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  * 3. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by the University of
   19  *      California, Berkeley and its contributors.
   20  * 4. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      from: @(#)vm_kern.c     8.3 (Berkeley) 1/12/94
   37  *
   38  *
   39  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   40  * All rights reserved.
   41  *
   42  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   43  *
   44  * Permission to use, copy, modify and distribute this software and
   45  * its documentation is hereby granted, provided that both the copyright
   46  * notice and this permission notice appear in all copies of the
   47  * software, derivative works or modified versions, and any portions
   48  * thereof, and that both notices appear in supporting documentation.
   49  *
   50  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   51  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   52  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   53  *
   54  * Carnegie Mellon requests users of this software to return to
   55  *
   56  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   57  *  School of Computer Science
   58  *  Carnegie Mellon University
   59  *  Pittsburgh PA 15213-3890
   60  *
   61  * any improvements or extensions that they make and grant Carnegie the
   62  * rights to redistribute these changes.
   63  */
   64 
   65 /*
   66  *      Kernel memory management.
   67  */
   68 
   69 #include <sys/cdefs.h>
   70 __FBSDID("$FreeBSD: releng/5.2/sys/vm/vm_kern.c 122383 2003-11-10 00:44:00Z mini $");
   71 
   72 #include <sys/param.h>
   73 #include <sys/systm.h>
   74 #include <sys/kernel.h>         /* for ticks and hz */
   75 #include <sys/lock.h>
   76 #include <sys/mutex.h>
   77 #include <sys/proc.h>
   78 #include <sys/malloc.h>
   79 
   80 #include <vm/vm.h>
   81 #include <vm/vm_param.h>
   82 #include <vm/pmap.h>
   83 #include <vm/vm_map.h>
   84 #include <vm/vm_object.h>
   85 #include <vm/vm_page.h>
   86 #include <vm/vm_pageout.h>
   87 #include <vm/vm_extern.h>
   88 
   89 vm_map_t kernel_map=0;
   90 vm_map_t kmem_map=0;
   91 vm_map_t exec_map=0;
   92 vm_map_t pipe_map;
   93 vm_map_t buffer_map=0;
   94 
   95 /*
   96  *      kmem_alloc_pageable:
   97  *
   98  *      Allocate pageable memory to the kernel's address map.
   99  *      "map" must be kernel_map or a submap of kernel_map.
  100  */
  101 vm_offset_t
  102 kmem_alloc_pageable(map, size)
  103         vm_map_t map;
  104         vm_size_t size;
  105 {
  106         vm_offset_t addr;
  107         int result;
  108 
  109         size = round_page(size);
  110         addr = vm_map_min(map);
  111         result = vm_map_find(map, NULL, 0,
  112             &addr, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, 0);
  113         if (result != KERN_SUCCESS) {
  114                 return (0);
  115         }
  116         return (addr);
  117 }
  118 
  119 /*
  120  *      kmem_alloc_nofault:
  121  *
  122  *      Allocate a virtual address range with no underlying object and
  123  *      no initial mapping to physical memory.  Any mapping from this
  124  *      range to physical memory must be explicitly created prior to
  125  *      its use, typically with pmap_qenter().  Any attempt to create
  126  *      a mapping on demand through vm_fault() will result in a panic. 
  127  */
  128 vm_offset_t
  129 kmem_alloc_nofault(map, size)
  130         vm_map_t map;
  131         vm_size_t size;
  132 {
  133         vm_offset_t addr;
  134         int result;
  135 
  136         size = round_page(size);
  137         addr = vm_map_min(map);
  138         result = vm_map_find(map, NULL, 0,
  139             &addr, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  140         if (result != KERN_SUCCESS) {
  141                 return (0);
  142         }
  143         return (addr);
  144 }
  145 
  146 /*
  147  *      Allocate wired-down memory in the kernel's address map
  148  *      or a submap.
  149  */
  150 vm_offset_t
  151 kmem_alloc(map, size)
  152         vm_map_t map;
  153         vm_size_t size;
  154 {
  155         vm_offset_t addr;
  156         vm_offset_t offset;
  157         vm_offset_t i;
  158 
  159         size = round_page(size);
  160 
  161         /*
  162          * Use the kernel object for wired-down kernel pages. Assume that no
  163          * region of the kernel object is referenced more than once.
