src/unexcoff.c

   1 /* Copyright (C) 1985-1988, 1992-1994, 2001-2011  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 extern char *start_of_data (void);              /* Start of initialized data */
 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 <setjmp.h>
 124 #include "lisp.h"
 125
 126 static void
 127 report_error (const char *file, int fd)
 128 {
 129   if (fd)
 130     close (fd);
 131   report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
 132 }
 133
 134 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
 135 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 136 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 137
 138 static void
 139 report_error_1 (int fd, const char *msg, int a1, int a2)
 140 {
 141   close (fd);
 142   error (msg, a1, a2);
 143 }
 144 \f
 145 static int make_hdr (int, int, const char *, const char *);
 146 static int copy_text_and_data (int, int);
 147 static int copy_sym (int, int, const char *, const char *);
 148 static void mark_x (const char *);
 149
 150 /* ****************************************************************
 151  * make_hdr
 152  *
 153  * Make the header in the new a.out from the header in core.
 154  * Modify the text and data sizes.
 155  */
 156 static int
 157 make_hdr (int new, int a_out,
 158           const char *a_name, const char *new_name)
 159 {
 160   auto struct scnhdr f_thdr;            /* Text section header */
 161   auto struct scnhdr f_dhdr;            /* Data section header */
 162   auto struct scnhdr f_bhdr;            /* Bss section header */
 163   auto struct scnhdr scntemp;           /* Temporary section header */
 164   register int scns;
 165   unsigned int bss_start;
 166   unsigned int data_start;
 167
 168   pagemask = getpagesize () - 1;
 169
 170   /* Adjust text/data boundary. */
 171   data_start = (int) start_of_data ();
 172   data_start = ADDR_CORRECT (data_start);
 173   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 174
 175   bss_start = ADDR_CORRECT (sbrk (0)) + pagemask;
 176   bss_start &= ~ pagemask;
 177
 178   if (data_start > bss_start)   /* Can't have negative data size. */
 179     {
 180       ERROR2 ("unexec: data_start (%u) can't be greater than bss_start (%u)",
 181               data_start, bss_start);
 182     }
 183
 184   coff_offset = 0L;             /* stays zero, except in DJGPP */
 185
 186   /* Salvage as much info from the existing file as possible */
 187   if (a_out >= 0)
 188     {
 189 #ifdef MSDOS
 190       /* Support the coff-go32-exe format with a prepended stub, since
 191          this is what GCC 2.8.0 and later generates by default in DJGPP.  */
 192       unsigned short mz_header[3];
 193
 194       if (read (a_out, &mz_header, sizeof (mz_header)) != sizeof (mz_header))
 195         {
 196           PERROR (a_name);
 197         }
 198       if (mz_header[0] == 0x5a4d || mz_header[0] == 0x4d5a) /* "MZ" or "ZM" */
 199         {
 200           coff_offset = (long)mz_header[2] * 512L;
 201           if (mz_header[1])
 202             coff_offset += (long)mz_header[1] - 512L;
 203           lseek (a_out, coff_offset, 0);
 204         }
 205       else
 206         lseek (a_out, 0L, 0);
 207 #endif /* MSDOS */
 208       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 209         {
 210           PERROR (a_name);
 211         }
 212       block_copy_start += sizeof (f_hdr);
 213       if (f_hdr.f_opthdr > 0)
 214         {
 215           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 216             {
 217               PERROR (a_name);
 218             }
 219           block_copy_start += sizeof (f_ohdr);
 220         }
 221       /* Loop through section headers, copying them in */
 222       lseek (a_out, coff_offset + sizeof (f_hdr) + f_hdr.f_opthdr, 0);
 223       for (scns = f_hdr.f_nscns; scns > 0; scns--) {
 224         if (read (a_out, &scntemp, sizeof (scntemp)) != sizeof (scntemp))
 225           {
 226             PERROR (a_name);
 227           }
 228         if (scntemp.s_scnptr > 0L)
 229           {
 230             if (block_copy_start < scntemp.s_scnptr + scntemp.s_size)
 231               block_copy_start = scntemp.s_scnptr + scntemp.s_size;
 232           }
 233         if (strcmp (scntemp.s_name, ".text") == 0)
 234           {
 235             f_thdr = scntemp;
 236           }
 237         else if (strcmp (scntemp.s_name, ".data") == 0)
 238           {
 239             f_dhdr = scntemp;
 240           }
 241         else if (strcmp (scntemp.s_name, ".bss") == 0)
 242           {
 243             f_bhdr = scntemp;
 244           }
 245       }
 246     }
 247   else
 248     {
 249       ERROR0 ("can't build a COFF file from scratch yet");
 250     }
 251
