vm_kern.c

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/*-
 * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
 *
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * 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, 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 *
 *      from: @(#)vm_kern.c     8.3 (Berkeley) 1/12/94
 *
 *
 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
 *
 * Permission to use, copy, modify and distribute this software and
 * its documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */
 
/*
 *      Kernel memory management.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_vm.h"
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/asan.h>
#include <sys/domainset.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sysctl.h>
#include <sys/vmem.h>
#include <sys/vmmeter.h>
 
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_domainset.h>
#include <vm/vm_kern.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pagequeue.h>
#include <vm/vm_phys.h>
#include <vm/vm_radix.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
 
struct vm_map kernel_map_store;
struct vm_map exec_map_store;
struct vm_map pipe_map_store;
 
const void *zero_region;
CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
 
/* NB: Used by kernel debuggers. */
const u_long vm_maxuser_address = VM_MAXUSER_ADDRESS;
 
u_int exec_map_entry_size;
u_int exec_map_entries;
 
SYSCTL_ULONG(_vm, OID_AUTO, min_kernel_address, CTLFLAG_RD,
    SYSCTL_NULL_ULONG_PTR, VM_MIN_KERNEL_ADDRESS, "Min kernel address");
 
SYSCTL_ULONG(_vm, OID_AUTO, max_kernel_address, CTLFLAG_RD,
#if defined(__arm__)
    &vm_max_kernel_address, 0,
#else
    SYSCTL_NULL_ULONG_PTR, VM_MAX_KERNEL_ADDRESS,
#endif
    "Max kernel address");
 
#if VM_NRESERVLEVEL > 0
#define KVA_QUANTUM_SHIFT       (VM_LEVEL_0_ORDER + PAGE_SHIFT)
#else
/* On non-superpage architectures we want large import sizes. */
#define KVA_QUANTUM_SHIFT       (8 + PAGE_SHIFT)
#endif
#define KVA_QUANTUM             (1ul << KVA_QUANTUM_SHIFT)
#define KVA_NUMA_IMPORT_QUANTUM (KVA_QUANTUM * 128)
 
extern void     uma_startup2(void);
 
/*
 *      kva_alloc:
 *
 *      Allocate a virtual address range with no underlying object and
 *      no initial mapping to physical memory.  Any mapping from this
 *      range to physical memory must be explicitly created prior to
 *      its use, typically with pmap_qenter().  Any attempt to create
 *      a mapping on demand through vm_fault() will result in a panic. 
 */
vm_offset_t
kva_alloc(vm_size_t size)
{
        vm_offset_t addr;
 
        size = round_page(size);
        if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
                return (0);
 
        return (addr);
}
 
/*
 *      kva_free:
 *
 *      Release a region of kernel virtual memory allocated
 *      with kva_alloc, and return the physical pages
 *      associated with that region.
 *
 *      This routine may not block on kernel maps.
 */
void
kva_free(vm_offset_t addr, vm_size_t size)
{
 
        size = round_page(size);
        vmem_free(kernel_arena, addr, size);
}
 
static vm_page_t
kmem_alloc_contig_pages(vm_object_t object, vm_pindex_t pindex, int domain,
    int pflags, u_long npages, vm_paddr_t low, vm_paddr_t high,
    u_long alignment, vm_paddr_t boundary, vm_memattr_t memattr)
{
        vm_page_t m;
        int tries;
        bool wait, reclaim;
 
        VM_OBJECT_ASSERT_WLOCKED(object);
 
        wait = (pflags & VM_ALLOC_WAITOK) != 0;
        reclaim = (pflags & VM_ALLOC_NORECLAIM) == 0;
        pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
        pflags |= VM_ALLOC_NOWAIT;
        for (tries = wait ? 3 : 1;; tries--) {
                m = vm_page_alloc_contig_domain(object, pindex, domain, pflags,
                    npages, low, high, alignment, boundary, memattr);
                if (m != NULL || tries == 0 || !reclaim)
                        break;
 
                VM_OBJECT_WUNLOCK(object);
                if (!vm_page_reclaim_contig_domain(domain, pflags, npages,
                    low, high, alignment, boundary) && wait)
                        vm_wait_domain(domain);
                VM_OBJECT_WLOCK(object);
        }
        return (m);
}
 
