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: releng/9.1/sys/vm/vm_kern.c 237949 2012-07-02 03:49:52Z alc $");
   67 
   68 #include <sys/param.h>
   69 #include <sys/systm.h>
   70 #include <sys/kernel.h>         /* for ticks and hz */
   71 #include <sys/eventhandler.h>
   72 #include <sys/lock.h>
   73 #include <sys/mutex.h>
   74 #include <sys/proc.h>
   75 #include <sys/malloc.h>
   76 #include <sys/sysctl.h>
   77 
   78 #include <vm/vm.h>
   79 #include <vm/vm_param.h>
   80 #include <vm/pmap.h>
   81 #include <vm/vm_map.h>
   82 #include <vm/vm_object.h>
   83 #include <vm/vm_page.h>
   84 #include <vm/vm_pageout.h>
   85 #include <vm/vm_extern.h>
   86 #include <vm/uma.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 pipe_map;
   92 vm_map_t buffer_map=0;
   93 
   94 const void *zero_region;
   95 CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
   96 
   97 /*
   98  *      kmem_alloc_nofault:
   99  *
  100  *      Allocate a virtual address range with no underlying object and
  101  *      no initial mapping to physical memory.  Any mapping from this
  102  *      range to physical memory must be explicitly created prior to
  103  *      its use, typically with pmap_qenter().  Any attempt to create
  104  *      a mapping on demand through vm_fault() will result in a panic. 
  105  */
  106 vm_offset_t
  107 kmem_alloc_nofault(map, size)
  108         vm_map_t map;
  109         vm_size_t size;
  110 {
  111         vm_offset_t addr;
  112         int result;
  113 
  114         size = round_page(size);
  115         addr = vm_map_min(map);
  116         result = vm_map_find(map, NULL, 0, &addr, size, VMFS_ANY_SPACE,
  117             VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  118         if (result != KERN_SUCCESS) {
  119                 return (0);
  120         }
  121         return (addr);
  122 }
  123 
  124 /*
  125  *      kmem_alloc_nofault_space:
  126  *
  127  *      Allocate a virtual address range with no underlying object and
  128  *      no initial mapping to physical memory within the specified
  129  *      address space.  Any mapping from this range to physical memory
  130  *      must be explicitly created prior to its use, typically with
  131  *      pmap_qenter().  Any attempt to create a mapping on demand
  132  *      through vm_fault() will result in a panic. 
  133  */
  134 vm_offset_t
  135 kmem_alloc_nofault_space(map, size, find_space)
  136         vm_map_t map;
  137         vm_size_t size;
  138         int find_space;
  139 {
  140         vm_offset_t addr;
  141         int result;
  142 
  143         size = round_page(size);
  144         addr = vm_map_min(map);
  145         result = vm_map_find(map, NULL, 0, &addr, size, find_space,
  146             VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  147         if (result != KERN_SUCCESS) {
  148                 return (0);
  149         }
  150         return (addr);
  151 }
  152 
  153 /*
  154  *      Allocate wired-down memory in the kernel's address map
  155  *      or a submap.
  156  */
  157 vm_offset_t
  158 kmem_alloc(map, size)
  159         vm_map_t map;
  160         vm_size_t size;
  161 {
  162         vm_offset_t addr;
  163         vm_offset_t offset;
  164 
  165         size = round_page(size);
  166 
  167         /*
  168          * Use the kernel object for wired-down kernel pages. Assume that no
  169          * region of the kernel object is referenced more than once.
  170          */
  171 
  172         /*
  173          * Locate sufficient space in the map.  This will give us the final
  174          * virtual address for the new memory, and thus will tell us the
  175          * offset within the kernel map.
  176          */
  177         vm_map_lock(map);
  178         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  179                 vm_map_unlock(map);
  180                 return (0);
  181         }
  182         offset = addr - VM_MIN_KERNEL_ADDRESS;
  183         vm_object_reference(kernel_object);
  184         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  185                 VM_PROT_ALL, VM_PROT_ALL, 0);
  186         vm_map_unlock(map);
  187 
  188         /*
  189          * And finally, mark the data as non-pageable.
