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  * 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  * $FreeBSD: releng/5.1/sys/vm/vm_kern.c 113489 2003-04-15 01:16:05Z alc $
   65  */
   66 
   67 /*
   68  *      Kernel memory management.
   69  */
   70 
   71 #include <sys/param.h>
   72 #include <sys/systm.h>
   73 #include <sys/kernel.h>         /* for ticks and hz */
   74 #include <sys/lock.h>
   75 #include <sys/mutex.h>
   76 #include <sys/proc.h>
   77 #include <sys/malloc.h>
   78 
   79 #include <vm/vm.h>
   80 #include <vm/vm_param.h>
   81 #include <vm/pmap.h>
   82 #include <vm/vm_map.h>
   83 #include <vm/vm_object.h>
   84 #include <vm/vm_page.h>
   85 #include <vm/vm_pageout.h>
   86 #include <vm/vm_extern.h>
   87 
   88 vm_map_t kernel_map=0;
   89 vm_map_t kmem_map=0;
   90 vm_map_t exec_map=0;
   91 vm_map_t clean_map=0;
   92 vm_map_t buffer_map=0;
   93 
   94 /*
   95  *      kmem_alloc_pageable:
   96  *
   97  *      Allocate pageable memory to the kernel's address map.
   98  *      "map" must be kernel_map or a submap of kernel_map.
   99  */
  100 vm_offset_t
  101 kmem_alloc_pageable(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, 0);
  112         if (result != KERN_SUCCESS) {
  113                 return (0);
  114         }
  115         return (addr);
  116 }
  117 
  118 /*
  119  *      kmem_alloc_nofault:
  120  *
  121  *      Same as kmem_alloc_pageable, except that it create a nofault entry.
  122  */
  123 vm_offset_t
  124 kmem_alloc_nofault(map, size)
  125         vm_map_t map;
  126         vm_size_t size;
  127 {
  128         vm_offset_t addr;
  129         int result;
  130 
  131         size = round_page(size);
  132         addr = vm_map_min(map);
  133         result = vm_map_find(map, NULL, 0,
  134             &addr, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  135         if (result != KERN_SUCCESS) {
  136                 return (0);
  137         }
  138         return (addr);
  139 }
  140 
  141 /*
  142  *      Allocate wired-down memory in the kernel's address map
  143  *      or a submap.
  144  */
  145 vm_offset_t
  146 kmem_alloc(map, size)
  147         vm_map_t map;
  148         vm_size_t size;
  149 {
  150         vm_offset_t addr;
  151         vm_offset_t offset;
  152         vm_offset_t i;
  153 
  154         GIANT_REQUIRED;
  155 
  156         size = round_page(size);
  157 
  158         /*
  159          * Use the kernel object for wired-down kernel pages. Assume that no
  160          * region of the kernel object is referenced more than once.
  161          */
  162 
  163         /*
  164          * Locate sufficient space in the map.  This will give us the final
  165          * virtual address for the new memory, and thus will tell us the
  166          * offset within the kernel map.
  167          */
  168         vm_map_lock(map);
  169         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  170                 vm_map_unlock(map);
  171                 return (0);
  172         }
  173         offset = addr - VM_MIN_KERNEL_ADDRESS;
  174         vm_object_reference(kernel_object);
  175         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  176                 VM_PROT_ALL, VM_PROT_ALL, 0);
  177         vm_map_unlock(map);
  178 
  179         /*
  180          * Guarantee that there are pages already in this object before
  181          * calling vm_map_pageable.  This is to prevent the following
  182          * scenario:
  183          *
  184          * 1) Threads have swapped out, so that there is a pager for the
  185          * kernel_object. 2) The kmsg zone is empty, and so we are
  186          * kmem_allocing a new page for it. 3) vm_map_pageable calls vm_fault;
  187          * there is no page, but there is a pager, so we call
  188          * pager_data_request.  But the kmsg zone is empty, so we must
  189          * kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
  190          * we get the data back from the pager, it will be (very stale)
  191          * non-zero data.  kmem_alloc is defined to return zero-filled memory.
