xref: /titanic_44/usr/src/cmd/sendmail/db/os/os_map.c (revision e1c679fa4b0ab8c4bcaa6263974ca0c46e5b027f)
1 /*-
2  * See the file LICENSE for redistribution information.
3  *
4  * Copyright (c) 1996, 1997, 1998
5  *	Sleepycat Software.  All rights reserved.
6  */
7 
8 #include "config.h"
9 
10 #ifndef lint
11 static const char sccsid[] = "@(#)os_map.c	10.24 (Sleepycat) 10/12/98";
12 #endif /* not lint */
13 
14 #ifndef NO_SYSTEM_INCLUDES
15 #include <sys/types.h>
16 #ifdef HAVE_MMAP
17 #include <sys/mman.h>
18 #endif
19 
20 #ifdef HAVE_SHMGET
21 #include <sys/ipc.h>
22 #include <sys/shm.h>
23 #endif
24 
25 #include <errno.h>
26 #include <string.h>
27 #endif
28 
29 #include "db_int.h"
30 #include "os_jump.h"
31 #include "common_ext.h"
32 
33 #ifdef HAVE_MMAP
34 static int __os_map __P((char *, int, size_t, int, int, int, void **));
35 #endif
36 #ifdef HAVE_SHMGET
37 static int __os_shmget __P((REGINFO *));
38 #endif
39 
40 /*
41  * __db_mapanon_ok --
42  *	Return if this OS can support anonymous memory regions.
43  *
44  * PUBLIC: int __db_mapanon_ok __P((int));
45  */
46 int
47 __db_mapanon_ok(need_names)
48 	int need_names;
49 {
50 	int ret;
51 
52 	ret = EINVAL;
53 
54 	/*
55 	 * If we don't have spinlocks, we have to have a file descriptor
56 	 * for fcntl(2) locking, which implies using mmap(2) to map in a
57 	 * regular file.  Theoretically, we could probably find ways to
58 	 * get a file descriptor to lock other types of shared regions,
59 	 * but I don't see any reason to do so.
60 	 *
61 	 * If need_names is set, the application wants to share anonymous
62 	 * memory among multiple processes, so we have to have a way to
63 	 * name it.  This requires shmget(2), on UNIX systems.
64 	 */
65 #ifdef HAVE_SPINLOCKS
66 #ifdef HAVE_SHMGET
67 	ret = 0;
68 #endif
69 #ifdef HAVE_MMAP
70 #ifdef MAP_ANON
71 	if (!need_names)
72 		ret = 0;
73 #endif
74 #ifdef MAP_ANONYMOUS
75 	if (!need_names)
76 		ret = 0;
77 #endif
78 #else
79 	COMPQUIET(need_names, 0);
80 #endif /* HAVE_MMAP */
81 #endif /* HAVE_SPINLOCKS */
82 
83 	return (ret);
84 }
85 
86 /*
87  * __db_mapinit --
88  *	Return if shared regions need to be initialized.
89  *
90  * PUBLIC: int __db_mapinit __P((void));
91  */
92 int
93 __db_mapinit()
94 {
95 	/*
96 	 * Historically, some systems required that all of the bytes of the
97 	 * region be written before it could be mmapped and accessed randomly.
98 	 * We have the option of setting REGION_INIT_NEEDED at configuration
99 	 * time if we're running on one of those systems.
100 	 */
101 #ifdef REGION_INIT_NEEDED
102 	return (1);
103 #else
104 	return (0);
105 #endif
106 }
107 
108 /*
109  * __db_mapregion --
110  *	Attach to a shared memory region.
111  *
112  * PUBLIC: int __db_mapregion __P((char *, REGINFO *));
113  */
114 int
115 __db_mapregion(path, infop)
116 	char *path;
117 	REGINFO *infop;
118 {
119 	int called, ret;
120 
121 	called = 0;
122 	ret = EINVAL;
123 
124 	/* If the user replaces the map call, call through their interface. */
125 	if (__db_jump.j_map != NULL) {
126 		F_SET(infop, REGION_HOLDINGSYS);
127 		return (__db_jump.j_map(path, infop->fd, infop->size,
128 		    1, F_ISSET(infop, REGION_ANONYMOUS), 0, &infop->addr));
129 	}
130 
131 	if (F_ISSET(infop, REGION_ANONYMOUS)) {
132 		/*
133 		 * !!!
134 		 * If we're creating anonymous regions:
135 		 *
136 		 * If it's private, we use mmap(2).  The problem with using
137 		 * shmget(2) is that we may be creating a region of which the
138 		 * application isn't aware, and if the application crashes
139 		 * we'll have no way to remove the system resources for the
140 		 * region.
141 		 *
142 		 * If it's not private, we use the shmget(2) interface if it's
143 		 * available, because it allows us to name anonymous memory.
144 		 * If shmget(2) isn't available, use the mmap(2) calls.
