FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_kern.c

     /*
      * (MPSAFE)
      *
      * 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.
     *
     * $FreeBSD: src/sys/vm/vm_kern.c,v 1.61.2.2 2002/03/12 18:25:26 tegge Exp $
     */
    
    /*
     *      Kernel memory management.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/malloc.h>
    #include <sys/kernel.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <sys/lock.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_kern.h>
    #include <vm/vm_extern.h>
    
    struct vm_map kernel_map;
    struct vm_map clean_map;
    struct vm_map buffer_map;
    
    /*
     * Allocate pageable memory to the kernel's address map.  "map" must
     * be kernel_map or a submap of kernel_map.
     *
     * No requirements.
     */
    vm_offset_t
    kmem_alloc_pageable(vm_map_t map, vm_size_t size)
    {
           vm_offset_t addr;
           int result;
   
           size = round_page(size);
           addr = vm_map_min(map);
           result = vm_map_find(map, NULL, (vm_offset_t) 0,
                                &addr, size, PAGE_SIZE,
                                TRUE, VM_MAPTYPE_NORMAL,
                                VM_PROT_ALL, VM_PROT_ALL,
                                0);
           if (result != KERN_SUCCESS)
                   return (0);
           return (addr);
   }
   
   /*
    * Same as kmem_alloc_pageable, except that it create a nofault entry.
    *
    * No requirements.
    */
   vm_offset_t
   kmem_alloc_nofault(vm_map_t map, vm_size_t size, vm_size_t align)
   {
           vm_offset_t addr;
           int result;
   
           size = round_page(size);
           addr = vm_map_min(map);
           result = vm_map_find(map, NULL, (vm_offset_t) 0,
                                &addr, size, align,
                                TRUE, VM_MAPTYPE_NORMAL,
                                VM_PROT_ALL, VM_PROT_ALL,
                                MAP_NOFAULT);
           if (result != KERN_SUCCESS)
                   return (0);
           return (addr);
   }
   
   /*
    * Allocate wired-down memory in the kernel's address map or a submap.
    *
    * No requirements.
    */
   vm_offset_t
   kmem_alloc3(vm_map_t map, vm_size_t size, int kmflags)
   {
           vm_offset_t addr;
           vm_offset_t gstart;
           vm_offset_t i;
           int count;
           int cow;
   
           size = round_page(size);
   
           if (kmflags & KM_KRESERVE)
                   count = vm_map_entry_kreserve(MAP_RESERVE_COUNT);
           else
                   count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
   
           if (kmflags & KM_STACK) {
                   cow = MAP_IS_KSTACK;
                   gstart = PAGE_SIZE;
           } else {
                   cow = 0;
                   gstart = 0;
           }
   
           /*
            * Use the kernel object for wired-down kernel pages. Assume that no
            * region of the kernel object is referenced more than once.
            *
            * Locate sufficient space in the map.  This will give us the final
            * virtual address for the new memory, and thus will tell us the
            * offset within the kernel map.
            */
           vm_map_lock(map);
           if (vm_map_findspace(map, vm_map_min(map), size, PAGE_SIZE, 0, &addr)) {
                   vm_map_unlock(map);
                   if (kmflags & KM_KRESERVE)
                           vm_map_entry_krelease(count);
                   else
                           vm_map_entry_release(count);
                   return (0);
           }
           vm_object_hold(&kernel_object);
           vm_object_reference_locked(&kernel_object);
           vm_map_insert(map, &count,
                         &kernel_object, addr, addr, addr + size,
                         VM_MAPTYPE_NORMAL,
                         VM_PROT_ALL, VM_PROT_ALL,
                         cow);
           vm_object_drop(&kernel_object);
   
           vm_map_unlock(map);
           if (kmflags & KM_KRESERVE)
                   vm_map_entry_krelease(count);
           else
                   vm_map_entry_release(count);
   
           /*
            * Guarantee that there are pages already in this object before
            * calling vm_map_wire.  This is to prevent the following
            * scenario:
            *
            * 1) Threads have swapped out, so that there is a pager for the
            * kernel_object. 2) The kmsg zone is empty, and so we are
            * kmem_allocing a new page for it. 3) vm_map_wire calls vm_fault;
            * there is no page, but there is a pager, so we call
            * pager_data_request.  But the kmsg zone is empty, so we must
            * kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
            * we get the data back from the pager, it will be (very stale)
            * non-zero data.  kmem_alloc is defined to return zero-filled memory.
            *
            * We're intentionally not activating the pages we allocate to prevent a
            * race with page-out.  vm_map_wire will wire the pages.
            */
           vm_object_hold(&kernel_object);
           for (i = gstart; i < size; i += PAGE_SIZE) {
                   vm_page_t mem;
   
                   mem = vm_page_grab(&kernel_object, OFF_TO_IDX(addr + i),
                                      VM_ALLOC_FORCE_ZERO | VM_ALLOC_NORMAL |
                                      VM_ALLOC_RETRY);
                   vm_page_unqueue_nowakeup(mem);
                   vm_page_wakeup(mem);
           }
           vm_object_drop(&kernel_object);
   
