src/unexenix.c

   1 /* Unexec for Xenix.
   2    Note that the GNU project considers support for Xenix operation
   3    a peripheral activity which should not be allowed to divert effort
   4    from development of the GNU system.  Changes in this code will be
   5    installed when Xenix users send them in, but aside from that
   6    we don't plan to think about it, or about whether other Emacs
   7    maintenance might break it.
   8
   9    Copyright (C) 1988, 1994, 2001, 2002, 2003, 2004,
  10                  2005, 2006, 2007, 2008  Free Software Foundation, Inc.
  11
  12 This file is part of GNU Emacs.
  13
  14 GNU Emacs is free software; you can redistribute it and/or modify
  15 it under the terms of the GNU General Public License as published by
  16 the Free Software Foundation; either version 3, or (at your option)
  17 any later version.
  18
  19 GNU Emacs is distributed in the hope that it will be useful,
  20 but WITHOUT ANY WARRANTY; without even the implied warranty of
  21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22 GNU General Public License for more details.
  23
  24 You should have received a copy of the GNU General Public License
  25 along with GNU Emacs; see the file COPYING.  If not, write to
  26 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  27 Boston, MA 02110-1301, USA.  */
  28
  29 \f
  30
  31 /*
  32   On 80386 Xenix, segmentation screws prevent us from modifying the text
  33   segment at all.  We basically just plug a new value for "data segment
  34   size" into the countless headers and copy the other records straight
  35   through.  The data segment is ORG'ed at the xs_rbase value of the data
  36   segment's xseg record (always @ 0x1880000, thanks to the "sophisticated
  37   memory management hardware" of the chip) and extends to sbrk(0), exactly.
  38   This code is afraid to malloc (should it be?), and alloca has to be the
  39   wimpy, malloc-based version; consequently, data is usually copied in
  40   smallish chunks.
  41
  42   gb@entity.com
  43 */
  44
  45 #include <config.h>
  46 #include <sys/types.h>
  47 #include <fcntl.h>
  48 #include <sys/file.h>
  49 #include <sys/stat.h>
  50 #include <stdio.h>
  51 #include <varargs.h>
  52 #include <a.out.h>
  53
  54 static void fatal_unexec ();
  55
  56 #define READ(_fd, _buffer, _size, _error_message, _error_arg) \
  57         errno = EEOF; \
  58         if (read(_fd, _buffer, _size) != _size) \
  59           fatal_unexec(_error_message, _error_arg);
  60
  61 #define WRITE(_fd, _buffer, _size, _error_message, _error_arg) \
  62         if (write(_fd, _buffer, _size) != _size) \
  63           fatal_unexec(_error_message, _error_arg);
  64
  65 #define SEEK(_fd, _position, _error_message, _error_arg) \
  66         errno = EEOF; \
  67         if (lseek(_fd, _position, L_SET) != _position) \
  68           fatal_unexec(_error_message, _error_arg);
  69
  70 extern int errno;
  71 extern char *strerror ();
  72 #define EEOF -1
  73
  74 #ifndef L_SET
  75 #define L_SET 0
  76 #endif
  77 \f
  78 /* Should check the magic number of the old executable;
  79    not yet written.  */
  80 check_exec (x)
  81      struct xexec *x;
  82 {
  83 }
  84
  85
  86 unexec (new_name, a_name, data_start, bss_start, entry_address)
  87      char *new_name, *a_name;
  88      unsigned data_start, bss_start, entry_address;
  89 {
  90   char *sbrk (), *datalim = sbrk (0), *data_org;
  91   long segpos, textseen, textpos, textlen, datapos, datadiff, datalen;
  92
  93   struct xexec u_xexec,       /*  a.out header */
  94               *u_xexecp = &u_xexec;
  95   struct xext  u_xext,        /*  extended header */
  96               *u_xextp  = &u_xext;
  97   struct xseg  u_xseg,        /*  segment table entry */
  98               *u_xsegp  = &u_xseg;
  99   int i, nsegs, isdata = 0, infd, outfd;
 100
 101   infd = open (a_name, O_RDONLY, 0);
 102   if (infd < 0) fatal_unexec ("opening %s", a_name);
 103
 104   outfd = creat (new_name, 0666);
 105   if (outfd < 0) fatal_unexec ("creating %s", new_name);
 106
 107   READ (infd, u_xexecp, sizeof (struct xexec),
 108         "error reading %s", a_name);
 109   check_exec (u_xexecp);
 110   READ (infd, u_xextp, sizeof (struct xext),
 111         "error reading %s", a_name);
 112   segpos = u_xextp->xe_segpos;
 113   nsegs = u_xextp->xe_segsize / sizeof (struct xseg);
 114   SEEK (infd, segpos, "seek error on %s", a_name);
 115   for (i = 0; i < nsegs; i ++)
 116     {
 117       READ (infd, u_xsegp, sizeof (struct xseg),
 118             "error reading %s", a_name);
 119       switch (u_xsegp->xs_type)
 120         {
 121         case XS_TTEXT:
 122           {
 123             if (i == 0)
