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 /* Report a fatal error and exit.  */
  78 static _Noreturn void
  79 unexec_error (char const *msg)
  80 {
  81   perror (msg);
  82   exit (1);
  83 }
  84
  85 /* Do an lseek and check the result.  */
  86 static void
  87 check_lseek (int fd, off_t offset, int whence)
  88 {
  89   if (lseek (fd, offset, whence) < 0)
  90     unexec_error ("Cannot lseek");
  91 }
  92
  93 /* Save current data space in the file, update header.  */
  94
  95 static void
  96 save_data_space (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr,
  97                  int size)
  98 {
  99   /* Write the entire data space out to the file */
 100   if (write (file, auxhdr->exec_dmem, size) != size)
 101     unexec_error ("Can't save new data space");
 102
 103   /* Update the header to reflect the new data size */
 104   auxhdr->exec_dsize = size;
 105   auxhdr->exec_bsize = 0;
 106 }
 107
 108 /* Update the values of file pointers when something is inserted.  */
 109
 110 static void
 111 update_file_ptrs (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr,
 112                   unsigned int location, int offset)
 113 {
 114   struct subspace_dictionary_record subspace;
 115   int i;
 116
 117   /* Increase the overall size of the module */
 118   hdr->som_length += offset;
 119
 120   /* Update the various file pointers in the header */
 121 #define update(ptr) if (ptr > location) ptr = ptr + offset
 122   update (hdr->aux_header_location);
 123   update (hdr->space_strings_location);
 124   update (hdr->init_array_location);
 125   update (hdr->compiler_location);
 126   update (hdr->symbol_location);
 127   update (hdr->fixup_request_location);
 128   update (hdr->symbol_strings_location);
 129   update (hdr->unloadable_sp_location);
 130   update (auxhdr->exec_tfile);
 131   update (auxhdr->exec_dfile);
 132
 133   /* Do for each subspace dictionary entry */
 134   check_lseek (file, hdr->subspace_location, 0);
 135   for (i = 0; i < hdr->subspace_total; i++)
 136     {
 137       ptrdiff_t subspace_size = sizeof subspace;
 138       if (read (file, &subspace, subspace_size) != subspace_size)
 139         unexec_error ("Can't read subspace record");
 140
 141       /* If subspace has a file location, update it */
 142       if (subspace.initialization_length > 0
 143           && subspace.file_loc_init_value > location)
 144         {
 145           subspace.file_loc_init_value += offset;
 146           check_lseek (file, -subspace_size, 1);
 147           if (write (file, &subspace, subspace_size) != subspace_size)
 148             unexec_error ("Can't update subspace record");
 149         }
 150     }
 151
 152   /* Do for each initialization pointer record */
 153   /* (I don't think it applies to executable files, only relocatables) */
 154 #undef update
 155 }
 156
 157 /* Read in the header records from an a.out file.  */
 158
 159 static void
 160 read_header (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr)
 161 {
 162
 163   /* Read the header in */
 164   check_lseek (file, 0, 0);
 165   if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 166     unexec_error ("Couldn't read header from a.out file");
 167
 168   if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
 169       &&  hdr->a_magic != DEMAND_MAGIC)
 170     {
 171       fprintf (stderr, "a.out file doesn't have valid magic number\n");
 172       exit (1);
 173     }
 174
 175   check_lseek (file, hdr->aux_header_location, 0);
 176   if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 177     unexec_error ("Couldn't read auxiliary header from a.out file");
 178 }
 179
 180 /* Write out the header records into an a.out file.  */
 181
 182 static void
 183 write_header (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr)
 184 {
 185   /* Update the checksum */
 186   hdr->checksum = calculate_checksum (hdr);
 187
 188   /* Write the header back into the a.out file */
 189   check_lseek (file, 0, 0);
 190   if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
 191     unexec_error ("Couldn't write header to a.out file");
 192   check_lseek (file, hdr->aux_header_location, 0);
 193   if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
 194     unexec_error ("Couldn't write auxiliary header to a.out file");
 195 }
 196
