
 101 #include "mem-limits.h"
 102
 103 static long block_copy_start;           /* Old executable start point */
 104 static struct filehdr f_hdr;            /* File header */
 105 static struct aouthdr f_ohdr;           /* Optional file header (a.out) */
 106 long bias;                      /* Bias to add for growth */
 107 long lnnoptr;                   /* Pointer to line-number info within file */
 108 #define SYMS_START block_copy_start
 109
 110 static long text_scnptr;
 111 static long data_scnptr;
 112
 113 static long coff_offset;
 114
 115 static int pagemask;
 116
 117 /* Correct an int which is the bit pattern of a pointer to a byte
 118    into an int which is the number of a byte.
 119    This is a no-op on ordinary machines, but not on all.  */
 120
 121 #define ADDR_CORRECT(x) ((char *)(x) - (char*)0)
 122
 123 #include "lisp.h"
 124
 125 static void
 126 report_error (const char *file, int fd)
 127 {
 128   if (fd)
 129     close (fd);
 130   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 131 }
 132
 133 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
 134 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 135 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 136
 137 static void
 138 report_error_1 (int fd, const char *msg, int a1, int a2)
 139 {
 140   close (fd);
 141   error (msg, a1, a2);
 142 }
 143 \f
 144 static int make_hdr (int, int, const char *, const char *);
 145 static int copy_text_and_data (int, int);
 146 static int copy_sym (int, int, const char *, const char *);
 147 static void mark_x (const char *);
 148
 149 /* ****************************************************************
 150  * make_hdr
 151  *
 152  * Make the header in the new a.out from the header in core.
 153  * Modify the text and data sizes.
 154  */
 155 static int
 156 make_hdr (int new, int a_out,
 157           const char *a_name, const char *new_name)
 158 {
 159   auto struct scnhdr f_thdr;            /* Text section header */
 160   auto struct scnhdr f_dhdr;            /* Data section header */
 161   auto struct scnhdr f_bhdr;            /* Bss section header */
 162   auto struct scnhdr scntemp;           /* Temporary section header */
 163   register int scns;
 164   unsigned int bss_start;
 165   unsigned int data_start;
 166
 167   pagemask = getpagesize () - 1;
 168
 169   /* Adjust text/data boundary. */
 170   data_start = (int) start_of_data ();
 171   data_start = ADDR_CORRECT (data_start);
 172   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 173
 174   bss_start = ADDR_CORRECT (sbrk (0)) + pagemask;
 175   bss_start &= ~ pagemask;
 176
 177   if (data_start > bss_start)   /* Can't have negative data size. */
 178     {
 179       ERROR2 ("unexec: data_start (%u) can't be greater than bss_start (%u)",
 180               data_start, bss_start);
 181     }
 182
 183   coff_offset = 0L;             /* stays zero, except in DJGPP */
 184
 185   /* Salvage as much info from the existing file as possible */
 186   if (a_out >= 0)
 187     {
 188 #ifdef MSDOS
 189       /* Support the coff-go32-exe format with a prepended stub, since
 190          this is what GCC 2.8.0 and later generates by default in DJGPP.  */
 191       unsigned short mz_header[3];
 192
 193       if (read (a_out, &mz_header, sizeof (mz_header)) != sizeof (mz_header))
 194         {
 195           PERROR (a_name);
 196         }
 197       if (mz_header[0] == 0x5a4d || mz_header[0] == 0x4d5a) /* "MZ" or "ZM" */
 198         {
 199           coff_offset = (long)mz_header[2] * 512L;
 200           if (mz_header[1])
 201             coff_offset += (long)mz_header[1] - 512L;
