FreeBSD/Linux Kernel Cross Reference
sys/vm/memguard.c
1 /*-
2 * Copyright (c) 2005, Bosko Milekic <bmilekic@FreeBSD.org>.
3 * Copyright (c) 2010 Isilon Systems, Inc. (http://www.isilon.com/)
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice unmodified, this list of conditions, and the following
11 * disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
30
31 /*
32 * MemGuard is a simple replacement allocator for debugging only
33 * which provides ElectricFence-style memory barrier protection on
34 * objects being allocated, and is used to detect tampering-after-free
35 * scenarios.
36 *
37 * See the memguard(9) man page for more information on using MemGuard.
38 */
39
40 #include "opt_vm.h"
41
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
45 #include <sys/types.h>
46 #include <sys/queue.h>
47 #include <sys/lock.h>
48 #include <sys/mutex.h>
49 #include <sys/malloc.h>
50 #include <sys/sysctl.h>
51 #include <sys/vmem.h>
52 #include <sys/vmmeter.h>
53
54 #include <vm/vm.h>
55 #include <vm/uma.h>
56 #include <vm/vm_param.h>
57 #include <vm/vm_page.h>
58 #include <vm/vm_map.h>
59 #include <vm/vm_object.h>
60 #include <vm/vm_kern.h>
61 #include <vm/vm_extern.h>
62 #include <vm/uma_int.h>
63 #include <vm/memguard.h>
64
65 static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data");
66 /*
67 * The vm_memguard_divisor variable controls how much of kmem_map should be
68 * reserved for MemGuard.
69 */
70 static u_int vm_memguard_divisor;
71 SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
72 &vm_memguard_divisor,
73 0, "(kmem_size/memguard_divisor) == memguard submap size");
74
75 /*
76 * Short description (ks_shortdesc) of memory type to monitor.
77 */
78 static char vm_memguard_desc[128] = "";
79 static struct malloc_type *vm_memguard_mtype = NULL;
80 TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc));
81 static int
82 memguard_sysctl_desc(SYSCTL_HANDLER_ARGS)
83 {
84 char desc[sizeof(vm_memguard_desc)];
85 int error;
86
87 strlcpy(desc, vm_memguard_desc, sizeof(desc));
88 error = sysctl_handle_string(oidp, desc, sizeof(desc), req);
89 if (error != 0 || req->newptr == NULL)
90 return (error);
91
92 mtx_lock(&malloc_mtx);
93 /* If mtp is NULL, it will be initialized in memguard_cmp() */
94 vm_memguard_mtype = malloc_desc2type(desc);
95 strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc));
96 mtx_unlock(&malloc_mtx);
97 return (error);
98 }
99 SYSCTL_PROC(_vm_memguard, OID_AUTO, desc,
100 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
101 memguard_sysctl_desc, "A", "Short description of memory type to monitor");
102
103 static vm_offset_t memguard_cursor;
104 static vm_offset_t memguard_base;
105 static vm_size_t memguard_mapsize;
106 static vm_size_t memguard_physlimit;
107 static u_long memguard_wasted;
108 static u_long memguard_wrap;
109 static u_long memguard_succ;
110 static u_long memguard_fail_kva;
111 static u_long memguard_fail_pgs;
112
113 SYSCTL_ULONG(_vm_memguard, OID_AUTO, cursor, CTLFLAG_RD,
114 &memguard_cursor, 0, "MemGuard cursor");
115 SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD,
116 &memguard_mapsize, 0, "MemGuard private arena size");
117 SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD,
118 &memguard_physlimit, 0, "Limit on MemGuard memory consumption");
119 SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD,
120 &memguard_wasted, 0, "Excess memory used through page promotion");
121 SYSCTL_ULONG(_vm_memguard, OID_AUTO, wrapcnt, CTLFLAG_RD,
122 &memguard_wrap, 0, "MemGuard cursor wrap count");
123 SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD,
124 &memguard_succ, 0, "Count of successful MemGuard allocations");
125 SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD,
126 &memguard_fail_kva, 0, "MemGuard failures due to lack of KVA");
127 SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD,
128 &memguard_fail_pgs, 0, "MemGuard failures due to lack of pages");
129
130 #define MG_GUARD_AROUND 0x001
131 #define MG_GUARD_ALLLARGE 0x002
132 #define MG_GUARD_NOFREE 0x004
133 static int memguard_options = MG_GUARD_AROUND;
134 SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RWTUN,
135 &memguard_options, 0,
136 "MemGuard options:\n"
137 "\t0x001 - add guard pages around each allocation\n"
138 "\t0x002 - always use MemGuard for allocations over a page\n"
139 "\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag");
140
141 static u_int memguard_minsize;
142 static u_long memguard_minsize_reject;
143 SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW,
144 &memguard_minsize, 0, "Minimum size for page promotion");
145 SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD,
146 &memguard_minsize_reject, 0, "# times rejected for size");
147
148 static u_int memguard_frequency;
149 static u_long memguard_frequency_hits;
150 SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RWTUN,
151 &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run");
152 SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD,
153 &memguard_frequency_hits, 0, "# times MemGuard randomly chose");
154
155
156 /*
157 * Return a fudged value to be used for vm_kmem_size for allocating
158 * the kmem_map. The memguard memory will be a submap.
