code.delx.au - gnu-emacs/blob - src/unexhp9k800.c

   1 /* Unexec for HP 9000 Series 800 machines.
   2    Bob Desinger <hpsemc!bd@hplabs.hp.com>
   3
   4    Note that the GNU project considers support for HP operation a
   5    peripheral activity which should not be allowed to divert effort
   6    from development of the GNU system.  Changes in this code will be
   7    installed when users send them in, but aside from that we don't
   8    plan to think about it, or about whether other Emacs maintenance
   9    might break it.
  10
  11
  12   Unexec creates a copy of the old a.out file, and replaces the old data
  13   area with the current data area.  When the new file is executed, the
  14   process will see the same data structures and data values that the
  15   original process had when unexec was called.
  16
  17   Unlike other versions of unexec, this one copies symbol table and
  18   debug information to the new a.out file.  Thus, the new a.out file
  19   may be debugged with symbolic debuggers.
  20
  21   If you fix any bugs in this, I'd like to incorporate your fixes.
  22   Send them to uunet!hpda!hpsemc!jmorris or jmorris%hpsemc@hplabs.HP.COM.
  23
  24   CAVEATS:
  25   This routine saves the current value of all static and external
  26   variables.  This means that any data structure that needs to be
  27   initialized must be explicitly reset.  Variables will not have their
  28   expected default values.
  29
  30   Unfortunately, the HP-UX signal handler has internal initialization
  31   flags which are not explicitly reset.  Thus, for signals to work in
  32   conjunction with this routine, the following code must executed when
  33   the new process starts up.
  34
  35   void _sigreturn ();
  36   ...
  37   sigsetreturn (_sigreturn);
  38 */
  39 \f
  40 #include <stdio.h>
  41 #include <fcntl.h>
  42 #include <errno.h>
  43
  44 #include <a.out.h>
  45
  46 #ifdef emacs
  47 #include <config.h>
  48 #endif
  49
  50 #ifdef HPUX_USE_SHLIBS
  51 #include <dl.h>
  52 #endif
  53
  54 /* brk value to restore, stored as a global.
  55    This is really used only if we used shared libraries.  */
  56 static long brk_on_dump = 0;
  57
  58 /* Called from main, if we use shared libraries.  */
  59 int
  60 run_time_remap (ignored)
  61      char *ignored;
  62 {
  63   brk (brk_on_dump);
  64 }
  65
  66 #define roundup(x,n) (((x) + ((n) - 1)) & ~((n) - 1))  /* n is power of 2 */
  67 #define min(x,y)  (((x) < (y)) ? (x) : (y))
  68
  69
  70 /* Create a new a.out file, same as old but with current data space */
  71
  72 unexec (new_name, old_name, new_end_of_text, dummy1, dummy2)
  73      char new_name[];           /* name of the new a.out file to be created */
  74      char old_name[];           /* name of the old a.out file */
  75      char *new_end_of_text;     /* ptr to new edata/etext; NOT USED YET */
  76      int dummy1, dummy2;        /* not used by emacs */
  77 {
  78   int old, new;
  79   int old_size, new_size;
  80   struct header hdr;
  81   struct som_exec_auxhdr auxhdr;
  82   long i;
  83
  84   /* For the greatest flexibility, should create a temporary file in
  85      the same directory as the new file.  When everything is complete,
  86      rename the temp file to the new name.
  87      This way, a program could update its own a.out file even while
  88      it is still executing.  If problems occur, everything is still
  89      intact.  NOT implemented.  */
  90
  91   /* Open the input and output a.out files */
  92   old = open (old_name, O_RDONLY);
  93   if (old < 0)
  94     { perror (old_name); exit (1); }
  95   new = open (new_name, O_CREAT|O_RDWR|O_TRUNC, 0777);
  96   if (new < 0)
  97     { perror (new_name); exit (1); }
  98
  99   /* Read the old headers */
 100   read_header (old, &hdr, &auxhdr);
 101
 102   brk_on_dump = sbrk (0);
 103
 104   /* Decide how large the new and old data areas are */
 105   old_size = auxhdr.exec_dsize;
 106   /* I suspect these two statements are separate
 107      to avoid a compiler bug in hpux version 8.  */
 108   i = sbrk (0);
 109   new_size = i - auxhdr.exec_dmem;
 110
 111   /* Copy the old file to the new, up to the data space */
 112   lseek (old, 0, 0);
 113   copy_file (old, new, auxhdr.exec_dfile);
 114
 115   /* Skip the old data segment and write a new one */
 116   lseek (old, old_size, 1);
 117   save_data_space (new, &hdr, &auxhdr, new_size);
 118
 119   /* Copy the rest of the file */
 120   copy_rest (old, new);
 121
 122   /* Update file pointers since we probably changed size of data area */
 123   update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
 124
 125   /* Save the modified header */
 126   write_header (new, &hdr, &auxhdr);
 127
 128   /* Close the binary file */
 129   close (old);
 130   close (new);
 131   return 0;
 132 }
 133
 134 /* Save current data space in the file, update header.  */
 135
 136 save_data_space (file, hdr, auxhdr, size)
 137      int file;
 138      struct header *hdr;
 139      struct som_exec_auxhdr *auxhdr;
 140      int size;
 141 {
 142   /* Write the entire data space out to the file */
 143   if (write (file, auxhdr->exec_dmem, size) != size)
 144     { perror ("Can't save new data space"); exit (1); }
 145
 146   /* Update the header to reflect the new data size */
 147   auxhdr->exec_dsize = size;
 148   auxhdr->exec_bsize = 0;
 149 }
 150
 151 /* Update the values of file pointers when something is inserted.  */
 152
 153 update_file_ptrs (file, hdr, auxhdr, location, offset)
 154      int file;