 252   /* Now we alter the contents of all the f_*hdr variables
 253      to correspond to what we want to dump.  */
 254
 255   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 256   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 257   f_ohdr.bsize = 0;
 258   f_thdr.s_size = f_ohdr.tsize;
 259   f_thdr.s_scnptr = sizeof (f_hdr) + sizeof (f_ohdr);
 260   f_thdr.s_scnptr += (f_hdr.f_nscns) * (sizeof (f_thdr));
 261   lnnoptr = f_thdr.s_lnnoptr;
 262   text_scnptr = f_thdr.s_scnptr;
 263   f_dhdr.s_paddr = f_ohdr.data_start;
 264   f_dhdr.s_vaddr = f_ohdr.data_start;
 265   f_dhdr.s_size = f_ohdr.dsize;
 266   f_dhdr.s_scnptr = f_thdr.s_scnptr + f_thdr.s_size;
 267   data_scnptr = f_dhdr.s_scnptr;
 268   f_bhdr.s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 269   f_bhdr.s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 270   f_bhdr.s_size = f_ohdr.bsize;
 271   f_bhdr.s_scnptr = 0L;
 272   bias = f_dhdr.s_scnptr + f_dhdr.s_size - block_copy_start;
 273
 274   if (f_hdr.f_symptr > 0L)
 275     {
 276       f_hdr.f_symptr += bias;
 277     }
 278
 279   if (f_thdr.s_lnnoptr > 0L)
 280     {
 281       f_thdr.s_lnnoptr += bias;
 282     }
 283
 284   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 285     {
 286       PERROR (new_name);
 287     }
 288
 289   if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 290     {
 291       PERROR (new_name);
 292     }
 293
 294   if (write (new, &f_thdr, sizeof (f_thdr)) != sizeof (f_thdr))
 295     {
 296       PERROR (new_name);
 297     }
 298
 299   if (write (new, &f_dhdr, sizeof (f_dhdr)) != sizeof (f_dhdr))
 300     {
 301       PERROR (new_name);
 302     }
 303
 304   if (write (new, &f_bhdr, sizeof (f_bhdr)) != sizeof (f_bhdr))
 305     {
 306       PERROR (new_name);
 307     }
 308
 309   return (0);
 310
 311 }
 312 \f
 313 void
 314 write_segment (int new, const char *ptr, const char *end)
 315 {
 316   register int i, nwrite, ret;
 317   /* This is the normal amount to write at once.
 318      It is the size of block that NFS uses.  */
 319   int writesize = 1 << 13;
 320   int pagesize = getpagesize ();
 321   char zeros[1 << 13];
 322
 323   memset (zeros, 0, sizeof (zeros));
 324
 325   for (i = 0; ptr < end;)
 326     {
 327       /* Distance to next multiple of writesize.  */
 328       nwrite = (((int) ptr + writesize) & -writesize) - (int) ptr;
 329       /* But not beyond specified end.  */
 330       if (nwrite > end - ptr) nwrite = end - ptr;
 331       ret = write (new, ptr, nwrite);
 332       /* If write gets a page fault, it means we reached
 333          a gap between the old text segment and the old data segment.
 334          This gap has probably been remapped into part of the text segment.
 335          So write zeros for it.  */
 336       if (ret == -1
 337 #ifdef EFAULT
 338           && errno == EFAULT
 339 #endif
 340           )
 341         {
 342           /* Write only a page of zeros at once,
 343              so that we don't overshoot the start
 344              of the valid memory in the old data segment.  */
 345           if (nwrite > pagesize)
 346             nwrite = pagesize;
 347           write (new, zeros, nwrite);
 348         }
 349       i += nwrite;
 350       ptr += nwrite;
 351     }
 352 }
 353 /* ****************************************************************
 354  * copy_text_and_data
 355  *
 356  * Copy the text and data segments from memory to the new a.out
 357  */
 358 static int
 359 copy_text_and_data (int new, int a_out)
 360 {
 361   register char *end;
 362   register char *ptr;
 363
 364 #ifdef MSDOS
 365   /* Dump the original table of exception handlers, not the one
 366      where our exception hooks are registered.  */
 367   __djgpp_exception_toggle ();
 368
 369   /* Switch off startup flags that might have been set at runtime
 370      and which might change the way that dumped Emacs works.  */
 371   save_djgpp_startup_flags = _crt0_startup_flags;
 372   _crt0_startup_flags &= ~(_CRT0_FLAG_NO_LFN | _CRT0_FLAG_NEARPTR);
 373 #endif
 374
 375   lseek (new, (long) text_scnptr, 0);
 376   ptr = (char *) f_ohdr.text_start;
 377   end = ptr + f_ohdr.tsize;
 378   write_segment (new, ptr, end);
 379
 380   lseek (new, (long) data_scnptr, 0);
 381   ptr = (char *) f_ohdr.data_start;
 382   end = ptr + f_ohdr.dsize;
 383   write_segment (new, ptr, end);
 384
 385 #ifdef MSDOS
 386   /* Restore our exception hooks.  */
 387   __djgpp_exception_toggle ();
 388
 389   /* Restore the startup flags.  */
 390   _crt0_startup_flags = save_djgpp_startup_flags;
 391 #endif
 392
 393
 394   return 0;
 395 }
 396 \f
 397 /* ****************************************************************
 398  * copy_sym
 399  *