  164          */
  165 
  166         /*
  167          * Locate sufficient space in the map.  This will give us the final
  168          * virtual address for the new memory, and thus will tell us the
  169          * offset within the kernel map.
  170          */
  171         vm_map_lock(map);
  172         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  173                 vm_map_unlock(map);
  174                 return (0);
  175         }
  176         offset = addr - VM_MIN_KERNEL_ADDRESS;
  177         vm_object_reference(kernel_object);
  178         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  179                 VM_PROT_ALL, VM_PROT_ALL, 0);
  180         vm_map_unlock(map);
  181 
  182         /*
  183          * Guarantee that there are pages already in this object before
  184          * calling vm_map_wire.  This is to prevent the following
  185          * scenario:
  186          *
  187          * 1) Threads have swapped out, so that there is a pager for the
  188          * kernel_object. 2) The kmsg zone is empty, and so we are
  189          * kmem_allocing a new page for it. 3) vm_map_wire calls vm_fault;
  190          * there is no page, but there is a pager, so we call
  191          * pager_data_request.  But the kmsg zone is empty, so we must
  192          * kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
  193          * we get the data back from the pager, it will be (very stale)
  194          * non-zero data.  kmem_alloc is defined to return zero-filled memory.
  195          *
  196          * We're intentionally not activating the pages we allocate to prevent a
  197          * race with page-out.  vm_map_wire will wire the pages.
  198          */
  199         VM_OBJECT_LOCK(kernel_object);
  200         for (i = 0; i < size; i += PAGE_SIZE) {
  201                 vm_page_t mem;
  202 
  203                 mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
  204                                 VM_ALLOC_ZERO | VM_ALLOC_RETRY);
  205                 if ((mem->flags & PG_ZERO) == 0)
  206                         pmap_zero_page(mem);
  207                 mem->valid = VM_PAGE_BITS_ALL;
  208                 vm_page_lock_queues();
  209                 vm_page_flag_clear(mem, PG_ZERO);
  210                 vm_page_wakeup(mem);
  211                 vm_page_unlock_queues();
  212         }
  213         VM_OBJECT_UNLOCK(kernel_object);
  214 
  215         /*
  216          * And finally, mark the data as non-pageable.
  217          */
  218         (void) vm_map_wire(map, addr, addr + size,
  219             VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
  220 
  221         return (addr);
  222 }
  223 
  224 /*
  225  *      kmem_free:
  226  *
  227  *      Release a region of kernel virtual memory allocated
  228  *      with kmem_alloc, and return the physical pages
  229  *      associated with that region.
  230  *
  231  *      This routine may not block on kernel maps.
  232  */
  233 void
  234 kmem_free(map, addr, size)
  235         vm_map_t map;
  236         vm_offset_t addr;
  237         vm_size_t size;
  238 {
  239 
  240         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  241 }
  242 
  243 /*
  244  *      kmem_suballoc:
  245  *
  246  *      Allocates a map to manage a subrange
  247  *      of the kernel virtual address space.
  248  *
  249  *      Arguments are as follows:
  250  *
  251  *      parent          Map to take range from
  252  *      min, max        Returned endpoints of map
  253  *      size            Size of range to find
  254  */
  255 vm_map_t
  256 kmem_suballoc(parent, min, max, size)
  257         vm_map_t parent;
  258         vm_offset_t *min, *max;
  259         vm_size_t size;
  260 {
  261         int ret;
  262         vm_map_t result;
  263 
  264         GIANT_REQUIRED;
  265 
  266         size = round_page(size);
  267 
  268         *min = (vm_offset_t) vm_map_min(parent);
  269         ret = vm_map_find(parent, NULL, (vm_offset_t) 0,
  270             min, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, 0);
  271         if (ret != KERN_SUCCESS) {
  272                 printf("kmem_suballoc: bad status return of %d.\n", ret);
  273                 panic("kmem_suballoc");
  274         }
  275         *max = *min + size;
  276         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  277         if (result == NULL)
  278                 panic("kmem_suballoc: cannot create submap");
  279         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  280                 panic("kmem_suballoc: unable to change range to submap");
  281         return (result);
  282 }
  283 
  284 /*
  285  *      kmem_malloc:
  286  *
  287  *      Allocate wired-down memory in the kernel's address map for the higher
  288  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  289  *      kmem_alloc() because we may need to allocate memory at interrupt
  290  *      level where we cannot block (canwait == FALSE).
