The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright (c) 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * The Mach Operating System project at Carnegie-Mellon University.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      from: @(#)vm_kern.c     8.3 (Berkeley) 1/12/94
   33  *
   34  *
   35  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   36  * All rights reserved.
   37  *
   38  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   39  *
   40  * Permission to use, copy, modify and distribute this software and
   41  * its documentation is hereby granted, provided that both the copyright
   42  * notice and this permission notice appear in all copies of the
   43  * software, derivative works or modified versions, and any portions
   44  * thereof, and that both notices appear in supporting documentation.
   45  *
   46  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   47  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   48  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   49  *
   50  * Carnegie Mellon requests users of this software to return to
   51  *
   52  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   53  *  School of Computer Science
   54  *  Carnegie Mellon University
   55  *  Pittsburgh PA 15213-3890
   56  *
   57  * any improvements or extensions that they make and grant Carnegie the
   58  * rights to redistribute these changes.
   59  */
   60 
   61 /*
   62  *      Kernel memory management.
   63  */
   64 
   65 #include <sys/cdefs.h>
   66 __FBSDID("$FreeBSD: src/sys/vm/vm_kern.c,v 1.122 2005/01/07 02:29:27 imp Exp $");
   67 
   68 #include <sys/param.h>
   69 #include <sys/systm.h>
   70 #include <sys/kernel.h>         /* for ticks and hz */
   71 #include <sys/lock.h>
   72 #include <sys/mutex.h>
   73 #include <sys/proc.h>
   74 #include <sys/malloc.h>
   75 
   76 #include <vm/vm.h>
   77 #include <vm/vm_param.h>
   78 #include <vm/pmap.h>
   79 #include <vm/vm_map.h>
   80 #include <vm/vm_object.h>
   81 #include <vm/vm_page.h>
   82 #include <vm/vm_pageout.h>
   83 #include <vm/vm_extern.h>
   84 
   85 vm_map_t kernel_map=0;
   86 vm_map_t kmem_map=0;
   87 vm_map_t exec_map=0;
   88 vm_map_t pipe_map;
   89 vm_map_t buffer_map=0;
   90 
   91 /*
   92  *      kmem_alloc_nofault:
   93  *
   94  *      Allocate a virtual address range with no underlying object and
   95  *      no initial mapping to physical memory.  Any mapping from this
   96  *      range to physical memory must be explicitly created prior to
   97  *      its use, typically with pmap_qenter().  Any attempt to create
   98  *      a mapping on demand through vm_fault() will result in a panic. 
   99  */
  100 vm_offset_t
  101 kmem_alloc_nofault(map, size)
  102         vm_map_t map;
  103         vm_size_t size;
  104 {
  105         vm_offset_t addr;
  106         int result;
  107 
  108         size = round_page(size);
  109         addr = vm_map_min(map);
  110         result = vm_map_find(map, NULL, 0,
  111             &addr, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  112         if (result != KERN_SUCCESS) {
  113                 return (0);
  114         }
  115         return (addr);
  116 }
  117 
  118 /*
  119  *      Allocate wired-down memory in the kernel's address map
  120  *      or a submap.
  121  */
  122 vm_offset_t
  123 kmem_alloc(map, size)
  124         vm_map_t map;
  125         vm_size_t size;
  126 {
  127         vm_offset_t addr;
  128         vm_offset_t offset;
  129         vm_offset_t i;
  130 
  131         size = round_page(size);
  132 
  133         /*
  134          * Use the kernel object for wired-down kernel pages. Assume that no
  135          * region of the kernel object is referenced more than once.
  136          */
  137 
  138         /*
  139          * Locate sufficient space in the map.  This will give us the final
  140          * virtual address for the new memory, and thus will tell us the
  141          * offset within the kernel map.
