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