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  * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
    3  *
    4  * Copyright (c) 1991, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * This code is derived from software contributed to Berkeley by
    8  * The Mach Operating System project at Carnegie-Mellon University.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      from: @(#)vm_kern.c     8.3 (Berkeley) 1/12/94
   35  *
   36  *
   37  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   38  * All rights reserved.
   39  *
   40  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   41  *
   42  * Permission to use, copy, modify and distribute this software and
   43  * its documentation is hereby granted, provided that both the copyright
   44  * notice and this permission notice appear in all copies of the
   45  * software, derivative works or modified versions, and any portions
   46  * thereof, and that both notices appear in supporting documentation.
   47  *
   48  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   49  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   50  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   51  *
   52  * Carnegie Mellon requests users of this software to return to
   53  *
   54  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   55  *  School of Computer Science
   56  *  Carnegie Mellon University
   57  *  Pittsburgh PA 15213-3890
   58  *
   59  * any improvements or extensions that they make and grant Carnegie the
   60  * rights to redistribute these changes.
   61  */
   62 
   63 /*
   64  *      Kernel memory management.
   65  */
   66 
   67 #include <sys/cdefs.h>
   68 __FBSDID("$FreeBSD: releng/12.0/sys/vm/vm_kern.c 340401 2018-11-13 18:21:47Z markj $");
   69 
   70 #include "opt_vm.h"
   71 
   72 #include <sys/param.h>
   73 #include <sys/systm.h>
   74 #include <sys/kernel.h>         /* for ticks and hz */
   75 #include <sys/domainset.h>
   76 #include <sys/eventhandler.h>
   77 #include <sys/lock.h>
   78 #include <sys/proc.h>
   79 #include <sys/malloc.h>
   80 #include <sys/rwlock.h>
   81 #include <sys/sysctl.h>
   82 #include <sys/vmem.h>
   83 #include <sys/vmmeter.h>
   84 
   85 #include <vm/vm.h>
   86 #include <vm/vm_param.h>
   87 #include <vm/vm_domainset.h>
   88 #include <vm/vm_kern.h>
   89 #include <vm/pmap.h>
   90 #include <vm/vm_map.h>
   91 #include <vm/vm_object.h>
   92 #include <vm/vm_page.h>
   93 #include <vm/vm_pageout.h>
   94 #include <vm/vm_phys.h>
   95 #include <vm/vm_pagequeue.h>
   96 #include <vm/vm_radix.h>
   97 #include <vm/vm_extern.h>
   98 #include <vm/uma.h>
   99 
  100 vm_map_t kernel_map;
  101 vm_map_t exec_map;
  102 vm_map_t pipe_map;
  103 
  104 const void *zero_region;
  105 CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
  106 
  107 /* NB: Used by kernel debuggers. */
  108 const u_long vm_maxuser_address = VM_MAXUSER_ADDRESS;
  109 
  110 u_int exec_map_entry_size;
  111 u_int exec_map_entries;
  112 
  113 SYSCTL_ULONG(_vm, OID_AUTO, min_kernel_address, CTLFLAG_RD,
  114     SYSCTL_NULL_ULONG_PTR, VM_MIN_KERNEL_ADDRESS, "Min kernel address");
  115 
  116 SYSCTL_ULONG(_vm, OID_AUTO, max_kernel_address, CTLFLAG_RD,
  117 #if defined(__arm__) || defined(__sparc64__)
  118     &vm_max_kernel_address, 0,
  119 #else
  120     SYSCTL_NULL_ULONG_PTR, VM_MAX_KERNEL_ADDRESS,
  121 #endif
  122     "Max kernel address");
  123 
  124 #if VM_NRESERVLEVEL > 0
  125 #define KVA_QUANTUM_SHIFT       (VM_LEVEL_0_ORDER + PAGE_SHIFT)
  126 #else
  127 /* On non-superpage architectures want large import sizes. */
  128 #define KVA_QUANTUM_SHIFT       (10 + PAGE_SHIFT)
  129 #endif
  130 #define KVA_QUANTUM             (1 << KVA_QUANTUM_SHIFT)
  131 
  132 /*
  133  *      kva_alloc:
  134  *
  135  *      Allocate a virtual address range with no underlying object and
  136  *      no initial mapping to physical memory.  Any mapping from this
  137  *      range to physical memory must be explicitly created prior to
  138  *      its use, typically with pmap_qenter().  Any attempt to create
  139  *      a mapping on demand through vm_fault() will result in a panic. 