  142          */
  143         vm_map_lock(map);
  144         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  145                 vm_map_unlock(map);
  146                 return (0);
  147         }
  148         offset = addr - VM_MIN_KERNEL_ADDRESS;
  149         vm_object_reference(kernel_object);
  150         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  151                 VM_PROT_ALL, VM_PROT_ALL, 0);
  152         vm_map_unlock(map);
  153 
  154         /*
  155          * Guarantee that there are pages already in this object before
  156          * calling vm_map_wire.  This is to prevent the following
  157          * scenario:
  158          *
  159          * 1) Threads have swapped out, so that there is a pager for the
  160          * kernel_object. 2) The kmsg zone is empty, and so we are
  161          * kmem_allocing a new page for it. 3) vm_map_wire calls vm_fault;
  162          * there is no page, but there is a pager, so we call
  163          * pager_data_request.  But the kmsg zone is empty, so we must
  164          * kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
  165          * we get the data back from the pager, it will be (very stale)
  166          * non-zero data.  kmem_alloc is defined to return zero-filled memory.
  167          *
  168          * We're intentionally not activating the pages we allocate to prevent a
  169          * race with page-out.  vm_map_wire will wire the pages.
  170          */
  171         VM_OBJECT_LOCK(kernel_object);
  172         for (i = 0; i < size; i += PAGE_SIZE) {
  173                 vm_page_t mem;
  174 
  175                 mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
  176                     VM_ALLOC_NOBUSY | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
  177                 mem->valid = VM_PAGE_BITS_ALL;
  178                 vm_page_lock_queues();
  179                 vm_page_unmanage(mem);
  180                 vm_page_unlock_queues();
  181         }
  182         VM_OBJECT_UNLOCK(kernel_object);
  183 
  184         /*
  185          * And finally, mark the data as non-pageable.
  186          */
  187         (void) vm_map_wire(map, addr, addr + size,
  188             VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
  189 
  190         return (addr);
  191 }
  192 
  193 /*
  194  *      kmem_free:
  195  *
  196  *      Release a region of kernel virtual memory allocated
  197  *      with kmem_alloc, and return the physical pages
  198  *      associated with that region.
  199  *
  200  *      This routine may not block on kernel maps.
  201  */
  202 void
  203 kmem_free(map, addr, size)
  204         vm_map_t map;
  205         vm_offset_t addr;
  206         vm_size_t size;
  207 {
  208 
  209         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  210 }
  211 
  212 /*
  213  *      kmem_suballoc:
  214  *
  215  *      Allocates a map to manage a subrange
  216  *      of the kernel virtual address space.
  217  *
  218  *      Arguments are as follows:
  219  *
  220  *      parent          Map to take range from
  221  *      min, max        Returned endpoints of map
  222  *      size            Size of range to find
  223  */
  224 vm_map_t
  225 kmem_suballoc(parent, min, max, size)
  226         vm_map_t parent;
  227         vm_offset_t *min, *max;
  228         vm_size_t size;
  229 {
  230         int ret;
  231         vm_map_t result;
  232 
  233         size = round_page(size);
  234 
  235         *min = (vm_offset_t) vm_map_min(parent);
  236         ret = vm_map_find(parent, NULL, (vm_offset_t) 0,
  237             min, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, 0);
  238         if (ret != KERN_SUCCESS) {
  239                 printf("kmem_suballoc: bad status return of %d.\n", ret);
  240                 panic("kmem_suballoc");
  241         }
  242         *max = *min + size;
  243         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  244         if (result == NULL)
  245                 panic("kmem_suballoc: cannot create submap");
  246         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  247                 panic("kmem_suballoc: unable to change range to submap");
  248         return (result);
  249 }
  250 
  251 /*
  252  *      kmem_malloc:
  253  *
  254  *      Allocate wired-down memory in the kernel's address map for the higher
  255  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  256  *      kmem_alloc() because we may need to allocate memory at interrupt
  257  *      level where we cannot block (canwait == FALSE).
  258  *
  259  *      This routine has its own private kernel submap (kmem_map) and object
  260  *      (kmem_object).  This, combined with the fact that only malloc uses
  261  *      this routine, ensures that we will never block in map or object waits.
  262  *
  263  *      Note that this still only works in a uni-processor environment and
  264  *      when called at splhigh().