  190          */
  191         (void) vm_map_wire(map, addr, addr + size,
  192             VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
  193 
  194         return (addr);
  195 }
  196 
  197 /*
  198  *      kmem_free:
  199  *
  200  *      Release a region of kernel virtual memory allocated
  201  *      with kmem_alloc, and return the physical pages
  202  *      associated with that region.
  203  *
  204  *      This routine may not block on kernel maps.
  205  */
  206 void
  207 kmem_free(map, addr, size)
  208         vm_map_t map;
  209         vm_offset_t addr;
  210         vm_size_t size;
  211 {
  212 
  213         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  214 }
  215 
  216 /*
  217  *      kmem_suballoc:
  218  *
  219  *      Allocates a map to manage a subrange
  220  *      of the kernel virtual address space.
  221  *
  222  *      Arguments are as follows:
  223  *
  224  *      parent          Map to take range from
  225  *      min, max        Returned endpoints of map
  226  *      size            Size of range to find
  227  *      superpage_align Request that min is superpage aligned
  228  */
  229 vm_map_t
  230 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  231     vm_size_t size, boolean_t superpage_align)
  232 {
  233         int ret;
  234         vm_map_t result;
  235 
  236         size = round_page(size);
  237 
  238         *min = vm_map_min(parent);
  239         ret = vm_map_find(parent, NULL, 0, min, size, superpage_align ?
  240             VMFS_ALIGNED_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  241             MAP_ACC_NO_CHARGE);
  242         if (ret != KERN_SUCCESS)
  243                 panic("kmem_suballoc: bad status return of %d", ret);
  244         *max = *min + size;
  245         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  246         if (result == NULL)
  247                 panic("kmem_suballoc: cannot create submap");
  248         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  249                 panic("kmem_suballoc: unable to change range to submap");
  250         return (result);
  251 }
  252 
  253 /*
  254  *      kmem_malloc:
  255  *
  256  *      Allocate wired-down memory in the kernel's address map for the higher
  257  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  258  *      kmem_alloc() because we may need to allocate memory at interrupt
  259  *      level where we cannot block (canwait == FALSE).
  260  *
  261  *      This routine has its own private kernel submap (kmem_map) and object
  262  *      (kmem_object).  This, combined with the fact that only malloc uses
  263  *      this routine, ensures that we will never block in map or object waits.
  264  *
  265  *      We don't worry about expanding the map (adding entries) since entries
  266  *      for wired maps are statically allocated.
  267  *
  268  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  269  *      which we never free.
  270  */
  271 vm_offset_t
  272 kmem_malloc(map, size, flags)
  273         vm_map_t map;
  274         vm_size_t size;
  275         int flags;
  276 {
  277         vm_offset_t addr;
  278         int i, rv;
  279 
  280         size = round_page(size);
  281         addr = vm_map_min(map);
  282 
  283         /*
  284          * Locate sufficient space in the map.  This will give us the final
  285          * virtual address for the new memory, and thus will tell us the
  286          * offset within the kernel map.
  287          */
  288         vm_map_lock(map);
  289         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  290                 vm_map_unlock(map);
  291                 if ((flags & M_NOWAIT) == 0) {
  292                         for (i = 0; i < 8; i++) {
  293                                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  294                                 uma_reclaim();
  295                                 vm_map_lock(map);
  296                                 if (vm_map_findspace(map, vm_map_min(map),
  297                                     size, &addr) == 0) {
  298                                         break;
  299                                 }
  300                                 vm_map_unlock(map);
  301                                 tsleep(&i, 0, "nokva", (hz / 4) * (i + 1));
  302                         }
  303                         if (i == 8) {
  304                                 panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
  305                                     (long)size, (long)map->size);
  306                         }
  307                 } else {
  308                         return (0);
  309                 }
  310         }
  311 
  312         rv = kmem_back(map, addr, size, flags);
  313         vm_map_unlock(map);
  314         return (rv == KERN_SUCCESS ? addr : 0);
  315 }
  316 
  317 /*
  318  *      kmem_back:
  319  *
  320  *      Allocate physical pages for the specified virtual address range.