  140  */
  141 vm_offset_t
  142 kva_alloc(vm_size_t size)
  143 {
  144         vm_offset_t addr;
  145 
  146         size = round_page(size);
  147         if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
  148                 return (0);
  149 
  150         return (addr);
  151 }
  152 
  153 /*
  154  *      kva_free:
  155  *
  156  *      Release a region of kernel virtual memory allocated
  157  *      with kva_alloc, and return the physical pages
  158  *      associated with that region.
  159  *
  160  *      This routine may not block on kernel maps.
  161  */
  162 void
  163 kva_free(vm_offset_t addr, vm_size_t size)
  164 {
  165 
  166         size = round_page(size);
  167         vmem_free(kernel_arena, addr, size);
  168 }
  169 
  170 /*
  171  *      Allocates a region from the kernel address map and physical pages
  172  *      within the specified address range to the kernel object.  Creates a
  173  *      wired mapping from this region to these pages, and returns the
  174  *      region's starting virtual address.  The allocated pages are not
  175  *      necessarily physically contiguous.  If M_ZERO is specified through the
  176  *      given flags, then the pages are zeroed before they are mapped.
  177  */
  178 static vm_offset_t
  179 kmem_alloc_attr_domain(int domain, vm_size_t size, int flags, vm_paddr_t low,
  180     vm_paddr_t high, vm_memattr_t memattr)
  181 {
  182         vmem_t *vmem;
  183         vm_object_t object = kernel_object;
  184         vm_offset_t addr, i, offset;
  185         vm_page_t m;
  186         int pflags, tries;
  187 
  188         size = round_page(size);
  189         vmem = vm_dom[domain].vmd_kernel_arena;
  190         if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
  191                 return (0);
  192         offset = addr - VM_MIN_KERNEL_ADDRESS;
  193         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  194         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  195         pflags |= VM_ALLOC_NOWAIT;
  196         VM_OBJECT_WLOCK(object);
  197         for (i = 0; i < size; i += PAGE_SIZE) {
  198                 tries = 0;
  199 retry:
  200                 m = vm_page_alloc_contig_domain(object, atop(offset + i),
  201                     domain, pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  202                 if (m == NULL) {
  203                         VM_OBJECT_WUNLOCK(object);
  204                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  205                                 if (!vm_page_reclaim_contig_domain(domain,
  206                                     pflags, 1, low, high, PAGE_SIZE, 0) &&
  207                                     (flags & M_WAITOK) != 0)
  208                                         vm_wait_domain(domain);
  209                                 VM_OBJECT_WLOCK(object);
  210                                 tries++;
  211                                 goto retry;
  212                         }
  213                         kmem_unback(object, addr, i);
  214                         vmem_free(vmem, addr, size);
  215                         return (0);
  216                 }
  217                 KASSERT(vm_phys_domain(m) == domain,
  218                     ("kmem_alloc_attr_domain: Domain mismatch %d != %d",
  219                     vm_phys_domain(m), domain));
  220                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  221                         pmap_zero_page(m);
  222                 m->valid = VM_PAGE_BITS_ALL;
  223                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_RW,
  224                     VM_PROT_RW | PMAP_ENTER_WIRED, 0);
  225         }
  226         VM_OBJECT_WUNLOCK(object);
  227         return (addr);
  228 }
  229 
  230 vm_offset_t
  231 kmem_alloc_attr(vm_size_t size, int flags, vm_paddr_t low, vm_paddr_t high,
  232     vm_memattr_t memattr)
  233 {
  234 
  235         return (kmem_alloc_attr_domainset(DOMAINSET_RR(), size, flags, low,
  236             high, memattr));
  237 }
  238 
  239 vm_offset_t
  240 kmem_alloc_attr_domainset(struct domainset *ds, vm_size_t size, int flags,
  241     vm_paddr_t low, vm_paddr_t high, vm_memattr_t memattr)
  242 {
  243         struct vm_domainset_iter di;
  244         vm_offset_t addr;
  245         int domain;
  246 
  247         vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
  248         do {
  249                 addr = kmem_alloc_attr_domain(domain, size, flags, low, high,
  250                     memattr);
  251                 if (addr != 0)
  252                         break;
  253         } while (vm_domainset_iter_policy(&di, &domain) == 0);
  254 
  255         return (addr);
  256 }
  257 
  258 /*
  259  *      Allocates a region from the kernel address map and physically
  260  *      contiguous pages within the specified address range to the kernel
  261  *      object.  Creates a wired mapping from this region to these pages, and
  262  *      returns the region's starting virtual address.  If M_ZERO is specified
  263  *      through the given flags, then the pages are zeroed before they are
  264  *      mapped.
