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