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[emacs.git] / src / unexsunos4.c
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1 /* Unexec for Sunos 4 using shared libraries.
2 Copyright (C) 1990, 1994 Free Software Foundation, Inc.
4 This file is part of GNU Emacs.
6 GNU Emacs is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
11 GNU Emacs is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU Emacs; see the file COPYING. If not, write to
18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* Contributed by Viktor Dukhovni. */
23 * Unexec for Berkeley a.out format + SUNOS shared libraries
24 * The unexeced executable contains the __DYNAMIC area from the
25 * original text file, and then the rest of data + bss + malloced area of
26 * the current process. (The __DYNAMIC area is at the top of the process
27 * data segment, we use "data_start" defined externally to mark the start
28 * of the "real" data segment.)
30 * For programs that want to remap some of the data segment read only
31 * a run_time_remap is provided. This attempts to remap largest area starting
32 * and ending on page boundaries between "data_start" and "bndry"
33 * For this it to figure out where the text file is located. A path search
34 * is attempted after trying argv[0] and if all fails we simply do not remap
36 * One feature of run_time_remap () is mandatory: reseting the break.
38 * Note that we can no longer map data into the text segment, as this causes
39 * the __DYNAMIC struct to become read only, breaking the runtime loader.
40 * Thus we no longer need to mess with a private crt0.c, the standard one
41 * will do just fine, since environ can live in the writable area between
42 * __DYNAMIC and data_start, just make sure that pre-crt0.o (the name
43 * is somewhat abused here) is loaded first!
46 #include <sys/param.h>
47 #include <sys/mman.h>
48 #include <sys/file.h>
49 #include <sys/stat.h>
50 #include <string.h>
51 #include <stdio.h>
52 #include <a.out.h>
54 /* Do this after the above #include's in case a configuration file wants
55 to define things for this file based on what <a.out.h> defines. */
56 #ifdef emacs
57 #include <config.h>
58 #endif
60 #if defined (SUNOS4) || defined (__FreeBSD__) || defined (__NetBSD__)
61 #define UNDO_RELOCATION
62 #endif
64 #ifdef UNDO_RELOCATION
65 #include <link.h>
66 #endif
68 #ifdef HAVE_UNISTD_H
69 #include <unistd.h>
70 #endif
72 /* NetBSD needs this bit, but SunOS does not have it. */
73 #ifndef MAP_FILE
74 #define MAP_FILE 0
75 #endif
79 * for programs other than emacs
80 * define data_start + initialized here, and make sure
81 * this object is loaded first!
82 * emacs will define these elsewhere, and load the object containing
83 * data_start (pre-crt0.o or firstfile.o?) first!
84 * The custom crt0.o *must not* be loaded!
86 #ifndef emacs
87 static int data_start = 0;
88 static int initialized = 0;
89 #else
90 extern int initialized;
91 extern unsigned data_start;
92 extern int pureptr;
93 #endif
95 extern char *getenv ();
96 static unsigned brk_value;
97 static struct exec nhdr;
98 static int rd_only_len;
99 static long cookie;
102 unexec (new_name, a_name, bndry, bss_start, entry)
103 char *new_name, *a_name;
104 unsigned bndry, bss_start, entry;
106 int fd, new;
107 char *old;
108 struct exec ohdr; /* Allocate on the stack, not needed in the next life */
109 struct stat stat;
111 if ((fd = open (a_name, O_RDONLY)) < 0)
113 fprintf (stderr, "%s: open: ", a_name);
114 perror (a_name);
115 exit (1);
117 if ((new = open (new_name, O_WRONLY | O_CREAT, 0666)) == -1)
119 fprintf (stderr, "%s: open: ", a_name);
120 perror (new_name);
121 exit (1);
124 if ((fstat (fd, &stat) == -1))
126 fprintf (stderr, "%s: ", a_name);
127 perror ("fstat");
128 exit (1);
131 old = (char *)mmap (0, stat.st_size, PROT_READ, MAP_FILE|MAP_SHARED, fd, 0);
132 if (old == (char *)-1)
134 fprintf (stderr, "%s: ", a_name);
135 perror ("mmap");
136 exit (1);
138 close (fd);
140 nhdr = ohdr = (*(struct exec *)old);
144 * Remember a magic cookie so we know we've got the right binary
145 * when remapping.
