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/*
* Copyright (c) 2005,
* Bosko Milekic <bmilekic@freebsd.org>
*
* 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 <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/memguard.h>
/*
* 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 STAILQ_HEAD(memguard_fifo, memguard_entry) memguard_fifo_pool;
/*
* Local prototypes.
*/
static void memguard_guard(void *addr);
static void memguard_unguard(void *addr);
/*
* 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;
/* 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);
memguard_map->system_map = 1;
memguard_mapsize = size;
memguard_mapused = 0;
MEMGUARD_CRIT_SECTION_INIT;
MEMGUARD_CRIT_SECTION_ENTER;
STAILQ_INIT(&memguard_fifo_pool);
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 = NULL;
struct memguard_entry *e = NULL;
/* XXX: MemGuard does not handle > PAGE_SIZE objects. */
if (size > PAGE_SIZE)
panic("MEMGUARD: Cannot handle objects > PAGE_SIZE");
/*
* 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);
if (e != NULL) {
STAILQ_REMOVE(&memguard_fifo_pool, e,
memguard_entry, entries);
MEMGUARD_CRIT_SECTION_EXIT;
obj = e->ptr;
free(e, M_TEMP);
memguard_unguard(obj);
if (flags & M_ZERO)
bzero(obj, PAGE_SIZE);
return obj;
}
MEMGUARD_CRIT_SECTION_EXIT;
if (flags & M_WAITOK)
panic("MEMGUARD: Failed with M_WAITOK: " \
"memguard_map too small");
return NULL;
} else
memguard_mapused += PAGE_SIZE;
MEMGUARD_CRIT_SECTION_EXIT;
if (obj == NULL)
obj = (void *)kmem_malloc(memguard_map, PAGE_SIZE, flags);
if (obj != NULL) {
memguard_unguard(obj);
if (flags & M_ZERO)
bzero(obj, PAGE_SIZE);
} else {
MEMGUARD_CRIT_SECTION_ENTER;
memguard_mapused -= PAGE_SIZE;
MEMGUARD_CRIT_SECTION_EXIT;
}
return obj;
}
/*
* Free specified single object.
*/
void
memguard_free(void *addr)
{
struct memguard_entry *e;
memguard_guard(addr);
e = malloc(sizeof(struct memguard_entry), M_TEMP, M_NOWAIT);
if (e == NULL) {
MEMGUARD_CRIT_SECTION_ENTER;
memguard_mapused -= PAGE_SIZE;
MEMGUARD_CRIT_SECTION_EXIT;
kmem_free(memguard_map, (vm_offset_t)round_page(
(unsigned long)addr), PAGE_SIZE);
return;
}
e->ptr = (void *)round_page((unsigned long)addr);
MEMGUARD_CRIT_SECTION_ENTER;
STAILQ_INSERT_TAIL(&memguard_fifo_pool, e, entries);
MEMGUARD_CRIT_SECTION_EXIT;
}
/*
* Guard a page containing specified object (make it read-only so that
* future writes to it fail).
*/
static void
memguard_guard(void *addr)
{
void *a = (void *)round_page((unsigned long)addr);
(void)vm_map_protect(memguard_map, (vm_offset_t)a,
(vm_offset_t)((unsigned long)a + PAGE_SIZE), VM_PROT_READ, 0);
}
/*
* Unguard a page containing specified object (make it read-and-write to
* allow full data access).
*/
static void
memguard_unguard(void *addr)
{
void *a = (void *)round_page((unsigned long)addr);
(void)vm_map_protect(memguard_map, (vm_offset_t)a,
(vm_offset_t)((unsigned long)a + PAGE_SIZE),
VM_PROT_READ | VM_PROT_WRITE, 0);
}
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