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freebsd/sys/vm/memguard.c

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/*
* Copyright (c) 2005,
* Bosko Milekic <bmilekic@FreeBSD.org>. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* MemGuard is a simple replacement allocator for debugging only
* which provides ElectricFence-style memory barrier protection on
* objects being allocated, and is used to detect tampering-after-free
* scenarios.
*
* See the memguard(9) man page for more information on using MemGuard.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/types.h>
#include <sys/queue.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/memguard.h>
/*
* The maximum number of pages allowed per allocation. If you're using
* MemGuard to override very large items (> MAX_PAGES_PER_ITEM in size),
* you need to increase MAX_PAGES_PER_ITEM.
*/
#define MAX_PAGES_PER_ITEM 64
SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data");
/*
* The vm_memguard_divisor variable controls how much of kmem_map should be
* reserved for MemGuard.
*/
u_int vm_memguard_divisor;
SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RD, &vm_memguard_divisor,
0, "(kmem_size/memguard_divisor) == memguard submap size");
/*
* Short description (ks_shortdesc) of memory type to monitor.
*/
static char vm_memguard_desc[128] = "";
static struct malloc_type *vm_memguard_mtype = NULL;
TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc));
static int
memguard_sysctl_desc(SYSCTL_HANDLER_ARGS)
{
struct malloc_type_internal *mtip;
struct malloc_type_stats *mtsp;
struct malloc_type *mtp;
char desc[128];
long bytes;
int error, i;
strlcpy(desc, vm_memguard_desc, sizeof(desc));
error = sysctl_handle_string(oidp, desc, sizeof(desc), req);
if (error != 0 || req->newptr == NULL)
return (error);
/*
* We can change memory type when no memory has been allocated for it
* or when there is no such memory type yet (ie. it will be loaded with
* kernel module).
*/
bytes = 0;
mtx_lock(&malloc_mtx);
mtp = malloc_desc2type(desc);
if (mtp != NULL) {
mtip = mtp->ks_handle;
for (i = 0; i < MAXCPU; i++) {
mtsp = &mtip->mti_stats[i];
bytes += mtsp->mts_memalloced;
bytes -= mtsp->mts_memfreed;
}
}
if (bytes > 0)
error = EBUSY;
else {
/*
* If mtp is NULL, it will be initialized in memguard_cmp().
*/
vm_memguard_mtype = mtp;
strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc));
}
mtx_unlock(&malloc_mtx);
return (error);
}
SYSCTL_PROC(_vm_memguard, OID_AUTO, desc, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
memguard_sysctl_desc, "A", "Short description of memory type to monitor");
/*
* Global MemGuard data.
*/
static vm_map_t memguard_map;
static unsigned long memguard_mapsize;
static unsigned long memguard_mapused;
struct memguard_entry {
STAILQ_ENTRY(memguard_entry) entries;
void *ptr;
};
static struct memguard_fifo {
struct memguard_entry *stqh_first;
struct memguard_entry **stqh_last;
int index;
} memguard_fifo_pool[MAX_PAGES_PER_ITEM];
/*
* Local prototypes.
*/
static void memguard_guard(void *addr, int numpgs);
static void memguard_unguard(void *addr, int numpgs);
static struct memguard_fifo *vtomgfifo(vm_offset_t va);
static void vsetmgfifo(vm_offset_t va, struct memguard_fifo *mgfifo);
static void vclrmgfifo(vm_offset_t va);
/*
* Local macros. MemGuard data is global, so replace these with whatever
* your system uses to protect global data (if it is kernel-level
* parallelized). This is for porting among BSDs.
*/
#define MEMGUARD_CRIT_SECTION_DECLARE static struct mtx memguard_mtx
#define MEMGUARD_CRIT_SECTION_INIT \
mtx_init(&memguard_mtx, "MemGuard mtx", NULL, MTX_DEF)
#define MEMGUARD_CRIT_SECTION_ENTER mtx_lock(&memguard_mtx)
#define MEMGUARD_CRIT_SECTION_EXIT mtx_unlock(&memguard_mtx)
MEMGUARD_CRIT_SECTION_DECLARE;
/*
* Initialize the MemGuard mock allocator. All objects from MemGuard come
* out of a single VM map (contiguous chunk of address space).
