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

     /*-
      * 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.
     * 4. 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: releng/9.0/sys/vm/vm_kern.c 224746 2011-08-09 21:01:36Z kib $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>         /* for ticks and hz */
    #include <sys/eventhandler.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/malloc.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.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_extern.h>
    #include <vm/uma.h>
    
    vm_map_t kernel_map=0;
    vm_map_t kmem_map=0;
    vm_map_t exec_map=0;
    vm_map_t pipe_map;
    vm_map_t buffer_map=0;
    
    const void *zero_region;
    CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
    
    /*
     *      kmem_alloc_nofault:
     *
    *      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
   kmem_alloc_nofault(map, size)
           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, 0, &addr, size, VMFS_ANY_SPACE,
               VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
           if (result != KERN_SUCCESS) {
                   return (0);
           }
           return (addr);
   }
   
   /*
    *      kmem_alloc_nofault_space:
    *
    *      Allocate a virtual address range with no underlying object and
    *      no initial mapping to physical memory within the specified
    *      address space.  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
   kmem_alloc_nofault_space(map, size, find_space)
           vm_map_t map;
           vm_size_t size;
           int find_space;
   {
           vm_offset_t addr;
           int result;
   
           size = round_page(size);
           addr = vm_map_min(map);
           result = vm_map_find(map, NULL, 0, &addr, size, find_space,
               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.
    */
   vm_offset_t
   kmem_alloc(map, size)
           vm_map_t map;
           vm_size_t size;
   {
           vm_offset_t addr;
           vm_offset_t offset;
           vm_offset_t i;
   
           size = round_page(size);
   
           /*
            * 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, &addr)) {
                   vm_map_unlock(map);
                   return (0);
           }
           offset = addr - VM_MIN_KERNEL_ADDRESS;
           vm_object_reference(kernel_object);
           vm_map_insert(map, kernel_object, offset, addr, addr + size,
                   VM_PROT_ALL, VM_PROT_ALL, 0);
           vm_map_unlock(map);
   
           /*
            * 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_LOCK(kernel_object);
           for (i = 0; i < size; i += PAGE_SIZE) {
                   vm_page_t mem;
   
                   mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
                       VM_ALLOC_NOBUSY | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
                   mem->valid = VM_PAGE_BITS_ALL;
                   KASSERT((mem->oflags & VPO_UNMANAGED) != 0,
                       ("kmem_alloc: page %p is managed", mem));
           }
           VM_OBJECT_UNLOCK(kernel_object);
   
           /*
            * And finally, mark the data as non-pageable.
            */
           (void) vm_map_wire(map, addr, addr + size,
               VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
   
           return (addr);
   }
   
   /*
    *      kmem_free:
    *
    *      Release a region of kernel virtual memory allocated
    *      with kmem_alloc, and return the physical pages
    *      associated with that region.
    *
    *      This routine may not block on kernel maps.
    */
   void
   kmem_free(map, addr, size)
           vm_map_t map;
           vm_offset_t addr;
           vm_size_t size;
   {
   
           (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
   }
   
   /*
    *      kmem_suballoc:
    *
    *      Allocates 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
    */
   vm_map_t
   kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
       vm_size_t size, boolean_t superpage_align)
   {
           int ret;
           vm_map_t result;
   
           size = round_page(size);
   
           *min = vm_map_min(parent);
           ret = vm_map_find(parent, NULL, 0, min, size, superpage_align ?
               VMFS_ALIGNED_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
               MAP_ACC_NO_CHARGE);
           if (ret != KERN_SUCCESS)
                   panic("kmem_suballoc: bad status return of %d", ret);
           *max = *min + size;
           result = vm_map_create(vm_map_pmap(parent), *min, *max);
           if (result == NULL)
                   panic("kmem_suballoc: cannot create submap");
           if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
                   panic("kmem_suballoc: unable to change range to submap");
           return (result);
   }
   