  265  */
  266 static vm_offset_t
  267 kmem_alloc_contig_domain(int domain, vm_size_t size, int flags, vm_paddr_t low,
  268     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  269     vm_memattr_t memattr)
  270 {
  271         vmem_t *vmem;
  272         vm_object_t object = kernel_object;
  273         vm_offset_t addr, offset, tmp;
  274         vm_page_t end_m, m;
  275         u_long npages;
  276         int pflags, tries;
  277  
  278         size = round_page(size);
  279         vmem = vm_dom[domain].vmd_kernel_arena;
  280         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  281                 return (0);
  282         offset = addr - VM_MIN_KERNEL_ADDRESS;
  283         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  284         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  285         pflags |= VM_ALLOC_NOWAIT;
  286         npages = atop(size);
  287         VM_OBJECT_WLOCK(object);
  288         tries = 0;
  289 retry:
  290         m = vm_page_alloc_contig_domain(object, atop(offset), domain, pflags,
  291             npages, low, high, alignment, boundary, memattr);
  292         if (m == NULL) {
  293                 VM_OBJECT_WUNLOCK(object);
  294                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  295                         if (!vm_page_reclaim_contig_domain(domain, pflags,
  296                             npages, low, high, alignment, boundary) &&
  297                             (flags & M_WAITOK) != 0)
  298                                 vm_wait_domain(domain);
  299                         VM_OBJECT_WLOCK(object);
  300                         tries++;
  301                         goto retry;
  302                 }
  303                 vmem_free(vmem, addr, size);
  304                 return (0);
  305         }
  306         KASSERT(vm_phys_domain(m) == domain,
  307             ("kmem_alloc_contig_domain: Domain mismatch %d != %d",
  308             vm_phys_domain(m), domain));
  309         end_m = m + npages;
  310         tmp = addr;
  311         for (; m < end_m; m++) {
  312                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  313                         pmap_zero_page(m);
  314                 m->valid = VM_PAGE_BITS_ALL;
  315                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_RW,
  316                     VM_PROT_RW | PMAP_ENTER_WIRED, 0);
  317                 tmp += PAGE_SIZE;
  318         }
  319         VM_OBJECT_WUNLOCK(object);
  320         return (addr);
  321 }
  322 
  323 vm_offset_t
  324 kmem_alloc_contig(vm_size_t size, int flags, vm_paddr_t low, vm_paddr_t high,
  325     u_long alignment, vm_paddr_t boundary, vm_memattr_t memattr)
  326 {
  327 
  328         return (kmem_alloc_contig_domainset(DOMAINSET_RR(), size, flags, low,
  329             high, alignment, boundary, memattr));
  330 }
  331 
  332 vm_offset_t
  333 kmem_alloc_contig_domainset(struct domainset *ds, vm_size_t size, int flags,
  334     vm_paddr_t low, vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  335     vm_memattr_t memattr)
  336 {
  337         struct vm_domainset_iter di;
  338         vm_offset_t addr;
  339         int domain;
  340 
  341         vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
  342         do {
  343                 addr = kmem_alloc_contig_domain(domain, size, flags, low, high,
  344                     alignment, boundary, memattr);
  345                 if (addr != 0)
  346                         break;
  347         } while (vm_domainset_iter_policy(&di, &domain) == 0);
  348 
  349         return (addr);
  350 }
  351 
  352 /*
  353  *      kmem_suballoc:
  354  *
  355  *      Allocates a map to manage a subrange
  356  *      of the kernel virtual address space.
