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/11.1/sys/vm/vm_kern.c 316073 2017-03-28 06:07:59Z 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/proc.h>
    #include <sys/malloc.h>
    #include <sys/rwlock.h>
    #include <sys/sysctl.h>
    #include <sys/vmem.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.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_extern.h>
    #include <vm/uma.h>
    
    vm_map_t kernel_map;
    vm_map_t exec_map;
    vm_map_t pipe_map;
    
    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;
    
   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__) || defined(__sparc64__)
       &vm_max_kernel_address, 0,
   #else
       SYSCTL_NULL_ULONG_PTR, VM_MAX_KERNEL_ADDRESS,
   #endif
       "Max kernel address");
   
   /*
    *      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(size)
           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(addr, size)
           vm_offset_t addr;
           vm_size_t size;
   {
   
           size = round_page(size);
           vmem_free(kernel_arena, addr, size);
   }
   
   /*
    *      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(vmem_t *vmem, vm_size_t size, int flags, vm_paddr_t low,
       vm_paddr_t high, vm_memattr_t memattr)
   {
           vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
           vm_offset_t addr, i, offset;
           vm_page_t m;
           int pflags, tries;
   
           size = round_page(size);
           if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
                   return (0);
           offset = addr - VM_MIN_KERNEL_ADDRESS;
           pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
           VM_OBJECT_WLOCK(object);
           for (i = 0; i < size; i += PAGE_SIZE) {
                   tries = 0;
   retry:
                   m = vm_page_alloc_contig(object, atop(offset + i),
                       pflags, 1, low, high, PAGE_SIZE, 0, memattr);
                   if (m == NULL) {
                           VM_OBJECT_WUNLOCK(object);
                           if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
                                   if (!vm_page_reclaim_contig(pflags, 1,
                                       low, high, PAGE_SIZE, 0) &&
                                       (flags & M_WAITOK) != 0)
                                           VM_WAIT;
                                   VM_OBJECT_WLOCK(object);
                                   tries++;
                                   goto retry;
                           }
                           kmem_unback(object, addr, i);
                           vmem_free(vmem, addr, size);
                           return (0);
                   }
                   if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
                           pmap_zero_page(m);
                   m->valid = VM_PAGE_BITS_ALL;
                   pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
                       VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
           }
           VM_OBJECT_WUNLOCK(object);
           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.
    */
   vm_offset_t
   kmem_alloc_contig(struct vmem *vmem, 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)
   {
           vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
           vm_offset_t addr, offset, tmp;
           vm_page_t end_m, m;
           u_long npages;
           int pflags, tries;
    
           size = round_page(size);
           if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
                   return (0);
           offset = addr - VM_MIN_KERNEL_ADDRESS;
           pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
           npages = atop(size);
           VM_OBJECT_WLOCK(object);
           tries = 0;
   retry:
           m = vm_page_alloc_contig(object, atop(offset), pflags,
               npages, low, high, alignment, boundary, memattr);
           if (m == NULL) {
                   VM_OBJECT_WUNLOCK(object);
                   if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
                           if (!vm_page_reclaim_contig(pflags, npages, low, high,
                               alignment, boundary) && (flags & M_WAITOK) != 0)
                                   VM_WAIT;
                           VM_OBJECT_WLOCK(object);
                           tries++;
                           goto retry;
                   }
                   vmem_free(vmem, addr, size);
                   return (0);
           }
           end_m = m + npages;
           tmp = addr;
           for (; m < end_m; m++) {
                   if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
                           pmap_zero_page(m);
                   m->valid = VM_PAGE_BITS_ALL;
                   pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
                       VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
                   tmp += PAGE_SIZE;
           }
           VM_OBJECT_WUNLOCK(object);
           return (addr);
   }
   
   /*
    *      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, 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_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 pages in the kernel's address space.
    */
   vm_offset_t
   kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
   {
           vm_offset_t addr;
           int rv;
   
           size = round_page(size);
           if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
                   return (0);
   
           rv = kmem_back((vmem == kmem_arena) ? kmem_object : kernel_object,
               addr, size, flags);
           if (rv != KERN_SUCCESS) {
                   vmem_free(vmem, addr, size);
                   return (0);
           }
           return (addr);
   }
   
   /*
    *      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 offset, i;
           vm_page_t m;
           int pflags;
   
           KASSERT(object == kmem_object || object == kernel_object,
               ("kmem_back: only supports kernel objects."));
   
           offset = addr - VM_MIN_KERNEL_ADDRESS;
           pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
   
           VM_OBJECT_WLOCK(object);
           for (i = 0; i < size; i += PAGE_SIZE) {
   retry:
                   m = vm_page_alloc(object, atop(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) {
                           VM_OBJECT_WUNLOCK(object);
                           if ((flags & M_NOWAIT) == 0) {
                                   VM_WAIT;
                                   VM_OBJECT_WLOCK(object);
                                   goto retry;
                           }
                           kmem_unback(object, addr, i);
                           return (KERN_NO_SPACE);
                   }
                   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));
                   m->valid = VM_PAGE_BITS_ALL;
                   pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
                       VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
           }
           VM_OBJECT_WUNLOCK(object);
   
           return (KERN_SUCCESS);
   }
   
   /*
    *      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.
    */
   void
   kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
   {
           vm_page_t m;
           vm_offset_t i, offset;
   
           KASSERT(object == kmem_object || object == kernel_object,
               ("kmem_unback: only supports kernel objects."));
   
           pmap_remove(kernel_pmap, addr, addr + size);
           offset = addr - VM_MIN_KERNEL_ADDRESS;
           VM_OBJECT_WLOCK(object);
           for (i = 0; i < size; i += PAGE_SIZE) {
                   m = vm_page_lookup(object, atop(offset + i));
                   vm_page_unwire(m, PQ_NONE);
                   vm_page_free(m);
           }
           VM_OBJECT_WUNLOCK(object);
   }
   
   /*
    *      kmem_free:
    *
    *      Free memory allocated with kmem_malloc.  The size must match the
    *      original allocation.
    */
   void
   kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
   {
   
           size = round_page(size);
           kmem_unback((vmem == kmem_arena) ? kmem_object : kernel_object,
               addr, size);
           vmem_free(vmem, 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(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);
   }
   
   /*
    *      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(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);
   }
   
   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(NULL, 0, VM_ALLOC_NORMAL |
               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);
           pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
   
           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);
   }
   
   #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 & ~(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_RW, 0, 0,
       debug_vm_lowmem, "I", "set to trigger vm_lowmem event with given flags");
   #endif

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