src/unexcoff.c

   1 /* Copyright (C) 1985-1988, 1992-1994, 2001-2015 Free Software
   2  * Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software: you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation, either version 3 of the License, or
   9 (at your option) any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19
  20 /*
  21  * unexcoff.c - Convert a running program into an a.out or COFF file.
  22  *
  23  * ==================================================================
  24  * Note: This file is currently used only by the MSDOS (a.k.a. DJGPP)
  25  * build of Emacs.  If you are not interested in the MSDOS build, you
  26  * are looking at the wrong version of unexec!
  27  * ==================================================================
  28  *
  29  * Author:      Spencer W. Thomas
  30  *              Computer Science Dept.
  31  *              University of Utah
  32  * Date:        Tue Mar  2 1982
  33  * Originally under the name unexec.c.
  34  * Modified heavily since then.
  35  *
  36  * Synopsis:
  37  *      unexec (const char *new_name, const char *old_name);
  38  *
  39  * Takes a snapshot of the program and makes an a.out format file in the
  40  * file named by the string argument new_name.
  41  * If a_name is non-NULL, the symbol table will be taken from the given file.
  42  * On some machines, an existing a_name file is required.
  43  *
  44  * If you make improvements I'd like to get them too.
  45  * harpo!utah-cs!thomas, thomas@Utah-20
  46  *
  47  */
  48
  49 /* Modified to support SysVr3 shared libraries by James Van Artsdalen
  50  * of Dell Computer Corporation.  james@bigtex.cactus.org.
  51  */
  52
  53 #include <config.h>
  54 #include "unexec.h"
  55 #include "lisp.h"
  56
  57 #define PERROR(file) report_error (file, new)
  58
  59 #ifndef CANNOT_DUMP  /* all rest of file!  */
  60
  61 #ifdef HAVE_COFF_H
  62 #include <coff.h>
  63 #ifdef MSDOS
  64 #include <fcntl.h>  /* for O_RDONLY, O_RDWR */
  65 #include <crt0.h>   /* for _crt0_startup_flags and its bits */
  66 #include <sys/exceptn.h>
  67 static int save_djgpp_startup_flags;
  68 #include <libc/atexit.h>
  69 static struct __atexit *save_atexit_ptr;
  70 #define filehdr external_filehdr
  71 #define scnhdr external_scnhdr
  72 #define syment external_syment
  73 #define auxent external_auxent
  74 #define n_numaux e_numaux
  75 #define n_type e_type
  76 struct aouthdr
  77 {
  78   unsigned short        magic;  /* type of file                         */
  79   unsigned short        vstamp; /* version stamp                        */
  80   unsigned long         tsize;  /* text size in bytes, padded to FW bdry*/
  81   unsigned long         dsize;  /* initialized data "  "                */
  82   unsigned long         bsize;  /* uninitialized data "   "             */
  83   unsigned long         entry;  /* entry pt.                            */
  84   unsigned long         text_start;/* base of text used for this file */
  85   unsigned long         data_start;/* base of data used for this file */
  86 };
  87 #endif /* MSDOS */
  88 #else  /* not HAVE_COFF_H */
  89 #include <a.out.h>
  90 #endif /* not HAVE_COFF_H */
  91
  92 /* Define getpagesize if the system does not.
  93    Note that this may depend on symbols defined in a.out.h.  */
  94 #include "getpagesize.h"
  95
  96 #ifndef makedev                 /* Try to detect types.h already loaded */
  97 #include <sys/types.h>
  98 #endif /* makedev */
  99 #include <stdio.h>
 100 #include <sys/stat.h>
 101 #include <errno.h>
 102
 103 #include <sys/file.h>
 104
 105 extern int etext;
 106
 107 static long block_copy_start;           /* Old executable start point */
 108 static struct filehdr f_hdr;            /* File header */
 109 static struct aouthdr f_ohdr;           /* Optional file header (a.out) */
 110 long bias;                      /* Bias to add for growth */
 111 long lnnoptr;                   /* Pointer to line-number info within file */
 112 #define SYMS_START block_copy_start
 113
 114 static long text_scnptr;
 115 static long data_scnptr;
 116
 117 static long coff_offset;
 118
 119 static int pagemask;
 120
 121 /* Correct an int which is the bit pattern of a pointer to a byte
 122    into an int which is the number of a byte.
