/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005, Bosko Milekic <bmilekic@FreeBSD.org>.
 * Copyright (c) 2010 Isilon Systems, Inc. (http://www.isilon.com/)
 * 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>
/*
 * 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 "opt_vm.h"

#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 <sys/vmem.h>
#include <sys/vmmeter.h>

#include <vm/vm.h>
#include <vm/uma.h>
#include <vm/vm_param.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/uma_int.h>
#include <vm/memguard.h>

static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
    "MemGuard data");
/*
 * The vm_memguard_divisor variable controls how much of kernel_arena should be
 * reserved for MemGuard.
 */
static u_int vm_memguard_divisor;
SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
    &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)
{
        char desc[sizeof(vm_memguard_desc)];
        int error;

        strlcpy(desc, vm_memguard_desc, sizeof(desc));
        error = sysctl_handle_string(oidp, desc, sizeof(desc), req);
        if (error != 0 || req->newptr == NULL)
                return (error);

        mtx_lock(&malloc_mtx);
        /* If mtp is NULL, it will be initialized in memguard_cmp() */
        vm_memguard_mtype = malloc_desc2type(desc);
        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 | CTLFLAG_MPSAFE, 0, 0,
    memguard_sysctl_desc, "A", "Short description of memory type to monitor");

static int
memguard_sysctl_mapused(SYSCTL_HANDLER_ARGS)
{
        vmem_size_t size;

        size = vmem_size(memguard_arena, VMEM_ALLOC);
        return (sysctl_handle_long(oidp, &size, sizeof(size), req));
}

static vm_offset_t memguard_base;
static vm_size_t memguard_mapsize;
static vm_size_t memguard_physlimit;
static u_long memguard_wasted;
static u_long memguard_succ;
static u_long memguard_fail_kva;
static u_long memguard_fail_pgs;

SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD,
    &memguard_mapsize, 0, "MemGuard private arena size");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD,
    &memguard_physlimit, 0, "Limit on MemGuard memory consumption");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD,
    &memguard_wasted, 0, "Excess memory used through page promotion");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD,
    &memguard_succ, 0, "Count of successful MemGuard allocations");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD,
    &memguard_fail_kva, 0, "MemGuard failures due to lack of KVA");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD,
    &memguard_fail_pgs, 0, "MemGuard failures due to lack of pages");

#define MG_GUARD_AROUND         0x001
#define MG_GUARD_ALLLARGE       0x002
#define MG_GUARD_NOFREE         0x004
static int memguard_options = MG_GUARD_AROUND;
SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RWTUN,
    &memguard_options, 0,
    "MemGuard options:\n"
    "\t0x001 - add guard pages around each allocation\n"
    "\t0x002 - always use MemGuard for allocations over a page\n"
    "\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag");

static u_int memguard_minsize;
static u_long memguard_minsize_reject;
SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW,
    &memguard_minsize, 0, "Minimum size for page promotion");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD,
    &memguard_minsize_reject, 0, "# times rejected for size");

static u_int memguard_frequency;
static u_long memguard_frequency_hits;
SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RWTUN,
    &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run");
SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD,
    &memguard_frequency_hits, 0, "# times MemGuard randomly chose");

/*
 * Return a fudged value to be used for vm_kmem_size for allocating
 * the kernel_arena.
 */
unsigned long
memguard_fudge(unsigned long km_size, const struct vm_map *parent_map)
{
        u_long mem_pgs, parent_size;

        vm_memguard_divisor = 10;
        /* CTFLAG_RDTUN doesn't work during the early boot process. */
        TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor);

        parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) +
            PAGE_SIZE;
        /* Pick a conservative value if provided value sucks. */
        if ((vm_memguard_divisor <= 0) ||
            ((parent_size / vm_memguard_divisor) == 0))
                vm_memguard_divisor = 10;
        /*
         * Limit consumption of physical pages to
         * 1/vm_memguard_divisor of system memory.  If the KVA is
         * smaller than this then the KVA limit comes into play first.
         * This prevents memguard's page promotions from completely
         * using up memory, since most malloc(9) calls are sub-page.
         */
        mem_pgs = vm_cnt.v_page_count;
        memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE;
        /*
         * We want as much KVA as we can take safely.  Use at most our
         * allotted fraction of the parent map's size.  Limit this to
         * twice the physical memory to avoid using too much memory as
         * pagetable pages (size must be multiple of PAGE_SIZE).
         */
        memguard_mapsize = round_page(parent_size / vm_memguard_divisor);
        if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs)
                memguard_mapsize = mem_pgs * 2 * PAGE_SIZE;
        if (km_size + memguard_mapsize > parent_size)
                memguard_mapsize = 0;
        return (km_size + memguard_mapsize);
}