  265  *
  266  *      We don't worry about expanding the map (adding entries) since entries
  267  *      for wired maps are statically allocated.
  268  *
  269  *      NOTE:  This routine is not supposed to block if M_NOWAIT is set, but
  270  *      I have not verified that it actually does not block.
  271  *
  272  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  273  *      which we never free.
  274  */
  275 vm_offset_t
  276 kmem_malloc(map, size, flags)
  277         vm_map_t map;
  278         vm_size_t size;
  279         int flags;
  280 {
  281         vm_offset_t offset, i;
  282         vm_map_entry_t entry;
  283         vm_offset_t addr;
  284         vm_page_t m;
  285         int pflags;
  286 
  287         size = round_page(size);
  288         addr = vm_map_min(map);
  289 
  290         /*
  291          * Locate sufficient space in the map.  This will give us the final
  292          * virtual address for the new memory, and thus will tell us the
  293          * offset within the kernel map.
  294          */
  295         vm_map_lock(map);
  296         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  297                 vm_map_unlock(map);
  298                 if ((flags & M_NOWAIT) == 0)
  299                         panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
  300                                 (long)size, (long)map->size);
  301                 return (0);
  302         }
  303         offset = addr - VM_MIN_KERNEL_ADDRESS;
  304         vm_object_reference(kmem_object);
  305         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  306                 VM_PROT_ALL, VM_PROT_ALL, 0);
  307 
  308         /*
  309          * Note: if M_NOWAIT specified alone, allocate from 
  310          * interrupt-safe queues only (just the free list).  If 
  311          * M_USE_RESERVE is also specified, we can also
  312          * allocate from the cache.  Neither of the latter two
  313          * flags may be specified from an interrupt since interrupts
  314          * are not allowed to mess with the cache queue.
  315          */
  316 
  317         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  318                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  319         else
  320                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  321 
  322         if (flags & M_ZERO)
  323                 pflags |= VM_ALLOC_ZERO;
  324 
  325         VM_OBJECT_LOCK(kmem_object);
  326         for (i = 0; i < size; i += PAGE_SIZE) {
  327 retry:
  328                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  329 
  330                 /*
  331                  * Ran out of space, free everything up and return. Don't need
  332                  * to lock page queues here as we know that the pages we got
  333                  * aren't on any queues.
  334                  */
  335                 if (m == NULL) {
  336                         if ((flags & M_NOWAIT) == 0) {
  337                                 VM_OBJECT_UNLOCK(kmem_object);
  338                                 vm_map_unlock(map);
  339                                 VM_WAIT;
  340                                 vm_map_lock(map);
  341                                 VM_OBJECT_LOCK(kmem_object);
  342                                 goto retry;
  343                         }
  344                         /* 
  345                          * Free the pages before removing the map entry.
  346                          * They are already marked busy.  Calling
  347                          * vm_map_delete before the pages has been freed or
  348                          * unbusied will cause a deadlock.
  349                          */
  350                         while (i != 0) {
  351                                 i -= PAGE_SIZE;
  352                                 m = vm_page_lookup(kmem_object,
  353                                                    OFF_TO_IDX(offset + i));
  354                                 vm_page_lock_queues();
  355                                 vm_page_unwire(m, 0);
  356                                 vm_page_free(m);
  357                                 vm_page_unlock_queues();
  358                         }
  359                         VM_OBJECT_UNLOCK(kmem_object);
  360                         vm_map_delete(map, addr, addr + size);
  361                         vm_map_unlock(map);
  362                         return (0);
  363                 }
  364                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  365                         pmap_zero_page(m);
  366                 m->valid = VM_PAGE_BITS_ALL;
  367                 vm_page_lock_queues();
  368                 vm_page_unmanage(m);
  369                 vm_page_unlock_queues();
  370         }
  371         VM_OBJECT_UNLOCK(kmem_object);
  372 
  373         /*
  374          * Mark map entry as non-pageable. Assert: vm_map_insert() will never
  375          * be able to extend the previous entry so there will be a new entry
  376          * exactly corresponding to this address range and it will have
  377          * wired_count == 0.
