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 #undef roundup
  67 #define roundup(x,n) (((x) + ((n) - 1)) & ~((n) - 1))  /* n is power of 2 */
  68 #define min(x,y)  (((x) < (y)) ? (x) : (y))
  69
  70
  71 /* Create a new a.out file, same as old but with current data space */
  72
  73 unexec (new_name, old_name, new_end_of_text, dummy1, dummy2)
  74      char new_name[];           /* name of the new a.out file to be created */
  75      char old_name[];           /* name of the old a.out file */
  76      char *new_end_of_text;     /* ptr to new edata/etext; NOT USED YET */
  77      int dummy1, dummy2;        /* not used by emacs */
  78 {
  79   int old, new;
  80   int old_size, new_size;
  81   struct header hdr;
  82   struct som_exec_auxhdr auxhdr;
  83   long i;
  84
  85   /* For the greatest flexibility, should create a temporary file in
  86      the same directory as the new file.  When everything is complete,
  87      rename the temp file to the new name.
  88      This way, a program could update its own a.out file even while
  89      it is still executing.  If problems occur, everything is still
  90      intact.  NOT implemented.  */
  91
  92   /* Open the input and output a.out files */
  93   old = open (old_name, O_RDONLY);
  94   if (old < 0)
  95     { perror (old_name); exit (1); }
  96   new = open (new_name, O_CREAT|O_RDWR|O_TRUNC, 0777);
  97   if (new < 0)
  98     { perror (new_name); exit (1); }
  99
 100   /* Read the old headers */
 101   read_header (old, &hdr, &auxhdr);
 102
 103   brk_on_dump = sbrk (0);
 104
 105   /* Decide how large the new and old data areas are */
 106   old_size = auxhdr.exec_dsize;
 107   /* I suspect these two statements are separate
 108      to avoid a compiler bug in hpux version 8.  */
 109   i = sbrk (0);
 110   new_size = i - auxhdr.exec_dmem;
 111
 112   /* Copy the old file to the new, up to the data space */
 113   lseek (old, 0, 0);
 114   copy_file (old, new, auxhdr.exec_dfile);
 115
 116   /* Skip the old data segment and write a new one */
 117   lseek (old, old_size, 1);
 118   save_data_space (new, &hdr, &auxhdr, new_size);
 119
 120   /* Copy the rest of the file */
 121   copy_rest (old, new);
 122
 123   /* Update file pointers since we probably changed size of data area */
 124   update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
 125
 126   /* Save the modified header */
 127   write_header (new, &hdr, &auxhdr);
 128
 129   /* Close the binary file */
 130   close (old);
 131   close (new);
 132   return 0;
 133 }
 134
 135 /* Save current data space in the file, update header.  */
 136
 137 save_data_space (file, hdr, auxhdr, size)
 138      int file;
 139      struct header *hdr;
 140      struct som_exec_auxhdr *auxhdr;
 141      int size;
 142 {
 143   /* Write the entire data space out to the file */
 144   if (write (file, auxhdr->exec_dmem, size) != size)
 145     { perror ("Can't save new data space"); exit (1); }
 146
 147   /* Update the header to reflect the new data size */
 148   auxhdr->exec_dsize = size;
 149   auxhdr->exec_bsize = 0;
 150 }
 151
 152 /* Update the values of file pointers when something is inserted.  */
 153
 154 update_file_ptrs (file, hdr, auxhdr, location, offset)
 155      int file;
 156      struct header *hdr;
 157      struct som_exec_auxhdr *auxhdr;
 158      unsigned int location;
 159      int offset;
 160 {
 161   struct subspace_dictionary_record subspace;
 162   int i;
 163
 164   /* Increase the overall size of the module */
 165   hdr->som_length += offset;
 166
 167   /* Update the various file pointers in the header */
 168 #define update(ptr) if (ptr > location) ptr = ptr + offset
 169   update (hdr->aux_header_location);
 170   update (hdr->space_strings_location);
 171   update (hdr->init_array_location);
 172   update (hdr->compiler_location);
 173   update (hdr->symbol_location);
 174   update (hdr->fixup_request_location);
 175   update (hdr->symbol_strings_location);
 176   update (hdr->unloadable_sp_location);
 177   update (auxhdr->exec_tfile);
 178   update (auxhdr->exec_dfile);
 179
 180   /* Do for each subspace dictionary entry */
 181   lseek (file, hdr->subspace_location, 0);
 182   for (i = 0; i < hdr->subspace_total; i++)
 183     {
 184       if (read (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 185         { perror ("Can't read subspace record"); exit (1); }
 186
