2 * Copyright (c) 2005, Bosko Milekic <bmilekic@FreeBSD.org>.
3 * Copyright (c) 2010 Isilon Systems, Inc. (http://www.isilon.com/)
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice unmodified, this list of conditions, and the following
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.
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.
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
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
37 * See the memguard(9) man page for more information on using MemGuard.
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>
48 #include <sys/mutex.h>
49 #include <sys/malloc.h>
50 #include <sys/sysctl.h>
55 #include <vm/vm_param.h>
56 #include <vm/vm_page.h>
57 #include <vm/vm_map.h>
58 #include <vm/vm_object.h>
59 #include <vm/vm_kern.h>
60 #include <vm/vm_extern.h>
61 #include <vm/uma_int.h>
62 #include <vm/memguard.h>
64 static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data");
66 * The vm_memguard_divisor variable controls how much of kmem_map should be
67 * reserved for MemGuard.
69 static u_int vm_memguard_divisor;
70 SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN,
72 0, "(kmem_size/memguard_divisor) == memguard submap size");
75 * Short description (ks_shortdesc) of memory type to monitor.
77 static char vm_memguard_desc[128] = "";
78 static struct malloc_type *vm_memguard_mtype = NULL;
79 TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc));
81 memguard_sysctl_desc(SYSCTL_HANDLER_ARGS)
83 char desc[sizeof(vm_memguard_desc)];
86 strlcpy(desc, vm_memguard_desc, sizeof(desc));
87 error = sysctl_handle_string(oidp, desc, sizeof(desc), req);
88 if (error != 0 || req->newptr == NULL)
91 mtx_lock(&malloc_mtx);
93 * If mtp is NULL, it will be initialized in memguard_cmp().
95 vm_memguard_mtype = malloc_desc2type(desc);
96 strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc));
97 mtx_unlock(&malloc_mtx);
100 SYSCTL_PROC(_vm_memguard, OID_AUTO, desc,
101 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
102 memguard_sysctl_desc, "A", "Short description of memory type to monitor");
104 static vm_offset_t memguard_cursor;
105 static vm_offset_t memguard_base;
106 static vm_size_t memguard_mapsize;
107 static vm_size_t memguard_physlimit;
108 static u_long memguard_wasted;
109 static u_long memguard_wrap;
110 static u_long memguard_succ;
111 static u_long memguard_fail_kva;
112 static u_long memguard_fail_pgs;
114 SYSCTL_ULONG(_vm_memguard, OID_AUTO, cursor, CTLFLAG_RD,
115 &memguard_cursor, 0, "MemGuard cursor");
116 SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD,
117 &memguard_mapsize, 0, "MemGuard private arena size");
118 SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD,
119 &memguard_physlimit, 0, "Limit on MemGuard memory consumption");
120 SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD,
121 &memguard_wasted, 0, "Excess memory used through page promotion");
122 SYSCTL_ULONG(_vm_memguard, OID_AUTO, wrapcnt, CTLFLAG_RD,
123 &memguard_wrap, 0, "MemGuard cursor wrap count");
124 SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD,
125 &memguard_succ, 0, "Count of successful MemGuard allocations");
126 SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD,
127 &memguard_fail_kva, 0, "MemGuard failures due to lack of KVA");
128 SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD,
129 &memguard_fail_pgs, 0, "MemGuard failures due to lack of pages");
131 #define MG_GUARD_AROUND 0x001
132 #define MG_GUARD_ALLLARGE 0x002
133 #define MG_GUARD_NOFREE 0x004
134 static int memguard_options = MG_GUARD_AROUND;
135 TUNABLE_INT("vm.memguard.options", &memguard_options);
136 SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RW,
137 &memguard_options, 0,
138 "MemGuard options:\n"
139 "\t0x001 - add guard pages around each allocation\n"
140 "\t0x002 - always use MemGuard for allocations over a page\n"
141 "\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag");
143 static u_int memguard_minsize;
144 static u_long memguard_minsize_reject;
145 SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW,
146 &memguard_minsize, 0, "Minimum size for page promotion");
147 SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD,
148 &memguard_minsize_reject, 0, "# times rejected for size");
150 static u_int memguard_frequency;
151 static u_long memguard_frequency_hits;
152 TUNABLE_INT("vm.memguard.frequency", &memguard_frequency);
153 SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RW,
154 &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run");
155 SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD,
156 &memguard_frequency_hits, 0, "# times MemGuard randomly chose");
160 * Return a fudged value to be used for vm_kmem_size for allocating
161 * the kmem_map. The memguard memory will be a submap.