  291  *
  292  *      This routine has its own private kernel submap (kmem_map) and object
  293  *      (kmem_object).  This, combined with the fact that only malloc uses
  294  *      this routine, ensures that we will never block in map or object waits.
  295  *
  296  *      Note that this still only works in a uni-processor environment and
  297  *      when called at splhigh().
  298  *
  299  *      We don't worry about expanding the map (adding entries) since entries
  300  *      for wired maps are statically allocated.
  301  *
  302  *      NOTE:  This routine is not supposed to block if M_NOWAIT is set, but
  303  *      I have not verified that it actually does not block.
  304  *
  305  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  306  *      which we never free.
  307  */
  308 vm_offset_t
  309 kmem_malloc(map, size, flags)
  310         vm_map_t map;
  311         vm_size_t size;
  312         int flags;
  313 {
  314         vm_offset_t offset, i;
  315         vm_map_entry_t entry;
  316         vm_offset_t addr;
  317         vm_page_t m;
  318         int pflags;
  319 
  320         size = round_page(size);
  321         addr = vm_map_min(map);
  322 
  323         /*
  324          * Locate sufficient space in the map.  This will give us the final
  325          * virtual address for the new memory, and thus will tell us the
  326          * offset within the kernel map.
  327          */
  328         vm_map_lock(map);
  329         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  330                 vm_map_unlock(map);
  331                 if (map != kmem_map) {
  332                         static int last_report; /* when we did it (in ticks) */
  333                         if (ticks < last_report ||
  334                             (ticks - last_report) >= hz) {
  335                                 last_report = ticks;
  336                                 printf("Out of mbuf address space!\n");
  337                                 printf("Consider increasing NMBCLUSTERS\n");
  338                         }
  339                         return (0);
  340                 }
  341                 if ((flags & M_NOWAIT) == 0)
  342                         panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
  343                                 (long)size, (long)map->size);
  344                 return (0);
  345         }
  346         offset = addr - VM_MIN_KERNEL_ADDRESS;
  347         vm_object_reference(kmem_object);
  348         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  349                 VM_PROT_ALL, VM_PROT_ALL, 0);
  350 
  351         /*
  352          * Note: if M_NOWAIT specified alone, allocate from 
  353          * interrupt-safe queues only (just the free list).  If 
  354          * M_USE_RESERVE is also specified, we can also
  355          * allocate from the cache.  Neither of the latter two
  356          * flags may be specified from an interrupt since interrupts
  357          * are not allowed to mess with the cache queue.
  358          */
  359 
  360         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  361                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  362         else
  363                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  364 
  365         if (flags & M_ZERO)
  366                 pflags |= VM_ALLOC_ZERO;
  367 
  368         VM_OBJECT_LOCK(kmem_object);
  369         for (i = 0; i < size; i += PAGE_SIZE) {
  370 retry:
  371                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  372 
  373                 /*
  374                  * Ran out of space, free everything up and return. Don't need
  375                  * to lock page queues here as we know that the pages we got
  376                  * aren't on any queues.
  377                  */
  378                 if (m == NULL) {
  379                         if ((flags & M_NOWAIT) == 0) {
  380                                 VM_OBJECT_UNLOCK(kmem_object);
  381                                 vm_map_unlock(map);
  382                                 VM_WAIT;
  383                                 vm_map_lock(map);
  384                                 VM_OBJECT_LOCK(kmem_object);
  385                                 goto retry;
  386                         }
  387                         /* 
  388                          * Free the pages before removing the map entry.
  389                          * They are already marked busy.  Calling
  390                          * vm_map_delete before the pages has been freed or
  391                          * unbusied will cause a deadlock.
  392                          */
  393                         while (i != 0) {
  394                                 i -= PAGE_SIZE;
  395                                 m = vm_page_lookup(kmem_object,
  396                                                    OFF_TO_IDX(offset + i));
  397                                 vm_page_lock_queues();
  398                                 vm_page_unwire(m, 0);
  399                                 vm_page_free(m);
  400                                 vm_page_unlock_queues();
  401                         }
  402                         VM_OBJECT_UNLOCK(kmem_object);
  403                         vm_map_delete(map, addr, addr + size);
  404                         vm_map_unlock(map);
  405                         return (0);
  406                 }
  407                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  408                         pmap_zero_page(m);
  409                 m->valid = VM_PAGE_BITS_ALL;
  410                 vm_page_lock_queues();
  411                 vm_page_flag_clear(m, PG_ZERO);
  412                 vm_page_unmanage(m);
  413                 vm_page_unlock_queues();
  414         }
  415         VM_OBJECT_UNLOCK(kmem_object);
  416 
  417         /*
  418          * Mark map entry as non-pageable. Assert: vm_map_insert() will never
  419          * be able to extend the previous entry so there will be a new entry
  420          * exactly corresponding to this address range and it will have
  421          * wired_count == 0.