*/
void
memguard_init(vm_map_t parent_map, unsigned long size)
{
char *base, *limit;
int i;
/* size must be multiple of PAGE_SIZE */
size /= PAGE_SIZE;
size++;
size *= PAGE_SIZE;
memguard_map = kmem_suballoc(parent_map, (vm_offset_t *)&base,
(vm_offset_t *)&limit, (vm_size_t)size, FALSE);
memguard_map->system_map = 1;
memguard_mapsize = size;
memguard_mapused = 0;
MEMGUARD_CRIT_SECTION_INIT;
MEMGUARD_CRIT_SECTION_ENTER;
for (i = 0; i < MAX_PAGES_PER_ITEM; i++) {
STAILQ_INIT(&memguard_fifo_pool[i]);
memguard_fifo_pool[i].index = i;
}
MEMGUARD_CRIT_SECTION_EXIT;
printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
printf("\tMEMGUARD map base: %p\n", base);
printf("\tMEMGUARD map limit: %p\n", limit);
printf("\tMEMGUARD map size: %ld (Bytes)\n", size);
}
/*
* Allocate a single object of specified size with specified flags (either
* M_WAITOK or M_NOWAIT).
*/
void *
memguard_alloc(unsigned long size, int flags)
{
void *obj;
struct memguard_entry *e = NULL;
int numpgs;
numpgs = size / PAGE_SIZE;
if ((size % PAGE_SIZE) != 0)
numpgs++;
if (numpgs > MAX_PAGES_PER_ITEM)
panic("MEMGUARD: You must increase MAX_PAGES_PER_ITEM " \
"in memguard.c (requested: %d pages)", numpgs);
if (numpgs == 0)
return NULL;
/*
* If we haven't exhausted the memguard_map yet, allocate from
* it and grab a new page, even if we have recycled pages in our
* FIFO. This is because we wish to allow recycled pages to live
* guarded in the FIFO for as long as possible in order to catch
* even very late tamper-after-frees, even though it means that
* we end up wasting more memory, this is only a DEBUGGING allocator
* after all.
*/
MEMGUARD_CRIT_SECTION_ENTER;
if (memguard_mapused >= memguard_mapsize) {
e = STAILQ_FIRST(&memguard_fifo_pool[numpgs - 1]);
if (e != NULL) {
STAILQ_REMOVE(&memguard_fifo_pool[numpgs - 1], e,
memguard_entry, entries);
MEMGUARD_CRIT_SECTION_EXIT;
obj = e->ptr;
free(e, M_TEMP);
memguard_unguard(obj, numpgs);
if (flags & M_ZERO)
bzero(obj, PAGE_SIZE * numpgs);
return obj;
}
MEMGUARD_CRIT_SECTION_EXIT;
if (flags & M_WAITOK)
panic("MEMGUARD: Failed with M_WAITOK: " \
"memguard_map too small");
return NULL;
}
memguard_mapused += (PAGE_SIZE * numpgs);
MEMGUARD_CRIT_SECTION_EXIT;
obj = (void *)kmem_malloc(memguard_map, PAGE_SIZE * numpgs, flags);
if (obj != NULL) {
vsetmgfifo((vm_offset_t)obj, &memguard_fifo_pool[numpgs - 1]);
if (flags & M_ZERO)
bzero(obj, PAGE_SIZE * numpgs);
} else {
MEMGUARD_CRIT_SECTION_ENTER;
memguard_mapused -= (PAGE_SIZE * numpgs);
MEMGUARD_CRIT_SECTION_EXIT;
}
return obj;
}
/*
* Free specified single object.
*/
void
memguard_free(void *addr)
{
struct memguard_entry *e;
struct memguard_fifo *mgfifo;
int idx;
int *temp;
addr = (void *)trunc_page((unsigned long)addr);
/*
* Page should not be guarded by now, so force a write.
* The purpose of this is to increase the likelihood of catching a
* double-free, but not necessarily a tamper-after-free (the second
* thread freeing might not write before freeing, so this forces it
* to and, subsequently, trigger a fault).
