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 #include <config.h>
  53 #include <stdio.h>
  54 #include <fcntl.h>
  55 #include <errno.h>
  56 #include <a.out.h>
  57 #include <dl.h>
  58
  59 /* brk value to restore, stored as a global.
  60    This is really used only if we used shared libraries.  */
  61 static long brk_on_dump = 0;
  62
  63 /* Called from main, if we use shared libraries.  */
  64 int
  65 run_time_remap (ignored)
  66      char *ignored;
  67 {
  68   brk ((char *) brk_on_dump);
  69 }
  70
  71 #undef roundup
  72 #define roundup(x,n) (((x) + ((n) - 1)) & ~((n) - 1))  /* n is power of 2 */
  73 #define min(x,y)  (((x) < (y)) ? (x) : (y))
  74
  75
  76 /* Create a new a.out file, same as old but with current data space */
  77 int
  78 unexec (const char *new_name,      /* name of the new a.out file to be created */
  79         const char *old_name)       /* name of the old a.out file */
  80 {
  81   int old, new;
  82   int old_size, new_size;
  83   struct header hdr;
  84   struct som_exec_auxhdr auxhdr;
  85   long i;
  86
  87   /* For the greatest flexibility, should create a temporary file in
  88      the same directory as the new file.  When everything is complete,
  89      rename the temp file to the new name.
  90      This way, a program could update its own a.out file even while
  91      it is still executing.  If problems occur, everything is still
  92      intact.  NOT implemented.  */
  93
  94   /* Open the input and output a.out files */
  95   old = open (old_name, O_RDONLY);
  96   if (old < 0)
  97     { perror (old_name); exit (1); }
  98   new = open (new_name, O_CREAT|O_RDWR|O_TRUNC, 0777);
  99   if (new < 0)
 100     { perror (new_name); exit (1); }
 101
 102   /* Read the old headers */
 103   read_header (old, &hdr, &auxhdr);
 104
 105   brk_on_dump = (long) sbrk (0);
 106
 107   /* Decide how large the new and old data areas are */
 108   old_size = auxhdr.exec_dsize;
 109   /* I suspect these two statements are separate
 110      to avoid a compiler bug in hpux version 8.  */
 111   i = (long) sbrk (0);
 112   new_size = i - auxhdr.exec_dmem;
 113
 114   /* Copy the old file to the new, up to the data space */
 115   lseek (old, 0, 0);
 116   copy_file (old, new, auxhdr.exec_dfile);
 117
 118   /* Skip the old data segment and write a new one */
 119   lseek (old, old_size, 1);
 120   save_data_space (new, &hdr, &auxhdr, new_size);
 121
 122   /* Copy the rest of the file */
 123   copy_rest (old, new);
 124
 125   /* Update file pointers since we probably changed size of data area */
 126   update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
 127
 128   /* Save the modified header */
 129   write_header (new, &hdr, &auxhdr);
 130
 131   /* Close the binary file */
 132   close (old);
 133   close (new);
 134   return 0;
 135 }
 136
 137 /* Save current data space in the file, update header.  */
 138
 139 save_data_space (file, hdr, auxhdr, size)
 140      int file;
 141      struct header *hdr;
 142      struct som_exec_auxhdr *auxhdr;
 143      int size;
 144 {
 145   /* Write the entire data space out to the file */
 146   if (write (file, auxhdr->exec_dmem, size) != size)
 147     { perror ("Can't save new data space"); exit (1); }
 148
 149   /* Update the header to reflect the new data size */
 150   auxhdr->exec_dsize = size;
 151   auxhdr->exec_bsize = 0;
 152 }
 153
 154 /* Update the values of file pointers when something is inserted.  */
 155
 156 update_file_ptrs (file, hdr, auxhdr, location, offset)
 157      int file;
 158      struct header *hdr;
 159      struct som_exec_auxhdr *auxhdr;
 160      unsigned int location;
 161      int offset;
 162 {
 163   struct subspace_dictionary_record subspace;
 164   int i;
 165
 166   /* Increase the overall size of the module */
 167   hdr->som_length += offset;
 168
 169   /* Update the various file pointers in the header */
 170 #define update(ptr) if (ptr > location) ptr = ptr + offset
 171   update (hdr->aux_header_location);
 172   update (hdr->space_strings_location);
 173   update (hdr->init_array_location);
 174   update (hdr->compiler_location);
 175   update (hdr->symbol_location);
 176   update (hdr->fixup_request_location);
 177   update (hdr->symbol_strings_location);
 178   update (hdr->unloadable_sp_location);
 179   update (auxhdr->exec_tfile);
 180   update (auxhdr->exec_dfile);
 181
 182   /* Do for each subspace dictionary entry */
 183   lseek (file, hdr->subspace_location, 0);
 184   for (i = 0; i < hdr->subspace_total; i++)
 185     {
