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
52#ifdef emacs
53#include <config.h>
54#endif
55
56#include <stdio.h>
57#include <fcntl.h>
58#include <errno.h>
59
60#include <a.out.h>
61
62#ifdef HPUX_USE_SHLIBS
63#include <dl.h>
64#endif
65
66/* brk value to restore, stored as a global.
67   This is really used only if we used shared libraries.  */
68static long brk_on_dump = 0;
69
70/* Called from main, if we use shared libraries.  */
71int
72run_time_remap (ignored)
73     char *ignored;
74{
75  brk ((char *) brk_on_dump);
76}
77
78#undef roundup
79#define roundup(x,n) (((x) + ((n) - 1)) & ~((n) - 1))  /* n is power of 2 */
80#define min(x,y)  (((x) < (y)) ? (x) : (y))
81
82
83/* Create a new a.out file, same as old but with current data space */
84
85unexec (new_name, old_name, new_end_of_text, dummy1, dummy2)
86     char new_name[];		/* name of the new a.out file to be created */
87     char old_name[];		/* name of the old a.out file */
88     char *new_end_of_text;	/* ptr to new edata/etext; NOT USED YET */
89     int dummy1, dummy2;	/* not used by emacs */
90{
91  int old, new;
92  int old_size, new_size;
93  struct header hdr;
94  struct som_exec_auxhdr auxhdr;
95  long i;
96
97  /* For the greatest flexibility, should create a temporary file in
98     the same directory as the new file.  When everything is complete,
99     rename the temp file to the new name.
100     This way, a program could update its own a.out file even while
101     it is still executing.  If problems occur, everything is still
102     intact.  NOT implemented.  */
103
104  /* Open the input and output a.out files */
105  old = open (old_name, O_RDONLY);
106  if (old < 0)
107    { perror (old_name); exit (1); }
108  new = open (new_name, O_CREAT|O_RDWR|O_TRUNC, 0777);
109  if (new < 0)
110    { perror (new_name); exit (1); }
111
112  /* Read the old headers */
113  read_header (old, &hdr, &auxhdr);
114
115  brk_on_dump = (long) sbrk (0);
116
117  /* Decide how large the new and old data areas are */
118  old_size = auxhdr.exec_dsize;
119  /* I suspect these two statements are separate
120     to avoid a compiler bug in hpux version 8.  */
121  i = (long) sbrk (0);
122  new_size = i - auxhdr.exec_dmem;
123
124  /* Copy the old file to the new, up to the data space */
125  lseek (old, 0, 0);
126  copy_file (old, new, auxhdr.exec_dfile);
127
128  /* Skip the old data segment and write a new one */
129  lseek (old, old_size, 1);
130  save_data_space (new, &hdr, &auxhdr, new_size);
131
132  /* Copy the rest of the file */
133  copy_rest (old, new);
134
135  /* Update file pointers since we probably changed size of data area */
136  update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
137
138  /* Save the modified header */
139  write_header (new, &hdr, &auxhdr);
140
141  /* Close the binary file */
142  close (old);
143  close (new);
144  return 0;
145}
146
147/* Save current data space in the file, update header.  */
148
149save_data_space (file, hdr, auxhdr, size)
150     int file;
151     struct header *hdr;
152     struct som_exec_auxhdr *auxhdr;
153     int size;
154{
155  /* Write the entire data space out to the file */
156  if (write (file, auxhdr->exec_dmem, size) != size)
157    { perror ("Can't save new data space"); exit (1); }
158
159  /* Update the header to reflect the new data size */
160  auxhdr->exec_dsize = size;
161  auxhdr->exec_bsize = 0;
162}
163
164/* Update the values of file pointers when something is inserted.  */
165
166update_file_ptrs (file, hdr, auxhdr, location, offset)
167     int file;
168     struct header *hdr;
169     struct som_exec_auxhdr *auxhdr;
170     unsigned int location;
171     int offset;
172{
173  struct subspace_dictionary_record subspace;
174  int i;
175
176  /* Increase the overall size of the module */
177  hdr->som_length += offset;
178
179  /* Update the various file pointers in the header */
180#define update(ptr) if (ptr > location) ptr = ptr + offset
181  update (hdr->aux_header_location);
182  update (hdr->space_strings_location);
183  update (hdr->init_array_location);
184  update (hdr->compiler_location);
185  update (hdr->symbol_location);
186  update (hdr->fixup_request_location);
187  update (hdr->symbol_strings_location);
188  update (hdr->unloadable_sp_location);
189  update (auxhdr->exec_tfile);
190  update (auxhdr->exec_dfile);
191
192  /* Do for each subspace dictionary entry */
193  lseek (file, hdr->subspace_location, 0);