/*
 *      Allocates a region from the kernel address map and physical pages
 *      within the specified address range to the kernel object.  Creates a
 *      wired mapping from this region to these pages, and returns the
 *      region's starting virtual address.  The allocated pages are not
 *      necessarily physically contiguous.  If M_ZERO is specified through the
 *      given flags, then the pages are zeroed before they are mapped.
 */
static vm_offset_t
kmem_alloc_attr_domain(int domain, vm_size_t size, int flags, vm_paddr_t low,
    vm_paddr_t high, vm_memattr_t memattr)
{
        vmem_t *vmem;
        vm_object_t object;
        vm_offset_t addr, i, offset;
        vm_page_t m;
        vm_size_t asize;
        int pflags;
        vm_prot_t prot;
 
        object = kernel_object;
        asize = round_page(size);
        vmem = vm_dom[domain].vmd_kernel_arena;
        if (vmem_alloc(vmem, asize, M_BESTFIT | flags, &addr))
                return (0);
        offset = addr - VM_MIN_KERNEL_ADDRESS;
        pflags = malloc2vm_flags(flags) | VM_ALLOC_WIRED;
        prot = (flags & M_EXEC) != 0 ? VM_PROT_ALL : VM_PROT_RW;
        VM_OBJECT_WLOCK(object);
        for (i = 0; i < asize; i += PAGE_SIZE) {
                m = kmem_alloc_contig_pages(object, atop(offset + i),
                    domain, pflags, 1, low, high, PAGE_SIZE, 0, memattr);
                if (m == NULL) {
                        VM_OBJECT_WUNLOCK(object);
                        kmem_unback(object, addr, i);
                        vmem_free(vmem, addr, asize);
                        return (0);
                }
                KASSERT(vm_page_domain(m) == domain,
                    ("kmem_alloc_attr_domain: Domain mismatch %d != %d",
                    vm_page_domain(m), domain));
                if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
                        pmap_zero_page(m);
                vm_page_valid(m);
                pmap_enter(kernel_pmap, addr + i, m, prot,
                    prot | PMAP_ENTER_WIRED, 0);
        }
        VM_OBJECT_WUNLOCK(object);
        kasan_mark((void *)addr, size, asize, KASAN_KMEM_REDZONE);
        return (addr);
}
 
vm_offset_t
kmem_alloc_attr(vm_size_t size, int flags, vm_paddr_t low, vm_paddr_t high,
    vm_memattr_t memattr)
{
 
        return (kmem_alloc_attr_domainset(DOMAINSET_RR(), size, flags, low,
            high, memattr));
}
 
vm_offset_t
kmem_alloc_attr_domainset(struct domainset *ds, vm_size_t size, int flags,
    vm_paddr_t low, vm_paddr_t high, vm_memattr_t memattr)
{
        struct vm_domainset_iter di;
        vm_offset_t addr;
        int domain;
 
        vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
        do {
                addr = kmem_alloc_attr_domain(domain, size, flags, low, high,
                    memattr);
                if (addr != 0)
                        break;
        } while (vm_domainset_iter_policy(&di, &domain) == 0);
 
        return (addr);
}
 
/*
 *      Allocates a region from the kernel address map and physically
 *      contiguous pages within the specified address range to the kernel
 *      object.  Creates a wired mapping from this region to these pages, and
 *      returns the region's starting virtual address.  If M_ZERO is specified
 *      through the given flags, then the pages are zeroed before they are
 *      mapped.
 */
static vm_offset_t
kmem_alloc_contig_domain(int domain, vm_size_t size, int flags, vm_paddr_t low,
    vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
    vm_memattr_t memattr)
{
        vmem_t *vmem;
        vm_object_t object;
        vm_offset_t addr, offset, tmp;
        vm_page_t end_m, m;
        vm_size_t asize;
        u_long npages;
        int pflags;
 