  192          *
  193          * We're intentionally not activating the pages we allocate to prevent a
  194          * race with page-out.  vm_map_pageable will wire the pages.
  195          */
  196         for (i = 0; i < size; i += PAGE_SIZE) {
  197                 vm_page_t mem;
  198 
  199                 mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
  200                                 VM_ALLOC_ZERO | VM_ALLOC_RETRY);
  201                 if ((mem->flags & PG_ZERO) == 0)
  202                         pmap_zero_page(mem);
  203                 vm_page_lock_queues();
  204                 mem->valid = VM_PAGE_BITS_ALL;
  205                 vm_page_flag_clear(mem, PG_ZERO);
  206                 vm_page_wakeup(mem);
  207                 vm_page_unlock_queues();
  208         }
  209 
  210         /*
  211          * And finally, mark the data as non-pageable.
  212          */
  213         (void) vm_map_wire(map, addr, addr + size, FALSE);
  214 
  215         return (addr);
  216 }
  217 
  218 /*
  219  *      kmem_free:
  220  *
  221  *      Release a region of kernel virtual memory allocated
  222  *      with kmem_alloc, and return the physical pages
  223  *      associated with that region.
  224  *
  225  *      This routine may not block on kernel maps.
  226  */
  227 void
  228 kmem_free(map, addr, size)
  229         vm_map_t map;
  230         vm_offset_t addr;
  231         vm_size_t size;
  232 {
  233 
  234         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  235 }
  236 
  237 /*
  238  *      kmem_suballoc:
  239  *
  240  *      Allocates a map to manage a subrange
  241  *      of the kernel virtual address space.
  242  *
  243  *      Arguments are as follows:
  244  *
  245  *      parent          Map to take range from
  246  *      min, max        Returned endpoints of map
  247  *      size            Size of range to find
  248  */
  249 vm_map_t
  250 kmem_suballoc(parent, min, max, size)
  251         vm_map_t parent;
  252         vm_offset_t *min, *max;
  253         vm_size_t size;
  254 {
  255         int ret;
  256         vm_map_t result;
  257 
  258         GIANT_REQUIRED;
  259 
  260         size = round_page(size);
  261 
  262         *min = (vm_offset_t) vm_map_min(parent);
  263         ret = vm_map_find(parent, NULL, (vm_offset_t) 0,
  264             min, size, TRUE, VM_PROT_ALL, VM_PROT_ALL, 0);
  265         if (ret != KERN_SUCCESS) {
  266                 printf("kmem_suballoc: bad status return of %d.\n", ret);
  267                 panic("kmem_suballoc");
  268         }
  269         *max = *min + size;
  270         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  271         if (result == NULL)
  272                 panic("kmem_suballoc: cannot create submap");
  273         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  274                 panic("kmem_suballoc: unable to change range to submap");
  275         return (result);
  276 }
  277 
  278 /*
  279  *      kmem_malloc:
  280  *
  281  *      Allocate wired-down memory in the kernel's address map for the higher
  282  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  283  *      kmem_alloc() because we may need to allocate memory at interrupt
  284  *      level where we cannot block (canwait == FALSE).
  285  *
  286  *      This routine has its own private kernel submap (kmem_map) and object
  287  *      (kmem_object).  This, combined with the fact that only malloc uses
  288  *      this routine, ensures that we will never block in map or object waits.
  289  *
  290  *      Note that this still only works in a uni-processor environment and
  291  *      when called at splhigh().
  292  *
  293  *      We don't worry about expanding the map (adding entries) since entries
  294  *      for wired maps are statically allocated.
  295  *
  296  *      NOTE:  This routine is not supposed to block if M_NOWAIT is set, but
  297  *      I have not verified that it actually does not block.
  298  *
  299  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  300  *      which we never free.