 123    This is a no-op on ordinary machines, but not on all.  */
 124
 125 #define ADDR_CORRECT(x) ((char *)(x) - (char*)0)
 126
 127 #include "lisp.h"
 128
 129 static void
 130 report_error (const char *file, int fd)
 131 {
 132   int err = errno;
 133   if (fd)
 134     emacs_close (fd);
 135   report_file_errno ("Cannot unexec", build_string (file), err);
 136 }
 137
 138 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1
 139 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 140 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 141
 142 static void
 143 report_error_1 (int fd, const char *msg, int a1, int a2)
 144 {
 145   emacs_close (fd);
 146   error (msg, a1, a2);
 147 }
 148 \f
 149 static int make_hdr (int, int, const char *, const char *);
 150 static int copy_text_and_data (int, int);
 151 static int copy_sym (int, int, const char *, const char *);
 152 static void mark_x (const char *);
 153
 154 /* ****************************************************************
 155  * make_hdr
 156  *
 157  * Make the header in the new a.out from the header in core.
 158  * Modify the text and data sizes.
 159  */
 160 static int
 161 make_hdr (int new, int a_out,
 162           const char *a_name, const char *new_name)
 163 {
 164   auto struct scnhdr f_thdr;            /* Text section header */
 165   auto struct scnhdr f_dhdr;            /* Data section header */
 166   auto struct scnhdr f_bhdr;            /* Bss section header */
 167   auto struct scnhdr scntemp;           /* Temporary section header */
 168   register int scns;
 169   unsigned int bss_start;
 170   unsigned int data_start;
 171
 172   pagemask = getpagesize () - 1;
 173
 174   /* Adjust text/data boundary. */
 175   data_start = (int) DATA_START;
 176   data_start = ADDR_CORRECT (data_start);
 177   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 178
 179   bss_start = ADDR_CORRECT (sbrk (0)) + pagemask;
 180   bss_start &= ~ pagemask;
 181
 182   if (data_start > bss_start)   /* Can't have negative data size. */
 183     {
 184       ERROR2 ("unexec: data_start (%u) can't be greater than bss_start (%u)",
 185               data_start, bss_start);
 186     }
 187
 188   coff_offset = 0L;             /* stays zero, except in DJGPP */
 189
 190   /* Salvage as much info from the existing file as possible */
 191   if (a_out >= 0)
 192     {
 193 #ifdef MSDOS
 194       /* Support the coff-go32-exe format with a prepended stub, since
 195          this is what GCC 2.8.0 and later generates by default in DJGPP.  */
 196       unsigned short mz_header[3];
 197
 198       if (read (a_out, &mz_header, sizeof (mz_header)) != sizeof (mz_header))
 199         {
 200           PERROR (a_name);
 201         }
 202       if (mz_header[0] == 0x5a4d || mz_header[0] == 0x4d5a) /* "MZ" or "ZM" */
 203         {
 204           coff_offset = (long)mz_header[2] * 512L;
 205           if (mz_header[1])
 206             coff_offset += (long)mz_header[1] - 512L;
 207           lseek (a_out, coff_offset, 0);
 208         }
 209       else
 210         lseek (a_out, 0L, 0);
 211 #endif /* MSDOS */
 212       if (read (a_out, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 213         {
 214           PERROR (a_name);
 215         }
 216       block_copy_start += sizeof (f_hdr);