 202           lseek (a_out, coff_offset, 0);
 203         }
 204       else
 205         lseek (a_out, 0L, 0);
 206 #endif /* MSDOS */
 207       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 208         {
 209           PERROR (a_name);
 210         }
 211       block_copy_start += sizeof (f_hdr);
 212       if (f_hdr.f_opthdr > 0)
 213         {
 214           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 215             {
 216               PERROR (a_name);
 217             }
 218           block_copy_start += sizeof (f_ohdr);
 219         }
 220       /* Loop through section headers, copying them in */
 221       lseek (a_out, coff_offset + sizeof (f_hdr) + f_hdr.f_opthdr, 0);
 222       for (scns = f_hdr.f_nscns; scns > 0; scns--) {
 223         if (read (a_out, &scntemp, sizeof (scntemp)) != sizeof (scntemp))
 224           {
 225             PERROR (a_name);
 226           }
 227         if (scntemp.s_scnptr > 0L)
 228           {
 229             if (block_copy_start < scntemp.s_scnptr + scntemp.s_size)
 230               block_copy_start = scntemp.s_scnptr + scntemp.s_size;
 231           }
 232         if (strcmp (scntemp.s_name, ".text") == 0)
 233           {
 234             f_thdr = scntemp;
 235           }
 236         else if (strcmp (scntemp.s_name, ".data") == 0)
 237           {
 238             f_dhdr = scntemp;
 239           }
 240         else if (strcmp (scntemp.s_name, ".bss") == 0)
 241           {
 242             f_bhdr = scntemp;
 243           }
 244       }
 245     }
 246   else
 247     {
 248       ERROR0 ("can't build a COFF file from scratch yet");
 249     }
 250
 251   /* Now we alter the contents of all the f_*hdr variables
 252      to correspond to what we want to dump.  */
 253
 254   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 255   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 256   f_ohdr.bsize = 0;
 257   f_thdr.s_size = f_ohdr.tsize;
 258   f_thdr.s_scnptr = sizeof (f_hdr) + sizeof (f_ohdr);
 259   f_thdr.s_scnptr += (f_hdr.f_nscns) * (sizeof (f_thdr));
 260   lnnoptr = f_thdr.s_lnnoptr;
 261   text_scnptr = f_thdr.s_scnptr;
 262   f_dhdr.s_paddr = f_ohdr.data_start;
 263   f_dhdr.s_vaddr = f_ohdr.data_start;
 264   f_dhdr.s_size = f_ohdr.dsize;
 265   f_dhdr.s_scnptr = f_thdr.s_scnptr + f_thdr.s_size;
 266   data_scnptr = f_dhdr.s_scnptr;
 267   f_bhdr.s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 268   f_bhdr.s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 269   f_bhdr.s_size = f_ohdr.bsize;
 270   f_bhdr.s_scnptr = 0L;
 271   bias = f_dhdr.s_scnptr + f_dhdr.s_size - block_copy_start;
 272
 273   if (f_hdr.f_symptr > 0L)
 274     {
 275       f_hdr.f_symptr += bias;
 276     }
 277
 278   if (f_thdr.s_lnnoptr > 0L)
 279     {
 280       f_thdr.s_lnnoptr += bias;
 281     }
 282
 283   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 284     {
 285       PERROR (new_name);
 286     }
 287
 288   if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 289     {
 290       PERROR (new_name);
 291     }
 292
 293   if (write (new, &f_thdr, sizeof (f_thdr)) != sizeof (f_thdr))
 294     {
 295       PERROR (new_name);
 296     }
 297
 298   if (write (new, &f_dhdr, sizeof (f_dhdr)) != sizeof (f_dhdr))
 299     {
 300       PERROR (new_name);
 301     }
 302
 303   if (write (new, &f_bhdr, sizeof (f_bhdr)) != sizeof (f_bhdr))
 304     {
 305       PERROR (new_name);
 306     }
 307
 308   return (0);
 309
 310 }
 311 \f
 312 void
 313 write_segment (int new, const char *ptr, const char *end)
 314 {
 315   register int i, nwrite, ret;
 316   /* This is the normal amount to write at once.