        object = kernel_object;
        asize = round_page(size);
        vmem = vm_dom[domain].vmd_kernel_arena;
        if (vmem_alloc(vmem, asize, flags | M_BESTFIT, &addr))
                return (0);
        offset = addr - VM_MIN_KERNEL_ADDRESS;
        pflags = malloc2vm_flags(flags) | VM_ALLOC_WIRED;
        npages = atop(asize);
        VM_OBJECT_WLOCK(object);
        m = kmem_alloc_contig_pages(object, atop(offset), domain,
            pflags, npages, low, high, alignment, boundary, memattr);
        if (m == NULL) {
                VM_OBJECT_WUNLOCK(object);
                vmem_free(vmem, addr, asize);
                return (0);
        }
        KASSERT(vm_page_domain(m) == domain,
            ("kmem_alloc_contig_domain: Domain mismatch %d != %d",
            vm_page_domain(m), domain));
        end_m = m + npages;
        tmp = addr;
        for (; m < end_m; m++) {
                if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
                        pmap_zero_page(m);
                vm_page_valid(m);
                pmap_enter(kernel_pmap, tmp, m, VM_PROT_RW,
                    VM_PROT_RW | PMAP_ENTER_WIRED, 0);
                tmp += PAGE_SIZE;
        }
        VM_OBJECT_WUNLOCK(object);
        kasan_mark((void *)addr, size, asize, KASAN_KMEM_REDZONE);
        return (addr);
}
 
vm_offset_t
kmem_alloc_contig(vm_size_t size, int flags, vm_paddr_t low, vm_paddr_t high,
    u_long alignment, vm_paddr_t boundary, vm_memattr_t memattr)
{
 
        return (kmem_alloc_contig_domainset(DOMAINSET_RR(), size, flags, low,
            high, alignment, boundary, memattr));
}
 
vm_offset_t
kmem_alloc_contig_domainset(struct domainset *ds, vm_size_t size, int flags,
    vm_paddr_t low, vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
    vm_memattr_t memattr)
{
        struct vm_domainset_iter di;
        vm_offset_t addr;
        int domain;
 
        vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
        do {
                addr = kmem_alloc_contig_domain(domain, size, flags, low, high,
                    alignment, boundary, memattr);
                if (addr != 0)
                        break;
        } while (vm_domainset_iter_policy(&di, &domain) == 0);
 
        return (addr);
}
 
/*
 *      kmem_subinit:
 *
 *      Initializes a map to manage a subrange
 *      of the kernel virtual address space.
 *
 *      Arguments are as follows:
 *
 *      parent          Map to take range from
 *      min, max        Returned endpoints of map
 *      size            Size of range to find
 *      superpage_align Request that min is superpage aligned
 */
void
kmem_subinit(vm_map_t map, vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
    vm_size_t size, bool superpage_align)
{
        int ret;
 
        size = round_page(size);
 
        *min = vm_map_min(parent);
        ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
            VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
            MAP_ACC_NO_CHARGE);
        if (ret != KERN_SUCCESS)
                panic("kmem_subinit: bad status return of %d", ret);
        *max = *min + size;
        vm_map_init(map, vm_map_pmap(parent), *min, *max);
        if (vm_map_submap(parent, *min, *max, map) != KERN_SUCCESS)
                panic("kmem_subinit: unable to change range to submap");
}
 
/*
 *      kmem_malloc_domain:
 *
 *      Allocate wired-down pages in the kernel's address space.
 */
static vm_offset_t
kmem_malloc_domain(int domain, vm_size_t size, int flags)
{
        vmem_t *arena;
        vm_offset_t addr;
        vm_size_t asize;
        int rv;
 
        if (__predict_true((flags & M_EXEC) == 0))
                arena = vm_dom[domain].vmd_kernel_arena;
        else
                arena = vm_dom[domain].vmd_kernel_rwx_arena;
        asize = round_page(size);
        if (vmem_alloc(arena, asize, flags | M_BESTFIT, &addr))
                return (0);
 
        rv = kmem_back_domain(domain, kernel_object, addr, asize, flags);
        if (rv != KERN_SUCCESS) {
                vmem_free(arena, addr, asize);
                return (0);
        }
        kasan_mark((void *)addr, size, asize, KASAN_KMEM_REDZONE);
        return (addr);
}
 
