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:

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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: head/sys/vm/memguard.c 238502 2012-07-15 20:29:48Z mdf $");
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.

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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
52#include <vm/vm.h>
53#include <vm/uma.h>
54#include <vm/vm_param.h>
55#include <vm/vm_page.h>
56#include <vm/vm_map.h>
57#include <vm/vm_object.h>
58#include <vm/vm_extern.h>

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94 strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc));
95 mtx_unlock(&malloc_mtx);
96 return (error);
97}
98SYSCTL_PROC(_vm_memguard, OID_AUTO, desc,
99 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
100 memguard_sysctl_desc, "A", "Short description of memory type to monitor");
101
102static vm_map_t memguard_map = NULL;
103static vm_offset_t memguard_cursor;
104static vm_size_t memguard_mapsize;
105static vm_size_t memguard_physlimit;
106static u_long memguard_wasted;
107static u_long memguard_wrap;
108static u_long memguard_succ;
109static u_long memguard_fail_kva;
110static u_long memguard_fail_pgs;
111
112SYSCTL_ULONG(_vm_memguard, OID_AUTO, cursor, CTLFLAG_RD,
113 &memguard_cursor, 0, "MemGuard cursor");
114SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD,
115 &memguard_mapsize, 0, "MemGuard private vm_map size");
116SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD,
117 &memguard_physlimit, 0, "Limit on MemGuard memory consumption");
118SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD,
119 &memguard_wasted, 0, "Excess memory used through page promotion");
120SYSCTL_ULONG(_vm_memguard, OID_AUTO, wrapcnt, CTLFLAG_RD,
121 &memguard_wrap, 0, "MemGuard cursor wrap count");
122SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD,
123 &memguard_succ, 0, "Count of successful MemGuard allocations");

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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 */
202void
203memguard_init(vm_map_t parent_map)
204{
205 vm_offset_t base, limit;
206
207 memguard_map = kmem_suballoc(parent_map, &base, &limit,
208 memguard_mapsize, FALSE);
209 memguard_map->system_map = 1;
210 KASSERT(memguard_mapsize == limit - base,
211 ("Expected %lu, got %lu", (u_long)memguard_mapsize,
212 (u_long)(limit - base)));
213 memguard_cursor = base;
214
215 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
216 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base);
217 printf("\tMEMGUARD map limit: 0x%lx\n", (u_long)limit);
218 printf("\tMEMGUARD map size: %jd KBytes\n",
219 (uintmax_t)memguard_mapsize >> 10);
220}
221
222/*
223 * Run things that can't be done as early as memguard_init().
224 */
225static void
226memguard_sysinit(void)
227{
228 struct sysctl_oid_list *parent;
229
230 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard);
231
232 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapstart", CTLFLAG_RD,
233 &memguard_map->min_offset, "MemGuard KVA base");
234 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "maplimit", CTLFLAG_RD,
235 &memguard_map->max_offset, "MemGuard KVA end");
236 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD,
237 &memguard_map->size, "MemGuard KVA used");
238}
239SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL);
240
241/*
242 * v2sizep() converts a virtual address of the first page allocated for
243 * an item to a pointer to u_long recording the size of the original
244 * allocation request.
245 *

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258 if (pa == 0)
259 panic("MemGuard detected double-free of %p", (void *)va);
260 p = PHYS_TO_VM_PAGE(pa);
261 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
262 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
263 return ((u_long *)&p->pageq.tqe_next);
264}
265
266/*
267 * Allocate a single object of specified size with specified flags
268 * (either M_WAITOK or M_NOWAIT).
269 */
270void *
271memguard_alloc(unsigned long req_size, int flags)
272{
273 vm_offset_t addr;