159 */
160 unsigned long
161 memguard_fudge(unsigned long km_size, const struct vm_map *parent_map)
162 {
163 u_long mem_pgs, parent_size;
164
165 vm_memguard_divisor = 10;
166 /* CTFLAG_RDTUN doesn't work during the early boot process. */
167 TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor);
168
169 parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) +
170 PAGE_SIZE;
171 /* Pick a conservative value if provided value sucks. */
172 if ((vm_memguard_divisor <= 0) ||
173 ((parent_size / vm_memguard_divisor) == 0))
174 vm_memguard_divisor = 10;
175 /*
176 * Limit consumption of physical pages to
177 * 1/vm_memguard_divisor of system memory. If the KVA is
178 * smaller than this then the KVA limit comes into play first.
179 * This prevents memguard's page promotions from completely
180 * using up memory, since most malloc(9) calls are sub-page.
181 */
182 mem_pgs = vm_cnt.v_page_count;
183 memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE;
184 /*
185 * We want as much KVA as we can take safely. Use at most our
186 * allotted fraction of the parent map's size. Limit this to
187 * twice the physical memory to avoid using too much memory as
188 * pagetable pages (size must be multiple of PAGE_SIZE).
189 */
190 memguard_mapsize = round_page(parent_size / vm_memguard_divisor);
191 if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs)
192 memguard_mapsize = mem_pgs * 2 * PAGE_SIZE;
193 if (km_size + memguard_mapsize > parent_size)
194 memguard_mapsize = 0;
195 return (km_size + memguard_mapsize);
196 }
197
198 /*
199 * Initialize the MemGuard mock allocator. All objects from MemGuard come
200 * out of a single VM map (contiguous chunk of address space).
201 */
202 void
203 memguard_init(vmem_t *parent)
204 {
205 vm_offset_t base;
206
207 vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base);
208 vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize,
209 PAGE_SIZE, 0, M_WAITOK);
210 memguard_cursor = base;
211 memguard_base = base;
212
213 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
214 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base);
215 printf("\tMEMGUARD map size: %jd KBytes\n",
216 (uintmax_t)memguard_mapsize >> 10);
217 }
218
219 /*
220 * Run things that can't be done as early as memguard_init().
221 */
222 static void
223 memguard_sysinit(void)
224 {
225 struct sysctl_oid_list *parent;
226
227 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard);
228
229 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "mapstart", CTLFLAG_RD,
230 &memguard_base, "MemGuard KVA base");
231 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "maplimit", CTLFLAG_RD,
232 &memguard_mapsize, "MemGuard KVA size");
233 #if 0
234 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD,
235 &memguard_map->size, "MemGuard KVA used");
236 #endif
237 }
238 SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL);
239
240 /*
241 * v2sizep() converts a virtual address of the first page allocated for
242 * an item to a pointer to u_long recording the size of the original
243 * allocation request.
244 *
245 * This routine is very similar to those defined by UMA in uma_int.h.
246 * The difference is that this routine stores the originally allocated
247 * size in one of the page's fields that is unused when the page is
248 * wired rather than the object field, which is used.