  357  *
  358  *      Arguments are as follows:
  359  *
  360  *      parent          Map to take range from
  361  *      min, max        Returned endpoints of map
  362  *      size            Size of range to find
  363  *      superpage_align Request that min is superpage aligned
  364  */
  365 vm_map_t
  366 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  367     vm_size_t size, boolean_t superpage_align)
  368 {
  369         int ret;
  370         vm_map_t result;
  371 
  372         size = round_page(size);
  373 
  374         *min = vm_map_min(parent);
  375         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  376             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  377             MAP_ACC_NO_CHARGE);
  378         if (ret != KERN_SUCCESS)
  379                 panic("kmem_suballoc: bad status return of %d", ret);
  380         *max = *min + size;
  381         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  382         if (result == NULL)
  383                 panic("kmem_suballoc: cannot create submap");
  384         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  385                 panic("kmem_suballoc: unable to change range to submap");
  386         return (result);
  387 }
  388 
  389 /*
  390  *      kmem_malloc_domain:
  391  *
  392  *      Allocate wired-down pages in the kernel's address space.
  393  */
  394 static vm_offset_t
  395 kmem_malloc_domain(int domain, vm_size_t size, int flags)
  396 {
  397         vmem_t *arena;
  398         vm_offset_t addr;
  399         int rv;
  400 
  401 #if VM_NRESERVLEVEL > 0
  402         if (__predict_true((flags & M_EXEC) == 0))
  403                 arena = vm_dom[domain].vmd_kernel_arena;
  404         else
  405                 arena = vm_dom[domain].vmd_kernel_rwx_arena;
  406 #else
  407         arena = vm_dom[domain].vmd_kernel_arena;
  408 #endif
  409         size = round_page(size);
  410         if (vmem_alloc(arena, size, flags | M_BESTFIT, &addr))
  411                 return (0);
  412 
  413         rv = kmem_back_domain(domain, kernel_object, addr, size, flags);
  414         if (rv != KERN_SUCCESS) {
  415                 vmem_free(arena, addr, size);
  416                 return (0);
  417         }
  418         return (addr);
  419 }
  420 
  421 vm_offset_t
  422 kmem_malloc(vm_size_t size, int flags)
  423 {
  424 
  425         return (kmem_malloc_domainset(DOMAINSET_RR(), size, flags));
  426 }
  427 
  428 vm_offset_t
  429 kmem_malloc_domainset(struct domainset *ds, vm_size_t size, int flags)
  430 {
  431         struct vm_domainset_iter di;
  432         vm_offset_t addr;
  433         int domain;
  434 
  435         vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
  436         do {
  437                 addr = kmem_malloc_domain(domain, size, flags);
  438                 if (addr != 0)
  439                         break;
  440         } while (vm_domainset_iter_policy(&di, &domain) == 0);
  441 
  442         return (addr);
  443 }
  444 
  445 /*
  446  *      kmem_back_domain:
  447  *
  448  *      Allocate physical pages from the specified domain for the specified
  449  *      virtual address range.
  450  */
  451 int
  452 kmem_back_domain(int domain, vm_object_t object, vm_offset_t addr,
  453     vm_size_t size, int flags)
  454 {
  455         vm_offset_t offset, i;
  456         vm_page_t m, mpred;
  457         vm_prot_t prot;
  458         int pflags;
  459 
  460         KASSERT(object == kernel_object,
  461             ("kmem_back_domain: only supports kernel object."));
  462 
  463         offset = addr - VM_MIN_KERNEL_ADDRESS;
  464         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  465         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  466         if (flags & M_WAITOK)
  467                 pflags |= VM_ALLOC_WAITFAIL;
  468         prot = (flags & M_EXEC) != 0 ? VM_PROT_ALL : VM_PROT_RW;
  469 
  470         i = 0;
  471         VM_OBJECT_WLOCK(object);
  472 retry:
  473         mpred = vm_radix_lookup_le(&object->rtree, atop(offset + i));
  474         for (; i < size; i += PAGE_SIZE, mpred = m) {
  475                 m = vm_page_alloc_domain_after(object, atop(offset + i),
  476                     domain, pflags, mpred);
  477 
  478                 /*
  479                  * Ran out of space, free everything up and return. Don't need
  480                  * to lock page queues here as we know that the pages we got
  481                  * aren't on any queues.