  301  */
  302 vm_offset_t
  303 kmem_malloc(map, size, flags)
  304         vm_map_t map;
  305         vm_size_t size;
  306         int flags;
  307 {
  308         vm_offset_t offset, i;
  309         vm_map_entry_t entry;
  310         vm_offset_t addr;
  311         vm_page_t m;
  312         int pflags;
  313 
  314         if ((flags & M_NOWAIT) == 0)
  315                 GIANT_REQUIRED;
  316 
  317         size = round_page(size);
  318         addr = vm_map_min(map);
  319 
  320         /*
  321          * Locate sufficient space in the map.  This will give us the final
  322          * virtual address for the new memory, and thus will tell us the
  323          * offset within the kernel map.
  324          */
  325         vm_map_lock(map);
  326         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  327                 vm_map_unlock(map);
  328                 if (map != kmem_map) {
  329                         static int last_report; /* when we did it (in ticks) */
  330                         if (ticks < last_report ||
  331                             (ticks - last_report) >= hz) {
  332                                 last_report = ticks;
  333                                 printf("Out of mbuf address space!\n");
  334                                 printf("Consider increasing NMBCLUSTERS\n");
  335                         }
  336                         return (0);
  337                 }
  338                 if ((flags & M_NOWAIT) == 0)
  339                         panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
  340                                 (long)size, (long)map->size);
  341                 return (0);
  342         }
  343         offset = addr - VM_MIN_KERNEL_ADDRESS;
  344         vm_object_reference(kmem_object);
  345         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  346                 VM_PROT_ALL, VM_PROT_ALL, 0);
  347 
  348         /*
  349          * Note: if M_NOWAIT specified alone, allocate from 
  350          * interrupt-safe queues only (just the free list).  If 
  351          * M_USE_RESERVE is also specified, we can also
  352          * allocate from the cache.  Neither of the latter two
  353          * flags may be specified from an interrupt since interrupts
  354          * are not allowed to mess with the cache queue.
  355          */
  356 
  357         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  358                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  359         else
  360                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  361 
  362         if (flags & M_ZERO)
  363                 pflags |= VM_ALLOC_ZERO;
  364 
  365         VM_OBJECT_LOCK(kmem_object);
  366         for (i = 0; i < size; i += PAGE_SIZE) {
  367 retry:
  368                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  369 
  370                 /*
  371                  * Ran out of space, free everything up and return. Don't need
  372                  * to lock page queues here as we know that the pages we got
  373                  * aren't on any queues.
  374                  */
  375                 if (m == NULL) {
  376                         if ((flags & M_NOWAIT) == 0) {
  377                                 VM_OBJECT_UNLOCK(kmem_object);
  378                                 vm_map_unlock(map);
  379                                 VM_WAIT;
  380                                 vm_map_lock(map);
  381                                 VM_OBJECT_LOCK(kmem_object);
  382                                 goto retry;
  383                         }
  384                         /* 
  385                          * Free the pages before removing the map entry.
  386                          * They are already marked busy.  Calling
  387                          * vm_map_delete before the pages has been freed or
  388                          * unbusied will cause a deadlock.
  389                          */
  390                         while (i != 0) {
  391                                 i -= PAGE_SIZE;
  392                                 m = vm_page_lookup(kmem_object,
  393                                                    OFF_TO_IDX(offset + i));
  394                                 vm_page_lock_queues();
  395                                 vm_page_unwire(m, 0);
  396                                 vm_page_free(m);
  397                                 vm_page_unlock_queues();
  398                         }
  399                         VM_OBJECT_UNLOCK(kmem_object);
  400                         vm_map_delete(map, addr, addr + size);
  401                         vm_map_unlock(map);
  402                         return (0);
  403                 }
  404                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  405                         pmap_zero_page(m);
  406                 vm_page_lock_queues();
  407                 vm_page_flag_clear(m, PG_ZERO);
  408                 m->valid = VM_PAGE_BITS_ALL;
  409                 vm_page_unlock_queues();
  410         }
  411         VM_OBJECT_UNLOCK(kmem_object);
  412 
  413         /*
  414          * Mark map entry as non-pageable. Assert: vm_map_insert() will never
  415          * be able to extend the previous entry so there will be a new entry
  416          * exactly corresponding to this address range and it will have
  417          * wired_count == 0.