vm_offset_t
kmem_malloc(vm_size_t size, int flags)
{
 
        return (kmem_malloc_domainset(DOMAINSET_RR(), size, flags));
}
 
vm_offset_t
kmem_malloc_domainset(struct domainset *ds, vm_size_t size, int flags)
{
        struct vm_domainset_iter di;
        vm_offset_t addr;
        int domain;
 
        vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
        do {
                addr = kmem_malloc_domain(domain, size, flags);
                if (addr != 0)
                        break;
        } while (vm_domainset_iter_policy(&di, &domain) == 0);
 
        return (addr);
}
 
/*
 *      kmem_back_domain:
 *
 *      Allocate physical pages from the specified domain for the specified
 *      virtual address range.
 */
int
kmem_back_domain(int domain, vm_object_t object, vm_offset_t addr,
    vm_size_t size, int flags)
{
        vm_offset_t offset, i;
        vm_page_t m, mpred;
        vm_prot_t prot;
        int pflags;
 
        KASSERT(object == kernel_object,
            ("kmem_back_domain: only supports kernel object."));
 
        offset = addr - VM_MIN_KERNEL_ADDRESS;
        pflags = malloc2vm_flags(flags) | VM_ALLOC_WIRED;
        pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
        if (flags & M_WAITOK)
                pflags |= VM_ALLOC_WAITFAIL;
        prot = (flags & M_EXEC) != 0 ? VM_PROT_ALL : VM_PROT_RW;
 
        i = 0;
        VM_OBJECT_WLOCK(object);
retry:
        mpred = vm_radix_lookup_le(&object->rtree, atop(offset + i));
        for (; i < size; i += PAGE_SIZE, mpred = m) {
                m = vm_page_alloc_domain_after(object, atop(offset + i),
                    domain, pflags, mpred);
 
                /*
                 * Ran out of space, free everything up and return. Don't need
                 * to lock page queues here as we know that the pages we got
                 * aren't on any queues.
                 */
                if (m == NULL) {
                        if ((flags & M_NOWAIT) == 0)
                                goto retry;
                        VM_OBJECT_WUNLOCK(object);
                        kmem_unback(object, addr, i);
                        return (KERN_NO_SPACE);
                }
                KASSERT(vm_page_domain(m) == domain,
                    ("kmem_back_domain: Domain mismatch %d != %d",
                    vm_page_domain(m), domain));
                if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
                        pmap_zero_page(m);
                KASSERT((m->oflags & VPO_UNMANAGED) != 0,
                    ("kmem_malloc: page %p is managed", m));
                vm_page_valid(m);
                pmap_enter(kernel_pmap, addr + i, m, prot,
                    prot | PMAP_ENTER_WIRED, 0);
                if (__predict_false((prot & VM_PROT_EXECUTE) != 0))
                        m->oflags |= VPO_KMEM_EXEC;
        }
        VM_OBJECT_WUNLOCK(object);
 
        return (KERN_SUCCESS);
}
 
/*
 *      kmem_back:
 *
 *      Allocate physical pages for the specified virtual address range.
 */
int
kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
{
        vm_offset_t end, next, start;
        int domain, rv;
 
        KASSERT(object == kernel_object,
            ("kmem_back: only supports kernel object."));
 
        for (start = addr, end = addr + size; addr < end; addr = next) {
                /*
                 * We must ensure that pages backing a given large virtual page
                 * all come from the same physical domain.
                 */
                if (vm_ndomains > 1) {
                        domain = (addr >> KVA_QUANTUM_SHIFT) % vm_ndomains;
                        while (VM_DOMAIN_EMPTY(domain))
                                domain++;
                        next = roundup2(addr + 1, KVA_QUANTUM);
                        if (next > end || next < start)
                                next = end;
                } else {
                        domain = 0;
                        next = end;
                }
                rv = kmem_back_domain(domain, object, addr, next - addr, flags);
                if (rv != KERN_SUCCESS) {
                        kmem_unback(object, start, addr - start);
                        break;
                }
        }
        return (rv);
}
 
