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: head/sys/vm/vm_kern.c 345702 2019-03-29 16:53:46Z kib $");
   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 we want large import sizes. */
  128 #define KVA_QUANTUM_SHIFT       (8 + 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         vm_prot_t prot;
  188 
  189         size = round_page(size);
  190         vmem = vm_dom[domain].vmd_kernel_arena;
  191         if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
  192                 return (0);
  193         offset = addr - VM_MIN_KERNEL_ADDRESS;
  194         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  195         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  196         pflags |= VM_ALLOC_NOWAIT;
  197         prot = (flags & M_EXEC) != 0 ? VM_PROT_ALL : VM_PROT_RW;
  198         VM_OBJECT_WLOCK(object);
  199         for (i = 0; i < size; i += PAGE_SIZE) {
  200                 tries = 0;
  201 retry:
  202                 m = vm_page_alloc_contig_domain(object, atop(offset + i),
  203                     domain, pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  204                 if (m == NULL) {
  205                         VM_OBJECT_WUNLOCK(object);
  206                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  207                                 if (!vm_page_reclaim_contig_domain(domain,
  208                                     pflags, 1, low, high, PAGE_SIZE, 0) &&
  209                                     (flags & M_WAITOK) != 0)
  210                                         vm_wait_domain(domain);
  211                                 VM_OBJECT_WLOCK(object);
  212                                 tries++;
  213                                 goto retry;
  214                         }
  215                         kmem_unback(object, addr, i);
  216                         vmem_free(vmem, addr, size);
  217                         return (0);
  218                 }
  219                 KASSERT(vm_phys_domain(m) == domain,
  220                     ("kmem_alloc_attr_domain: Domain mismatch %d != %d",
  221                     vm_phys_domain(m), domain));
  222                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  223                         pmap_zero_page(m);
  224                 m->valid = VM_PAGE_BITS_ALL;
  225                 pmap_enter(kernel_pmap, addr + i, m, prot,
  226                     prot | PMAP_ENTER_WIRED, 0);
  227         }
  228         VM_OBJECT_WUNLOCK(object);
  229         return (addr);
  230 }
  231 
  232 vm_offset_t
  233 kmem_alloc_attr(vm_size_t size, int flags, vm_paddr_t low, vm_paddr_t high,
  234     vm_memattr_t memattr)
  235 {
  236 
  237         return (kmem_alloc_attr_domainset(DOMAINSET_RR(), size, flags, low,
  238             high, memattr));
  239 }
  240 
  241 vm_offset_t
  242 kmem_alloc_attr_domainset(struct domainset *ds, vm_size_t size, int flags,
  243     vm_paddr_t low, vm_paddr_t high, vm_memattr_t memattr)
  244 {
  245         struct vm_domainset_iter di;
  246         vm_offset_t addr;
  247         int domain;
  248 
  249         vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
  250         do {
  251                 addr = kmem_alloc_attr_domain(domain, size, flags, low, high,
  252                     memattr);
  253                 if (addr != 0)
  254                         break;
  255         } while (vm_domainset_iter_policy(&di, &domain) == 0);
  256 
  257         return (addr);
  258 }
  259 
  260 /*
  261  *      Allocates a region from the kernel address map and physically
  262  *      contiguous pages within the specified address range to the kernel
  263  *      object.  Creates a wired mapping from this region to these pages, and
  264  *      returns the region's starting virtual address.  If M_ZERO is specified
  265  *      through the given flags, then the pages are zeroed before they are
  266  *      mapped.
  267  */
  268 static vm_offset_t
  269 kmem_alloc_contig_domain(int domain, vm_size_t size, int flags, vm_paddr_t low,
  270     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  271     vm_memattr_t memattr)
  272 {
  273         vmem_t *vmem;
  274         vm_object_t object = kernel_object;
  275         vm_offset_t addr, offset, tmp;
  276         vm_page_t end_m, m;
  277         u_long npages;
  278         int pflags, tries;
  279  
  280         size = round_page(size);
  281         vmem = vm_dom[domain].vmd_kernel_arena;
  282         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  283                 return (0);
  284         offset = addr - VM_MIN_KERNEL_ADDRESS;
  285         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  286         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  287         pflags |= VM_ALLOC_NOWAIT;
  288         npages = atop(size);
  289         VM_OBJECT_WLOCK(object);
  290         tries = 0;
  291 retry:
  292         m = vm_page_alloc_contig_domain(object, atop(offset), domain, pflags,
  293             npages, low, high, alignment, boundary, memattr);
  294         if (m == NULL) {
  295                 VM_OBJECT_WUNLOCK(object);
  296                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  297                         if (!vm_page_reclaim_contig_domain(domain, pflags,
  298                             npages, low, high, alignment, boundary) &&
  299                             (flags & M_WAITOK) != 0)
  300                                 vm_wait_domain(domain);
  301                         VM_OBJECT_WLOCK(object);
  302                         tries++;
  303                         goto retry;
  304                 }
  305                 vmem_free(vmem, addr, size);
  306                 return (0);
  307         }
  308         KASSERT(vm_phys_domain(m) == domain,
  309             ("kmem_alloc_contig_domain: Domain mismatch %d != %d",
  310             vm_phys_domain(m), domain));
  311         end_m = m + npages;
  312         tmp = addr;
  313         for (; m < end_m; m++) {
  314                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  315                         pmap_zero_page(m);
  316                 m->valid = VM_PAGE_BITS_ALL;
  317                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_RW,
  318                     VM_PROT_RW | PMAP_ENTER_WIRED, 0);
  319                 tmp += PAGE_SIZE;
  320         }
  321         VM_OBJECT_WUNLOCK(object);
  322         return (addr);
  323 }
  324 
  325 vm_offset_t
  326 kmem_alloc_contig(vm_size_t size, int flags, vm_paddr_t low, vm_paddr_t high,
  327     u_long alignment, vm_paddr_t boundary, vm_memattr_t memattr)
  328 {
  329 
  330         return (kmem_alloc_contig_domainset(DOMAINSET_RR(), size, flags, low,
  331             high, alignment, boundary, memattr));
  332 }
  333 
  334 vm_offset_t
  335 kmem_alloc_contig_domainset(struct domainset *ds, vm_size_t size, int flags,
  336     vm_paddr_t low, vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  337     vm_memattr_t memattr)
  338 {
  339         struct vm_domainset_iter di;
  340         vm_offset_t addr;
  341         int domain;
  342 
  343         vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
  344         do {
  345                 addr = kmem_alloc_contig_domain(domain, size, flags, low, high,
  346                     alignment, boundary, memattr);
  347                 if (addr != 0)
  348                         break;
  349         } while (vm_domainset_iter_policy(&di, &domain) == 0);
  350 
  351         return (addr);
  352 }
  353 
  354 /*
  355  *      kmem_suballoc:
  356  *
  357  *      Allocates a map to manage a subrange
  358  *      of the kernel virtual address space.