  418          */
  419         if (!vm_map_lookup_entry(map, addr, &entry) ||
  420             entry->start != addr || entry->end != addr + size ||
  421             entry->wired_count != 0)
  422                 panic("kmem_malloc: entry not found or misaligned");
  423         entry->wired_count = 1;
  424 
  425         vm_map_simplify_entry(map, entry);
  426 
  427         /*
  428          * Loop thru pages, entering them in the pmap. (We cannot add them to
  429          * the wired count without wrapping the vm_page_queue_lock in
  430          * splimp...)
  431          */
  432         for (i = 0; i < size; i += PAGE_SIZE) {
  433                 VM_OBJECT_LOCK(kmem_object);
  434                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  435                 VM_OBJECT_UNLOCK(kmem_object);
  436                 /*
  437                  * Because this is kernel_pmap, this call will not block.
  438                  */
  439                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL, 1);
  440                 vm_page_lock_queues();
  441                 vm_page_flag_set(m, PG_WRITEABLE | PG_REFERENCED);
  442                 vm_page_wakeup(m);
  443                 vm_page_unlock_queues();
  444         }
  445         vm_map_unlock(map);
  446 
  447         return (addr);
  448 }
  449 
  450 /*
  451  *      kmem_alloc_wait:
  452  *
  453  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  454  *      has no room, the caller sleeps waiting for more memory in the submap.
  455  *
  456  *      This routine may block.
  457  */
  458 vm_offset_t
  459 kmem_alloc_wait(map, size)
  460         vm_map_t map;
  461         vm_size_t size;
  462 {
  463         vm_offset_t addr;
  464 
  465         size = round_page(size);
  466 
  467         for (;;) {
  468                 /*
  469                  * To make this work for more than one map, use the map's lock
  470                  * to lock out sleepers/wakers.
  471                  */
  472                 vm_map_lock(map);
  473                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  474                         break;
  475                 /* no space now; see if we can ever get space */
  476                 if (vm_map_max(map) - vm_map_min(map) < size) {
  477                         vm_map_unlock(map);
  478                         return (0);
  479                 }
  480                 map->needs_wakeup = TRUE;
  481                 vm_map_unlock_and_wait(map, FALSE);
  482         }
  483         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL, VM_PROT_ALL, 0);
  484         vm_map_unlock(map);
  485         return (addr);
  486 }
  487 
  488 /*
  489  *      kmem_free_wakeup:
  490  *
  491  *      Returns memory to a submap of the kernel, and wakes up any processes
  492  *      waiting for memory in that map.
  493  */
  494 void
  495 kmem_free_wakeup(map, addr, size)
  496         vm_map_t map;
  497         vm_offset_t addr;
  498         vm_size_t size;
  499 {
  500 
  501         vm_map_lock(map);
  502         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  503         if (map->needs_wakeup) {
  504                 map->needs_wakeup = FALSE;
  505                 vm_map_wakeup(map);
  506         }
  507         vm_map_unlock(map);
  508 }
  509 
  510 /*
  511  *      kmem_init:
  512  *
  513  *      Create the kernel map; insert a mapping covering kernel text, 
  514  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  515  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  516  *      `start' as allocated, and the range between `start' and `end' as free.
  517  */
  518 void
  519 kmem_init(start, end)
  520         vm_offset_t start, end;
  521 {
  522         vm_map_t m;
  523 
  524         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  525         m->system_map = 1;
  526         vm_map_lock(m);
  527         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  528         kernel_map = m;
  529         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  530             VM_MIN_KERNEL_ADDRESS, start, VM_PROT_ALL, VM_PROT_ALL, 0);
  531         /* ... and ending with the completion of the above `insert' */
  532         vm_map_unlock(m);
  533 }

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