   /*
    *      kmem_malloc:
    *
    *      Allocate wired-down memory in the kernel's address map for the higher
    *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
    *      kmem_alloc() because we may need to allocate memory at interrupt
    *      level where we cannot block (canwait == FALSE).
    *
    *      This routine has its own private kernel submap (kmem_map) and object
    *      (kmem_object).  This, combined with the fact that only malloc uses
    *      this routine, ensures that we will never block in map or object waits.
    *
    *      We don't worry about expanding the map (adding entries) since entries
    *      for wired maps are statically allocated.
    *
    *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
    *      which we never free.
    */
   vm_offset_t
   kmem_malloc(map, size, flags)
           vm_map_t map;
           vm_size_t size;
           int flags;
   {
           vm_offset_t addr;
           int i, rv;
   
           size = round_page(size);
           addr = vm_map_min(map);
   
           /*
            * 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, &addr)) {
                   vm_map_unlock(map);
                   if ((flags & M_NOWAIT) == 0) {
                           for (i = 0; i < 8; i++) {
                                   EVENTHANDLER_INVOKE(vm_lowmem, 0);
                                   uma_reclaim();
                                   vm_map_lock(map);
                                   if (vm_map_findspace(map, vm_map_min(map),
                                       size, &addr) == 0) {
                                           break;
                                   }
                                   vm_map_unlock(map);
                                   tsleep(&i, 0, "nokva", (hz / 4) * (i + 1));
                           }
                           if (i == 8) {
                                   panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
                                       (long)size, (long)map->size);
                           }
                   } else {
                           return (0);
                   }
           }
   
           rv = kmem_back(map, addr, size, flags);
           vm_map_unlock(map);
           return (rv == KERN_SUCCESS ? addr : 0);
   }
   
   /*
    *      kmem_back:
    *
    *      Allocate physical pages for the specified virtual address range.
    */
   int
   kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
   {
           vm_offset_t offset, i;
           vm_map_entry_t entry;
           vm_page_t m;
           int pflags;
           boolean_t found;
   
           KASSERT(vm_map_locked(map), ("kmem_back: map %p is not locked", map));
           offset = addr - VM_MIN_KERNEL_ADDRESS;
           vm_object_reference(kmem_object);
           vm_map_insert(map, kmem_object, offset, addr, addr + size,
               VM_PROT_ALL, VM_PROT_ALL, 0);
   
           /*
            * Assert: vm_map_insert() will never be able to extend the
            * previous entry so vm_map_lookup_entry() will find a new
            * entry exactly corresponding to this address range and it
            * will have wired_count == 0.
            */
           found = vm_map_lookup_entry(map, addr, &entry);
           KASSERT(found && entry->start == addr && entry->end == addr + size &&
               entry->wired_count == 0 && (entry->eflags & MAP_ENTRY_IN_TRANSITION)
               == 0, ("kmem_back: entry not found or misaligned"));
   
           if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
                   pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
           else
                   pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
   
           if (flags & M_ZERO)
                   pflags |= VM_ALLOC_ZERO;
   
           VM_OBJECT_LOCK(kmem_object);
           for (i = 0; i < size; i += PAGE_SIZE) {
   retry:
                   m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
   