  482                  */
  483                 if (m == NULL) {
  484                         if ((flags & M_NOWAIT) == 0)
  485                                 goto retry;
  486                         VM_OBJECT_WUNLOCK(object);
  487                         kmem_unback(object, addr, i);
  488                         return (KERN_NO_SPACE);
  489                 }
  490                 KASSERT(vm_phys_domain(m) == domain,
  491                     ("kmem_back_domain: Domain mismatch %d != %d",
  492                     vm_phys_domain(m), domain));
  493                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  494                         pmap_zero_page(m);
  495                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  496                     ("kmem_malloc: page %p is managed", m));
  497                 m->valid = VM_PAGE_BITS_ALL;
  498                 pmap_enter(kernel_pmap, addr + i, m, prot,
  499                     prot | PMAP_ENTER_WIRED, 0);
  500 #if VM_NRESERVLEVEL > 0
  501                 if (__predict_false((prot & VM_PROT_EXECUTE) != 0))
  502                         m->oflags |= VPO_KMEM_EXEC;
  503 #endif
  504         }
  505         VM_OBJECT_WUNLOCK(object);
  506 
  507         return (KERN_SUCCESS);
  508 }
  509 
  510 /*
  511  *      kmem_back:
  512  *
  513  *      Allocate physical pages for the specified virtual address range.
  514  */
  515 int
  516 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  517 {
  518         vm_offset_t end, next, start;
  519         int domain, rv;
  520 
  521         KASSERT(object == kernel_object,
  522             ("kmem_back: only supports kernel object."));
  523 
  524         for (start = addr, end = addr + size; addr < end; addr = next) {
  525                 /*
  526                  * We must ensure that pages backing a given large virtual page
  527                  * all come from the same physical domain.
  528                  */
  529                 if (vm_ndomains > 1) {
  530                         domain = (addr >> KVA_QUANTUM_SHIFT) % vm_ndomains;
  531                         while (VM_DOMAIN_EMPTY(domain))
  532                                 domain++;
  533                         next = roundup2(addr + 1, KVA_QUANTUM);
  534                         if (next > end || next < start)
  535                                 next = end;
  536                 } else {
  537                         domain = 0;
  538                         next = end;
  539                 }
  540                 rv = kmem_back_domain(domain, object, addr, next - addr, flags);
  541                 if (rv != KERN_SUCCESS) {
  542                         kmem_unback(object, start, addr - start);
  543                         break;
  544                 }
  545         }
  546         return (rv);
  547 }
  548 
  549 /*
  550  *      kmem_unback:
  551  *
  552  *      Unmap and free the physical pages underlying the specified virtual
  553  *      address range.
  554  *
  555  *      A physical page must exist within the specified object at each index
  556  *      that is being unmapped.
  557  */
  558 static struct vmem *
  559 _kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  560 {
  561         struct vmem *arena;
  562         vm_page_t m, next;
  563         vm_offset_t end, offset;
  564         int domain;
  565 
  566         KASSERT(object == kernel_object,
  567             ("kmem_unback: only supports kernel object."));
  568 
  569         if (size == 0)
  570                 return (NULL);
  571         pmap_remove(kernel_pmap, addr, addr + size);
  572         offset = addr - VM_MIN_KERNEL_ADDRESS;
  573         end = offset + size;
  574         VM_OBJECT_WLOCK(object);
  575         m = vm_page_lookup(object, atop(offset)); 
  576         domain = vm_phys_domain(m);
  577 #if VM_NRESERVLEVEL > 0
  578         if (__predict_true((m->oflags & VPO_KMEM_EXEC) == 0))
  579                 arena = vm_dom[domain].vmd_kernel_arena;
  580         else
  581                 arena = vm_dom[domain].vmd_kernel_rwx_arena;
  582 #else
  583         arena = vm_dom[domain].vmd_kernel_arena;
  584 #endif
  585         for (; offset < end; offset += PAGE_SIZE, m = next) {
  586                 next = vm_page_next(m);
  587                 vm_page_unwire(m, PQ_NONE);
  588                 vm_page_free(m);
  589         }
  590         VM_OBJECT_WUNLOCK(object);
  591 
  592         return (arena);
  593 }
  594 
  595 void
  596 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  597 {
  598 
  599         (void)_kmem_unback(object, addr, size);
  600 }
  601 
  602 /*
  603  *      kmem_free:
  604  *
  605  *      Free memory allocated with kmem_malloc.  The size must match the
  606  *      original allocation.
  607  */
  608 void
  609 kmem_free(vm_offset_t addr, vm_size_t size)
  610 {
  611         struct vmem *arena;
  612 
  613         size = round_page(size);
  614         arena = _kmem_unback(kernel_object, addr, size);
  615         if (arena != NULL)
  616                 vmem_free(arena, addr, size);
  617 }
  618 
  619 /*
  620  *      kmap_alloc_wait:
  621  *
  622  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  623  *      has no room, the caller sleeps waiting for more memory in the submap.