           /*
            * And finally, mark the data as non-pageable.
            *
            * NOTE: vm_map_wire() handles any kstack guard.
            */
           vm_map_wire(map, addr, addr + size, kmflags);
   
           return (addr);
   }
   
   /*
    * Release a region of kernel virtual memory allocated with kmem_alloc,
    * and return the physical pages associated with that region.
    *
    * WARNING!  If the caller entered pages into the region using pmap_kenter()
    * it must remove the pages using pmap_kremove[_quick]() before freeing the
    * underlying kmem, otherwise resident_count will be mistabulated.
    *
    * No requirements.
    */
   void
   kmem_free(vm_map_t map, vm_offset_t addr, vm_size_t size)
   {
           vm_map_remove(map, trunc_page(addr), round_page(addr + size));
   }
   
   /*
    * Used to break a system map into smaller maps, usually to reduce
    * contention and to provide large KVA spaces for subsystems like the
    * buffer cache.
    *
    *      parent          Map to take range from
    *      result  
    *      size            Size of range to find
    *      min, max        Returned endpoints of map
    *      pageable        Can the region be paged
    *
    * No requirements.
    */
   void
   kmem_suballoc(vm_map_t parent, vm_map_t result,
                 vm_offset_t *min, vm_offset_t *max, vm_size_t size)
   {
           int ret;
   
           size = round_page(size);
   
           *min = (vm_offset_t) vm_map_min(parent);
           ret = vm_map_find(parent, NULL, (vm_offset_t) 0,
                             min, size, PAGE_SIZE,
                             TRUE, VM_MAPTYPE_UNSPECIFIED,
                             VM_PROT_ALL, VM_PROT_ALL,
                             0);
           if (ret != KERN_SUCCESS) {
                   kprintf("kmem_suballoc: bad status return of %d.\n", ret);
                   panic("kmem_suballoc");
           }
           *max = *min + size;
           pmap_reference(vm_map_pmap(parent));
           vm_map_init(result, *min, *max, vm_map_pmap(parent));
           if ((ret = vm_map_submap(parent, *min, *max, result)) != KERN_SUCCESS)
                   panic("kmem_suballoc: unable to change range to submap");
   }
   
   /*
    * 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.
    *
    * No requirements.
    */
   vm_offset_t
   kmem_alloc_wait(vm_map_t map, vm_size_t size)
   {
           vm_offset_t addr;
           int count;
   
           size = round_page(size);
   
           count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
   
           for (;;) {
                   /*
                    * To make this work for more than one map, use the map's lock
                    * to lock out sleepers/wakers.
                    */
                   vm_map_lock(map);
                   if (vm_map_findspace(map, vm_map_min(map),
                                        size, PAGE_SIZE, 0, &addr) == 0) {
                           break;
                   }
                   /* no space now; see if we can ever get space */
                   if (vm_map_max(map) - vm_map_min(map) < size) {
                           vm_map_entry_release(count);
                           vm_map_unlock(map);
                           return (0);
                   }
                   vm_map_unlock(map);
                   tsleep(map, 0, "kmaw", 0);
           }
           vm_map_insert(map, &count,
                         NULL, (vm_offset_t) 0,
                         addr, addr + size,
                         VM_MAPTYPE_NORMAL,
                         VM_PROT_ALL, VM_PROT_ALL,
                         0);
           vm_map_unlock(map);
           vm_map_entry_release(count);
   
           return (addr);
   }
   
   /*
    *  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.
    */
   vm_offset_t
   kmem_alloc_attr(vm_map_t map, vm_size_t size, int flags, vm_paddr_t low,
       vm_paddr_t high, vm_memattr_t memattr)
   {
           vm_offset_t addr, i, offset;
           vm_page_t m;
           int count;
   
