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 Free Software Foundation, Inc.
  10
  11 This file is part of GNU Emacs.
  12
  13 GNU Emacs is free software; you can redistribute it and/or modify
  14 it under the terms of the GNU General Public License as published by
  15 the Free Software Foundation; either version 2, or (at your option)
  16 any later version.
  17
  18 GNU Emacs is distributed in the hope that it will be useful,
  19 but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 GNU General Public License for more details.
  22
  23 You should have received a copy of the GNU General Public License
  24 along with GNU Emacs; see the file COPYING.  If not, write to
  25 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  26 Boston, MA 02111-1307, USA.  */
  27
  28 \f
  29
  30 /*
  31   On 80386 Xenix, segmentation screws prevent us from modifying the text
  32   segment at all.  We basically just plug a new value for "data segment
  33   size" into the countless headers and copy the other records straight
  34   through.  The data segment is ORG'ed at the xs_rbase value of the data
  35   segment's xseg record (always @ 0x1880000, thanks to the "sophisticated
  36   memory management hardware" of the chip) and extends to sbrk(0), exactly.
  37   This code is afraid to malloc (should it be?), and alloca has to be the
  38   wimpy, malloc-based version; consequently, data is usually copied in
  39   smallish chunks.
  40
  41   gb@entity.com
  42 */
  43
  44 #include <config.h>
  45 #include <sys/types.h>
  46 #include <fcntl.h>
  47 #include <sys/file.h>
  48 #include <sys/stat.h>
  49 #include <stdio.h>
  50 #include <varargs.h>
  51 #include <a.out.h>
  52
  53 static void fatal_unexec ();
  54
  55 #define READ(_fd, _buffer, _size, _error_message, _error_arg) \
  56         errno = EEOF; \
  57         if (read(_fd, _buffer, _size) != _size) \
  58           fatal_unexec(_error_message, _error_arg);
  59
  60 #define WRITE(_fd, _buffer, _size, _error_message, _error_arg) \
  61         if (write(_fd, _buffer, _size) != _size) \
  62           fatal_unexec(_error_message, _error_arg);
  63
  64 #define SEEK(_fd, _position, _error_message, _error_arg) \
  65         errno = EEOF; \
  66         if (lseek(_fd, _position, L_SET) != _position) \
  67           fatal_unexec(_error_message, _error_arg);
  68
  69 extern int errno;
  70 extern char *strerror ();
  71 #define EEOF -1
  72
  73 #ifndef L_SET
  74 #define L_SET 0
  75 #endif
  76 \f
  77 /* Should check the magic number of the old executable;
  78    not yet written.  */
  79 check_exec (x)
  80      struct xexec *x;
  81 {
  82 }
  83
  84
  85 unexec (new_name, a_name, data_start, bss_start, entry_address)
  86      char *new_name, *a_name;
  87      unsigned data_start, bss_start, entry_address;
  88 {
  89   char *sbrk (), *datalim = sbrk (0), *data_org;
  90   long segpos, textseen, textpos, textlen, datapos, datadiff, datalen;
  91
  92   struct xexec u_xexec,       /*  a.out header */
  93               *u_xexecp = &u_xexec;
  94   struct xext  u_xext,        /*  extended header */
  95               *u_xextp  = &u_xext;
  96   struct xseg  u_xseg,        /*  segment table entry */
  97               *u_xsegp  = &u_xseg;
  98   int i, nsegs, isdata = 0, infd, outfd;
  99
 100   infd = open (a_name, O_RDONLY, 0);
 101   if (infd < 0) fatal_unexec ("opening %s", a_name);
 102
 103   outfd = creat (new_name, 0666);
 104   if (outfd < 0) fatal_unexec ("creating %s", new_name);
 105
 106   READ (infd, u_xexecp, sizeof (struct xexec),
 107         "error reading %s", a_name);
 108   check_exec (u_xexecp);
 109   READ (infd, u_xextp, sizeof (struct xext),
 110         "error reading %s", a_name);
 111   segpos = u_xextp->xe_segpos;
 112   nsegs = u_xextp->xe_segsize / sizeof (struct xseg);
 113   SEEK (infd, segpos, "seek error on %s", a_name);
 114   for (i = 0; i < nsegs; i ++)
 115     {
 116       READ (infd, u_xsegp, sizeof (struct xseg),
 117             "error reading %s", a_name);
 118       switch (u_xsegp->xs_type)
 119         {
 120         case XS_TTEXT:
 121           {
 122             if (i == 0)
 123               {
 124                 textpos = u_xsegp->xs_filpos;
 125                 textlen = u_xsegp->xs_psize;
 126                 break;
 127               }
 128             fatal_unexec ("invalid text segment in %s", a_name);