/*
 *      kmem_unback:
 *
 *      Unmap and free the physical pages underlying the specified virtual
 *      address range.
 *
 *      A physical page must exist within the specified object at each index
 *      that is being unmapped.
 */
static struct vmem *
_kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
{
        struct vmem *arena;
        vm_page_t m, next;
        vm_offset_t end, offset;
        int domain;
 
        KASSERT(object == kernel_object,
            ("kmem_unback: only supports kernel object."));
 
        if (size == 0)
                return (NULL);
        pmap_remove(kernel_pmap, addr, addr + size);
        offset = addr - VM_MIN_KERNEL_ADDRESS;
        end = offset + size;
        VM_OBJECT_WLOCK(object);
        m = vm_page_lookup(object, atop(offset)); 
        domain = vm_page_domain(m);
        if (__predict_true((m->oflags & VPO_KMEM_EXEC) == 0))
                arena = vm_dom[domain].vmd_kernel_arena;
        else
                arena = vm_dom[domain].vmd_kernel_rwx_arena;
        for (; offset < end; offset += PAGE_SIZE, m = next) {
                next = vm_page_next(m);
                vm_page_xbusy_claim(m);
                vm_page_unwire_noq(m);
                vm_page_free(m);
        }
        VM_OBJECT_WUNLOCK(object);
 
        return (arena);
}
 
void
kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
{
 
        (void)_kmem_unback(object, addr, size);
}
 
/*
 *      kmem_free:
 *
 *      Free memory allocated with kmem_malloc.  The size must match the
 *      original allocation.
 */
void
kmem_free(vm_offset_t addr, vm_size_t size)
{
        struct vmem *arena;
 
        size = round_page(size);
        kasan_mark((void *)addr, size, size, 0);
        arena = _kmem_unback(kernel_object, addr, size);
        if (arena != NULL)
                vmem_free(arena, addr, size);
}
 
/*
 *      kmap_alloc_wait:
 *
 *      Allocates pageable memory from a sub-map of the kernel.  If the submap
 *      has no room, the caller sleeps waiting for more memory in the submap.
 *
 *      This routine may block.
 */
vm_offset_t
kmap_alloc_wait(vm_map_t map, vm_size_t size)
{
        vm_offset_t addr;
 
        size = round_page(size);
        if (!swap_reserve(size))
                return (0);
 
        for (;;) {
                /*
                 * To make this work for more than one map, use the map's lock
                 * to lock out sleepers/wakers.
                 */
                vm_map_lock(map);
                addr = vm_map_findspace(map, vm_map_min(map), size);
                if (addr + size <= vm_map_max(map))
                        break;
                /* no space now; see if we can ever get space */
                if (vm_map_max(map) - vm_map_min(map) < size) {
                        vm_map_unlock(map);
                        swap_release(size);
                        return (0);
                }
                map->needs_wakeup = TRUE;
                vm_map_unlock_and_wait(map, 0);
        }
        vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_RW, VM_PROT_RW,
            MAP_ACC_CHARGED);
        vm_map_unlock(map);
        return (addr);
}
 
/*
 *      kmap_free_wakeup:
 *
 *      Returns memory to a submap of the kernel, and wakes up any processes
 *      waiting for memory in that map.
 */
void
kmap_free_wakeup(vm_map_t map, vm_offset_t addr, vm_size_t size)
{
 
        vm_map_lock(map);
        (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
        if (map->needs_wakeup) {
                map->needs_wakeup = FALSE;
                vm_map_wakeup(map);
        }
        vm_map_unlock(map);
}
 
void
kmem_init_zero_region(void)
{
        vm_offset_t addr, i;
        vm_page_t m;
 
        /*
         * Map a single physical page of zeros to a larger virtual range.
         * This requires less looping in places that want large amounts of
         * zeros, while not using much more physical resources.
         */
        addr = kva_alloc(ZERO_REGION_SIZE);
        m = vm_page_alloc_noobj(VM_ALLOC_WIRED | VM_ALLOC_ZERO);
        for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
                pmap_qenter(addr + i, &m, 1);
        pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
 
        zero_region = (const void *)addr;
}
 
/*
 * Import KVA from the kernel map into the kernel arena.
 */
static int
kva_import(void *unused, vmem_size_t size, int flags, vmem_addr_t *addrp)
{
        vm_offset_t addr;
        int result;
 