*/
temp = (int *)((unsigned long)addr + (PAGE_SIZE/2)); /* in page */
*temp = 0xd34dc0d3;
mgfifo = vtomgfifo((vm_offset_t)addr);
idx = mgfifo->index;
memguard_guard(addr, idx + 1);
e = malloc(sizeof(struct memguard_entry), M_TEMP, M_NOWAIT);
if (e == NULL) {
MEMGUARD_CRIT_SECTION_ENTER;
memguard_mapused -= (PAGE_SIZE * (idx + 1));
MEMGUARD_CRIT_SECTION_EXIT;
memguard_unguard(addr, idx + 1); /* just in case */
vclrmgfifo((vm_offset_t)addr);
kmem_free(memguard_map, (vm_offset_t)addr,
PAGE_SIZE * (idx + 1));
return;
}
e->ptr = addr;
MEMGUARD_CRIT_SECTION_ENTER;
STAILQ_INSERT_TAIL(mgfifo, e, entries);
MEMGUARD_CRIT_SECTION_EXIT;
}
int
memguard_cmp(struct malloc_type *mtp)
{
#if 1
/*
* The safest way of comparsion is to always compare short description
* string of memory type, but it is also the slowest way.
*/
return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0);
#else
/*
* If we compare pointers, there are two possible problems:
* 1. Memory type was unloaded and new memory type was allocated at the
* same address.
* 2. Memory type was unloaded and loaded again, but allocated at a
* different address.
*/
if (vm_memguard_mtype != NULL)
return (mtp == vm_memguard_mtype);
if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) {
vm_memguard_mtype = mtp;
return (1);
}
return (0);
#endif
}
/*
* Guard a page containing specified object (make it read-only so that
* future writes to it fail).
*/
static void
memguard_guard(void *addr, int numpgs)
{
void *a = (void *)trunc_page((unsigned long)addr);
if (vm_map_protect(memguard_map, (vm_offset_t)a,
(vm_offset_t)((unsigned long)a + (PAGE_SIZE * numpgs)),
VM_PROT_READ, FALSE) != KERN_SUCCESS)
panic("MEMGUARD: Unable to guard page!");
}
/*
* Unguard a page containing specified object (make it read-and-write to
* allow full data access).
*/
static void
memguard_unguard(void *addr, int numpgs)
{
void *a = (void *)trunc_page((unsigned long)addr);
if (vm_map_protect(memguard_map, (vm_offset_t)a,
(vm_offset_t)((unsigned long)a + (PAGE_SIZE * numpgs)),
VM_PROT_DEFAULT, FALSE) != KERN_SUCCESS)
panic("MEMGUARD: Unable to unguard page!");
}
/*
* vtomgfifo() converts a virtual address of the first page allocated for
* an item to a memguard_fifo_pool reference for the corresponding item's
* size.
*
* vsetmgfifo() sets a reference in an underlying page for the specified
* virtual address to an appropriate memguard_fifo_pool.
*
* These routines are very similar to those defined by UMA in uma_int.h.
* The difference is that these routines store the mgfifo in one of the
* page's fields that is unused when the page is wired rather than the
* object field, which is used.
*/
static struct memguard_fifo *
vtomgfifo(vm_offset_t va)
{
vm_page_t p;
struct memguard_fifo *mgfifo;
p = PHYS_TO_VM_PAGE(pmap_kextract(va));
KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
("MEMGUARD: Expected wired page in vtomgfifo!"));
mgfifo = (struct memguard_fifo *)p->pageq.tqe_next;
return mgfifo;
}
static void
vsetmgfifo(vm_offset_t va, struct memguard_fifo *mgfifo)
{
vm_page_t p;
p = PHYS_TO_VM_PAGE(pmap_kextract(va));
KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
("MEMGUARD: Expected wired page in vsetmgfifo!"));
p->pageq.tqe_next = (vm_page_t)mgfifo;
}
static void vclrmgfifo(vm_offset_t va)
{
vm_page_t p;
p = PHYS_TO_VM_PAGE(pmap_kextract(va));
KASSERT(p->wire_count != 0 && p->queue == PQ_NONE,
("MEMGUARD: Expected wired page in vclrmgfifo!"));
p->pageq.tqe_next = NULL;
}
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