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/11.0/sys/vm/vm_kern.c 292469 2015-12-19 18:42:50Z 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/proc.h>
   74 #include <sys/malloc.h>
   75 #include <sys/rwlock.h>
   76 #include <sys/sysctl.h>
   77 #include <sys/vmem.h>
   78 
   79 #include <vm/vm.h>
   80 #include <vm/vm_param.h>
   81 #include <vm/vm_kern.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 #include <vm/uma.h>
   89 
   90 vm_map_t kernel_map;
   91 vm_map_t exec_map;
   92 vm_map_t pipe_map;
   93 
   94 const void *zero_region;
   95 CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
   96 
   97 /* NB: Used by kernel debuggers. */
   98 const u_long vm_maxuser_address = VM_MAXUSER_ADDRESS;
   99 
  100 SYSCTL_ULONG(_vm, OID_AUTO, min_kernel_address, CTLFLAG_RD,
  101     SYSCTL_NULL_ULONG_PTR, VM_MIN_KERNEL_ADDRESS, "Min kernel address");
  102 
  103 SYSCTL_ULONG(_vm, OID_AUTO, max_kernel_address, CTLFLAG_RD,
  104 #if defined(__arm__) || defined(__sparc64__)
  105     &vm_max_kernel_address, 0,
  106 #else
  107     SYSCTL_NULL_ULONG_PTR, VM_MAX_KERNEL_ADDRESS,
  108 #endif
  109     "Max kernel address");
  110 
  111 /*
  112  *      kva_alloc:
  113  *
  114  *      Allocate a virtual address range with no underlying object and
  115  *      no initial mapping to physical memory.  Any mapping from this
  116  *      range to physical memory must be explicitly created prior to
  117  *      its use, typically with pmap_qenter().  Any attempt to create
  118  *      a mapping on demand through vm_fault() will result in a panic. 
  119  */
  120 vm_offset_t
  121 kva_alloc(size)
  122         vm_size_t size;
  123 {
  124         vm_offset_t addr;
  125 
  126         size = round_page(size);
  127         if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
  128                 return (0);
  129 
  130         return (addr);
  131 }
  132 
  133 /*
  134  *      kva_free:
  135  *
  136  *      Release a region of kernel virtual memory allocated
  137  *      with kva_alloc, and return the physical pages
  138  *      associated with that region.
  139  *
  140  *      This routine may not block on kernel maps.
  141  */
  142 void
  143 kva_free(addr, size)
  144         vm_offset_t addr;
  145         vm_size_t size;
  146 {
  147 
  148         size = round_page(size);
  149         vmem_free(kernel_arena, addr, size);
  150 }
  151 
  152 /*
  153  *      Allocates a region from the kernel address map and physical pages
  154  *      within the specified address range to the kernel object.  Creates a
  155  *      wired mapping from this region to these pages, and returns the
  156  *      region's starting virtual address.  The allocated pages are not
  157  *      necessarily physically contiguous.  If M_ZERO is specified through the
  158  *      given flags, then the pages are zeroed before they are mapped.