164 memguard_fudge(unsigned long km_size, const struct vm_map *parent_map)
166 u_long mem_pgs, parent_size;
168 vm_memguard_divisor = 10;
169 TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor);
171 parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) +
173 /* Pick a conservative value if provided value sucks. */
174 if ((vm_memguard_divisor <= 0) ||
175 ((parent_size / vm_memguard_divisor) == 0))
176 vm_memguard_divisor = 10;
178 * Limit consumption of physical pages to
179 * 1/vm_memguard_divisor of system memory. If the KVA is
180 * smaller than this then the KVA limit comes into play first.
181 * This prevents memguard's page promotions from completely
182 * using up memory, since most malloc(9) calls are sub-page.
184 mem_pgs = cnt.v_page_count;
185 memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE;
187 * We want as much KVA as we can take safely. Use at most our
188 * allotted fraction of the parent map's size. Limit this to
189 * twice the physical memory to avoid using too much memory as
190 * pagetable pages (size must be multiple of PAGE_SIZE).
192 memguard_mapsize = round_page(parent_size / vm_memguard_divisor);
193 if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs)
194 memguard_mapsize = mem_pgs * 2 * PAGE_SIZE;
195 if (km_size + memguard_mapsize > parent_size)
196 memguard_mapsize = 0;
197 return (km_size + memguard_mapsize);
201 * Initialize the MemGuard mock allocator. All objects from MemGuard come
202 * out of a single VM map (contiguous chunk of address space).
205 memguard_init(vmem_t *parent)
209 vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base);
210 vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize,
211 PAGE_SIZE, 0, M_WAITOK);
212 memguard_cursor = base;
213 memguard_base = base;
215 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
216 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base);
217 printf("\tMEMGUARD map size: %jd KBytes\n",
218 (uintmax_t)memguard_mapsize >> 10);
222 * Run things that can't be done as early as memguard_init().
225 memguard_sysinit(void)
227 struct sysctl_oid_list *parent;
229 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard);
231 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapstart", CTLFLAG_RD,
232 &memguard_base, "MemGuard KVA base");
233 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "maplimit", CTLFLAG_RD,
234 &memguard_mapsize, "MemGuard KVA size");
236 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD,
237 &memguard_map->size, "MemGuard KVA used");
240 SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL);
243 * v2sizep() converts a virtual address of the first page allocated for
244 * an item to a pointer to u_long recording the size of the original
245 * allocation request.
247 * This routine is very similar to those defined by UMA in uma_int.h.
248 * The difference is that this routine stores the originally allocated
249 * size in one of the page's fields that is unused when the page is
250 * wired rather than the object field, which is used.
253 v2sizep(vm_offset_t va)
258 pa = pmap_kextract(va);
260 panic("MemGuard detected double-free of %p", (void *)va);
261 p = PHYS_TO_VM_PAGE(pa);
262 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
263 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
264 return (&p->plinks.memguard.p);
268 v2sizev(vm_offset_t va)
273 pa = pmap_kextract(va);
275 panic("MemGuard detected double-free of %p", (void *)va);
276 p = PHYS_TO_VM_PAGE(pa);
277 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
278 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
279 return (&p->plinks.memguard.v);
283 * Allocate a single object of specified size with specified flags
284 * (either M_WAITOK or M_NOWAIT).
287 memguard_alloc(unsigned long req_size, int flags)
290 u_long size_p, size_v;
293 size_p = round_page(req_size);
297 * To ensure there are holes on both sides of the allocation,
298 * request 2 extra pages of KVA. We will only actually add a
299 * vm_map_entry and get pages for the original request. Save
300 * the value of memguard_options so we have a consistent
304 do_guard = (memguard_options & MG_GUARD_AROUND) != 0;
306 size_v += 2 * PAGE_SIZE;
309 * When we pass our memory limit, reject sub-page allocations.
310 * Page-size and larger allocations will use the same amount
311 * of physical memory whether we allocate or hand off to
312 * uma_large_alloc(), so keep those.
314 if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit &&
315 req_size < PAGE_SIZE) {
316 addr = (vm_offset_t)NULL;
321 * Keep a moving cursor so we don't recycle KVA as long as
322 * possible. It's not perfect, since we don't know in what
323 * order previous allocations will be free'd, but it's simple
324 * and fast, and requires O(1) additional storage if guard
325 * pages are not used.