 155      struct header *hdr;
 156      struct som_exec_auxhdr *auxhdr;
 157      unsigned int location;
 158      int offset;
 159 {
 160   struct subspace_dictionary_record subspace;
 161   int i;
 162
 163   /* Increase the overall size of the module */
 164   hdr->som_length += offset;
 165
 166   /* Update the various file pointers in the header */
 167 #define update(ptr) if (ptr > location) ptr = ptr + offset
 168   update (hdr->aux_header_location);
 169   update (hdr->space_strings_location);
 170   update (hdr->init_array_location);
 171   update (hdr->compiler_location);
 172   update (hdr->symbol_location);
 173   update (hdr->fixup_request_location);
 174   update (hdr->symbol_strings_location);
 175   update (hdr->unloadable_sp_location);
 176   update (auxhdr->exec_tfile);
 177   update (auxhdr->exec_dfile);
 178
 179   /* Do for each subspace dictionary entry */
 180   lseek (file, hdr->subspace_location, 0);
 181   for (i = 0; i < hdr->subspace_total; i++)
 182     {
 183       if (read (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 184         { perror ("Can't read subspace record"); exit (1); }
 185
 186       /* If subspace has a file location, update it */
 187       if (subspace.initialization_length > 0
 188           && subspace.file_loc_init_value > location)
 189         {
 190           subspace.file_loc_init_value += offset;
 191           lseek (file, -sizeof (subspace), 1);
 192           if (write (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 193             { perror ("Can't update subspace record"); exit (1); }
 194         }
 195     }
 196
 197   /* Do for each initialization pointer record */
 198   /* (I don't think it applies to executable files, only relocatables) */
 199 #undef update
 200 }
 201
 202 /* Read in the header records from an a.out file.  */
 203
 204 read_header (file, hdr, auxhdr)
 205      int file;
 206      struct header *hdr;
 207      struct som_exec_auxhdr *auxhdr;
 208 {
 209
 210   /* Read the header in */
 211   lseek (file, 0, 0);
 212   if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 213     { perror ("Couldn't read header from a.out file"); exit (1); }
 214
 215   if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
 216       &&  hdr->a_magic != DEMAND_MAGIC)
 217     {
 218       fprintf (stderr, "a.out file doesn't have legal magic number\n");
 219       exit (1);
 220     }
 221
 222   lseek (file, hdr->aux_header_location, 0);
 223   if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 224     {
 225       perror ("Couldn't read auxiliary header from a.out file");
 226       exit (1);
 227     }
 228 }
 229
 230 /* Write out the header records into an a.out file.  */
 231
 232 write_header (file, hdr, auxhdr)
 233      int file;
 234      struct header *hdr;
 235      struct som_exec_auxhdr *auxhdr;
 236 {
 237   /* Update the checksum */
 238   hdr->checksum = calculate_checksum (hdr);
 239
 240   /* Write the header back into the a.out file */
 241   lseek (file, 0, 0);
 242   if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 243     { perror ("Couldn't write header to a.out file"); exit (1); }
 244   lseek (file, hdr->aux_header_location, 0);
 245   if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 246     { perror ("Couldn't write auxiliary header to a.out file"); exit (1); }
 247 }
 248
 249 /* Calculate the checksum of a SOM header record. */
 250
 251 calculate_checksum (hdr)
 252      struct header *hdr;
 253 {
 254   int checksum, i, *ptr;
 255
 256   checksum = 0;  ptr = (int *) hdr;
 257
 258   for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
 259     checksum ^= ptr[i];
 260
 261   return (checksum);
 262 }
 263
 264 /* Copy size bytes from the old file to the new one.  */
 265
 266 copy_file (old, new, size)
 267      int new, old;
 268      int size;
 269 {
 270   int len;
 271   int buffer[8192];  /* word aligned will be faster */
 272
 273   for (; size > 0; size -= len)
 274     {
 275       len = min (size, sizeof (buffer));
 276       if (read (old, buffer, len) != len)
 277         { perror ("Read failure on a.out file"); exit (1); }
 278       if (write (new, buffer, len) != len)
 279         { perror ("Write failure in a.out file"); exit (1); }
 280     }
 281 }
 282
 283 /* Copy the rest of the file, up to EOF.  */
 284
 285 copy_rest (old, new)
 286      int new, old;
 287 {
 288   int buffer[4096];
 289   int len;
 290
 291   /* Copy bytes until end of file or error */
 292   while ((len = read (old, buffer, sizeof (buffer))) > 0)
 293     if (write (new, buffer, len) != len) break;
 294
 295   if (len != 0)
 296     { perror ("Unable to copy the rest of the file"); exit (1); }
 297 }
 298
 299 #ifdef  DEBUG
 300 display_header (hdr, auxhdr)
 301      struct header *hdr;
 302      struct som_exec_auxhdr *auxhdr;
 303 {
 304   /* Display the header information (debug) */
 305   printf ("\n\nFILE HEADER\n");
 306   printf ("magic number %d \n", hdr->a_magic);
 307   printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
 308   printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
 309   printf ("entry     %x \n",   auxhdr->exec_entry);
 310   printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
 311   printf ("\n");
 312   printf ("data file loc %d    size %d\n",
 313           auxhdr->exec_dfile, auxhdr->exec_dsize);
 314   printf ("som_length %d\n", hdr->som_length);
 315   printf ("unloadable sploc %d    size %d\n",
 316           hdr->unloadable_sp_location, hdr->unloadable_sp_size);
 317 }
 318 #endif /* DEBUG */