        KASSERT((size % KVA_QUANTUM) == 0,
            ("kva_import: Size %jd is not a multiple of %d",
            (intmax_t)size, (int)KVA_QUANTUM));
        addr = vm_map_min(kernel_map);
        result = vm_map_find(kernel_map, NULL, 0, &addr, size, 0,
            VMFS_SUPER_SPACE, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
        if (result != KERN_SUCCESS)
                return (ENOMEM);
 
        *addrp = addr;
 
        return (0);
}
 
/*
 * Import KVA from a parent arena into a per-domain arena.  Imports must be
 * KVA_QUANTUM-aligned and a multiple of KVA_QUANTUM in size.
 */
static int
kva_import_domain(void *arena, vmem_size_t size, int flags, vmem_addr_t *addrp)
{
 
        KASSERT((size % KVA_QUANTUM) == 0,
            ("kva_import_domain: Size %jd is not a multiple of %d",
            (intmax_t)size, (int)KVA_QUANTUM));
        return (vmem_xalloc(arena, size, KVA_QUANTUM, 0, 0, VMEM_ADDR_MIN,
            VMEM_ADDR_MAX, flags, addrp));
}
 
/*
 *      kmem_init:
 *
 *      Create the kernel map; insert a mapping covering kernel text, 
 *      data, bss, and all space allocated thus far (`boostrap' data).  The 
 *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
 *      `start' as allocated, and the range between `start' and `end' as free.
 *      Create the kernel vmem arena and its per-domain children.
 */
void
kmem_init(vm_offset_t start, vm_offset_t end)
{
        vm_size_t quantum;
        int domain;
 
        vm_map_init(kernel_map, kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
        kernel_map->system_map = 1;
        vm_map_lock(kernel_map);
        /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
        (void)vm_map_insert(kernel_map, NULL, 0,
#ifdef __amd64__
            KERNBASE,
#else                
            VM_MIN_KERNEL_ADDRESS,
#endif
            start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
        /* ... and ending with the completion of the above `insert' */
 
#ifdef __amd64__
        /*
         * Mark KVA used for the page array as allocated.  Other platforms
         * that handle vm_page_array allocation can simply adjust virtual_avail
         * instead.
         */
        (void)vm_map_insert(kernel_map, NULL, 0, (vm_offset_t)vm_page_array,
            (vm_offset_t)vm_page_array + round_2mpage(vm_page_array_size *
            sizeof(struct vm_page)),
            VM_PROT_RW, VM_PROT_RW, MAP_NOFAULT);
#endif
        vm_map_unlock(kernel_map);
 
        /*
         * Use a large import quantum on NUMA systems.  This helps minimize
         * interleaving of superpages, reducing internal fragmentation within
         * the per-domain arenas.
         */
        if (vm_ndomains > 1 && PMAP_HAS_DMAP)
                quantum = KVA_NUMA_IMPORT_QUANTUM;
        else
                quantum = KVA_QUANTUM;
 
        /*
         * Initialize the kernel_arena.  This can grow on demand.
         */
        vmem_init(kernel_arena, "kernel arena", 0, 0, PAGE_SIZE, 0, 0);
        vmem_set_import(kernel_arena, kva_import, NULL, NULL, quantum);
 
        for (domain = 0; domain < vm_ndomains; domain++) {
                /*
                 * Initialize the per-domain arenas.  These are used to color
                 * the KVA space in a way that ensures that virtual large pages
                 * are backed by memory from the same physical domain,
                 * maximizing the potential for superpage promotion.
                 */
                vm_dom[domain].vmd_kernel_arena = vmem_create(
                    "kernel arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
                vmem_set_import(vm_dom[domain].vmd_kernel_arena,
                    kva_import_domain, NULL, kernel_arena, quantum);
 