 400  * Copy the relocation information and symbol table from the a.out to the new
 401  */
 402 static int
 403 copy_sym (int new, int a_out, const char *a_name, const char *new_name)
 404 {
 405   char page[1024];
 406   int n;
 407
 408   if (a_out < 0)
 409     return 0;
 410
 411   if (SYMS_START == 0L)
 412     return 0;
 413
 414   if (lnnoptr)                  /* if there is line number info */
 415     lseek (a_out, coff_offset + lnnoptr, 0);    /* start copying from there */
 416   else
 417     lseek (a_out, coff_offset + SYMS_START, 0); /* Position a.out to symtab. */
 418
 419   while ((n = read (a_out, page, sizeof page)) > 0)
 420     {
 421       if (write (new, page, n) != n)
 422         {
 423           PERROR (new_name);
 424         }
 425     }
 426   if (n < 0)
 427     {
 428       PERROR (a_name);
 429     }
 430   return 0;
 431 }
 432 \f
 433 /* ****************************************************************
 434  * mark_x
 435  *
 436  * After successfully building the new a.out, mark it executable
 437  */
 438 static void
 439 mark_x (const char *name)
 440 {
 441   struct stat sbuf;
 442   int um;
 443   int new = 0;  /* for PERROR */
 444
 445   um = umask (777);
 446   umask (um);
 447   if (stat (name, &sbuf) == -1)
 448     {
 449       PERROR (name);
 450     }
 451   sbuf.st_mode |= 0111 & ~um;
 452   if (chmod (name, sbuf.st_mode) == -1)
 453     PERROR (name);
 454 }
 455 \f
 456
 457 /*
 458  *      If the COFF file contains a symbol table and a line number section,
 459  *      then any auxiliary entries that have values for x_lnnoptr must
 460  *      be adjusted by the amount that the line number section has moved
 461  *      in the file (bias computed in make_hdr).  The #@$%&* designers of
 462  *      the auxiliary entry structures used the absolute file offsets for
 463  *      the line number entry rather than an offset from the start of the
 464  *      line number section!
 465  *
 466  *      When I figure out how to scan through the symbol table and pick out
 467  *      the auxiliary entries that need adjustment, this routine will
 468  *      be fixed.  As it is now, all such entries are wrong and sdb
 469  *      will complain.   Fred Fish, UniSoft Systems Inc.
 470  */
 471
 472 /* This function is probably very slow.  Instead of reopening the new
 473    file for input and output it should copy from the old to the new
 474    using the two descriptors already open (WRITEDESC and READDESC).
 475    Instead of reading one small structure at a time it should use
 476    a reasonable size buffer.  But I don't have time to work on such
 477    things, so I am installing it as submitted to me.  -- RMS.  */
 478
 479 int
 480 adjust_lnnoptrs (int writedesc, int readdesc, const char *new_name)
 481 {
 482   register int nsyms;
 483   register int new;
 484   struct syment symentry;
 485   union auxent auxentry;
 486
 487   if (!lnnoptr || !f_hdr.f_symptr)
 488     return 0;
 489
 490 #ifdef MSDOS
 491   if ((new = writedesc) < 0)
 492 #else
 493   if ((new = open (new_name, O_RDWR)) < 0)
 494 #endif
 495     {
 496       PERROR (new_name);
 497       return -1;
 498     }
 499
 500   lseek (new, f_hdr.f_symptr, 0);
 501   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 502     {
 503       read (new, &symentry, SYMESZ);
 504       if (symentry.n_numaux)
 505         {
 506           read (new, &auxentry, AUXESZ);
 507           nsyms++;
 508           if (ISFCN (symentry.n_type) || symentry.n_type == 0x2400)
 509             {
 510               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 511               lseek (new, -AUXESZ, 1);
 512               write (new, &auxentry, AUXESZ);
 513             }
 514         }
 515     }
 516 #ifndef MSDOS
 517   close (new);
 518 #endif
 519   return 0;
 520 }
 521
 522 /* ****************************************************************
 523  * unexec
 524  *
 525  * driving logic.
 526  */
 527 void
 528 unexec (const char *new_name, const char *a_name)
 529 {
 530   int new = -1, a_out = -1;
 531
 532   if (a_name && (a_out = open (a_name, O_RDONLY)) < 0)
 533     {
 534       PERROR (a_name);
 535     }
 536   if ((new = creat (new_name, 0666)) < 0)
 537     {
 538       PERROR (new_name);
 539     }
 540
 541   if (make_hdr (new, a_out, a_name, new_name) < 0
 542       || copy_text_and_data (new, a_out) < 0
 543       || copy_sym (new, a_out, a_name, new_name) < 0
 544       || adjust_lnnoptrs (new, a_out, new_name) < 0
 545       )
 546     {
 547       close (new);
 548       return;
 549     }
 550
 551   close (new);
 552   if (a_out >= 0)
 553     close (a_out);
 554   mark_x (new_name);
 555 }
 556
 557 #endif /* not CANNOT_DUMP */