           size = round_page(size);
           count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
           vm_map_lock(map);
           if (vm_map_findspace(map, vm_map_min(map), size, PAGE_SIZE,
                                   flags, &addr)) {
                   vm_map_unlock(map);
                   vm_map_entry_release(count);
                   return (0);
           }
           offset = addr - vm_map_min(&kernel_map);
           vm_object_hold(&kernel_object);
           vm_object_reference_locked(&kernel_object);
           vm_map_insert(map, &count, &kernel_object, offset, addr, addr + size,
                   VM_MAPTYPE_NORMAL, VM_PROT_ALL, VM_PROT_ALL, 0);
           vm_map_unlock(map);
           vm_map_entry_release(count);
           vm_object_drop(&kernel_object);
           for (i = 0; i < size; i += PAGE_SIZE) {
                   m = vm_page_alloc_contig(low, high, PAGE_SIZE, 0, PAGE_SIZE, memattr);
                   if (!m) {
                           return (0);
                   }
                   vm_object_hold(&kernel_object);
                   vm_page_insert(m, &kernel_object, OFF_TO_IDX(offset + i));
                   vm_object_drop(&kernel_object);
                   if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
                           pmap_zero_page(VM_PAGE_TO_PHYS(m));
                   m->valid = VM_PAGE_BITS_ALL;
           }
           vm_map_wire(map, addr, addr + size, 0);
           return (addr);
   }
   
   
   /*
    * Returns memory to a submap of the kernel, and wakes up any processes
    * waiting for memory in that map.
    *
    * No requirements.
    */
   void
   kmem_free_wakeup(vm_map_t map, vm_offset_t addr, vm_size_t size)
   {
           int count;
   
           count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
           vm_map_lock(map);
           vm_map_delete(map, trunc_page(addr), round_page(addr + size), &count);
           wakeup(map);
           vm_map_unlock(map);
           vm_map_entry_release(count);
   }
   
   /*
    * Create the kernel_ma for (KvaStart,KvaEnd) and insert mappings to
    * cover areas already allocated or reserved thus far.
    *
    * The areas (virtual_start, virtual_end) and (virtual2_start, virtual2_end)
    * are available so the cutouts are the areas around these ranges between
    * KvaStart and KvaEnd.
    *
    * Depend on the zalloc bootstrap cache to get our vm_map_entry_t.
    * Called from the low level boot code only.
    */
   void
   kmem_init(void)
   {
           vm_offset_t addr;
           vm_map_t m;
           int count;
   
           m = vm_map_create(&kernel_map, &kernel_pmap, KvaStart, KvaEnd);
           vm_map_lock(m);
           /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
           m->system_map = 1;
           count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
           addr = KvaStart;
           if (virtual2_start) {
                   if (addr < virtual2_start) {
                           vm_map_insert(m, &count, NULL, (vm_offset_t) 0,
                                         addr, virtual2_start,
                                         VM_MAPTYPE_NORMAL,
                                         VM_PROT_ALL, VM_PROT_ALL,
                                         0);
                   }
                   addr = virtual2_end;
           }
           if (addr < virtual_start) {
                   vm_map_insert(m, &count, NULL, (vm_offset_t) 0,
                                 addr, virtual_start,
                                 VM_MAPTYPE_NORMAL,
                                 VM_PROT_ALL, VM_PROT_ALL,
                                 0);
           }
           addr = virtual_end;
           if (addr < KvaEnd) {
                   vm_map_insert(m, &count, NULL, (vm_offset_t) 0,
                                 addr, KvaEnd,
                                 VM_MAPTYPE_NORMAL,
                                 VM_PROT_ALL, VM_PROT_ALL,
                                 0);
           }
           /* ... and ending with the completion of the above `insert' */
           vm_map_unlock(m);
           vm_map_entry_release(count);
   }
   
   /*
    * No requirements.
    */
   static int
   kvm_size(SYSCTL_HANDLER_ARGS)
   {
           unsigned long ksize = KvaSize;
   
           return sysctl_handle_long(oidp, &ksize, 0, req);
   }
   SYSCTL_PROC(_vm, OID_AUTO, kvm_size, CTLTYPE_ULONG|CTLFLAG_RD,
       0, 0, kvm_size, "LU", "Size of KVM");
    
   /*
    * No requirements.
    */
   static int
   kvm_free(SYSCTL_HANDLER_ARGS)
   {
           unsigned long kfree = virtual_end - kernel_vm_end;
   
           return sysctl_handle_long(oidp, &kfree, 0, req);
   }
   SYSCTL_PROC(_vm, OID_AUTO, kvm_free, CTLTYPE_ULONG|CTLFLAG_RD,
       0, 0, kvm_free, "LU", "Amount of KVM free");
   

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