 124               {
 125                 textpos = u_xsegp->xs_filpos;
 126                 textlen = u_xsegp->xs_psize;
 127                 break;
 128               }
 129             fatal_unexec ("invalid text segment in %s", a_name);
 130           }
 131         case XS_TDATA:
 132           {
 133             if (i == 1)
 134               {
 135                 datapos = u_xsegp->xs_filpos;
 136                 datalen = datalim - (data_org = (char *)(u_xsegp->xs_rbase));
 137                 datadiff = datalen - u_xsegp->xs_psize;
 138                 break;
 139               }
 140             fatal_unexec ("invalid data segment in %s", a_name);
 141           }
 142         default:
 143           {
 144             if (i > 1) break;
 145             fatal_unexec ("invalid segment record in %s", a_name);
 146           }
 147         }
 148     }
 149   u_xexecp->x_data = datalen;
 150   u_xexecp->x_bss = 0;
 151   WRITE (outfd, u_xexecp, sizeof (struct xexec),
 152          "error writing %s", new_name);
 153   WRITE (outfd, u_xextp, sizeof (struct xext),
 154          "error writing %s", new_name);
 155   SEEK (infd, segpos, "seek error on %s", a_name);
 156   SEEK (outfd, segpos, "seek error on %s", new_name);
 157
 158   /* Copy the text segment record verbatim. */
 159
 160   copyrec (infd, outfd, sizeof (struct xseg), a_name, new_name);
 161
 162   /* Read, modify, write the data segment record. */
 163
 164   READ (infd, u_xsegp, sizeof (struct xseg),
 165         "error reading %s", a_name);
 166   u_xsegp->xs_psize = u_xsegp->xs_vsize = datalen;
 167   u_xsegp->xs_attr &= (~XS_AITER & ~XS_ABSS);
 168   WRITE (outfd, u_xsegp, sizeof (struct xseg),
 169          "error writing %s", new_name);
 170
 171   /* Now copy any additional segment records, adjusting their
 172      file position field */
 173
 174   for (i = 2; i < nsegs; i++)
 175     {
 176       READ (infd, u_xsegp, sizeof (struct xseg),
 177             "error reading %s", a_name);
 178       u_xsegp->xs_filpos += datadiff;
 179       WRITE (outfd, u_xsegp, sizeof (struct xseg),
 180              "error writing %s", new_name);
 181     }
 182
 183   SEEK (infd, textpos, "seek error on %s", a_name);
 184   SEEK (outfd, textpos, "seek error on %s", new_name);
 185   copyrec (infd, outfd, textlen, a_name, new_name);
 186
 187   SEEK (outfd, datapos, "seek error on %s", new_name);
 188   WRITE (outfd, data_org, datalen,
 189          "write error on %s", new_name);
 190
 191   for (i = 2, segpos += (2 * sizeof (struct xseg));
 192        i < nsegs;
 193        i++, segpos += sizeof (struct xseg))
 194     {
 195       SEEK (infd, segpos, "seek error on %s", a_name);
 196       READ (infd, u_xsegp, sizeof (struct xseg),
 197             "read error on %s", a_name);
 198       SEEK (infd, u_xsegp->xs_filpos, "seek error on %s", a_name);
 199       /* We should be at eof in the output file here, but we must seek
 200          because the xs_filpos and xs_psize fields in symbol table
 201          segments are inconsistent. */
 202       SEEK (outfd, u_xsegp->xs_filpos + datadiff, "seek error on %s", new_name);
 203       copyrec (infd, outfd, u_xsegp->xs_psize, a_name, new_name);
 204     }
 205   close (infd);
 206   close (outfd);
 207   mark_x (new_name);
 208   return 0;
 209 }
 210
 211 copyrec (infd, outfd, len, in_name, out_name)
 212      int infd, outfd, len;
 213      char *in_name, *out_name;
 214 {
 215   char buf[BUFSIZ];
 216   int chunk;
 217
 218   while (len)
 219     {
 220       chunk = BUFSIZ;
 221       if (chunk > len)
 222         chunk = len;
 223       READ (infd, buf, chunk, "error reading %s", in_name);
 224       WRITE (outfd, buf, chunk, "error writing %s", out_name);
 225       len -= chunk;
 226     }
 227 }
 228
 229 /*
 230  * mark_x
 231  *
 232  * After successfully building the new a.out, mark it executable
 233  */
 234 static
 235 mark_x (name)
 236      char *name;
 237 {
 238   struct stat sbuf;
 239   int um = umask (777);
 240   umask (um);
 241   if (stat (name, &sbuf) < 0)
 242     fatal_unexec ("getting protection on %s", name);
 243   sbuf.st_mode |= 0111 & ~um;
 244   if (chmod (name, sbuf.st_mode) < 0)
 245     fatal_unexec ("setting protection on %s", name);
 246 }
 247
 248 static void
 249 fatal_unexec (s, va_alist)
 250     va_dcl
 251 {
 252   va_list ap;
 253   if (errno == EEOF)
 254     fputs ("unexec: unexpected end of file, ", stderr);
 255   else
 256     fprintf (stderr, "unexec: %s, ", strerror (errno));
 257   va_start (ap);
 258   _doprnt (s, ap, stderr);
 259   fputs (".\n", stderr);
 260   exit (1);
 261 }
 262
 263 /* arch-tag: ce26be27-370a-438d-83b4-766059749a02
 264    (do not change this comment) */