  624  *
  625  *      This routine may block.
  626  */
  627 vm_offset_t
  628 kmap_alloc_wait(vm_map_t map, vm_size_t size)
  629 {
  630         vm_offset_t addr;
  631 
  632         size = round_page(size);
  633         if (!swap_reserve(size))
  634                 return (0);
  635 
  636         for (;;) {
  637                 /*
  638                  * To make this work for more than one map, use the map's lock
  639                  * to lock out sleepers/wakers.
  640                  */
  641                 vm_map_lock(map);
  642                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  643                         break;
  644                 /* no space now; see if we can ever get space */
  645                 if (vm_map_max(map) - vm_map_min(map) < size) {
  646                         vm_map_unlock(map);
  647                         swap_release(size);
  648                         return (0);
  649                 }
  650                 map->needs_wakeup = TRUE;
  651                 vm_map_unlock_and_wait(map, 0);
  652         }
  653         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  654             VM_PROT_ALL, MAP_ACC_CHARGED);
  655         vm_map_unlock(map);
  656         return (addr);
  657 }
  658 
  659 /*
  660  *      kmap_free_wakeup:
  661  *
  662  *      Returns memory to a submap of the kernel, and wakes up any processes
  663  *      waiting for memory in that map.
  664  */
  665 void
  666 kmap_free_wakeup(vm_map_t map, vm_offset_t addr, vm_size_t size)
  667 {
  668 
  669         vm_map_lock(map);
  670         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  671         if (map->needs_wakeup) {
  672                 map->needs_wakeup = FALSE;
  673                 vm_map_wakeup(map);
  674         }
  675         vm_map_unlock(map);
  676 }
  677 
  678 void
  679 kmem_init_zero_region(void)
  680 {
  681         vm_offset_t addr, i;
  682         vm_page_t m;
  683 
  684         /*
  685          * Map a single physical page of zeros to a larger virtual range.
  686          * This requires less looping in places that want large amounts of
  687          * zeros, while not using much more physical resources.
  688          */
  689         addr = kva_alloc(ZERO_REGION_SIZE);
  690         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  691             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  692         if ((m->flags & PG_ZERO) == 0)
  693                 pmap_zero_page(m);
  694         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  695                 pmap_qenter(addr + i, &m, 1);
  696         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  697 
  698         zero_region = (const void *)addr;
  699 }
  700 
  701 /*
  702  * Import KVA from the kernel map into the kernel arena.
  703  */
  704 static int
  705 kva_import(void *unused, vmem_size_t size, int flags, vmem_addr_t *addrp)
  706 {
  707         vm_offset_t addr;
  708         int result;
  709 
  710         KASSERT((size % KVA_QUANTUM) == 0,
  711             ("kva_import: Size %jd is not a multiple of %d",
  712             (intmax_t)size, (int)KVA_QUANTUM));
  713         addr = vm_map_min(kernel_map);
  714         result = vm_map_find(kernel_map, NULL, 0, &addr, size, 0,
  715             VMFS_SUPER_SPACE, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  716         if (result != KERN_SUCCESS)
  717                 return (ENOMEM);
  718 
  719         *addrp = addr;
  720 
  721         return (0);
  722 }
  723 
  724 /*
  725  * Import KVA from a parent arena into a per-domain arena.  Imports must be
  726  * KVA_QUANTUM-aligned and a multiple of KVA_QUANTUM in size.
  727  */
  728 static int
  729 kva_import_domain(void *arena, vmem_size_t size, int flags, vmem_addr_t *addrp)
  730 {
  731 
  732         KASSERT((size % KVA_QUANTUM) == 0,
  733             ("kva_import_domain: Size %jd is not a multiple of %d",
  734             (intmax_t)size, (int)KVA_QUANTUM));
  735         return (vmem_xalloc(arena, size, KVA_QUANTUM, 0, 0, VMEM_ADDR_MIN,
  736             VMEM_ADDR_MAX, flags, addrp));
  737 }
  738 
  739 /*
  740  *      kmem_init:
  741  *
  742  *      Create the kernel map; insert a mapping covering kernel text, 
  743  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  744  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  745  *      `start' as allocated, and the range between `start' and `end' as free.
  746  *      Create the kernel vmem arena and its per-domain children.