 317      It is the size of block that NFS uses.  */
 318   int writesize = 1 << 13;
 319   int pagesize = getpagesize ();
 320   char zeros[1 << 13];
 321
 322   memset (zeros, 0, sizeof (zeros));
 323
 324   for (i = 0; ptr < end;)
 325     {
 326       /* Distance to next multiple of writesize.  */
 327       nwrite = (((int) ptr + writesize) & -writesize) - (int) ptr;
 328       /* But not beyond specified end.  */
 329       if (nwrite > end - ptr) nwrite = end - ptr;
 330       ret = write (new, ptr, nwrite);
 331       /* If write gets a page fault, it means we reached
 332          a gap between the old text segment and the old data segment.
 333          This gap has probably been remapped into part of the text segment.
 334          So write zeros for it.  */
 335       if (ret == -1
 336 #ifdef EFAULT
 337           && errno == EFAULT
 338 #endif
 339           )
 340         {
 341           /* Write only a page of zeros at once,
 342              so that we don't overshoot the start
 343              of the valid memory in the old data segment.  */
 344           if (nwrite > pagesize)
 345             nwrite = pagesize;
 346           write (new, zeros, nwrite);
 347         }
 348       i += nwrite;
 349       ptr += nwrite;
 350     }
 351 }
 352 /* ****************************************************************
 353  * copy_text_and_data
 354  *
 355  * Copy the text and data segments from memory to the new a.out
 356  */
 357 static int
 358 copy_text_and_data (int new, int a_out)
 359 {
 360   register char *end;
 361   register char *ptr;
 362
 363 #ifdef MSDOS
 364   /* Dump the original table of exception handlers, not the one
 365      where our exception hooks are registered.  */
 366   __djgpp_exception_toggle ();
 367
 368   /* Switch off startup flags that might have been set at runtime
 369      and which might change the way that dumped Emacs works.  */
 370   save_djgpp_startup_flags = _crt0_startup_flags;
 371   _crt0_startup_flags &= ~(_CRT0_FLAG_NO_LFN | _CRT0_FLAG_NEARPTR);
 372 #endif
 373
 374   lseek (new, (long) text_scnptr, 0);
 375   ptr = (char *) f_ohdr.text_start;
 376   end = ptr + f_ohdr.tsize;
 377   write_segment (new, ptr, end);
 378
 379   lseek (new, (long) data_scnptr, 0);
 380   ptr = (char *) f_ohdr.data_start;
 381   end = ptr + f_ohdr.dsize;
 382   write_segment (new, ptr, end);
 383
 384 #ifdef MSDOS
 385   /* Restore our exception hooks.  */
 386   __djgpp_exception_toggle ();
 387
 388   /* Restore the startup flags.  */
 389   _crt0_startup_flags = save_djgpp_startup_flags;
 390 #endif
 391
 392
 393   return 0;
 394 }
 395 \f
 396 /* ****************************************************************
 397  * copy_sym
 398  *
 399  * Copy the relocation information and symbol table from the a.out to the new
 400  */
 401 static int
 402 copy_sym (int new, int a_out, const char *a_name, const char *new_name)
 403 {
 404   char page[1024];
 405   int n;
 406
 407   if (a_out < 0)
 408     return 0;
 409
 410   if (SYMS_START == 0L)
 411     return 0;
 412
 413   if (lnnoptr)                  /* if there is line number info */
 414     lseek (a_out, coff_offset + lnnoptr, 0);    /* start copying from there */
 415   else
 416     lseek (a_out, coff_offset + SYMS_START, 0); /* Position a.out to symtab. */
 417
 418   while ((n = read (a_out, page, sizeof page)) > 0)
 419     {
 420       if (write (new, page, n) != n)
 421         {
 422           PERROR (new_name);
 423         }
 424     }
 425   if (n < 0)
 426     {
 427       PERROR (a_name);
 428     }
 429   return 0;
 430 }
 431 \f
 432 /* ****************************************************************
 433  * mark_x
 434  *
 435  * After successfully building the new a.out, mark it executable
 436  */
 437 static void
 438 mark_x (const char *name)
 439 {
 440   struct stat sbuf;
 441   int um;
 442   int new = 0;  /* for PERROR */
 443
 444   um = umask (777);
 445   umask (um);
 446   if (stat (name, &sbuf) == -1)
 447     {
 448       PERROR (name);
 449     }
 450   sbuf.st_mode |= 0111 & ~um;
 451   if (chmod (name, sbuf.st_mode) == -1)
 452     PERROR (name);
 453 }
 454 \f
 455
 456 /*
 457  *      If the COFF file contains a symbol table and a line number section,
 458  *      then any auxiliary entries that have values for x_lnnoptr must
 459  *      be adjusted by the amount that the line number section has moved
 460  *      in the file (bias computed in make_hdr).  The #@$%&* designers of
 461  *      the auxiliary entry structures used the absolute file offsets for
 462  *      the line number entry rather than an offset from the start of the
 463  *      line number section!
