src/unexhp9k800.c

   1 /* Unexec for HP 9000 Series 800 machines.
   2
   3   This file is in the public domain.
   4
   5   Author: John V. Morris
   6
   7   This file was written by John V. Morris at Hewlett Packard.
   8   Both the author and Hewlett Packard Co. have disclaimed the
   9   copyright on this file, and it is therefore in the public domain.
  10   (Search for "hp9k800" in copyright.list.)
  11 */
  12
  13 /*
  14    Bob Desinger <hpsemc!bd@hplabs.hp.com>
  15
  16    Note that the GNU project considers support for HP operation a
  17    peripheral activity which should not be allowed to divert effort
  18    from development of the GNU system.  Changes in this code will be
  19    installed when users send them in, but aside from that we don't
  20    plan to think about it, or about whether other Emacs maintenance
  21    might break it.
  22
  23
  24   Unexec creates a copy of the old a.out file, and replaces the old data
  25   area with the current data area.  When the new file is executed, the
  26   process will see the same data structures and data values that the
  27   original process had when unexec was called.
  28
  29   Unlike other versions of unexec, this one copies symbol table and
  30   debug information to the new a.out file.  Thus, the new a.out file
  31   may be debugged with symbolic debuggers.
  32
  33   If you fix any bugs in this, I'd like to incorporate your fixes.
  34   Send them to uunet!hpda!hpsemc!jmorris or jmorris%hpsemc@hplabs.HP.COM.
  35
  36   CAVEATS:
  37   This routine saves the current value of all static and external
  38   variables.  This means that any data structure that needs to be
  39   initialized must be explicitly reset.  Variables will not have their
  40   expected default values.
  41
  42   Unfortunately, the HP-UX signal handler has internal initialization
  43   flags which are not explicitly reset.  Thus, for signals to work in
  44   conjunction with this routine, the following code must executed when
  45   the new process starts up.
  46
  47   void _sigreturn ();
  48   ...
  49   sigsetreturn (_sigreturn);
  50 */
  51 \f
  52 #ifdef emacs
  53 #include <config.h>
  54 #endif
  55
  56 #include <stdio.h>
  57 #include <fcntl.h>
  58 #include <errno.h>
  59
  60 #include <a.out.h>
  61
  62 #include <dl.h>
  63
  64 /* brk value to restore, stored as a global.
  65    This is really used only if we used shared libraries.  */
  66 static long brk_on_dump = 0;
  67
  68 /* Called from main, if we use shared libraries.  */
  69 int
  70 run_time_remap (ignored)
  71      char *ignored;
  72 {
  73   brk ((char *) brk_on_dump);
  74 }
  75
  76 #undef roundup
  77 #define roundup(x,n) (((x) + ((n) - 1)) & ~((n) - 1))  /* n is power of 2 */
  78 #define min(x,y)  (((x) < (y)) ? (x) : (y))
  79
  80
  81 /* Create a new a.out file, same as old but with current data space */
  82 int
  83 unexec (const char *new_name,      /* name of the new a.out file to be created */
  84         const char *old_name)       /* name of the old a.out file */
  85 {
  86   int old, new;
  87   int old_size, new_size;
  88   struct header hdr;
  89   struct som_exec_auxhdr auxhdr;
  90   long i;
  91
  92   /* For the greatest flexibility, should create a temporary file in
  93      the same directory as the new file.  When everything is complete,
  94      rename the temp file to the new name.
  95      This way, a program could update its own a.out file even while
  96      it is still executing.  If problems occur, everything is still
  97      intact.  NOT implemented.  */
  98
  99   /* Open the input and output a.out files */
 100   old = open (old_name, O_RDONLY);
 101   if (old < 0)
 102     { perror (old_name); exit (1); }
 103   new = open (new_name, O_CREAT|O_RDWR|O_TRUNC, 0777);
 104   if (new < 0)
 105     { perror (new_name); exit (1); }
 106
 107   /* Read the old headers */
 108   read_header (old, &hdr, &auxhdr);
 109
 110   brk_on_dump = (long) sbrk (0);
 111
 112   /* Decide how large the new and old data areas are */
 113   old_size = auxhdr.exec_dsize;
 114   /* I suspect these two statements are separate
 115      to avoid a compiler bug in hpux version 8.  */
 116   i = (long) sbrk (0);
 117   new_size = i - auxhdr.exec_dmem;
 118
 119   /* Copy the old file to the new, up to the data space */
 120   lseek (old, 0, 0);
 121   copy_file (old, new, auxhdr.exec_dfile);
 122
 123   /* Skip the old data segment and write a new one */
 124   lseek (old, old_size, 1);
 125   save_data_space (new, &hdr, &auxhdr, new_size);
 126
 127   /* Copy the rest of the file */
 128   copy_rest (old, new);
 129
 130   /* Update file pointers since we probably changed size of data area */
 131   update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
 132
 133   /* Save the modified header */
 134   write_header (new, &hdr, &auxhdr);
 135
 136   /* Close the binary file */
 137   close (old);
 138   close (new);
 139   return 0;
 140 }
 141
 142 /* Save current data space in the file, update header.  */
 143
 144 save_data_space (file, hdr, auxhdr, size)
 145      int file;
 146      struct header *hdr;
 147      struct som_exec_auxhdr *auxhdr;
 148      int size;
 149 {
 150   /* Write the entire data space out to the file */
 151   if (write (file, auxhdr->exec_dmem, size) != size)
 152     { perror ("Can't save new data space"); exit (1); }
 153
 154   /* Update the header to reflect the new data size */
 155   auxhdr->exec_dsize = size;
 156   auxhdr->exec_bsize = 0;
 157 }
 158
 159 /* Update the values of file pointers when something is inserted.  */
 160
 161 update_file_ptrs (file, hdr, auxhdr, location, offset)