327 * XXX This scheme will lead to greater fragmentation of the
328 * map, unless vm_map_findspace() is tweaked.
331 if (vmem_xalloc(memguard_arena, size_v, 0, 0, 0,
332 memguard_cursor, VMEM_ADDR_MAX,
333 M_BESTFIT | M_NOWAIT, &addr) == 0)
336 * The map has no space. This may be due to
337 * fragmentation, or because the cursor is near the
340 if (memguard_cursor == memguard_base) {
342 addr = (vm_offset_t)NULL;
346 memguard_cursor = memguard_base;
350 rv = kmem_back(kmem_object, addr, size_p, flags);
351 if (rv != KERN_SUCCESS) {
352 vmem_xfree(memguard_arena, addr, size_v);
354 addr = (vm_offset_t)NULL;
357 memguard_cursor = addr + size_v;
358 *v2sizep(trunc_page(addr)) = req_size;
359 *v2sizev(trunc_page(addr)) = size_v;
361 if (req_size < PAGE_SIZE) {
362 memguard_wasted += (PAGE_SIZE - req_size);
365 * Align the request to 16 bytes, and return
366 * an address near the end of the page, to
367 * better detect array overrun.
369 req_size = roundup2(req_size, 16);
370 addr += (PAGE_SIZE - req_size);
374 return ((void *)addr);
378 is_memguard_addr(void *addr)
380 vm_offset_t a = (vm_offset_t)(uintptr_t)addr;
382 return (a >= memguard_base && a < memguard_base + memguard_mapsize);
386 * Free specified single object.
389 memguard_free(void *ptr)
392 u_long req_size, size, sizev;
396 addr = trunc_page((uintptr_t)ptr);
397 req_size = *v2sizep(addr);
398 sizev = *v2sizev(addr);
399 size = round_page(req_size);
402 * Page should not be guarded right now, so force a write.
403 * The purpose of this is to increase the likelihood of
404 * catching a double-free, but not necessarily a
405 * tamper-after-free (the second thread freeing might not
406 * write before freeing, so this forces it to and,
407 * subsequently, trigger a fault).
410 for (i = 0; i < size; i += PAGE_SIZE)
414 * This requires carnal knowledge of the implementation of
415 * kmem_free(), but since we've already replaced kmem_malloc()
416 * above, it's not really any worse. We want to use the
417 * vm_map lock to serialize updates to memguard_wasted, since
418 * we had the lock at increment.
420 kmem_unback(kmem_object, addr, size);
423 vmem_xfree(memguard_arena, addr, sizev);
424 if (req_size < PAGE_SIZE)
425 memguard_wasted -= (PAGE_SIZE - req_size);
429 * Re-allocate an allocation that was originally guarded.
432 memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp,
439 * Allocate the new block. Force the allocation to be guarded
440 * as the original may have been guarded through random
441 * chance, and that should be preserved.
443 if ((newaddr = memguard_alloc(size, flags)) == NULL)
446 /* Copy over original contents. */
447 old_size = *v2sizep(trunc_page((uintptr_t)addr));
448 bcopy(addr, newaddr, min(size, old_size));
454 memguard_cmp(unsigned long size)
457 if (size < memguard_minsize) {
458 memguard_minsize_reject++;
461 if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE)
463 if (memguard_frequency > 0 &&
464 (random() % 100000) < memguard_frequency) {
465 memguard_frequency_hits++;
473 memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size)
476 if (memguard_cmp(size))
481 * The safest way of comparsion is to always compare short description
482 * string of memory type, but it is also the slowest way.
484 return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0);
487 * If we compare pointers, there are two possible problems:
488 * 1. Memory type was unloaded and new memory type was allocated at the
490 * 2. Memory type was unloaded and loaded again, but allocated at a
493 if (vm_memguard_mtype != NULL)
494 return (mtp == vm_memguard_mtype);
495 if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) {
496 vm_memguard_mtype = mtp;
504 memguard_cmp_zone(uma_zone_t zone)
507 if ((memguard_options & MG_GUARD_NOFREE) == 0 &&
508 zone->uz_flags & UMA_ZONE_NOFREE)
511 if (memguard_cmp(zone->uz_size))
515 * The safest way of comparsion is to always compare zone name,
516 * but it is also the slowest way.
518 return (strcmp(zone->uz_name, vm_memguard_desc) == 0);