  321  */
  322 int
  323 kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
  324 {
  325         vm_offset_t offset, i;
  326         vm_map_entry_t entry;
  327         vm_page_t m;
  328         int pflags;
  329         boolean_t found;
  330 
  331         KASSERT(vm_map_locked(map), ("kmem_back: map %p is not locked", map));
  332         offset = addr - VM_MIN_KERNEL_ADDRESS;
  333         vm_object_reference(kmem_object);
  334         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  335             VM_PROT_ALL, VM_PROT_ALL, 0);
  336 
  337         /*
  338          * Assert: vm_map_insert() will never be able to extend the
  339          * previous entry so vm_map_lookup_entry() will find a new
  340          * entry exactly corresponding to this address range and it
  341          * will have wired_count == 0.
  342          */
  343         found = vm_map_lookup_entry(map, addr, &entry);
  344         KASSERT(found && entry->start == addr && entry->end == addr + size &&
  345             entry->wired_count == 0 && (entry->eflags & MAP_ENTRY_IN_TRANSITION)
  346             == 0, ("kmem_back: entry not found or misaligned"));
  347 
  348         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  349                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  350         else
  351                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  352 
  353         if (flags & M_ZERO)
  354                 pflags |= VM_ALLOC_ZERO;
  355         if (flags & M_NODUMP)
  356                 pflags |= VM_ALLOC_NODUMP;
  357 
  358         VM_OBJECT_LOCK(kmem_object);
  359         for (i = 0; i < size; i += PAGE_SIZE) {
  360 retry:
  361                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  362 
  363                 /*
  364                  * Ran out of space, free everything up and return. Don't need
  365                  * to lock page queues here as we know that the pages we got
  366                  * aren't on any queues.
  367                  */
  368                 if (m == NULL) {
  369                         if ((flags & M_NOWAIT) == 0) {
  370                                 VM_OBJECT_UNLOCK(kmem_object);
  371                                 entry->eflags |= MAP_ENTRY_IN_TRANSITION;
  372                                 vm_map_unlock(map);
  373                                 VM_WAIT;
  374                                 vm_map_lock(map);
  375                                 KASSERT(
  376 (entry->eflags & (MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_NEEDS_WAKEUP)) ==
  377                                     MAP_ENTRY_IN_TRANSITION,
  378                                     ("kmem_back: volatile entry"));
  379                                 entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
  380                                 VM_OBJECT_LOCK(kmem_object);
  381                                 goto retry;
  382                         }
  383                         /* 
  384                          * Free the pages before removing the map entry.
  385                          * They are already marked busy.  Calling
  386                          * vm_map_delete before the pages has been freed or
  387                          * unbusied will cause a deadlock.
  388                          */
  389                         while (i != 0) {
  390                                 i -= PAGE_SIZE;
  391                                 m = vm_page_lookup(kmem_object,
  392                                                    OFF_TO_IDX(offset + i));
  393                                 vm_page_unwire(m, 0);
  394                                 vm_page_free(m);
  395                         }
  396                         VM_OBJECT_UNLOCK(kmem_object);
  397                         vm_map_delete(map, addr, addr + size);
  398                         return (KERN_NO_SPACE);
  399                 }
  400                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  401                         pmap_zero_page(m);
  402                 m->valid = VM_PAGE_BITS_ALL;
  403                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  404                     ("kmem_malloc: page %p is managed", m));
  405         }
  406         VM_OBJECT_UNLOCK(kmem_object);
  407 
  408         /*
  409          * Mark map entry as non-pageable.  Repeat the assert.
  410          */
  411         KASSERT(entry->start == addr && entry->end == addr + size &&
  412             entry->wired_count == 0,
  413             ("kmem_back: entry not found or misaligned after allocation"));
  414         entry->wired_count = 1;
  415 
  416         /*
  417          * At this point, the kmem_object must be unlocked because
  418          * vm_map_simplify_entry() calls vm_object_deallocate(), which
  419          * locks the kmem_object.
  420          */
  421         vm_map_simplify_entry(map, entry);
  422 
  423         /*
  424          * Loop thru pages, entering them in the pmap.
  425          */
  426         VM_OBJECT_LOCK(kmem_object);
  427         for (i = 0; i < size; i += PAGE_SIZE) {
  428                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  429                 /*
  430                  * Because this is kernel_pmap, this call will not block.