/*
 * Initialize the MemGuard mock allocator.  All objects from MemGuard come
 * out of a single contiguous chunk of kernel address space that is managed
 * by a vmem arena.
 */
void
memguard_init(vmem_t *parent)
{
        vm_offset_t base;

        vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base);
        vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize,
            PAGE_SIZE, 0, M_WAITOK);
        memguard_base = base;

        printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n");
        printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base);
        printf("\tMEMGUARD map size: %jd KBytes\n",
            (uintmax_t)memguard_mapsize >> 10);
}

/*
 * Run things that can't be done as early as memguard_init().
 */
static void
memguard_sysinit(void)
{
        struct sysctl_oid_list *parent;

        parent = SYSCTL_STATIC_CHILDREN(_vm_memguard);
        SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "mapstart",
            CTLFLAG_RD, &memguard_base,
            "MemGuard KVA base");
        SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "maplimit",
            CTLFLAG_RD, &memguard_mapsize,
            "MemGuard KVA size");
        SYSCTL_ADD_PROC(NULL, parent, OID_AUTO, "mapused",
            CTLFLAG_RD | CTLFLAG_MPSAFE | CTLTYPE_ULONG, NULL, 0, memguard_sysctl_mapused, "LU",
            "MemGuard KVA used");
}
SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL);

/*
 * v2sizep() converts a virtual address of the first page allocated for
 * an item to a pointer to u_long recording the size of the original
 * allocation request.
 *
 * This routine is very similar to those defined by UMA in uma_int.h.
 * The difference is that this routine stores the originally allocated
 * size in one of the page's fields that is unused when the page is
 * wired rather than the object field, which is used.
 */
static u_long *
v2sizep(vm_offset_t va)
{
        vm_paddr_t pa;
        struct vm_page *p;

        pa = pmap_kextract(va);
        if (pa == 0)
                panic("MemGuard detected double-free of %p", (void *)va);
        p = PHYS_TO_VM_PAGE(pa);
        KASSERT(vm_page_wired(p) && p->a.queue == PQ_NONE,
            ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
        return (&p->plinks.memguard.p);
}

static u_long *
v2sizev(vm_offset_t va)
{
        vm_paddr_t pa;
        struct vm_page *p;

        pa = pmap_kextract(va);
        if (pa == 0)
                panic("MemGuard detected double-free of %p", (void *)va);
        p = PHYS_TO_VM_PAGE(pa);
        KASSERT(vm_page_wired(p) && p->a.queue == PQ_NONE,
            ("MEMGUARD: Expected wired page %p in vtomgfifo!", p));
        return (&p->plinks.memguard.v);
}

/*
 * Allocate a single object of specified size with specified flags
 * (either M_WAITOK or M_NOWAIT).
 */
void *
memguard_alloc(unsigned long req_size, int flags)
{
        vm_offset_t addr, origaddr;
        u_long size_p, size_v;
        int do_guard, error, rv;

        size_p = round_page(req_size);
        if (size_p == 0)
                return (NULL);

        /*
         * To ensure there are holes on both sides of the allocation,
         * request 2 extra pages of KVA.  Save the value of memguard_options
         * so that we use a consistent value throughout this function.
         */
        size_v = size_p;
        do_guard = (memguard_options & MG_GUARD_AROUND) != 0;
        if (do_guard)
                size_v += 2 * PAGE_SIZE;

        /*
         * When we pass our memory limit, reject sub-page allocations.
         * Page-size and larger allocations will use the same amount
         * of physical memory whether we allocate or hand off to
         * malloc_large(), so keep those.
         */
        if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit &&
            req_size < PAGE_SIZE) {
                addr = (vm_offset_t)NULL;
                memguard_fail_pgs++;
                goto out;
        }