145 		 *
146 		 * In the case of anonymous memory, using mmap(2) means the
147 		 * memory isn't named and only the single process and its
148 		 * threads can access the region.
149 		 */
150 #ifdef	HAVE_MMAP
151 #ifdef	MAP_ANON
152 #define	HAVE_MMAP_ANONYMOUS	1
153 #else
154 #ifdef	MAP_ANONYMOUS
155 #define	HAVE_MMAP_ANONYMOUS	1
156 #endif
157 #endif
158 #endif
159 #ifdef HAVE_MMAP_ANONYMOUS
160 		if (!called && F_ISSET(infop, REGION_PRIVATE)) {
161 			called = 1;
162 			ret = __os_map(path,
163 			    infop->fd, infop->size, 1, 1, 0, &infop->addr);
164 		}
165 #endif
166 #ifdef HAVE_SHMGET
167 		if (!called) {
168 			called = 1;
169 			ret = __os_shmget(infop);
170 		}
171 #endif
172 #ifdef HAVE_MMAP
173 		/*
174 		 * If we're trying to join an unnamed anonymous region, fail --
175 		 * that's not possible.
176 		 */
177 		if (!called) {
178 			called = 1;
179 
180 			if (!F_ISSET(infop, REGION_CREATED)) {
181 				__db_err(infop->dbenv,
182 			    "cannot join region in unnamed anonymous memory");
183 				return (EINVAL);
184 			}
185 
186 			ret = __os_map(path,
187 			    infop->fd, infop->size, 1, 1, 0, &infop->addr);
188 		}
189 #endif
190 	} else {
191 		/*
192 		 * !!!
193 		 * If we're creating normal regions, we use the mmap(2)
194 		 * interface if it's available because it's POSIX 1003.1
195 		 * standard and we trust it more than we do shmget(2).
196 		 */
197 #ifdef HAVE_MMAP
198 		if (!called) {
199 			called = 1;
200 
201 			/* Mmap(2) regions that aren't anonymous can grow. */
202 			F_SET(infop, REGION_CANGROW);
203 
204 			ret = __os_map(path,
205 			    infop->fd, infop->size, 1, 0, 0, &infop->addr);
206 		}
207 #endif
208 #ifdef HAVE_SHMGET
209 		if (!called) {
210 			called = 1;
211 			ret = __os_shmget(infop);
212 		}
213 #endif
214 	}
215 	return (ret);
216 }
217 
218 /*
219  * __db_unmapregion --
220  *	Detach from the shared memory region.
221  *
222  * PUBLIC: int __db_unmapregion __P((REGINFO *));
223  */
224 int
225 __db_unmapregion(infop)
226 	REGINFO *infop;
227 {
228 	int called, ret;
229 
230 	called = 0;
231 	ret = EINVAL;
232 
233 	if (__db_jump.j_unmap != NULL)
234 		return (__db_jump.j_unmap(infop->addr, infop->size));
235 
236 #ifdef HAVE_SHMGET
237 	if (infop->segid != INVALID_SEGID) {
238 		called = 1;
239 		ret = shmdt(infop->addr) ? errno : 0;
240 	}
241 #endif
242 #ifdef HAVE_MMAP
243 	if (!called) {
244 		called = 1;
245 		ret = munmap(infop->addr, infop->size) ? errno : 0;
246 	}
247 #endif
248 	return (ret);
249 }
250 
251 /*
252  * __db_unlinkregion --
253  *	Remove the shared memory region.
254  *
255  * PUBLIC: int __db_unlinkregion __P((char *, REGINFO *));
256  */
257 int
258 __db_unlinkregion(name, infop)
259 	char *name;
260 	REGINFO *infop;
261 {
262 	int called, ret;
263 
264 	called = 0;
265 	ret = EINVAL;
266 
267 	if (__db_jump.j_runlink != NULL)
268 		return (__db_jump.j_runlink(name));
269 
270 #ifdef HAVE_SHMGET
271 	if (infop->segid != INVALID_SEGID) {
272 		called = 1;
273 		ret = shmctl(infop->segid, IPC_RMID, NULL) ? errno : 0;
274 	}
275 #endif
276 #ifdef HAVE_MMAP
277 	COMPQUIET(infop, NULL);
278 	if (!called) {
279 		called = 1;
280 		ret = 0;
281 	}
282 #endif
283 	return (ret);
284 }
285 
286 /*
287  * __db_mapfile --
288  *	Map in a shared memory file.
289  *
290  * PUBLIC: int __db_mapfile __P((char *, int, size_t, int, void **));
291  */
292 int
293 __db_mapfile(path, fd, len, is_rdonly, addr)
294 	char *path;
295 	int fd, is_rdonly;
296 	size_t len;
297 	void **addr;
298 {
299 	if (__db_jump.j_map != NULL)
300 		return (__db_jump.j_map(path, fd, len, 0, 0, is_rdonly, addr));
301 
302 #ifdef HAVE_MMAP
303 	return (__os_map(path, fd, len, 0, 0, is_rdonly, addr));
304 #else
305 	return (EINVAL);
306 #endif
307 }
308 
309 /*
310  * __db_unmapfile --
311  *	Unmap the shared memory file.