 217       if (f_hdr.f_opthdr > 0)
 218         {
 219           if (read (a_out, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 220             {
 221               PERROR (a_name);
 222             }
 223           block_copy_start += sizeof (f_ohdr);
 224         }
 225       /* Loop through section headers, copying them in */
 226       lseek (a_out, coff_offset + sizeof (f_hdr) + f_hdr.f_opthdr, 0);
 227       for (scns = f_hdr.f_nscns; scns > 0; scns--) {
 228         if (read (a_out, &scntemp, sizeof (scntemp)) != sizeof (scntemp))
 229           {
 230             PERROR (a_name);
 231           }
 232         if (scntemp.s_scnptr > 0L)
 233           {
 234             if (block_copy_start < scntemp.s_scnptr + scntemp.s_size)
 235               block_copy_start = scntemp.s_scnptr + scntemp.s_size;
 236           }
 237         if (strcmp (scntemp.s_name, ".text") == 0)
 238           {
 239             f_thdr = scntemp;
 240           }
 241         else if (strcmp (scntemp.s_name, ".data") == 0)
 242           {
 243             f_dhdr = scntemp;
 244           }
 245         else if (strcmp (scntemp.s_name, ".bss") == 0)
 246           {
 247             f_bhdr = scntemp;
 248           }
 249       }
 250     }
 251   else
 252     {
 253       ERROR0 ("can't build a COFF file from scratch yet");
 254     }
 255
 256   /* Now we alter the contents of all the f_*hdr variables
 257      to correspond to what we want to dump.  */
 258
 259   f_hdr.f_flags |= (F_RELFLG | F_EXEC);
 260   f_ohdr.dsize = bss_start - f_ohdr.data_start;
 261   f_ohdr.bsize = 0;
 262   f_thdr.s_size = f_ohdr.tsize;
 263   f_thdr.s_scnptr = sizeof (f_hdr) + sizeof (f_ohdr);
 264   f_thdr.s_scnptr += (f_hdr.f_nscns) * (sizeof (f_thdr));
 265   lnnoptr = f_thdr.s_lnnoptr;
 266   text_scnptr = f_thdr.s_scnptr;
 267   f_dhdr.s_paddr = f_ohdr.data_start;
 268   f_dhdr.s_vaddr = f_ohdr.data_start;
 269   f_dhdr.s_size = f_ohdr.dsize;
 270   f_dhdr.s_scnptr = f_thdr.s_scnptr + f_thdr.s_size;
 271   data_scnptr = f_dhdr.s_scnptr;
 272   f_bhdr.s_paddr = f_ohdr.data_start + f_ohdr.dsize;
 273   f_bhdr.s_vaddr = f_ohdr.data_start + f_ohdr.dsize;
 274   f_bhdr.s_size = f_ohdr.bsize;
 275   f_bhdr.s_scnptr = 0L;
 276   bias = f_dhdr.s_scnptr + f_dhdr.s_size - block_copy_start;
 277
 278   if (f_hdr.f_symptr > 0L)
 279     {
 280       f_hdr.f_symptr += bias;
 281     }
 282
 283   if (f_thdr.s_lnnoptr > 0L)
 284     {
 285       f_thdr.s_lnnoptr += bias;
 286     }
 287
 288   if (write (new, &f_hdr, sizeof (f_hdr)) != sizeof (f_hdr))
 289     {
 290       PERROR (new_name);
 291     }
 292
 293   if (write (new, &f_ohdr, sizeof (f_ohdr)) != sizeof (f_ohdr))
 294     {
 295       PERROR (new_name);
 296     }
 297
 298   if (write (new, &f_thdr, sizeof (f_thdr)) != sizeof (f_thdr))
 299     {
 300       PERROR (new_name);
 301     }
 302
 303   if (write (new, &f_dhdr, sizeof (f_dhdr)) != sizeof (f_dhdr))
 304     {
 305       PERROR (new_name);
 306     }
 307
 308   if (write (new, &f_bhdr, sizeof (f_bhdr)) != sizeof (f_bhdr))
 309     {
 310       PERROR (new_name);
 311     }
 312
 313   return (0);
 314
 315 }
 316 \f
 317 void
 318 write_segment (int new, const char *ptr, const char *end)
 319 {
 320   register int i, nwrite, ret;
 321   /* This is the normal amount to write at once.