 187       /* If subspace has a file location, update it */
 188       if (subspace.initialization_length > 0
 189           && subspace.file_loc_init_value > location)
 190         {
 191           subspace.file_loc_init_value += offset;
 192           lseek (file, -sizeof (subspace), 1);
 193           if (write (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 194             { perror ("Can't update subspace record"); exit (1); }
 195         }
 196     }
 197
 198   /* Do for each initialization pointer record */
 199   /* (I don't think it applies to executable files, only relocatables) */
 200 #undef update
 201 }
 202
 203 /* Read in the header records from an a.out file.  */
 204
 205 read_header (file, hdr, auxhdr)
 206      int file;
 207      struct header *hdr;
 208      struct som_exec_auxhdr *auxhdr;
 209 {
 210
 211   /* Read the header in */
 212   lseek (file, 0, 0);
 213   if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 214     { perror ("Couldn't read header from a.out file"); exit (1); }
 215
 216   if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
 217       &&  hdr->a_magic != DEMAND_MAGIC)
 218     {
 219       fprintf (stderr, "a.out file doesn't have legal magic number\n");
 220       exit (1);
 221     }
 222
 223   lseek (file, hdr->aux_header_location, 0);
 224   if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 225     {
 226       perror ("Couldn't read auxiliary header from a.out file");
 227       exit (1);
 228     }
 229 }
 230
 231 /* Write out the header records into an a.out file.  */
 232
 233 write_header (file, hdr, auxhdr)
 234      int file;
 235      struct header *hdr;
 236      struct som_exec_auxhdr *auxhdr;
 237 {
 238   /* Update the checksum */
 239   hdr->checksum = calculate_checksum (hdr);
 240
 241   /* Write the header back into the a.out file */
 242   lseek (file, 0, 0);
 243   if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 244     { perror ("Couldn't write header to a.out file"); exit (1); }
 245   lseek (file, hdr->aux_header_location, 0);
 246   if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 247     { perror ("Couldn't write auxiliary header to a.out file"); exit (1); }
 248 }
 249
 250 /* Calculate the checksum of a SOM header record. */
 251
 252 calculate_checksum (hdr)
 253      struct header *hdr;
 254 {
 255   int checksum, i, *ptr;
 256
 257   checksum = 0;  ptr = (int *) hdr;
 258
 259   for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
 260     checksum ^= ptr[i];
 261
 262   return (checksum);
 263 }
 264
 265 /* Copy size bytes from the old file to the new one.  */
 266
 267 copy_file (old, new, size)
 268      int new, old;
 269      int size;
 270 {
 271   int len;
 272   int buffer[8192];  /* word aligned will be faster */
 273
 274   for (; size > 0; size -= len)
 275     {
 276       len = min (size, sizeof (buffer));
 277       if (read (old, buffer, len) != len)
 278         { perror ("Read failure on a.out file"); exit (1); }
 279       if (write (new, buffer, len) != len)
 280         { perror ("Write failure in a.out file"); exit (1); }
 281     }
 282 }
 283
 284 /* Copy the rest of the file, up to EOF.  */
 285
 286 copy_rest (old, new)
 287      int new, old;
 288 {
 289   int buffer[4096];
 290   int len;
 291
 292   /* Copy bytes until end of file or error */
 293   while ((len = read (old, buffer, sizeof (buffer))) > 0)
 294     if (write (new, buffer, len) != len) break;
 295
 296   if (len != 0)
 297     { perror ("Unable to copy the rest of the file"); exit (1); }
 298 }
 299
 300 #ifdef  DEBUG
 301 display_header (hdr, auxhdr)
 302      struct header *hdr;
 303      struct som_exec_auxhdr *auxhdr;
 304 {
 305   /* Display the header information (debug) */
 306   printf ("\n\nFILE HEADER\n");
 307   printf ("magic number %d \n", hdr->a_magic);
 308   printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
 309   printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
 310   printf ("entry     %x \n",   auxhdr->exec_entry);
 311   printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
 312   printf ("\n");
 313   printf ("data file loc %d    size %d\n",
 314           auxhdr->exec_dfile, auxhdr->exec_dsize);
 315   printf ("som_length %d\n", hdr->som_length);
 316   printf ("unloadable sploc %d    size %d\n",
 317           hdr->unloadable_sp_location, hdr->unloadable_sp_size);
 318 }
 319 #endif /* DEBUG */