  422          */
  423         if (!vm_map_lookup_entry(map, addr, &entry) ||
  424             entry->start != addr || entry->end != addr + size ||
  425             entry->wired_count != 0)
  426                 panic("kmem_malloc: entry not found or misaligned");
  427         entry->wired_count = 1;
  428 
  429         vm_map_simplify_entry(map, entry);
  430 
  431         /*
  432          * Loop thru pages, entering them in the pmap. (We cannot add them to
  433          * the wired count without wrapping the vm_page_queue_lock in
  434          * splimp...)
  435          */
  436         for (i = 0; i < size; i += PAGE_SIZE) {
  437                 VM_OBJECT_LOCK(kmem_object);
  438                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  439                 VM_OBJECT_UNLOCK(kmem_object);
  440                 /*
  441                  * Because this is kernel_pmap, this call will not block.
  442                  */
  443                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL, 1);
  444                 vm_page_lock_queues();
  445                 vm_page_flag_set(m, PG_WRITEABLE | PG_REFERENCED);
  446                 vm_page_wakeup(m);
  447                 vm_page_unlock_queues();
  448         }
  449         vm_map_unlock(map);
  450 
  451         return (addr);
  452 }
  453 
  454 /*
  455  *      kmem_alloc_wait:
  456  *
  457  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  458  *      has no room, the caller sleeps waiting for more memory in the submap.
  459  *
  460  *      This routine may block.
  461  */
  462 vm_offset_t
  463 kmem_alloc_wait(map, size)
  464         vm_map_t map;
  465         vm_size_t size;
  466 {
  467         vm_offset_t addr;
  468 
  469         size = round_page(size);
  470 
  471         for (;;) {
  472                 /*
  473                  * To make this work for more than one map, use the map's lock
  474                  * to lock out sleepers/wakers.
  475                  */
  476                 vm_map_lock(map);
  477                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  478                         break;
  479                 /* no space now; see if we can ever get space */
  480                 if (vm_map_max(map) - vm_map_min(map) < size) {
  481                         vm_map_unlock(map);
  482                         return (0);
  483                 }
  484                 map->needs_wakeup = TRUE;
  485                 vm_map_unlock_and_wait(map, FALSE);
  486         }
  487         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL, VM_PROT_ALL, 0);
  488         vm_map_unlock(map);
  489         return (addr);
  490 }
  491 
  492 /*
  493  *      kmem_free_wakeup:
  494  *
  495  *      Returns memory to a submap of the kernel, and wakes up any processes
  496  *      waiting for memory in that map.
  497  */
  498 void
  499 kmem_free_wakeup(map, addr, size)
  500         vm_map_t map;
  501         vm_offset_t addr;
  502         vm_size_t size;
  503 {
  504 
  505         vm_map_lock(map);
  506         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  507         if (map->needs_wakeup) {
  508                 map->needs_wakeup = FALSE;
  509                 vm_map_wakeup(map);
  510         }
  511         vm_map_unlock(map);
  512 }
  513 
  514 /*
  515  *      kmem_init:
  516  *
  517  *      Create the kernel map; insert a mapping covering kernel text, 
  518  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  519  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  520  *      `start' as allocated, and the range between `start' and `end' as free.
  521  */
  522 void
  523 kmem_init(start, end)
  524         vm_offset_t start, end;
  525 {
  526         vm_map_t m;
  527 
  528         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  529         m->system_map = 1;
  530         vm_map_lock(m);
  531         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  532         kernel_map = m;
  533         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  534             VM_MIN_KERNEL_ADDRESS, start, VM_PROT_ALL, VM_PROT_ALL, 0);
  535         /* ... and ending with the completion of the above `insert' */
  536         vm_map_unlock(m);
  537 }

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