 464  *
 465  *      When I figure out how to scan through the symbol table and pick out
 466  *      the auxiliary entries that need adjustment, this routine will
 467  *      be fixed.  As it is now, all such entries are wrong and sdb
 468  *      will complain.   Fred Fish, UniSoft Systems Inc.
 469  */
 470
 471 /* This function is probably very slow.  Instead of reopening the new
 472    file for input and output it should copy from the old to the new
 473    using the two descriptors already open (WRITEDESC and READDESC).
 474    Instead of reading one small structure at a time it should use
 475    a reasonable size buffer.  But I don't have time to work on such
 476    things, so I am installing it as submitted to me.  -- RMS.  */
 477
 478 int
 479 adjust_lnnoptrs (int writedesc, int readdesc, const char *new_name)
 480 {
 481   register int nsyms;
 482   register int new;
 483   struct syment symentry;
 484   union auxent auxentry;
 485
 486   if (!lnnoptr || !f_hdr.f_symptr)
 487     return 0;
 488
 489 #ifdef MSDOS
 490   if ((new = writedesc) < 0)
 491 #else
 492   if ((new = open (new_name, O_RDWR)) < 0)
 493 #endif
 494     {
 495       PERROR (new_name);
 496       return -1;
 497     }
 498
 499   lseek (new, f_hdr.f_symptr, 0);
 500   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 501     {
 502       read (new, &symentry, SYMESZ);
 503       if (symentry.n_numaux)
 504         {
 505           read (new, &auxentry, AUXESZ);
 506           nsyms++;
 507           if (ISFCN (symentry.n_type) || symentry.n_type == 0x2400)
 508             {
 509               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 510               lseek (new, -AUXESZ, 1);
 511               write (new, &auxentry, AUXESZ);
 512             }
 513         }
 514     }
 515 #ifndef MSDOS
 516   close (new);
 517 #endif
 518   return 0;
 519 }
 520
 521 /* ****************************************************************
 522  * unexec
 523  *
 524  * driving logic.
 525  */
 526 void
 527 unexec (const char *new_name, const char *a_name)
 528 {
 529   int new = -1, a_out = -1;
 530
 531   if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
 532     {
 533       PERROR (a_name);
 534     }
 535   if ((new = creat (new_name, 0666)) < 0)
 536     {
 537       PERROR (new_name);
 538     }
 539
 540   if (make_hdr (new, a_out, a_name, new_name) < 0
 541       || copy_text_and_data (new, a_out) < 0
 542       || copy_sym (new, a_out, a_name, new_name) < 0
 543       || adjust_lnnoptrs (new, a_out, new_name) < 0
 544       )
 545     {
 546       close (new);
 547       return;
 548     }
 549
 550   close (new);
 551   if (a_out >= 0)
 552     close (a_out);
 553   mark_x (new_name);
 554 }
 555
 556 #endif /* not CANNOT_DUMP */