  431                  */
  432                 pmap_enter(kernel_pmap, addr + i, VM_PROT_ALL, m, VM_PROT_ALL,
  433                     TRUE);
  434                 vm_page_wakeup(m);
  435         }
  436         VM_OBJECT_UNLOCK(kmem_object);
  437 
  438         return (KERN_SUCCESS);
  439 }
  440 
  441 /*
  442  *      kmem_alloc_wait:
  443  *
  444  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  445  *      has no room, the caller sleeps waiting for more memory in the submap.
  446  *
  447  *      This routine may block.
  448  */
  449 vm_offset_t
  450 kmem_alloc_wait(map, size)
  451         vm_map_t map;
  452         vm_size_t size;
  453 {
  454         vm_offset_t addr;
  455 
  456         size = round_page(size);
  457         if (!swap_reserve(size))
  458                 return (0);
  459 
  460         for (;;) {
  461                 /*
  462                  * To make this work for more than one map, use the map's lock
  463                  * to lock out sleepers/wakers.
  464                  */
  465                 vm_map_lock(map);
  466                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  467                         break;
  468                 /* no space now; see if we can ever get space */
  469                 if (vm_map_max(map) - vm_map_min(map) < size) {
  470                         vm_map_unlock(map);
  471                         swap_release(size);
  472                         return (0);
  473                 }
  474                 map->needs_wakeup = TRUE;
  475                 vm_map_unlock_and_wait(map, 0);
  476         }
  477         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  478             VM_PROT_ALL, MAP_ACC_CHARGED);
  479         vm_map_unlock(map);
  480         return (addr);
  481 }
  482 
  483 /*
  484  *      kmem_free_wakeup:
  485  *
  486  *      Returns memory to a submap of the kernel, and wakes up any processes
  487  *      waiting for memory in that map.
  488  */
  489 void
  490 kmem_free_wakeup(map, addr, size)
  491         vm_map_t map;
  492         vm_offset_t addr;
  493         vm_size_t size;
  494 {
  495 
  496         vm_map_lock(map);
  497         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  498         if (map->needs_wakeup) {
  499                 map->needs_wakeup = FALSE;
  500                 vm_map_wakeup(map);
  501         }
  502         vm_map_unlock(map);
  503 }
  504 
  505 static void
  506 kmem_init_zero_region(void)
  507 {
  508         vm_offset_t addr, i;
  509         vm_page_t m;
  510         int error;
  511 
  512         /*
  513          * Map a single physical page of zeros to a larger virtual range.
  514          * This requires less looping in places that want large amounts of
  515          * zeros, while not using much more physical resources.
  516          */
  517         addr = kmem_alloc_nofault(kernel_map, ZERO_REGION_SIZE);
  518         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  519             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  520         if ((m->flags & PG_ZERO) == 0)
  521                 pmap_zero_page(m);
  522         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  523                 pmap_qenter(addr + i, &m, 1);
  524         error = vm_map_protect(kernel_map, addr, addr + ZERO_REGION_SIZE,
  525             VM_PROT_READ, TRUE);
  526         KASSERT(error == 0, ("error=%d", error));
  527 
  528         zero_region = (const void *)addr;
  529 }
  530 
  531 /*
  532  *      kmem_init:
  533  *
  534  *      Create the kernel map; insert a mapping covering kernel text, 
  535  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  536  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  537  *      `start' as allocated, and the range between `start' and `end' as free.
  538  */
  539 void
  540 kmem_init(start, end)
  541         vm_offset_t start, end;
  542 {
  543         vm_map_t m;
  544 
  545         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  546         m->system_map = 1;
  547         vm_map_lock(m);
  548         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  549         kernel_map = m;
  550         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  551 #ifdef __amd64__
  552             KERNBASE,
  553 #else                
  554             VM_MIN_KERNEL_ADDRESS,
  555 #endif
  556             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  557         /* ... and ending with the completion of the above `insert' */
  558         vm_map_unlock(m);
  559 
  560         kmem_init_zero_region();
  561 }
  562 
  563 #ifdef DIAGNOSTIC
  564 /*
  565  * Allow userspace to directly trigger the VM drain routine for testing
  566  * purposes.
  567  */
  568 static int
  569 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  570 {
  571         int error, i;
  572 
  573         i = 0;
  574         error = sysctl_handle_int(oidp, &i, 0, req);
  575         if (error)
  576                 return (error);
  577         if (i)   
  578                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  579         return (0);
  580 }
  581 
  582 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  583     debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
  584 #endif

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