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/11.1/sys/vm/vm_kern.c 316073 2017-03-28 06:07:59Z kib $");
   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, offset;
  166         vm_page_t m;
  167         int pflags, tries;
  168 
  169         size = round_page(size);
  170         if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
  171                 return (0);
  172         offset = addr - VM_MIN_KERNEL_ADDRESS;
  173         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  174         VM_OBJECT_WLOCK(object);
  175         for (i = 0; i < size; i += PAGE_SIZE) {
  176                 tries = 0;
  177 retry:
  178                 m = vm_page_alloc_contig(object, atop(offset + i),
  179                     pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  180                 if (m == NULL) {
  181                         VM_OBJECT_WUNLOCK(object);
  182                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  183                                 if (!vm_page_reclaim_contig(pflags, 1,
  184                                     low, high, PAGE_SIZE, 0) &&
  185                                     (flags & M_WAITOK) != 0)
  186                                         VM_WAIT;
  187                                 VM_OBJECT_WLOCK(object);
  188                                 tries++;
  189                                 goto retry;
  190                         }
  191                         kmem_unback(object, addr, i);
  192                         vmem_free(vmem, addr, size);
  193                         return (0);
  194                 }
  195                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  196                         pmap_zero_page(m);
  197                 m->valid = VM_PAGE_BITS_ALL;
  198                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  199                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  200         }
  201         VM_OBJECT_WUNLOCK(object);
  202         return (addr);
  203 }
  204 
  205 /*
  206  *      Allocates a region from the kernel address map and physically
  207  *      contiguous pages within the specified address range to the kernel
  208  *      object.  Creates a wired mapping from this region to these pages, and
  209  *      returns the region's starting virtual address.  If M_ZERO is specified
  210  *      through the given flags, then the pages are zeroed before they are
  211  *      mapped.
  212  */
  213 vm_offset_t
  214 kmem_alloc_contig(struct vmem *vmem, vm_size_t size, int flags, vm_paddr_t low,
  215     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  216     vm_memattr_t memattr)
  217 {
  218         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  219         vm_offset_t addr, offset, tmp;
  220         vm_page_t end_m, m;
  221         u_long npages;
  222         int pflags, tries;
  223  
  224         size = round_page(size);
  225         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  226                 return (0);
  227         offset = addr - VM_MIN_KERNEL_ADDRESS;
  228         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  229         npages = atop(size);
  230         VM_OBJECT_WLOCK(object);
  231         tries = 0;
  232 retry:
  233         m = vm_page_alloc_contig(object, atop(offset), pflags,
  234             npages, low, high, alignment, boundary, memattr);
  235         if (m == NULL) {
  236                 VM_OBJECT_WUNLOCK(object);
  237                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  238                         if (!vm_page_reclaim_contig(pflags, npages, low, high,
  239                             alignment, boundary) && (flags & M_WAITOK) != 0)
  240                                 VM_WAIT;
  241                         VM_OBJECT_WLOCK(object);
  242                         tries++;
  243                         goto retry;
  244                 }
  245                 vmem_free(vmem, addr, size);
  246                 return (0);
  247         }
  248         end_m = m + npages;
  249         tmp = addr;
  250         for (; m < end_m; m++) {
  251                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  252                         pmap_zero_page(m);
  253                 m->valid = VM_PAGE_BITS_ALL;
  254                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
  255                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  256                 tmp += PAGE_SIZE;
  257         }
  258         VM_OBJECT_WUNLOCK(object);
  259         return (addr);
  260 }
  261 
  262 /*
  263  *      kmem_suballoc:
  264  *
  265  *      Allocates a map to manage a subrange
  266  *      of the kernel virtual address space.