        /*
         * Attempt to avoid address reuse for as long as possible, to increase
         * the likelihood of catching a use-after-free.
         */
        error = vmem_alloc(memguard_arena, size_v, M_NEXTFIT | M_NOWAIT,
            &origaddr);
        if (error != 0) {
                memguard_fail_kva++;
                addr = (vm_offset_t)NULL;
                goto out;
        }
        addr = origaddr;
        if (do_guard)
                addr += PAGE_SIZE;
        rv = kmem_back(kernel_object, addr, size_p, flags);
        if (rv != KERN_SUCCESS) {
                vmem_xfree(memguard_arena, origaddr, size_v);
                memguard_fail_pgs++;
                addr = (vm_offset_t)NULL;
                goto out;
        }
        *v2sizep(trunc_page(addr)) = req_size;
        *v2sizev(trunc_page(addr)) = size_v;
        memguard_succ++;
        if (req_size < PAGE_SIZE) {
                memguard_wasted += (PAGE_SIZE - req_size);
                if (do_guard) {
                        /*
                         * Align the request to 16 bytes, and return
                         * an address near the end of the page, to
                         * better detect array overrun.
                         */
                        req_size = roundup2(req_size, 16);
                        addr += (PAGE_SIZE - req_size);
                }
        }
out:
        return ((void *)addr);
}

int
is_memguard_addr(void *addr)
{
        vm_offset_t a = (vm_offset_t)(uintptr_t)addr;

        return (a >= memguard_base && a < memguard_base + memguard_mapsize);
}

/*
 * Free specified single object.
 */
void
memguard_free(void *ptr)
{
        vm_offset_t addr;
        u_long req_size, size, sizev;
        char *temp;
        int i;

        addr = trunc_page((uintptr_t)ptr);
        req_size = *v2sizep(addr);
        sizev = *v2sizev(addr);
        size = round_page(req_size);

        /*
         * Page should not be guarded right 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 = ptr;
        for (i = 0; i < size; i += PAGE_SIZE)
                temp[i] = 'M';

        /*
         * This requires carnal knowledge of the implementation of
         * kmem_free(), but since we've already replaced kmem_malloc()
         * above, it's not really any worse.  We want to use the
         * vm_map lock to serialize updates to memguard_wasted, since
         * we had the lock at increment.
         */
        kmem_unback(kernel_object, addr, size);
        if (sizev > size)
                addr -= PAGE_SIZE;
        vmem_xfree(memguard_arena, addr, sizev);
        if (req_size < PAGE_SIZE)
                memguard_wasted -= (PAGE_SIZE - req_size);
}

/*
 * Re-allocate an allocation that was originally guarded.
 */
void *
memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp,
    int flags)
{
        void *newaddr;
        u_long old_size;

        /*
         * Allocate the new block.  Force the allocation to be guarded
         * as the original may have been guarded through random
         * chance, and that should be preserved.
         */
        if ((newaddr = memguard_alloc(size, flags)) == NULL)
                return (NULL);

        /* Copy over original contents. */
        old_size = *v2sizep(trunc_page((uintptr_t)addr));
        bcopy(addr, newaddr, min(size, old_size));
        memguard_free(addr);
        return (newaddr);
}

static int
memguard_cmp(unsigned long size)
{

        if (size < memguard_minsize) {
                memguard_minsize_reject++;
                return (0);
        }
        if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE)
                return (1);
        if (memguard_frequency > 0 &&
            (random() % 100000) < memguard_frequency) {
                memguard_frequency_hits++;
                return (1);
        }

        return (0);
}

int
memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size)
{

        if (memguard_cmp(size))
                return(1);

#if 1
        /*
         * The safest way of comparison 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
}

int
memguard_cmp_zone(uma_zone_t zone)
{

        if ((memguard_options & MG_GUARD_NOFREE) == 0 &&
            zone->uz_flags & UMA_ZONE_NOFREE)
                return (0);

        if (memguard_cmp(zone->uz_size))
                return (1);

        /*
         * The safest way of comparison is to always compare zone name,
         * but it is also the slowest way.
         */
        return (strcmp(zone->uz_name, vm_memguard_desc) == 0);
}

unsigned long
memguard_get_req_size(const void *addr)
{
        return (*v2sizep(trunc_page((uintptr_t)addr)));
}