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 void
  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 }
 137
 138 /* Save current data space in the file, update header.  */
 139
 140 save_data_space (file, hdr, auxhdr, size)
 141      int file;
 142      struct header *hdr;
 143      struct som_exec_auxhdr *auxhdr;
 144      int size;
 145 {
 146   /* Write the entire data space out to the file */
 147   if (write (file, auxhdr->exec_dmem, size) != size)
 148     { perror ("Can't save new data space"); exit (1); }
 149
 150   /* Update the header to reflect the new data size */
 151   auxhdr->exec_dsize = size;
 152   auxhdr->exec_bsize = 0;
 153 }
 154
 155 /* Update the values of file pointers when something is inserted.  */
 156
 157 update_file_ptrs (file, hdr, auxhdr, location, offset)
 158      int file;
 159      struct header *hdr;
 160      struct som_exec_auxhdr *auxhdr;
 161      unsigned int location;
 162      int offset;
 163 {
 164   struct subspace_dictionary_record subspace;
 165   int i;
 166
 167   /* Increase the overall size of the module */
 168   hdr->som_length += offset;
 169
 170   /* Update the various file pointers in the header */
 171 #define update(ptr) if (ptr > location) ptr = ptr + offset
 172   update (hdr->aux_header_location);
 173   update (hdr->space_strings_location);
 174   update (hdr->init_array_location);
 175   update (hdr->compiler_location);
 176   update (hdr->symbol_location);
 177   update (hdr->fixup_request_location);
 178   update (hdr->symbol_strings_location);
 179   update (hdr->unloadable_sp_location);
 180   update (auxhdr->exec_tfile);
 181   update (auxhdr->exec_dfile);
 182
 183   /* Do for each subspace dictionary entry */
 184   lseek (file, hdr->subspace_location, 0);
 185   for (i = 0; i < hdr->subspace_total; i++)
 186     {
 187       if (read (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 188         { perror ("Can't read subspace record"); exit (1); }
 189
 190       /* If subspace has a file location, update it */
 191       if (subspace.initialization_length > 0
 192           && subspace.file_loc_init_value > location)
 193         {
 194           subspace.file_loc_init_value += offset;
 195           lseek (file, -sizeof (subspace), 1);
 196           if (write (file, &subspace, sizeof (subspace)) != sizeof (subspace))
 197             { perror ("Can't update subspace record"); exit (1); }
 198         }
 199     }
 200
 201   /* Do for each initialization pointer record */
 202   /* (I don't think it applies to executable files, only relocatables) */
 203 #undef update
 204 }
 205
 206 /* Read in the header records from an a.out file.  */
 207
 208 read_header (file, hdr, auxhdr)
 209      int file;
 210      struct header *hdr;
 211      struct som_exec_auxhdr *auxhdr;
 212 {
 213
 214   /* Read the header in */
 215   lseek (file, 0, 0);
 216   if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 217     { perror ("Couldn't read header from a.out file"); exit (1); }
 218
 219   if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
 220       &&  hdr->a_magic != DEMAND_MAGIC)
 221     {
 222       fprintf (stderr, "a.out file doesn't have valid magic number\n");
 223       exit (1);
 224     }
 225
 226   lseek (file, hdr->aux_header_location, 0);
 227   if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 228     {
 229       perror ("Couldn't read auxiliary header from a.out file");
 230       exit (1);
 231     }
 232 }
 233
 234 /* Write out the header records into an a.out file.  */
 235
 236 write_header (file, hdr, auxhdr)
 237      int file;
 238      struct header *hdr;
 239      struct som_exec_auxhdr *auxhdr;
 240 {
 241   /* Update the checksum */
 242   hdr->checksum = calculate_checksum (hdr);
 243
 244   /* Write the header back into the a.out file */
 245   lseek (file, 0, 0);
 246   if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 247     { perror ("Couldn't write header to a.out file"); exit (1); }
 248   lseek (file, hdr->aux_header_location, 0);
 249   if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 250     { perror ("Couldn't write auxiliary header to a.out file"); exit (1); }
 251 }
 252
 253 /* Calculate the checksum of a SOM header record. */
 254
 255 calculate_checksum (hdr)
 256      struct header *hdr;
 257 {
 258   int checksum, i, *ptr;
 259
 260   checksum = 0;  ptr = (int *) hdr;
 261
 262   for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
 263     checksum ^= ptr[i];
 264
 265   return (checksum);
 266 }
 267
 268 /* Copy size bytes from the old file to the new one.  */
 269
 270 copy_file (old, new, size)
 271      int new, old;
 272      int size;
 273 {
 274   int len;
 275   int buffer[8192];  /* word aligned will be faster */
 276
 277   for (; size > 0; size -= len)
 278     {
 279       len = min (size, sizeof (buffer));
 280       if (read (old, buffer, len) != len)
 281         { perror ("Read failure on a.out file"); exit (1); }
 282       if (write (new, buffer, len) != len)
 283         { perror ("Write failure in a.out file"); exit (1); }
 284     }
 285 }
 286
 287 /* Copy the rest of the file, up to EOF.  */
 288
 289 copy_rest (old, new)
 290      int new, old;
 291 {
 292   int buffer[4096];
 293   int len;
 294
 295   /* Copy bytes until end of file or error */
 296   while ((len = read (old, buffer, sizeof (buffer))) > 0)
 297     if (write (new, buffer, len) != len) break;
 298
 299   if (len != 0)
 300     { perror ("Unable to copy the rest of the file"); exit (1); }
 301 }
 302
 303 #ifdef  DEBUG
 304 display_header (hdr, auxhdr)
 305      struct header *hdr;
 306      struct som_exec_auxhdr *auxhdr;
 307 {
 308   /* Display the header information (debug) */
 309   printf ("\n\nFILE HEADER\n");
 310   printf ("magic number %d \n", hdr->a_magic);
 311   printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
 312   printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
 313   printf ("entry     %x \n",   auxhdr->exec_entry);
 314   printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
 315   printf ("\n");
 316   printf ("data file loc %d    size %d\n",
 317           auxhdr->exec_dfile, auxhdr->exec_dsize);
 318   printf ("som_length %d\n", hdr->som_length);
 319   printf ("unloadable sploc %d    size %d\n",
 320           hdr->unloadable_sp_location, hdr->unloadable_sp_size);
 321 }
 322 #endif /* DEBUG */