147 cookie = time (0);
149 /* Save the break, it is reset to &_end (by ld.so?). */
150 brk_value = (unsigned) sbrk (0);
153 * Round up data start to a page boundary (Lose if not a 2 power!)
155 data_start = ((((int)&data_start) - 1) & ~(N_PAGSIZ (nhdr) - 1)) + N_PAGSIZ (nhdr);
158 * Round down read only pages to a multiple of the page size
160 if (bndry)
161 rd_only_len = ((int)bndry & ~(N_PAGSIZ (nhdr) - 1)) - data_start;
163 #ifndef emacs
164 /* Have to do this some time before dumping the data */
165 initialized = 1;
166 #endif
168 /* Handle new data and bss sizes and optional new entry point.
169 No one actually uses bss_start and entry, but tradition compels
170 one to support them.
171 Could complain if bss_start > brk_value,
172 but the caller is *supposed* to know what she is doing. */
173 nhdr.a_data = (bss_start ? bss_start : brk_value) - N_DATADDR (nhdr);
174 nhdr.a_bss = bss_start ? brk_value - bss_start : 0;
175 if (entry)
176 nhdr.a_entry = entry;
179 * Write out the text segment with new header
180 * Dynamic executables are ZMAGIC with N_TXTOFF==0 and the header
181 * part of the text segment, but no need to rely on this.
182 * So write the TEXT first, then go back replace the header.
183 * Doing it in the other order is less general!
185 lseek (new, N_TXTOFF (nhdr), L_SET);
186 write (new, old + N_TXTOFF (ohdr), N_TXTOFF (ohdr) + ohdr.a_text);
187 lseek (new, 0L, L_SET);
188 write (new, &nhdr, sizeof (nhdr));
191 * Write out the head of the old data segment from the file not
192 * from core, this has the unresolved __DYNAMIC relocation data
193 * we need to reload
195 lseek (new, N_DATOFF (nhdr), L_SET);
196 write (new, old + N_DATOFF (ohdr), (int)&data_start - N_DATADDR (ohdr));
199 * Copy the rest of the data from core
201 write (new, &data_start, N_BSSADDR (nhdr) - (int)&data_start);
204 * Copy the symbol table and line numbers
206 lseek (new, N_TRELOFF (nhdr), L_SET);
207 write (new, old + N_TRELOFF (ohdr), stat.st_size - N_TRELOFF (ohdr));
209 /* Some other BSD systems use this file.
210 We don't know whether this change is right for them. */
211 #ifdef UNDO_RELOCATION
212 /* Undo the relocations done at startup by ld.so.
213 It will do these relocations again when we start the dumped Emacs.
214 Doing them twice gives incorrect results. */
216 unsigned long daddr = N_DATADDR (ohdr);
217 unsigned long rel, erel;
218 #ifdef SUNOS4
219 #ifdef SUNOS4_SHARED_LIBRARIES
220 extern struct link_dynamic _DYNAMIC;
222 /* SunOS4.x's ld_rel is relative to N_TXTADDR. */
223 if (!ohdr.a_dynamic)
224 /* This was statically linked. */
225 rel = erel = 0;
226 else if (_DYNAMIC.ld_version < 2)
228 rel = _DYNAMIC.ld_un.ld_1->ld_rel + N_TXTADDR (ohdr);
229 erel = _DYNAMIC.ld_un.ld_1->ld_hash + N_TXTADDR (ohdr);
231 else
233 rel = _DYNAMIC.ld_un.ld_2->ld_rel + N_TXTADDR (ohdr);
234 erel = _DYNAMIC.ld_un.ld_2->ld_hash + N_TXTADDR (ohdr);
236 #else /* not SUNOS4_SHARED_LIBRARIES */
237 rel = erel = 0;
238 #endif /* not SUNOS4_SHARED_LIBRARIES */
239 #ifdef sparc
240 #define REL_INFO_TYPE struct reloc_info_sparc
241 #else
242 #define REL_INFO_TYPE struct relocation_info
243 #endif /* sparc */
244 #define REL_TARGET_ADDRESS(r) (((REL_INFO_TYPE *)(r))->r_address)
245 #endif /* SUNOS4 */