  747  */
  748 void
  749 kmem_init(vm_offset_t start, vm_offset_t end)
  750 {
  751         vm_map_t m;
  752         int domain;
  753 
  754         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  755         m->system_map = 1;
  756         vm_map_lock(m);
  757         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  758         kernel_map = m;
  759         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  760 #ifdef __amd64__
  761             KERNBASE,
  762 #else                
  763             VM_MIN_KERNEL_ADDRESS,
  764 #endif
  765             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  766         /* ... and ending with the completion of the above `insert' */
  767         vm_map_unlock(m);
  768 
  769         /*
  770          * Initialize the kernel_arena.  This can grow on demand.
  771          */
  772         vmem_init(kernel_arena, "kernel arena", 0, 0, PAGE_SIZE, 0, 0);
  773         vmem_set_import(kernel_arena, kva_import, NULL, NULL, KVA_QUANTUM);
  774 
  775         for (domain = 0; domain < vm_ndomains; domain++) {
  776                 /*
  777                  * Initialize the per-domain arenas.  These are used to color
  778                  * the KVA space in a way that ensures that virtual large pages
  779                  * are backed by memory from the same physical domain,
  780                  * maximizing the potential for superpage promotion.
  781                  */
  782                 vm_dom[domain].vmd_kernel_arena = vmem_create(
  783                     "kernel arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
  784                 vmem_set_import(vm_dom[domain].vmd_kernel_arena,
  785                     kva_import_domain, NULL, kernel_arena, KVA_QUANTUM);
  786 
  787                 /*
  788                  * In architectures with superpages, maintain separate arenas
  789                  * for allocations with permissions that differ from the
  790                  * "standard" read/write permissions used for kernel memory,
  791                  * so as not to inhibit superpage promotion.
  792                  */
  793 #if VM_NRESERVLEVEL > 0
  794                 vm_dom[domain].vmd_kernel_rwx_arena = vmem_create(
  795                     "kernel rwx arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
  796                 vmem_set_import(vm_dom[domain].vmd_kernel_rwx_arena,
  797                     kva_import_domain, (vmem_release_t *)vmem_xfree,
  798                     kernel_arena, KVA_QUANTUM);
  799 #endif
  800         }
  801 }
  802 
  803 /*
  804  *      kmem_bootstrap_free:
  805  *
  806  *      Free pages backing preloaded data (e.g., kernel modules) to the
  807  *      system.  Currently only supported on platforms that create a
  808  *      vm_phys segment for preloaded data.
  809  */
  810 void
  811 kmem_bootstrap_free(vm_offset_t start, vm_size_t size)
  812 {
  813 #if defined(__i386__) || defined(__amd64__)
  814         struct vm_domain *vmd;
  815         vm_offset_t end, va;
  816         vm_paddr_t pa;
  817         vm_page_t m;
  818 
  819         end = trunc_page(start + size);
  820         start = round_page(start);
  821 
  822         for (va = start; va < end; va += PAGE_SIZE) {
  823                 pa = pmap_kextract(va);
  824                 m = PHYS_TO_VM_PAGE(pa);
  825 
  826                 vmd = vm_pagequeue_domain(m);
  827                 vm_domain_free_lock(vmd);
  828                 vm_phys_free_pages(m, 0);
  829                 vm_domain_free_unlock(vmd);
  830 
  831                 vm_domain_freecnt_inc(vmd, 1);
  832                 vm_cnt.v_page_count++;
  833         }
  834         pmap_remove(kernel_pmap, start, end);
  835         (void)vmem_add(kernel_arena, start, end - start, M_WAITOK);
  836 #endif
  837 }
  838 
  839 #ifdef DIAGNOSTIC
  840 /*
  841  * Allow userspace to directly trigger the VM drain routine for testing
  842  * purposes.
  843  */
  844 static int
  845 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  846 {
  847         int error, i;
  848 
  849         i = 0;
  850         error = sysctl_handle_int(oidp, &i, 0, req);
  851         if (error)
  852                 return (error);
  853         if ((i & ~(VM_LOW_KMEM | VM_LOW_PAGES)) != 0)
  854                 return (EINVAL);
  855         if (i != 0)
  856                 EVENTHANDLER_INVOKE(vm_lowmem, i);
  857         return (0);
  858 }
  859 
  860 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  861     debug_vm_lowmem, "I", "set to trigger vm_lowmem event with given flags");
  862 #endif

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