 129           }
 130         case XS_TDATA:
 131           {
 132             if (i == 1)
 133               {
 134                 datapos = u_xsegp->xs_filpos;
 135                 datalen = datalim - (data_org = (char *)(u_xsegp->xs_rbase));
 136                 datadiff = datalen - u_xsegp->xs_psize;
 137                 break;
 138               }
 139             fatal_unexec ("invalid data segment in %s", a_name);
 140           }
 141         default:
 142           {
 143             if (i > 1) break;
 144             fatal_unexec ("invalid segment record in %s", a_name);
 145           }
 146         }
 147     }
 148   u_xexecp->x_data = datalen;
 149   u_xexecp->x_bss = 0;
 150   WRITE (outfd, u_xexecp, sizeof (struct xexec),
 151          "error writing %s", new_name);
 152   WRITE (outfd, u_xextp, sizeof (struct xext),
 153          "error writing %s", new_name);
 154   SEEK (infd, segpos, "seek error on %s", a_name);
 155   SEEK (outfd, segpos, "seek error on %s", new_name);
 156
 157   /* Copy the text segment record verbatim. */
 158
 159   copyrec (infd, outfd, sizeof (struct xseg), a_name, new_name);
 160
 161   /* Read, modify, write the data segment record. */
 162
 163   READ (infd, u_xsegp, sizeof (struct xseg),
 164         "error reading %s", a_name);
 165   u_xsegp->xs_psize = u_xsegp->xs_vsize = datalen;
 166   u_xsegp->xs_attr &= (~XS_AITER & ~XS_ABSS);
 167   WRITE (outfd, u_xsegp, sizeof (struct xseg),
 168          "error writing %s", new_name);
 169
 170   /* Now copy any additional segment records, adjusting their
 171      file position field */
 172
 173   for (i = 2; i < nsegs; i++)
 174     {
 175       READ (infd, u_xsegp, sizeof (struct xseg),
 176             "error reading %s", a_name);
 177       u_xsegp->xs_filpos += datadiff;
 178       WRITE (outfd, u_xsegp, sizeof (struct xseg),
 179              "error writing %s", new_name);
 180     }
 181
 182   SEEK (infd, textpos, "seek error on %s", a_name);
 183   SEEK (outfd, textpos, "seek error on %s", new_name);
 184   copyrec (infd, outfd, textlen, a_name, new_name);
 185
 186   SEEK (outfd, datapos, "seek error on %s", new_name);
 187   WRITE (outfd, data_org, datalen,
 188          "write error on %s", new_name);
 189
 190   for (i = 2, segpos += (2 * sizeof (struct xseg));
 191        i < nsegs;
 192        i++, segpos += sizeof (struct xseg))
 193     {
 194       SEEK (infd, segpos, "seek error on %s", a_name);
 195       READ (infd, u_xsegp, sizeof (struct xseg),
 196             "read error on %s", a_name);
 197       SEEK (infd, u_xsegp->xs_filpos, "seek error on %s", a_name);
 198       /* We should be at eof in the output file here, but we must seek
 199          because the xs_filpos and xs_psize fields in symbol table
 200          segments are inconsistent. */
 201       SEEK (outfd, u_xsegp->xs_filpos + datadiff, "seek error on %s", new_name);
 202       copyrec (infd, outfd, u_xsegp->xs_psize, a_name, new_name);
 203     }
 204   close (infd);
 205   close (outfd);
 206   mark_x (new_name);
 207   return 0;
 208 }
 209
 210 copyrec (infd, outfd, len, in_name, out_name)
 211      int infd, outfd, len;
 212      char *in_name, *out_name;
 213 {
 214   char buf[BUFSIZ];
 215   int chunk;
 216
 217   while (len)
 218     {
 219       chunk = BUFSIZ;
 220       if (chunk > len)
 221         chunk = len;
 222       READ (infd, buf, chunk, "error reading %s", in_name);
 223       WRITE (outfd, buf, chunk, "error writing %s", out_name);
 224       len -= chunk;
 225     }
 226 }
 227
 228 /*
 229  * mark_x
 230  *
 231  * After successfully building the new a.out, mark it executable
 232  */
 233 static
 234 mark_x (name)
 235      char *name;
 236 {
 237   struct stat sbuf;
 238   int um = umask (777);
 239   umask (um);
 240   if (stat (name, &sbuf) < 0)
 241     fatal_unexec ("getting protection on %s", name);
 242   sbuf.st_mode |= 0111 & ~um;
 243   if (chmod (name, sbuf.st_mode) < 0)
 244     fatal_unexec ("setting protection on %s", name);
 245 }
 246
 247 static void
 248 fatal_unexec (s, va_alist)
 249     va_dcl
 250 {
 251   va_list ap;
 252   if (errno == EEOF)
 253     fputs ("unexec: unexpected end of file, ", stderr);
 254   else
 255     fprintf (stderr, "unexec: %s, ", strerror (errno));
 256   va_start (ap);
 257   _doprnt (s, ap, stderr);
 258   fputs (".\n", stderr);
 259   exit (1);
 260 }