 322      It is the size of block that NFS uses.  */
 323   int writesize = 1 << 13;
 324   int pagesize = getpagesize ();
 325   char zeros[1 << 13];
 326
 327   memset (zeros, 0, sizeof (zeros));
 328
 329   for (i = 0; ptr < end;)
 330     {
 331       /* Distance to next multiple of writesize.  */
 332       nwrite = (((int) ptr + writesize) & -writesize) - (int) ptr;
 333       /* But not beyond specified end.  */
 334       if (nwrite > end - ptr) nwrite = end - ptr;
 335       ret = write (new, ptr, nwrite);
 336       /* If write gets a page fault, it means we reached
 337          a gap between the old text segment and the old data segment.
 338          This gap has probably been remapped into part of the text segment.
 339          So write zeros for it.  */
 340       if (ret == -1 && errno == EFAULT)
 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
 374   /* Zero out the 'atexit' chain in the dumped executable, to avoid
 375      calling the atexit functions twice.  (emacs.c:main installs an
 376      atexit function.)  */
 377   save_atexit_ptr = __atexit_ptr;
 378   __atexit_ptr = NULL;
 379 #endif
 380
 381   lseek (new, (long) text_scnptr, 0);
 382   ptr = (char *) f_ohdr.text_start;
 383   end = ptr + f_ohdr.tsize;
 384   write_segment (new, ptr, end);
 385
 386   lseek (new, (long) data_scnptr, 0);
 387   ptr = (char *) f_ohdr.data_start;
 388   end = ptr + f_ohdr.dsize;
 389   write_segment (new, ptr, end);
 390
 391 #ifdef MSDOS
 392   /* Restore our exception hooks.  */
 393   __djgpp_exception_toggle ();
 394
 395   /* Restore the startup flags.  */
 396   _crt0_startup_flags = save_djgpp_startup_flags;
 397
 398   /* Restore the atexit chain.  */
 399   __atexit_ptr = save_atexit_ptr;
 400 #endif
 401
 402
 403   return 0;
 404 }
 405 \f
 406 /* ****************************************************************
 407  * copy_sym
 408  *
 409  * Copy the relocation information and symbol table from the a.out to the new
 410  */
 411 static int
 412 copy_sym (int new, int a_out, const char *a_name, const char *new_name)
 413 {
 414   char page[1024];
 415   int n;
 416
 417   if (a_out < 0)
 418     return 0;
 419
 420   if (SYMS_START == 0L)
 421     return 0;
 422
 423   if (lnnoptr)                  /* if there is line number info */
 424     lseek (a_out, coff_offset + lnnoptr, 0);    /* start copying from there */
 425   else
 426     lseek (a_out, coff_offset + SYMS_START, 0); /* Position a.out to symtab. */
 427
 428   while ((n = read (a_out, page, sizeof page)) > 0)
 429     {
 430       if (write (new, page, n) != n)
 431         {
 432           PERROR (new_name);
 433         }
 434     }
 435   if (n < 0)
 436     {
 437       PERROR (a_name);
 438     }
 439   return 0;
 440 }
 441 \f
 442 /* ****************************************************************
 443  * mark_x
 444  *
 445  * After successfully building the new a.out, mark it executable
 446  */
 447 static void
 448 mark_x (const char *name)
 449 {
 450   struct stat sbuf;
 451   int um;
 452   int new = 0;  /* for PERROR */
 453
 454   um = umask (777);
 455   umask (um);
 456   if (stat (name, &sbuf) == -1)
 457     {
 458       PERROR (name);
 459     }
 460   sbuf.st_mode |= 0111 & ~um;
 461   if (chmod (name, sbuf.st_mode) == -1)
 462     PERROR (name);
 463 }
 464 \f
 465
 466 /*
 467  *      If the COFF file contains a symbol table and a line number section,
 468  *      then any auxiliary entries that have values for x_lnnoptr must
 469  *      be adjusted by the amount that the line number section has moved
 470  *      in the file (bias computed in make_hdr).  The #@$%&* designers of
 471  *      the auxiliary entry structures used the absolute file offsets for
 472  *      the line number entry rather than an offset from the start of the
 473  *      line number section!