  159  */
  160 vm_offset_t
  161 kmem_alloc_attr(vmem_t *vmem, vm_size_t size, int flags, vm_paddr_t low,
  162     vm_paddr_t high, vm_memattr_t memattr)
  163 {
  164         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  165         vm_offset_t addr, i;
  166         vm_ooffset_t offset;
  167         vm_page_t m;
  168         int pflags, tries;
  169 
  170         size = round_page(size);
  171         if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
  172                 return (0);
  173         offset = addr - VM_MIN_KERNEL_ADDRESS;
  174         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  175         VM_OBJECT_WLOCK(object);
  176         for (i = 0; i < size; i += PAGE_SIZE) {
  177                 tries = 0;
  178 retry:
  179                 m = vm_page_alloc_contig(object, OFF_TO_IDX(offset + i),
  180                     pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  181                 if (m == NULL) {
  182                         VM_OBJECT_WUNLOCK(object);
  183                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  184                                 if (!vm_page_reclaim_contig(pflags, 1,
  185                                     low, high, PAGE_SIZE, 0) &&
  186                                     (flags & M_WAITOK) != 0)
  187                                         VM_WAIT;
  188                                 VM_OBJECT_WLOCK(object);
  189                                 tries++;
  190                                 goto retry;
  191                         }
  192                         kmem_unback(object, addr, i);
  193                         vmem_free(vmem, addr, size);
  194                         return (0);
  195                 }
  196                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  197                         pmap_zero_page(m);
  198                 m->valid = VM_PAGE_BITS_ALL;
  199                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  200                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  201         }
  202         VM_OBJECT_WUNLOCK(object);
  203         return (addr);
  204 }
  205 
  206 /*
  207  *      Allocates a region from the kernel address map and physically
  208  *      contiguous pages within the specified address range to the kernel
  209  *      object.  Creates a wired mapping from this region to these pages, and
  210  *      returns the region's starting virtual address.  If M_ZERO is specified
  211  *      through the given flags, then the pages are zeroed before they are
  212  *      mapped.
  213  */
  214 vm_offset_t
  215 kmem_alloc_contig(struct vmem *vmem, vm_size_t size, int flags, vm_paddr_t low,
  216     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  217     vm_memattr_t memattr)
  218 {
  219         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  220         vm_offset_t addr, tmp;
  221         vm_ooffset_t offset;
  222         vm_page_t end_m, m;
  223         u_long npages;
  224         int pflags, tries;
  225  
  226         size = round_page(size);
  227         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  228                 return (0);
  229         offset = addr - VM_MIN_KERNEL_ADDRESS;
  230         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  231         npages = atop(size);
  232         VM_OBJECT_WLOCK(object);
  233         tries = 0;
  234 retry:
  235         m = vm_page_alloc_contig(object, OFF_TO_IDX(offset), pflags,
  236             npages, low, high, alignment, boundary, memattr);
  237         if (m == NULL) {
  238                 VM_OBJECT_WUNLOCK(object);
  239                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  240                         if (!vm_page_reclaim_contig(pflags, npages, low, high,
  241                             alignment, boundary) && (flags & M_WAITOK) != 0)
  242                                 VM_WAIT;
  243                         VM_OBJECT_WLOCK(object);
  244                         tries++;
  245                         goto retry;
  246                 }
  247                 vmem_free(vmem, addr, size);
  248                 return (0);
  249         }
  250         end_m = m + npages;
  251         tmp = addr;
  252         for (; m < end_m; m++) {
  253                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  254                         pmap_zero_page(m);
  255                 m->valid = VM_PAGE_BITS_ALL;
  256                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
  257                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  258                 tmp += PAGE_SIZE;
  259         }
  260         VM_OBJECT_WUNLOCK(object);
  261         return (addr);
  262 }
  263 
  264 /*
  265  *      kmem_suballoc:
  266  *
  267  *      Allocates a map to manage a subrange
  268  *      of the kernel virtual address space.
  269  *
  270  *      Arguments are as follows:
  271  *
  272  *      parent          Map to take range from
  273  *      min, max        Returned endpoints of map
  274  *      size            Size of range to find
  275  *      superpage_align Request that min is superpage aligned
  276  */
  277 vm_map_t
  278 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  279     vm_size_t size, boolean_t superpage_align)
  280 {
  281         int ret;
  282         vm_map_t result;
  283 
  284         size = round_page(size);
  285 
  286         *min = vm_map_min(parent);
  287         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  288             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  289             MAP_ACC_NO_CHARGE);
  290         if (ret != KERN_SUCCESS)
  291                 panic("kmem_suballoc: bad status return of %d", ret);
  292         *max = *min + size;
  293         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  294         if (result == NULL)
  295                 panic("kmem_suballoc: cannot create submap");
  296         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  297                 panic("kmem_suballoc: unable to change range to submap");
  298         return (result);
  299 }
  300 
  301 /*
  302  *      kmem_malloc:
  303  *
  304  *      Allocate wired-down pages in the kernel's address space.