                /*
                 * In architectures with superpages, maintain separate arenas
                 * for allocations with permissions that differ from the
                 * "standard" read/write permissions used for kernel memory,
                 * so as not to inhibit superpage promotion.
                 *
                 * Use the base import quantum since this arena is rarely used.
                 */
#if VM_NRESERVLEVEL > 0
                vm_dom[domain].vmd_kernel_rwx_arena = vmem_create(
                    "kernel rwx arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
                vmem_set_import(vm_dom[domain].vmd_kernel_rwx_arena,
                    kva_import_domain, (vmem_release_t *)vmem_xfree,
                    kernel_arena, KVA_QUANTUM);
#else
                vm_dom[domain].vmd_kernel_rwx_arena =
                    vm_dom[domain].vmd_kernel_arena;
#endif
        }
 
        /*
         * This must be the very first call so that the virtual address
         * space used for early allocations is properly marked used in
         * the map.
         */
        uma_startup2();
}
 
/*
 *      kmem_bootstrap_free:
 *
 *      Free pages backing preloaded data (e.g., kernel modules) to the
 *      system.  Currently only supported on platforms that create a
 *      vm_phys segment for preloaded data.
 */
void
kmem_bootstrap_free(vm_offset_t start, vm_size_t size)
{
#if defined(__i386__) || defined(__amd64__)
        struct vm_domain *vmd;
        vm_offset_t end, va;
        vm_paddr_t pa;
        vm_page_t m;
 
        end = trunc_page(start + size);
        start = round_page(start);
 
#ifdef __amd64__
        /*
         * Preloaded files do not have execute permissions by default on amd64.
         * Restore the default permissions to ensure that the direct map alias
         * is updated.
         */
        pmap_change_prot(start, end - start, VM_PROT_RW);
#endif
        for (va = start; va < end; va += PAGE_SIZE) {
                pa = pmap_kextract(va);
                m = PHYS_TO_VM_PAGE(pa);
 
                vmd = vm_pagequeue_domain(m);
                vm_domain_free_lock(vmd);
                vm_phys_free_pages(m, 0);
                vm_domain_free_unlock(vmd);
 
                vm_domain_freecnt_inc(vmd, 1);
                vm_cnt.v_page_count++;
        }
        pmap_remove(kernel_pmap, start, end);
        (void)vmem_add(kernel_arena, start, end - start, M_WAITOK);
#endif
}
 
/*
 * Allow userspace to directly trigger the VM drain routine for testing
 * purposes.
 */
static int
debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
{
        int error, i;
 
        i = 0;
        error = sysctl_handle_int(oidp, &i, 0, req);
        if (error != 0)
                return (error);
        if ((i & ~(VM_LOW_KMEM | VM_LOW_PAGES)) != 0)
                return (EINVAL);
        if (i != 0)
                EVENTHANDLER_INVOKE(vm_lowmem, i);
        return (0);
}
SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem,
    CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, 0, debug_vm_lowmem, "I",
    "set to trigger vm_lowmem event with given flags");
 
static int
debug_uma_reclaim(SYSCTL_HANDLER_ARGS)
{
        int error, i;
 
        i = 0;
        error = sysctl_handle_int(oidp, &i, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (i != UMA_RECLAIM_TRIM && i != UMA_RECLAIM_DRAIN &&
            i != UMA_RECLAIM_DRAIN_CPU)
                return (EINVAL);
        uma_reclaim(i);
        return (0);
}
SYSCTL_PROC(_debug, OID_AUTO, uma_reclaim,
    CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, 0, debug_uma_reclaim, "I",
    "set to generate request to reclaim uma caches");
 
static int
debug_uma_reclaim_domain(SYSCTL_HANDLER_ARGS)
{
        int domain, error, request;
 
        request = 0;
        error = sysctl_handle_int(oidp, &request, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
 
        domain = request >> 4;
        request &= 0xf;
        if (request != UMA_RECLAIM_TRIM && request != UMA_RECLAIM_DRAIN &&
            request != UMA_RECLAIM_DRAIN_CPU)
                return (EINVAL);
        if (domain < 0 || domain >= vm_ndomains)
                return (EINVAL);
        uma_reclaim_domain(request, domain);
        return (0);
}
SYSCTL_PROC(_debug, OID_AUTO, uma_reclaim_domain,
    CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, 0,
    debug_uma_reclaim_domain, "I",
    "");