312  *
313  * PUBLIC: int __db_unmapfile __P((void *, size_t));
314  */
315 int
316 __db_unmapfile(addr, len)
317 	void *addr;
318 	size_t len;
319 {
320 	if (__db_jump.j_unmap != NULL)
321 		return (__db_jump.j_unmap(addr, len));
322 
323 #ifdef HAVE_MMAP
324 	return (munmap(addr, len) ? errno : 0);
325 #else
326 	return (EINVAL);
327 #endif
328 }
329 
330 #ifdef HAVE_MMAP
331 /*
332  * __os_map --
333  *	Call the mmap(2) function.
334  */
335 static int
336 __os_map(path, fd, len, is_region, is_anonymous, is_rdonly, addr)
337 	char *path;
338 	int fd, is_region, is_anonymous, is_rdonly;
339 	size_t len;
340 	void **addr;
341 {
342 	void *p;
343 	int flags, prot;
344 
345 	COMPQUIET(path, NULL);
346 
347 	/*
348 	 * If it's read-only, it's private, and if it's not, it's shared.
349 	 * Don't bother with an additional parameter.
350 	 */
351 	flags = is_rdonly ? MAP_PRIVATE : MAP_SHARED;
352 
353 	if (is_region && is_anonymous) {
354 		/*
355 		 * BSD derived systems use MAP_ANON; Digital Unix and HP/UX
356 		 * use MAP_ANONYMOUS.
357 		 */
358 #ifdef MAP_ANON
359 		flags |= MAP_ANON;
360 #endif
361 #ifdef MAP_ANONYMOUS
362 		flags |= MAP_ANONYMOUS;
363 #endif
364 		fd = -1;
365 	}
366 #ifdef MAP_FILE
367 	if (!is_region || !is_anonymous) {
368 		/*
369 		 * Historically, MAP_FILE was required for mapping regular
370 		 * files, even though it was the default.  Some systems have
371 		 * it, some don't, some that have it set it to 0.
372 		 */
373 		flags |= MAP_FILE;
374 	}
375 #endif
376 
377 	/*
378 	 * I know of no systems that implement the flag to tell the system
379 	 * that the region contains semaphores, but it's not an unreasonable
380 	 * thing to do, and has been part of the design since forever.  I
381 	 * don't think anyone will object, but don't set it for read-only
382 	 * files, it doesn't make sense.
383 	 */
384 #ifdef MAP_HASSEMAPHORE
385 	if (!is_rdonly)
386 		flags |= MAP_HASSEMAPHORE;
387 #endif
388 
389 	prot = PROT_READ | (is_rdonly ? 0 : PROT_WRITE);
390 
391 /*
392  * XXX
393  * Work around a bug in the VMS V7.1 mmap() implementation.  To map a file
394  * into memory on VMS it needs to be opened in a certain way, originally.
395  * To get the file opened in that certain way, the VMS mmap() closes the
396  * file and re-opens it.  When it does this, it doesn't flush any caches
397  * out to disk before closing.  The problem this causes us is that when the
398  * memory cache doesn't get written out, the file isn't big enough to match
399  * the memory chunk and the mmap() call fails.  This call to fsync() fixes
400  * the problem.  DEC thinks this isn't a bug because of language in XPG5
401  * discussing user responsibility for on-disk and in-memory synchronization.
402  */
403 #ifdef VMS
404 	if (__os_fsync(fd) == -1)
405 		return(errno);
406 #endif
407 
408 	/* MAP_FAILED was not defined in early mmap implementations. */
409 #ifndef MAP_FAILED
410 #define	MAP_FAILED	-1
411 #endif
412 	if ((p =
413 	    mmap(NULL, len, prot, flags, fd, (off_t)0)) == (void *)MAP_FAILED)
414 		return (errno);
415 
416 	*addr = p;
417 	return (0);
418 }
419 #endif
420 
421 #ifdef HAVE_SHMGET
422 /*
423  * __os_shmget --
424  *	Call the shmget(2) family of functions.
425  */
426 static int
427 __os_shmget(infop)
428 	REGINFO *infop;
429 {
430 	if (F_ISSET(infop, REGION_CREATED) &&
431 	   (infop->segid = shmget(0, infop->size, IPC_PRIVATE | 0600)) == -1)
432 		return (errno);
433 
434 	if ((infop->addr = shmat(infop->segid, NULL, 0)) == (void *)-1) {
435 		/*
436 		 * If we're trying to join the region and failing, assume
437 		 * that there was a reboot and the region no longer exists.
438 		 */
439 		if (!F_ISSET(infop, REGION_CREATED))
440 			errno = EAGAIN;
441 		return (errno);
442 	}
443 
444 	F_SET(infop, REGION_HOLDINGSYS);
445 	return (0);
446 }
447 #endif
448