                   /*
                    * 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) {
                                   VM_OBJECT_UNLOCK(kmem_object);
                                   entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                                   vm_map_unlock(map);
                                   VM_WAIT;
                                   vm_map_lock(map);
                                   KASSERT(
   (entry->eflags & (MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_NEEDS_WAKEUP)) ==
                                       MAP_ENTRY_IN_TRANSITION,
                                       ("kmem_back: volatile entry"));
                                   entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
                                   VM_OBJECT_LOCK(kmem_object);
                                   goto retry;
                           }
                           /* 
                            * Free the pages before removing the map entry.
                            * They are already marked busy.  Calling
                            * vm_map_delete before the pages has been freed or
                            * unbusied will cause a deadlock.
                            */
                           while (i != 0) {
                                   i -= PAGE_SIZE;
                                   m = vm_page_lookup(kmem_object,
                                                      OFF_TO_IDX(offset + i));
                                   vm_page_unwire(m, 0);
                                   vm_page_free(m);
                           }
                           VM_OBJECT_UNLOCK(kmem_object);
                           vm_map_delete(map, addr, addr + size);
                           return (KERN_NO_SPACE);
                   }
                   if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
                           pmap_zero_page(m);
                   m->valid = VM_PAGE_BITS_ALL;
                   KASSERT((m->oflags & VPO_UNMANAGED) != 0,
                       ("kmem_malloc: page %p is managed", m));
           }
           VM_OBJECT_UNLOCK(kmem_object);
   
           /*
            * Mark map entry as non-pageable.  Repeat the assert.
            */
           KASSERT(entry->start == addr && entry->end == addr + size &&
               entry->wired_count == 0,
               ("kmem_back: entry not found or misaligned after allocation"));
           entry->wired_count = 1;
   
           /*
            * At this point, the kmem_object must be unlocked because
            * vm_map_simplify_entry() calls vm_object_deallocate(), which
            * locks the kmem_object.
            */
           vm_map_simplify_entry(map, entry);
   
           /*
            * Loop thru pages, entering them in the pmap.
            */
           VM_OBJECT_LOCK(kmem_object);
           for (i = 0; i < size; i += PAGE_SIZE) {
                   m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
                   /*
                    * Because this is kernel_pmap, this call will not block.
                    */
                   pmap_enter(kernel_pmap, addr + i, VM_PROT_ALL, m, VM_PROT_ALL,
                       TRUE);
                   vm_page_wakeup(m);
           }
           VM_OBJECT_UNLOCK(kmem_object);
   
           return (KERN_SUCCESS);
   }
   
   /*
    *      kmem_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
   kmem_alloc_wait(map, size)
           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);
                   if (vm_map_findspace(map, vm_map_min(map), size, &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_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_ALL,
               VM_PROT_ALL, MAP_ACC_CHARGED);
           vm_map_unlock(map);
           return (addr);
   }
   
   /*
    *      kmem_free_wakeup:
    *
    *      Returns memory to a submap of the kernel, and wakes up any processes
    *      waiting for memory in that map.
    */
   void
   kmem_free_wakeup(map, addr, size)
           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);
   }
   
   static void
   kmem_init_zero_region(void)
   {
           vm_offset_t addr, i;
           vm_page_t m;
           int error;
   
           /*
            * 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 = kmem_alloc_nofault(kernel_map, ZERO_REGION_SIZE);
           m = vm_page_alloc(NULL, OFF_TO_IDX(addr - VM_MIN_KERNEL_ADDRESS),
               VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
           if ((m->flags & PG_ZERO) == 0)
                   pmap_zero_page(m);
           for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
                   pmap_qenter(addr + i, &m, 1);
           error = vm_map_protect(kernel_map, addr, addr + ZERO_REGION_SIZE,
               VM_PROT_READ, TRUE);
           KASSERT(error == 0, ("error=%d", error));
   
           zero_region = (const void *)addr;
   }
   
   /*
    *      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.
    */
   void
   kmem_init(start, end)
           vm_offset_t start, end;
   {
           vm_map_t m;
   
           m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
           m->system_map = 1;
           vm_map_lock(m);
           /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
           kernel_map = m;
           (void) vm_map_insert(m, NULL, (vm_ooffset_t) 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' */
           vm_map_unlock(m);
   
           kmem_init_zero_region();
   }
   
   #ifdef DIAGNOSTIC
   /*
    * 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)
                   return (error);
           if (i)   
                   EVENTHANDLER_INVOKE(vm_lowmem, 0);
           return (0);
   }
   
   SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
       debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
   #endif

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