  305  */
  306 vm_offset_t
  307 kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
  308 {
  309         vm_offset_t addr;
  310         int rv;
  311 
  312         size = round_page(size);
  313         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  314                 return (0);
  315 
  316         rv = kmem_back((vmem == kmem_arena) ? kmem_object : kernel_object,
  317             addr, size, flags);
  318         if (rv != KERN_SUCCESS) {
  319                 vmem_free(vmem, addr, size);
  320                 return (0);
  321         }
  322         return (addr);
  323 }
  324 
  325 /*
  326  *      kmem_back:
  327  *
  328  *      Allocate physical pages for the specified virtual address range.
  329  */
  330 int
  331 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  332 {
  333         vm_offset_t offset, i;
  334         vm_page_t m;
  335         int pflags;
  336 
  337         KASSERT(object == kmem_object || object == kernel_object,
  338             ("kmem_back: only supports kernel objects."));
  339 
  340         offset = addr - VM_MIN_KERNEL_ADDRESS;
  341         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  342 
  343         VM_OBJECT_WLOCK(object);
  344         for (i = 0; i < size; i += PAGE_SIZE) {
  345 retry:
  346                 m = vm_page_alloc(object, OFF_TO_IDX(offset + i), pflags);
  347 
  348                 /*
  349                  * Ran out of space, free everything up and return. Don't need
  350                  * to lock page queues here as we know that the pages we got
  351                  * aren't on any queues.
  352                  */
  353                 if (m == NULL) {
  354                         VM_OBJECT_WUNLOCK(object);
  355                         if ((flags & M_NOWAIT) == 0) {
  356                                 VM_WAIT;
  357                                 VM_OBJECT_WLOCK(object);
  358                                 goto retry;
  359                         }
  360                         kmem_unback(object, addr, i);
  361                         return (KERN_NO_SPACE);
  362                 }
  363                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  364                         pmap_zero_page(m);
  365                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  366                     ("kmem_malloc: page %p is managed", m));
  367                 m->valid = VM_PAGE_BITS_ALL;
  368                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  369                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  370         }
  371         VM_OBJECT_WUNLOCK(object);
  372 
  373         return (KERN_SUCCESS);
  374 }
  375 
  376 /*
  377  *      kmem_unback:
  378  *
  379  *      Unmap and free the physical pages underlying the specified virtual
  380  *      address range.
  381  *
  382  *      A physical page must exist within the specified object at each index
  383  *      that is being unmapped.
  384  */
  385 void
  386 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  387 {
  388         vm_page_t m;
  389         vm_offset_t i, offset;
  390 
  391         KASSERT(object == kmem_object || object == kernel_object,
  392             ("kmem_unback: only supports kernel objects."));
  393 
  394         pmap_remove(kernel_pmap, addr, addr + size);
  395         offset = addr - VM_MIN_KERNEL_ADDRESS;
  396         VM_OBJECT_WLOCK(object);
  397         for (i = 0; i < size; i += PAGE_SIZE) {
  398                 m = vm_page_lookup(object, OFF_TO_IDX(offset + i));
  399                 vm_page_unwire(m, PQ_NONE);
  400                 vm_page_free(m);
  401         }
  402         VM_OBJECT_WUNLOCK(object);
  403 }
  404 
  405 /*
  406  *      kmem_free:
  407  *
  408  *      Free memory allocated with kmem_malloc.  The size must match the
  409  *      original allocation.
  410  */
  411 void
  412 kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
  413 {
  414 
  415         size = round_page(size);
  416         kmem_unback((vmem == kmem_arena) ? kmem_object : kernel_object,
  417             addr, size);
  418         vmem_free(vmem, addr, size);
  419 }
  420 
  421 /*
  422  *      kmap_alloc_wait:
  423  *
  424  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  425  *      has no room, the caller sleeps waiting for more memory in the submap.