 474  *
 475  *      When I figure out how to scan through the symbol table and pick out
 476  *      the auxiliary entries that need adjustment, this routine will
 477  *      be fixed.  As it is now, all such entries are wrong and sdb
 478  *      will complain.   Fred Fish, UniSoft Systems Inc.
 479  */
 480
 481 /* This function is probably very slow.  Instead of reopening the new
 482    file for input and output it should copy from the old to the new
 483    using the two descriptors already open (WRITEDESC and READDESC).
 484    Instead of reading one small structure at a time it should use
 485    a reasonable size buffer.  But I don't have time to work on such
 486    things, so I am installing it as submitted to me.  -- RMS.  */
 487
 488 int
 489 adjust_lnnoptrs (int writedesc, int readdesc, const char *new_name)
 490 {
 491   register int nsyms;
 492   register int new;
 493   struct syment symentry;
 494   union auxent auxentry;
 495
 496   if (!lnnoptr || !f_hdr.f_symptr)
 497     return 0;
 498
 499 #ifdef MSDOS
 500   if ((new = writedesc) < 0)
 501 #else
 502   if ((new = emacs_open (new_name, O_RDWR, 0)) < 0)
 503 #endif
 504     {
 505       PERROR (new_name);
 506       return -1;
 507     }
 508
 509   lseek (new, f_hdr.f_symptr, 0);
 510   for (nsyms = 0; nsyms < f_hdr.f_nsyms; nsyms++)
 511     {
 512       read (new, &symentry, SYMESZ);
 513       if (symentry.n_numaux)
 514         {
 515           read (new, &auxentry, AUXESZ);
 516           nsyms++;
 517           if (ISFCN (symentry.n_type) || symentry.n_type == 0x2400)
 518             {
 519               auxentry.x_sym.x_fcnary.x_fcn.x_lnnoptr += bias;
 520               lseek (new, -AUXESZ, 1);
 521               write (new, &auxentry, AUXESZ);
 522             }
 523         }
 524     }
 525 #ifndef MSDOS
 526   emacs_close (new);
 527 #endif
 528   return 0;
 529 }
 530
 531 /* ****************************************************************
 532  * unexec
 533  *
 534  * driving logic.
 535  */
 536 void
 537 unexec (const char *new_name, const char *a_name)
 538 {
 539   int new = -1, a_out = -1;
 540
 541   if (a_name && (a_out = emacs_open (a_name, O_RDONLY, 0)) < 0)
 542     {
 543       PERROR (a_name);
 544     }
 545   if ((new = emacs_open (new_name, O_WRONLY | O_CREAT | O_TRUNC, 0666)) < 0)
 546     {
 547       PERROR (new_name);
 548     }
 549
 550   if (make_hdr (new, a_out, a_name, new_name) < 0
 551       || copy_text_and_data (new, a_out) < 0
 552       || copy_sym (new, a_out, a_name, new_name) < 0
 553       || adjust_lnnoptrs (new, a_out, new_name) < 0
 554       )
 555     {
 556       emacs_close (new);
 557       return;
 558     }
 559
 560   emacs_close (new);
 561   if (a_out >= 0)
 562     emacs_close (a_out);
 563   mark_x (new_name);
 564 }
 565
 566 #endif /* not CANNOT_DUMP */