194  for (i = 0; i < hdr->subspace_total; i++)
195    {
196      if (read (file, &subspace, sizeof (subspace)) != sizeof (subspace))
197	{ perror ("Can't read subspace record"); exit (1); }
198
199      /* If subspace has a file location, update it */
200      if (subspace.initialization_length > 0
201	  && subspace.file_loc_init_value > location)
202	{
203	  subspace.file_loc_init_value += offset;
204	  lseek (file, -sizeof (subspace), 1);
205	  if (write (file, &subspace, sizeof (subspace)) != sizeof (subspace))
206	    { perror ("Can't update subspace record"); exit (1); }
207	}
208    }
209
210  /* Do for each initialization pointer record */
211  /* (I don't think it applies to executable files, only relocatables) */
212#undef update
213}
214
215/* Read in the header records from an a.out file.  */
216
217read_header (file, hdr, auxhdr)
218     int file;
219     struct header *hdr;
220     struct som_exec_auxhdr *auxhdr;
221{
222
223  /* Read the header in */
224  lseek (file, 0, 0);
225  if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
226    { perror ("Couldn't read header from a.out file"); exit (1); }
227
228  if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
229      &&  hdr->a_magic != DEMAND_MAGIC)
230    {
231      fprintf (stderr, "a.out file doesn't have legal magic number\n");
232      exit (1);
233    }
234
235  lseek (file, hdr->aux_header_location, 0);
236  if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
237    {
238      perror ("Couldn't read auxiliary header from a.out file");
239      exit (1);
240    }
241}
242
243/* Write out the header records into an a.out file.  */
244
245write_header (file, hdr, auxhdr)
246     int file;
247     struct header *hdr;
248     struct som_exec_auxhdr *auxhdr;
249{
250  /* Update the checksum */
251  hdr->checksum = calculate_checksum (hdr);
252
253  /* Write the header back into the a.out file */
254  lseek (file, 0, 0);
255  if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr))
256    { perror ("Couldn't write header to a.out file"); exit (1); }
257  lseek (file, hdr->aux_header_location, 0);
258  if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr))
259    { perror ("Couldn't write auxiliary header to a.out file"); exit (1); }
260}
261
262/* Calculate the checksum of a SOM header record. */
263
264calculate_checksum (hdr)
265     struct header *hdr;
266{
267  int checksum, i, *ptr;
268
269  checksum = 0;  ptr = (int *) hdr;
270
271  for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++)
272    checksum ^= ptr[i];
273
274  return (checksum);
275}
276
277/* Copy size bytes from the old file to the new one.  */
278
279copy_file (old, new, size)
280     int new, old;
281     int size;
282{
283  int len;
284  int buffer[8192];  /* word aligned will be faster */
285
286  for (; size > 0; size -= len)
287    {
288      len = min (size, sizeof (buffer));
289      if (read (old, buffer, len) != len)
290	{ perror ("Read failure on a.out file"); exit (1); }
291      if (write (new, buffer, len) != len)
292	{ perror ("Write failure in a.out file"); exit (1); }
293    }
294}
295
296/* Copy the rest of the file, up to EOF.  */
297
298copy_rest (old, new)
299     int new, old;
300{
301  int buffer[4096];
302  int len;
303
304  /* Copy bytes until end of file or error */
305  while ((len = read (old, buffer, sizeof (buffer))) > 0)
306    if (write (new, buffer, len) != len) break;
307
308  if (len != 0)
309    { perror ("Unable to copy the rest of the file"); exit (1); }
310}
311
312#ifdef	DEBUG
313display_header (hdr, auxhdr)
314     struct header *hdr;
315     struct som_exec_auxhdr *auxhdr;
316{
317  /* Display the header information (debug) */
318  printf ("\n\nFILE HEADER\n");
319  printf ("magic number %d \n", hdr->a_magic);
320  printf ("text loc %.8x   size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
321  printf ("data loc %.8x   size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
322  printf ("entry     %x \n",   auxhdr->exec_entry);
323  printf ("Bss  segment size %u\n", auxhdr->exec_bsize);
324  printf ("\n");
325  printf ("data file loc %d    size %d\n",
326	  auxhdr->exec_dfile, auxhdr->exec_dsize);
327  printf ("som_length %d\n", hdr->som_length);
328  printf ("unloadable sploc %d    size %d\n",
329	  hdr->unloadable_sp_location, hdr->unloadable_sp_size);
330}
331#endif /* DEBUG */
332
333/* arch-tag: d55a09ac-9427-4ec4-8496-cb9d7710774f
334   (do not change this comment) */
335