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