 186       if (read (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 187         { perror ("Can't read subspace record"); exit (1); }
 188
 189       /* If subspace has a file location, update it */
 190       if (subspace.initialization_length > 0
 191           && subspace.file_loc_init_value > location)
 192         {
 193           subspace.file_loc_init_value += offset;
 194           lseek (file, -sizeof (subspace), 1);
 195           if (write (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 196             { perror ("Can't update subspace record"); exit (1); }
 197         }
 198     }
 199
 200   /* Do for each initialization pointer record */
 201   /* (I don't think it applies to executable files, only relocatables) */
 202 #undef update
 203 }
 204
 205 /* Read in the header records from an a.out file.  */
 206
 207 read_header (file, hdr, auxhdr)
 208      int file;
 209      struct header *hdr;
 210      struct som_exec_auxhdr *auxhdr;
 211 {
 212
 213   /* Read the header in */
 214   lseek (file, 0, 0);
 215   if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 216     { perror ("Couldn't read header from a.out file"); exit (1); }
 217
 218   if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
 219       &&  hdr->a_magic != DEMAND_MAGIC)
 220     {
 221       fprintf (stderr, "a.out file doesn't have valid magic number\n");
 222       exit (1);
 223     }
 224
 225   lseek (file, hdr->aux_header_location, 0);
 226   if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 227     {
 228       perror ("Couldn't read auxiliary header from a.out file");
 229       exit (1);
 230     }
 231 }
 232
 233 /* Write out the header records into an a.out file.  */
 234
 235 write_header (file, hdr, auxhdr)
 236      int file;
 237      struct header *hdr;
 238      struct som_exec_auxhdr *auxhdr;
 239 {
 240   /* Update the checksum */
 241   hdr->checksum = calculate_checksum (hdr);
 242
 243   /* Write the header back into the a.out file */
 244   lseek (file, 0, 0);
 245   if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 246     { perror ("Couldn't write header to a.out file"); exit (1); }
 247   lseek (file, hdr->aux_header_location, 0);
 248   if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 249     { perror ("Couldn't write auxiliary header to a.out file"); exit (1); }
 250 }
 251
 252 /* Calculate the checksum of a SOM header record. */
 253
 254 calculate_checksum (hdr)
 255      struct header *hdr;
 256 {
 257   int checksum, i, *ptr;
 258
 259   checksum = 0;  ptr = (int *) hdr;
 260
 261   for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
 262     checksum ^= ptr[i];
 263
 264   return (checksum);
 265 }
 266
 267 /* Copy size bytes from the old file to the new one.  */
 268
 269 copy_file (old, new, size)
 270      int new, old;
 271      int size;
 272 {
 273   int len;
 274   int buffer[8192];  /* word aligned will be faster */
 275
 276   for (; size > 0; size -= len)
 277     {
 278       len = min (size, sizeof (buffer));
 279       if (read (old, buffer, len) != len)
 280         { perror ("Read failure on a.out file"); exit (1); }
 281       if (write (new, buffer, len) != len)
 282         { perror ("Write failure in a.out file"); exit (1); }
 283     }
 284 }
 285
 286 /* Copy the rest of the file, up to EOF.  */
 287
 288 copy_rest (old, new)
 289      int new, old;
 290 {
 291   int buffer[4096];
 292   int len;
 293
 294   /* Copy bytes until end of file or error */
 295   while ((len = read (old, buffer, sizeof (buffer))) > 0)
 296     if (write (new, buffer, len) != len) break;
 297
 298   if (len != 0)
 299     { perror ("Unable to copy the rest of the file"); exit (1); }
 300 }
 301
 302 #ifdef  DEBUG
 303 display_header (hdr, auxhdr)
 304      struct header *hdr;
 305      struct som_exec_auxhdr *auxhdr;
 306 {
 307   /* Display the header information (debug) */
 308   printf ("\n\nFILE HEADER\n");
 309   printf ("magic number %d \n", hdr->a_magic);
 310   printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
 311   printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
 312   printf ("entry     %x \n",   auxhdr->exec_entry);
 313   printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
 314   printf ("\n");
 315   printf ("data file loc %d    size %d\n",
 316           auxhdr->exec_dfile, auxhdr->exec_dsize);
 317   printf ("som_length %d\n", hdr->som_length);
 318   printf ("unloadable sploc %d    size %d\n",
 319           hdr->unloadable_sp_location, hdr->unloadable_sp_size);
 320 }
 321 #endif /* DEBUG */
 322