249 */
250 static u_long *
251 v2sizep(vm_offset_t va)
252 {
253 vm_paddr_t pa;
254 struct vm_page *p;
255
256 pa = pmap_kextract(va);
257 if (pa == 0)
258 panic("MemGuard detected double-free of %p", (void *)va);
259 p = PHYS_TO_VM_PAGE(pa);
260 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
261 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
262 return (&p->plinks.memguard.p);
263 }
264
265 static u_long *
266 v2sizev(vm_offset_t va)
267 {
268 vm_paddr_t pa;
269 struct vm_page *p;
270
271 pa = pmap_kextract(va);
272 if (pa == 0)
273 panic("MemGuard detected double-free of %p", (void *)va);
274 p = PHYS_TO_VM_PAGE(pa);
275 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
276 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
277 return (&p->plinks.memguard.v);
278 }
279
280 /*
281 * Allocate a single object of specified size with specified flags
282 * (either M_WAITOK or M_NOWAIT).
283 */
284 void *
285 memguard_alloc(unsigned long req_size, int flags)
286 {
287 vm_offset_t addr, origaddr;
288 u_long size_p, size_v;
289 int do_guard, rv;
290
291 size_p = round_page(req_size);
292 if (size_p == 0)
293 return (NULL);
294 /*
295 * To ensure there are holes on both sides of the allocation,
296 * request 2 extra pages of KVA. We will only actually add a
297 * vm_map_entry and get pages for the original request. Save
298 * the value of memguard_options so we have a consistent
299 * value.
300 */
301 size_v = size_p;
302 do_guard = (memguard_options & MG_GUARD_AROUND) != 0;
303 if (do_guard)
304 size_v += 2 * PAGE_SIZE;
305
306 /*
307 * When we pass our memory limit, reject sub-page allocations.
308 * Page-size and larger allocations will use the same amount
309 * of physical memory whether we allocate or hand off to
310 * uma_large_alloc(), so keep those.
311 */
312 if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit &&
313 req_size < PAGE_SIZE) {
314 addr = (vm_offset_t)NULL;
315 memguard_fail_pgs++;
316 goto out;
317 }
318 /*
319 * Keep a moving cursor so we don't recycle KVA as long as
320 * possible. It's not perfect, since we don't know in what
321 * order previous allocations will be free'd, but it's simple
322 * and fast, and requires O(1) additional storage if guard
323 * pages are not used.
324 *
325 * XXX This scheme will lead to greater fragmentation of the
326 * map, unless vm_map_findspace() is tweaked.
327 */
328 for (;;) {
329 if (vmem_xalloc(memguard_arena, size_v, 0, 0, 0,
330 memguard_cursor, VMEM_ADDR_MAX,
331 M_BESTFIT | M_NOWAIT, &origaddr) == 0)
332 break;
333 /*
334 * The map has no space. This may be due to
335 * fragmentation, or because the cursor is near the
336 * end of the map.
337 */
338 if (memguard_cursor == memguard_base) {
339 memguard_fail_kva++;
340 addr = (vm_offset_t)NULL;
341 goto out;
342 }
343 memguard_wrap++;
344 memguard_cursor = memguard_base;
345 }
346 addr = origaddr;
347 if (do_guard)
348 addr += PAGE_SIZE;
349 rv = kmem_back(kmem_object, addr, size_p, flags);
350 if (rv != KERN_SUCCESS) {
351 vmem_xfree(memguard_arena, origaddr, size_v);
352 memguard_fail_pgs++;
353 addr = (vm_offset_t)NULL;
354 goto out;
355 }
356 memguard_cursor = addr + size_v;
357 *v2sizep(trunc_page(addr)) = req_size;
358 *v2sizev(trunc_page(addr)) = size_v;
359 memguard_succ++;
360 if (req_size < PAGE_SIZE) {
361 memguard_wasted += (PAGE_SIZE - req_size);
362 if (do_guard) {
363 /*
364 * Align the request to 16 bytes, and return
365 * an address near the end of the page, to
366 * better detect array overrun.