  267  *
  268  *      Arguments are as follows:
  269  *
  270  *      parent          Map to take range from
  271  *      min, max        Returned endpoints of map
  272  *      size            Size of range to find
  273  *      superpage_align Request that min is superpage aligned
  274  */
  275 vm_map_t
  276 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  277     vm_size_t size, boolean_t superpage_align)
  278 {
  279         int ret;
  280         vm_map_t result;
  281 
  282         size = round_page(size);
  283 
  284         *min = vm_map_min(parent);
  285         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  286             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  287             MAP_ACC_NO_CHARGE);
  288         if (ret != KERN_SUCCESS)
  289                 panic("kmem_suballoc: bad status return of %d", ret);
  290         *max = *min + size;
  291         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  292         if (result == NULL)
  293                 panic("kmem_suballoc: cannot create submap");
  294         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  295                 panic("kmem_suballoc: unable to change range to submap");
  296         return (result);
  297 }
  298 
  299 /*
  300  *      kmem_malloc:
  301  *
  302  *      Allocate wired-down pages in the kernel's address space.
  303  */
  304 vm_offset_t
  305 kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
  306 {
  307         vm_offset_t addr;
  308         int rv;
  309 
  310         size = round_page(size);
  311         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  312                 return (0);
  313 
  314         rv = kmem_back((vmem == kmem_arena) ? kmem_object : kernel_object,
  315             addr, size, flags);
  316         if (rv != KERN_SUCCESS) {
  317                 vmem_free(vmem, addr, size);
  318                 return (0);
  319         }
  320         return (addr);
  321 }
  322 
  323 /*
  324  *      kmem_back:
  325  *
  326  *      Allocate physical pages for the specified virtual address range.
  327  */
  328 int
  329 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  330 {
  331         vm_offset_t offset, i;
  332         vm_page_t m;
  333         int pflags;
  334 
  335         KASSERT(object == kmem_object || object == kernel_object,
  336             ("kmem_back: only supports kernel objects."));
  337 
  338         offset = addr - VM_MIN_KERNEL_ADDRESS;
  339         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  340 
  341         VM_OBJECT_WLOCK(object);
  342         for (i = 0; i < size; i += PAGE_SIZE) {
  343 retry:
  344                 m = vm_page_alloc(object, atop(offset + i), pflags);
  345 
  346                 /*
  347                  * Ran out of space, free everything up and return. Don't need
  348                  * to lock page queues here as we know that the pages we got
  349                  * aren't on any queues.
  350                  */
  351                 if (m == NULL) {
  352                         VM_OBJECT_WUNLOCK(object);
  353                         if ((flags & M_NOWAIT) == 0) {
  354                                 VM_WAIT;
  355                                 VM_OBJECT_WLOCK(object);
  356                                 goto retry;
  357                         }
  358                         kmem_unback(object, addr, i);
  359                         return (KERN_NO_SPACE);
  360                 }
  361                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  362                         pmap_zero_page(m);
  363                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  364                     ("kmem_malloc: page %p is managed", m));
  365                 m->valid = VM_PAGE_BITS_ALL;
  366                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  367                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  368         }
  369         VM_OBJECT_WUNLOCK(object);
  370 
  371         return (KERN_SUCCESS);
  372 }
  373 
  374 /*
  375  *      kmem_unback:
  376  *
  377  *      Unmap and free the physical pages underlying the specified virtual
  378  *      address range.
  379  *
  380  *      A physical page must exist within the specified object at each index
  381  *      that is being unmapped.
  382  */
  383 void
  384 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  385 {
  386         vm_page_t m;
  387         vm_offset_t i, offset;
  388 
  389         KASSERT(object == kmem_object || object == kernel_object,
  390             ("kmem_unback: only supports kernel objects."));
  391 
  392         pmap_remove(kernel_pmap, addr, addr + size);
  393         offset = addr - VM_MIN_KERNEL_ADDRESS;
  394         VM_OBJECT_WLOCK(object);
  395         for (i = 0; i < size; i += PAGE_SIZE) {
  396                 m = vm_page_lookup(object, atop(offset + i));
  397                 vm_page_unwire(m, PQ_NONE);
  398                 vm_page_free(m);
  399         }
  400         VM_OBJECT_WUNLOCK(object);
  401 }
  402 
  403 /*
  404  *      kmem_free:
  405  *
  406  *      Free memory allocated with kmem_malloc.  The size must match the
  407  *      original allocation.