 197 /* Calculate the checksum of a SOM header record. */
 198
 199 static int
 200 calculate_checksum (struct header *hdr)
 201 {
 202   int checksum, i, *ptr;
 203
 204   checksum = 0;  ptr = (int *) hdr;
 205
 206   for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
 207     checksum ^= ptr[i];
 208
 209   return (checksum);
 210 }
 211
 212 /* Copy size bytes from the old file to the new one.  */
 213
 214 static void
 215 copy_file (int old, int new, int size)
 216 {
 217   int len;
 218   int buffer[8192];  /* word aligned will be faster */
 219
 220   for (; size > 0; size -= len)
 221     {
 222       len = min (size, sizeof (buffer));
 223       if (read (old, buffer, len) != len)
 224         unexec_error ("Read failure on a.out file");
 225       if (write (new, buffer, len) != len)
 226         unexec_error ("Write failure in a.out file");
 227     }
 228 }
 229
 230 /* Copy the rest of the file, up to EOF.  */
 231
 232 static void
 233 copy_rest (int old, int new)
 234 {
 235   int buffer[4096];
 236   int len;
 237
 238   /* Copy bytes until end of file or error */
 239   while ((len = read (old, buffer, sizeof (buffer))) > 0)
 240     if (write (new, buffer, len) != len) break;
 241
 242   if (len != 0)
 243     unexec_error ("Unable to copy the rest of the file");
 244 }
 245
 246 #ifdef  DEBUG
 247 static void
 248 display_header (struct header *hdr, struct som_exec_auxhdr *auxhdr)
 249 {
 250   /* Display the header information (debug) */
 251   printf ("\n\nFILE HEADER\n");
 252   printf ("magic number %d \n", hdr->a_magic);
 253   printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
 254   printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
 255   printf ("entry     %x \n",   auxhdr->exec_entry);
 256   printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
 257   printf ("\n");
 258   printf ("data file loc %d    size %d\n",
 259           auxhdr->exec_dfile, auxhdr->exec_dsize);
 260   printf ("som_length %d\n", hdr->som_length);
 261   printf ("unloadable sploc %d    size %d\n",
 262           hdr->unloadable_sp_location, hdr->unloadable_sp_size);
 263 }
 264 #endif /* DEBUG */
 265
 266
 267 /* Create a new a.out file, same as old but with current data space */
 268 void
 269 unexec (const char *new_name,      /* name of the new a.out file to be created */
 270         const char *old_name)       /* name of the old a.out file */
 271 {
 272   int old, new;
 273   int old_size, new_size;
 274   struct header hdr;
 275   struct som_exec_auxhdr auxhdr;
 276   long i;
 277
 278   /* For the greatest flexibility, should create a temporary file in
 279      the same directory as the new file.  When everything is complete,
 280      rename the temp file to the new name.
 281      This way, a program could update its own a.out file even while
 282      it is still executing.  If problems occur, everything is still
 283      intact.  NOT implemented.  */
 284
 285   /* Open the input and output a.out files.  */
 286   old = emacs_open (old_name, O_RDONLY, 0);
 287   if (old < 0)
 288     unexec_error (old_name);
 289   new = emacs_open (new_name, O_CREAT | O_RDWR | O_TRUNC, 0777);
 290   if (new < 0)
 291     unexec_error (new_name);
 292
 293   /* Read the old headers.  */
 294   read_header (old, &hdr, &auxhdr);
 295
 296   brk_on_dump = (long) sbrk (0);
 297
 298   /* Decide how large the new and old data areas are.  */
 299   old_size = auxhdr.exec_dsize;
 300   /* I suspect these two statements are separate
 301      to avoid a compiler bug in hpux version 8.  */
 302   i = (long) sbrk (0);
 303   new_size = i - auxhdr.exec_dmem;
 304
 305   /* Copy the old file to the new, up to the data space.  */
 306   check_lseek (old, 0, 0);
 307   copy_file (old, new, auxhdr.exec_dfile);
 308
 309   /* Skip the old data segment and write a new one.  */
 310   check_lseek (old, old_size, 1);
 311   save_data_space (new, &hdr, &auxhdr, new_size);
 312
 313   /* Copy the rest of the file.  */
 314   copy_rest (old, new);
 315
 316   /* Update file pointers since we probably changed size of data area.  */
 317   update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
 318
 319   /* Save the modified header.  */
 320   write_header (new, &hdr, &auxhdr);
 321
 322   /* Close the binary file.  */
 323   emacs_close (old);
 324   emacs_close (new);
 325 }