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284 * the value of memguard_options so we have a consistent
285 * value.
286 */
287 size_v = size_p;
288 do_guard = (memguard_options & MG_GUARD_AROUND) != 0;
289 if (do_guard)
290 size_v += 2 * PAGE_SIZE;
291
292 vm_map_lock(memguard_map);
293 /*
294 * When we pass our memory limit, reject sub-page allocations.
295 * Page-size and larger allocations will use the same amount
296 * of physical memory whether we allocate or hand off to
297 * uma_large_alloc(), so keep those.
298 */
299 if (memguard_map->size >= memguard_physlimit &&
300 req_size < PAGE_SIZE) {
301 addr = (vm_offset_t)NULL;
302 memguard_fail_pgs++;
303 goto out;
304 }
305 /*
306 * Keep a moving cursor so we don't recycle KVA as long as
307 * possible. It's not perfect, since we don't know in what
308 * order previous allocations will be free'd, but it's simple
309 * and fast, and requires O(1) additional storage if guard
310 * pages are not used.
311 *
312 * XXX This scheme will lead to greater fragmentation of the
313 * map, unless vm_map_findspace() is tweaked.
314 */
315 for (;;) {
316 rv = vm_map_findspace(memguard_map, memguard_cursor,
317 size_v, &addr);
318 if (rv == KERN_SUCCESS)
319 break;
320 /*
321 * The map has no space. This may be due to
322 * fragmentation, or because the cursor is near the
323 * end of the map.
324 */
325 if (memguard_cursor == vm_map_min(memguard_map)) {
326 memguard_fail_kva++;
327 addr = (vm_offset_t)NULL;
328 goto out;
329 }
330 memguard_wrap++;
331 memguard_cursor = vm_map_min(memguard_map);
332 }
333 if (do_guard)
334 addr += PAGE_SIZE;
335 rv = kmem_back(memguard_map, addr, size_p, flags);
336 if (rv != KERN_SUCCESS) {
337 memguard_fail_pgs++;
338 addr = (vm_offset_t)NULL;
339 goto out;
340 }
341 memguard_cursor = addr + size_p;
342 *v2sizep(trunc_page(addr)) = req_size;
343 memguard_succ++;
344 if (req_size < PAGE_SIZE) {
345 memguard_wasted += (PAGE_SIZE - req_size);
346 if (do_guard) {
347 /*
348 * Align the request to 16 bytes, and return
349 * an address near the end of the page, to
350 * better detect array overrun.
351 */
352 req_size = roundup2(req_size, 16);
353 addr += (PAGE_SIZE - req_size);
354 }
355 }
356out:
357 vm_map_unlock(memguard_map);
358 return ((void *)addr);
359}
360
361int
362is_memguard_addr(void *addr)
363{
364 vm_offset_t a = (vm_offset_t)(uintptr_t)addr;
365
366 return (a >= memguard_map->min_offset && a < memguard_map->max_offset);
367}
368
369/*
370 * Free specified single object.
371 */
372void
373memguard_free(void *ptr)
374{
375 vm_offset_t addr;
376 u_long req_size, size;
377 char *temp;
378 int i;
379
380 addr = trunc_page((uintptr_t)ptr);
381 req_size = *v2sizep(addr);
382 size = round_page(req_size);
383
384 /*
385 * Page should not be guarded right now, so force a write.
386 * The purpose of this is to increase the likelihood of
387 * catching a double-free, but not necessarily a
388 * tamper-after-free (the second thread freeing might not
389 * write before freeing, so this forces it to and,

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395
396 /*
397 * This requires carnal knowledge of the implementation of
398 * kmem_free(), but since we've already replaced kmem_malloc()
399 * above, it's not really any worse. We want to use the
400 * vm_map lock to serialize updates to memguard_wasted, since
401 * we had the lock at increment.
402 */
403 vm_map_lock(memguard_map);
404 if (req_size < PAGE_SIZE)
405 memguard_wasted -= (PAGE_SIZE - req_size);
406 (void)vm_map_delete(memguard_map, addr, addr + size);
407 vm_map_unlock(memguard_map);
408}
409
410/*
411 * Re-allocate an allocation that was originally guarded.
412 */
413void *
414memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp,
415 int flags)

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