246 #if defined (__FreeBSD__) || defined (__NetBSD__)
247 extern struct _dynamic _DYNAMIC;
249 /* FreeBSD's LD_REL is a virtual address itself. */
250 rel = LD_REL (&_DYNAMIC);
251 erel = rel + LD_RELSZ (&_DYNAMIC);
252 #define REL_INFO_TYPE struct relocation_info
253 #define REL_TARGET_ADDRESS(r) (((REL_INFO_TYPE *)(r))->r_address)
254 #endif
256 for (; rel < erel; rel += sizeof (REL_INFO_TYPE))
258 /* This is the virtual address where ld.so will do relocation. */
259 unsigned long target = REL_TARGET_ADDRESS (rel);
260 /* This is the offset in the data segment. */
261 unsigned long segoffset = target - daddr;
263 /* If it is located below data_start, we have to do nothing here,
264 because the old data has been already written to the location. */
265 if (target < (unsigned long)&data_start)
266 continue;
268 lseek (new, N_DATOFF (nhdr) + segoffset, L_SET);
269 write (new, old + N_DATOFF (ohdr) + segoffset, sizeof (unsigned long));
272 #endif /* UNDO_RELOCATION */
274 fchmod (new, 0755);
277 void
278 run_time_remap (progname)
279 char *progname;
281 char aout[MAXPATHLEN];
282 register char *path, *p;
284 /* Just in case */
285 if (!initialized)
286 return;
288 /* Restore the break */
289 brk ((char *) brk_value);
291 /* If nothing to remap: we are done! */
292 if (rd_only_len == 0)
293 return;
296 * Attempt to find the executable
297 * First try argv[0], will almost always succeed as shells tend to give
298 * the full path from the hash list rather than using execvp ()
300 if (is_it (progname))
301 return;
304 * If argv[0] is a full path and does not exist, not much sense in
305 * searching further
307 if (strchr (progname, '/'))
308 return;
311 * Try to search for argv[0] on the PATH
313 path = getenv ("PATH");
314 if (path == NULL)
315 return;
317 while (*path)
319 /* copy through ':' or end */
320 for (p = aout; *p = *path; ++p, ++path)
321 if (*p == ':')
323 ++path; /* move past ':' */
324 break;
326 *p++ = '/';
327 strcpy (p, progname);
329 * aout is a candidate full path name
331 if (is_it (aout))
332 return;
336 is_it (filename)
337 char *filename;
339 int fd;
340 long filenames_cookie;
341 struct exec hdr;
344 * Open an executable and check for a valid header!
345 * Can't bcmp the header with what we had, it may have been stripped!
346 * so we may save looking at non executables with the same name, mostly
347 * directories.
349 fd = open (filename, O_RDONLY);
350 if (fd != -1)
352 if (read (fd, &hdr, sizeof (hdr)) == sizeof (hdr)
353 && !N_BADMAG (hdr) && N_DATOFF (hdr) == N_DATOFF (nhdr)
354 && N_TRELOFF (hdr) == N_TRELOFF (nhdr))
356 /* compare cookies */
357 lseek (fd, N_DATOFF (hdr) + (int)&cookie - N_DATADDR (hdr), L_SET);
358 read (fd, &filenames_cookie, sizeof (filenames_cookie));
359 if (filenames_cookie == cookie)
360 { /* Eureka */
363 * Do the mapping
364 * The PROT_EXEC may not be needed, but it is safer this way.
365 * should the shared library decide to indirect through
366 * addresses in the data segment not part of __DYNAMIC
368 mmap ((char *) data_start, rd_only_len, PROT_READ | PROT_EXEC,
369 MAP_FILE | MAP_SHARED | MAP_FIXED, fd,
370 N_DATOFF (hdr) + data_start - N_DATADDR (hdr));
371 close (fd);
372 return 1;
375 close (fd);
377 return 0;