  426  *
  427  *      This routine may block.
  428  */
  429 vm_offset_t
  430 kmap_alloc_wait(map, size)
  431         vm_map_t map;
  432         vm_size_t size;
  433 {
  434         vm_offset_t addr;
  435 
  436         size = round_page(size);
  437         if (!swap_reserve(size))
  438                 return (0);
  439 
  440         for (;;) {
  441                 /*
  442                  * To make this work for more than one map, use the map's lock
  443                  * to lock out sleepers/wakers.
  444                  */
  445                 vm_map_lock(map);
  446                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  447                         break;
  448                 /* no space now; see if we can ever get space */
  449                 if (vm_map_max(map) - vm_map_min(map) < size) {
  450                         vm_map_unlock(map);
  451                         swap_release(size);
  452                         return (0);
  453                 }
  454                 map->needs_wakeup = TRUE;
  455                 vm_map_unlock_and_wait(map, 0);
  456         }
  457         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  458             VM_PROT_ALL, MAP_ACC_CHARGED);
  459         vm_map_unlock(map);
  460         return (addr);
  461 }
  462 
  463 /*
  464  *      kmap_free_wakeup:
  465  *
  466  *      Returns memory to a submap of the kernel, and wakes up any processes
  467  *      waiting for memory in that map.
  468  */
  469 void
  470 kmap_free_wakeup(map, addr, size)
  471         vm_map_t map;
  472         vm_offset_t addr;
  473         vm_size_t size;
  474 {
  475 
  476         vm_map_lock(map);
  477         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  478         if (map->needs_wakeup) {
  479                 map->needs_wakeup = FALSE;
  480                 vm_map_wakeup(map);
  481         }
  482         vm_map_unlock(map);
  483 }
  484 
  485 void
  486 kmem_init_zero_region(void)
  487 {
  488         vm_offset_t addr, i;
  489         vm_page_t m;
  490 
  491         /*
  492          * Map a single physical page of zeros to a larger virtual range.
  493          * This requires less looping in places that want large amounts of
  494          * zeros, while not using much more physical resources.
  495          */
  496         addr = kva_alloc(ZERO_REGION_SIZE);
  497         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  498             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  499         if ((m->flags & PG_ZERO) == 0)
  500                 pmap_zero_page(m);
  501         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  502                 pmap_qenter(addr + i, &m, 1);
  503         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  504 
  505         zero_region = (const void *)addr;
  506 }
  507 
  508 /*
  509  *      kmem_init:
  510  *
  511  *      Create the kernel map; insert a mapping covering kernel text, 
  512  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  513  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  514  *      `start' as allocated, and the range between `start' and `end' as free.
  515  */
  516 void
  517 kmem_init(start, end)
  518         vm_offset_t start, end;
  519 {
  520         vm_map_t m;
  521 
  522         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  523         m->system_map = 1;
  524         vm_map_lock(m);
  525         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  526         kernel_map = m;
  527         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  528 #ifdef __amd64__
  529             KERNBASE,
  530 #else                
  531             VM_MIN_KERNEL_ADDRESS,
  532 #endif
  533             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  534         /* ... and ending with the completion of the above `insert' */
  535         vm_map_unlock(m);
  536 }
  537 
  538 #ifdef DIAGNOSTIC
  539 /*
  540  * Allow userspace to directly trigger the VM drain routine for testing
  541  * purposes.
  542  */
  543 static int
  544 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  545 {
  546         int error, i;
  547 
  548         i = 0;
  549         error = sysctl_handle_int(oidp, &i, 0, req);
  550         if (error)
  551                 return (error);
  552         if (i)   
  553                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  554         return (0);
  555 }
  556 
  557 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  558     debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
  559 #endif

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