 162      int file;
 163      struct header *hdr;
 164      struct som_exec_auxhdr *auxhdr;
 165      unsigned int location;
 166      int offset;
 167 {
 168   struct subspace_dictionary_record subspace;
 169   int i;
 170
 171   /* Increase the overall size of the module */
 172   hdr->som_length += offset;
 173
 174   /* Update the various file pointers in the header */
 175 #define update(ptr) if (ptr > location) ptr = ptr + offset
 176   update (hdr->aux_header_location);
 177   update (hdr->space_strings_location);
 178   update (hdr->init_array_location);
 179   update (hdr->compiler_location);
 180   update (hdr->symbol_location);
 181   update (hdr->fixup_request_location);
 182   update (hdr->symbol_strings_location);
 183   update (hdr->unloadable_sp_location);
 184   update (auxhdr->exec_tfile);
 185   update (auxhdr->exec_dfile);
 186
 187   /* Do for each subspace dictionary entry */
 188   lseek (file, hdr->subspace_location, 0);
 189   for (i = 0; i < hdr->subspace_total; i++)
 190     {
 191       if (read (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 192         { perror ("Can't read subspace record"); exit (1); }
 193
 194       /* If subspace has a file location, update it */
 195       if (subspace.initialization_length > 0
 196           && subspace.file_loc_init_value > location)
 197         {
 198           subspace.file_loc_init_value += offset;
 199           lseek (file, -sizeof (subspace), 1);
 200           if (write (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 201             { perror ("Can't update subspace record"); exit (1); }
 202         }
 203     }
 204
 205   /* Do for each initialization pointer record */
 206   /* (I don't think it applies to executable files, only relocatables) */
 207 #undef update
 208 }
 209
 210 /* Read in the header records from an a.out file.  */
 211
 212 read_header (file, hdr, auxhdr)
 213      int file;
 214      struct header *hdr;
 215      struct som_exec_auxhdr *auxhdr;
 216 {
 217
 218   /* Read the header in */
 219   lseek (file, 0, 0);
 220   if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 221     { perror ("Couldn't read header from a.out file"); exit (1); }
 222
 223   if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
 224       &&  hdr->a_magic != DEMAND_MAGIC)
 225     {
 226       fprintf (stderr, "a.out file doesn't have valid magic number\n");
 227       exit (1);
 228     }
 229
 230   lseek (file, hdr->aux_header_location, 0);
 231   if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 232     {
 233       perror ("Couldn't read auxiliary header from a.out file");
 234       exit (1);
 235     }
 236 }
 237
 238 /* Write out the header records into an a.out file.  */
 239
 240 write_header (file, hdr, auxhdr)
 241      int file;
 242      struct header *hdr;
 243      struct som_exec_auxhdr *auxhdr;
 244 {
 245   /* Update the checksum */
 246   hdr->checksum = calculate_checksum (hdr);
 247
 248   /* Write the header back into the a.out file */
 249   lseek (file, 0, 0);
 250   if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 251     { perror ("Couldn't write header to a.out file"); exit (1); }
 252   lseek (file, hdr->aux_header_location, 0);
 253   if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 254     { perror ("Couldn't write auxiliary header to a.out file"); exit (1); }
 255 }
 256
 257 /* Calculate the checksum of a SOM header record. */
 258
 259 calculate_checksum (hdr)
 260      struct header *hdr;
 261 {
 262   int checksum, i, *ptr;
 263
 264   checksum = 0;  ptr = (int *) hdr;
 265
 266   for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
 267     checksum ^= ptr[i];
 268
 269   return (checksum);
 270 }
 271
 272 /* Copy size bytes from the old file to the new one.  */
 273
 274 copy_file (old, new, size)
 275      int new, old;
 276      int size;
 277 {
 278   int len;
 279   int buffer[8192];  /* word aligned will be faster */
 280
 281   for (; size > 0; size -= len)
 282     {
 283       len = min (size, sizeof (buffer));
 284       if (read (old, buffer, len) != len)
 285         { perror ("Read failure on a.out file"); exit (1); }
 286       if (write (new, buffer, len) != len)
 287         { perror ("Write failure in a.out file"); exit (1); }
 288     }
 289 }
 290
 291 /* Copy the rest of the file, up to EOF.  */
 292
 293 copy_rest (old, new)
 294      int new, old;
 295 {
 296   int buffer[4096];
 297   int len;
 298
 299   /* Copy bytes until end of file or error */
 300   while ((len = read (old, buffer, sizeof (buffer))) > 0)
 301     if (write (new, buffer, len) != len) break;
 302
 303   if (len != 0)
 304     { perror ("Unable to copy the rest of the file"); exit (1); }
 305 }
 306
 307 #ifdef  DEBUG
 308 display_header (hdr, auxhdr)
 309      struct header *hdr;
 310      struct som_exec_auxhdr *auxhdr;
 311 {
 312   /* Display the header information (debug) */
 313   printf ("\n\nFILE HEADER\n");
 314   printf ("magic number %d \n", hdr->a_magic);
 315   printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
 316   printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
 317   printf ("entry     %x \n",   auxhdr->exec_entry);
 318   printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
 319   printf ("\n");
 320   printf ("data file loc %d    size %d\n",
 321           auxhdr->exec_dfile, auxhdr->exec_dsize);
 322   printf ("som_length %d\n", hdr->som_length);
 323   printf ("unloadable sploc %d    size %d\n",
 324           hdr->unloadable_sp_location, hdr->unloadable_sp_size);
 325 }
 326 #endif /* DEBUG */
 327
 328 /* arch-tag: d55a09ac-9427-4ec4-8496-cb9d7710774f
 329    (do not change this comment) */