  408  */
  409 void
  410 kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
  411 {
  412 
  413         size = round_page(size);
  414         kmem_unback((vmem == kmem_arena) ? kmem_object : kernel_object,
  415             addr, size);
  416         vmem_free(vmem, addr, size);
  417 }
  418 
  419 /*
  420  *      kmap_alloc_wait:
  421  *
  422  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  423  *      has no room, the caller sleeps waiting for more memory in the submap.
  424  *
  425  *      This routine may block.
  426  */
  427 vm_offset_t
  428 kmap_alloc_wait(map, size)
  429         vm_map_t map;
  430         vm_size_t size;
  431 {
  432         vm_offset_t addr;
  433 
  434         size = round_page(size);
  435         if (!swap_reserve(size))
  436                 return (0);
  437 
  438         for (;;) {
  439                 /*
  440                  * To make this work for more than one map, use the map's lock
  441                  * to lock out sleepers/wakers.
  442                  */
  443                 vm_map_lock(map);
  444                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  445                         break;
  446                 /* no space now; see if we can ever get space */
  447                 if (vm_map_max(map) - vm_map_min(map) < size) {
  448                         vm_map_unlock(map);
  449                         swap_release(size);
  450                         return (0);
  451                 }
  452                 map->needs_wakeup = TRUE;
  453                 vm_map_unlock_and_wait(map, 0);
  454         }
  455         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  456             VM_PROT_ALL, MAP_ACC_CHARGED);
  457         vm_map_unlock(map);
  458         return (addr);
  459 }
  460 
  461 /*
  462  *      kmap_free_wakeup:
  463  *
  464  *      Returns memory to a submap of the kernel, and wakes up any processes
  465  *      waiting for memory in that map.
  466  */
  467 void
  468 kmap_free_wakeup(map, addr, size)
  469         vm_map_t map;
  470         vm_offset_t addr;
  471         vm_size_t size;
  472 {
  473 
  474         vm_map_lock(map);
  475         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  476         if (map->needs_wakeup) {
  477                 map->needs_wakeup = FALSE;
  478                 vm_map_wakeup(map);
  479         }
  480         vm_map_unlock(map);
  481 }
  482 
  483 void
  484 kmem_init_zero_region(void)
  485 {
  486         vm_offset_t addr, i;
  487         vm_page_t m;
  488 
  489         /*
  490          * Map a single physical page of zeros to a larger virtual range.
  491          * This requires less looping in places that want large amounts of
  492          * zeros, while not using much more physical resources.
  493          */
  494         addr = kva_alloc(ZERO_REGION_SIZE);
  495         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  496             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  497         if ((m->flags & PG_ZERO) == 0)
  498                 pmap_zero_page(m);
  499         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  500                 pmap_qenter(addr + i, &m, 1);
  501         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  502 
  503         zero_region = (const void *)addr;
  504 }
  505 
  506 /*
  507  *      kmem_init:
  508  *
  509  *      Create the kernel map; insert a mapping covering kernel text, 
  510  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  511  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  512  *      `start' as allocated, and the range between `start' and `end' as free.
  513  */
  514 void
  515 kmem_init(start, end)
  516         vm_offset_t start, end;
  517 {
  518         vm_map_t m;
  519 
  520         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  521         m->system_map = 1;
  522         vm_map_lock(m);
  523         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  524         kernel_map = m;
  525         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  526 #ifdef __amd64__
  527             KERNBASE,
  528 #else                
  529             VM_MIN_KERNEL_ADDRESS,
  530 #endif
  531             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  532         /* ... and ending with the completion of the above `insert' */
  533         vm_map_unlock(m);
  534 }
  535 
  536 #ifdef DIAGNOSTIC
  537 /*
  538  * Allow userspace to directly trigger the VM drain routine for testing
  539  * purposes.
  540  */
  541 static int
  542 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  543 {
  544         int error, i;
  545 
  546         i = 0;
  547         error = sysctl_handle_int(oidp, &i, 0, req);
  548         if (error)
  549                 return (error);
  550         if ((i & ~(VM_LOW_KMEM | VM_LOW_PAGES)) != 0)
  551                 return (EINVAL);
  552         if (i != 0)
  553                 EVENTHANDLER_INVOKE(vm_lowmem, i);
  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 with given flags");
  559 #endif

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