  378          */
  379         if (!vm_map_lookup_entry(map, addr, &entry) ||
  380             entry->start != addr || entry->end != addr + size ||
  381             entry->wired_count != 0)
  382                 panic("kmem_malloc: entry not found or misaligned");
  383         entry->wired_count = 1;
  384 
  385         /*
  386          * At this point, the kmem_object must be unlocked because
  387          * vm_map_simplify_entry() calls vm_object_deallocate(), which
  388          * locks the kmem_object.
  389          */
  390         vm_map_simplify_entry(map, entry);
  391 
  392         /*
  393          * Loop thru pages, entering them in the pmap. (We cannot add them to
  394          * the wired count without wrapping the vm_page_queue_lock in
  395          * splimp...)
  396          */
  397         VM_OBJECT_LOCK(kmem_object);
  398         for (i = 0; i < size; i += PAGE_SIZE) {
  399                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  400                 /*
  401                  * Because this is kernel_pmap, this call will not block.
  402                  */
  403                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL, 1);
  404                 vm_page_lock_queues();
  405                 vm_page_flag_set(m, PG_WRITEABLE | PG_REFERENCED);
  406                 vm_page_wakeup(m);
  407                 vm_page_unlock_queues();
  408         }
  409         VM_OBJECT_UNLOCK(kmem_object);
  410         vm_map_unlock(map);
  411 
  412         return (addr);
  413 }
  414 
  415 /*
  416  *      kmem_alloc_wait:
  417  *
  418  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  419  *      has no room, the caller sleeps waiting for more memory in the submap.
  420  *
  421  *      This routine may block.
  422  */
  423 vm_offset_t
  424 kmem_alloc_wait(map, size)
  425         vm_map_t map;
  426         vm_size_t size;
  427 {
  428         vm_offset_t addr;
  429 
  430         size = round_page(size);
  431 
  432         for (;;) {
  433                 /*
  434                  * To make this work for more than one map, use the map's lock
  435                  * to lock out sleepers/wakers.
  436                  */
  437                 vm_map_lock(map);
  438                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  439                         break;
  440                 /* no space now; see if we can ever get space */
  441                 if (vm_map_max(map) - vm_map_min(map) < size) {
  442                         vm_map_unlock(map);
  443                         return (0);
  444                 }
  445                 map->needs_wakeup = TRUE;
  446                 vm_map_unlock_and_wait(map, FALSE);
  447         }
  448         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL, VM_PROT_ALL, 0);
  449         vm_map_unlock(map);
  450         return (addr);
  451 }
  452 
  453 /*
  454  *      kmem_free_wakeup:
  455  *
  456  *      Returns memory to a submap of the kernel, and wakes up any processes
  457  *      waiting for memory in that map.
  458  */
  459 void
  460 kmem_free_wakeup(map, addr, size)
  461         vm_map_t map;
  462         vm_offset_t addr;
  463         vm_size_t size;
  464 {
  465 
  466         vm_map_lock(map);
  467         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  468         if (map->needs_wakeup) {
  469                 map->needs_wakeup = FALSE;
  470                 vm_map_wakeup(map);
  471         }
  472         vm_map_unlock(map);
  473 }
  474 
  475 /*
  476  *      kmem_init:
  477  *
  478  *      Create the kernel map; insert a mapping covering kernel text, 
  479  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  480  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  481  *      `start' as allocated, and the range between `start' and `end' as free.
  482  */
  483 void
  484 kmem_init(start, end)
  485         vm_offset_t start, end;
  486 {
  487         vm_map_t m;
  488 
  489         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  490         m->system_map = 1;
  491         vm_map_lock(m);
  492         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  493         kernel_map = m;
  494         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  495             VM_MIN_KERNEL_ADDRESS, start, VM_PROT_ALL, VM_PROT_ALL, 0);
  496         /* ... and ending with the completion of the above `insert' */
  497         vm_map_unlock(m);
  498 }

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