367 */
368 req_size = roundup2(req_size, 16);
369 addr += (PAGE_SIZE - req_size);
370 }
371 }
372 out:
373 return ((void *)addr);
374 }
375
376 int
377 is_memguard_addr(void *addr)
378 {
379 vm_offset_t a = (vm_offset_t)(uintptr_t)addr;
380
381 return (a >= memguard_base && a < memguard_base + memguard_mapsize);
382 }
383
384 /*
385 * Free specified single object.
386 */
387 void
388 memguard_free(void *ptr)
389 {
390 vm_offset_t addr;
391 u_long req_size, size, sizev;
392 char *temp;
393 int i;
394
395 addr = trunc_page((uintptr_t)ptr);
396 req_size = *v2sizep(addr);
397 sizev = *v2sizev(addr);
398 size = round_page(req_size);
399
400 /*
401 * Page should not be guarded right now, so force a write.
402 * The purpose of this is to increase the likelihood of
403 * catching a double-free, but not necessarily a
404 * tamper-after-free (the second thread freeing might not
405 * write before freeing, so this forces it to and,
406 * subsequently, trigger a fault).
407 */
408 temp = ptr;
409 for (i = 0; i < size; i += PAGE_SIZE)
410 temp[i] = 'M';
411
412 /*
413 * This requires carnal knowledge of the implementation of
414 * kmem_free(), but since we've already replaced kmem_malloc()
415 * above, it's not really any worse. We want to use the
416 * vm_map lock to serialize updates to memguard_wasted, since
417 * we had the lock at increment.
418 */
419 kmem_unback(kmem_object, addr, size);
420 if (sizev > size)
421 addr -= PAGE_SIZE;
422 vmem_xfree(memguard_arena, addr, sizev);
423 if (req_size < PAGE_SIZE)
424 memguard_wasted -= (PAGE_SIZE - req_size);
425 }
426
427 /*
428 * Re-allocate an allocation that was originally guarded.
429 */
430 void *
431 memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp,
432 int flags)
433 {
434 void *newaddr;
435 u_long old_size;
436
437 /*
438 * Allocate the new block. Force the allocation to be guarded
439 * as the original may have been guarded through random
440 * chance, and that should be preserved.
441 */
442 if ((newaddr = memguard_alloc(size, flags)) == NULL)
443 return (NULL);
444
445 /* Copy over original contents. */
446 old_size = *v2sizep(trunc_page((uintptr_t)addr));
447 bcopy(addr, newaddr, min(size, old_size));
448 memguard_free(addr);
449 return (newaddr);
450 }
451
452 static int
453 memguard_cmp(unsigned long size)
454 {
455
456 if (size < memguard_minsize) {
457 memguard_minsize_reject++;
458 return (0);
459 }
460 if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE)
461 return (1);
462 if (memguard_frequency > 0 &&
463 (random() % 100000) < memguard_frequency) {
464 memguard_frequency_hits++;
465 return (1);
466 }
467
468 return (0);
469 }
470
471 int
472 memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size)
473 {
474
475 if (memguard_cmp(size))
476 return(1);
477
478 #if 1
479 /*
480 * The safest way of comparsion is to always compare short description
481 * string of memory type, but it is also the slowest way.
482 */
483 return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0);
484 #else
485 /*
486 * If we compare pointers, there are two possible problems:
487 * 1. Memory type was unloaded and new memory type was allocated at the
488 * same address.
489 * 2. Memory type was unloaded and loaded again, but allocated at a
490 * different address.
491 */
492 if (vm_memguard_mtype != NULL)
493 return (mtp == vm_memguard_mtype);
494 if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) {
495 vm_memguard_mtype = mtp;
496 return (1);
497 }
498 return (0);
499 #endif
500 }
501
502 int
503 memguard_cmp_zone(uma_zone_t zone)
504 {
505
506 if ((memguard_options & MG_GUARD_NOFREE) == 0 &&
507 zone->uz_flags & UMA_ZONE_NOFREE)
508 return (0);
509
510 if (memguard_cmp(zone->uz_size))
511 return (1);
512
513 /*
514 * The safest way of comparsion is to always compare zone name,
515 * but it is also the slowest way.
516 */
517 return (strcmp(zone->uz_name, vm_memguard_desc) == 0);
518 }
Cache object: 8d90758c9aa8d85a2fb7c2193cbff112
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