  359  *
  360  *      Arguments are as follows:
  361  *
  362  *      parent          Map to take range from
  363  *      min, max        Returned endpoints of map
  364  *      size            Size of range to find
  365  *      superpage_align Request that min is superpage aligned
  366  */
  367 vm_map_t
  368 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  369     vm_size_t size, boolean_t superpage_align)
  370 {
  371         int ret;
  372         vm_map_t result;
  373 
  374         size = round_page(size);
  375 
  376         *min = vm_map_min(parent);
  377         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  378             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  379             MAP_ACC_NO_CHARGE);
  380         if (ret != KERN_SUCCESS)
  381                 panic("kmem_suballoc: bad status return of %d", ret);
  382         *max = *min + size;
  383         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  384         if (result == NULL)
  385                 panic("kmem_suballoc: cannot create submap");
  386         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  387                 panic("kmem_suballoc: unable to change range to submap");
  388         return (result);
  389 }
  390 
  391 /*
  392  *      kmem_malloc_domain:
  393  *
  394  *      Allocate wired-down pages in the kernel's address space.
  395  */
  396 static vm_offset_t
  397 kmem_malloc_domain(int domain, vm_size_t size, int flags)
  398 {
  399         vmem_t *arena;
  400         vm_offset_t addr;
  401         int rv;
  402 
  403 #if VM_NRESERVLEVEL > 0
  404         if (__predict_true((flags & M_EXEC) == 0))
  405                 arena = vm_dom[domain].vmd_kernel_arena;
  406         else
  407                 arena = vm_dom[domain].vmd_kernel_rwx_arena;
  408 #else
  409         arena = vm_dom[domain].vmd_kernel_arena;
  410 #endif
  411         size = round_page(size);
  412         if (vmem_alloc(arena, size, flags | M_BESTFIT, &addr))
  413                 return (0);
  414 
  415         rv = kmem_back_domain(domain, kernel_object, addr, size, flags);
  416         if (rv != KERN_SUCCESS) {
  417                 vmem_free(arena, addr, size);
  418                 return (0);
  419         }
  420         return (addr);
  421 }
  422 
  423 vm_offset_t
  424 kmem_malloc(vm_size_t size, int flags)
  425 {
  426 
  427         return (kmem_malloc_domainset(DOMAINSET_RR(), size, flags));
  428 }
  429 
  430 vm_offset_t
  431 kmem_malloc_domainset(struct domainset *ds, vm_size_t size, int flags)
  432 {
  433         struct vm_domainset_iter di;
  434         vm_offset_t addr;
  435         int domain;
  436 
  437         vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
  438         do {
  439                 addr = kmem_malloc_domain(domain, size, flags);
  440                 if (addr != 0)
  441                         break;
  442         } while (vm_domainset_iter_policy(&di, &domain) == 0);
  443 
  444         return (addr);
  445 }
  446 
  447 /*
  448  *      kmem_back_domain:
  449  *
  450  *      Allocate physical pages from the specified domain for the specified
  451  *      virtual address range.
  452  */
  453 int
  454 kmem_back_domain(int domain, vm_object_t object, vm_offset_t addr,
  455     vm_size_t size, int flags)
  456 {
  457         vm_offset_t offset, i;
  458         vm_page_t m, mpred;
  459         vm_prot_t prot;
  460         int pflags;
  461 
  462         KASSERT(object == kernel_object,
  463             ("kmem_back_domain: only supports kernel object."));
  464 
  465         offset = addr - VM_MIN_KERNEL_ADDRESS;
  466         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  467         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  468         if (flags & M_WAITOK)
  469                 pflags |= VM_ALLOC_WAITFAIL;
  470         prot = (flags & M_EXEC) != 0 ? VM_PROT_ALL : VM_PROT_RW;
  471 
  472         i = 0;
  473         VM_OBJECT_WLOCK(object);
  474 retry:
  475         mpred = vm_radix_lookup_le(&object->rtree, atop(offset + i));
  476         for (; i < size; i += PAGE_SIZE, mpred = m) {
  477                 m = vm_page_alloc_domain_after(object, atop(offset + i),
  478                     domain, pflags, mpred);
  479 
  480                 /*
  481                  * Ran out of space, free everything up and return. Don't need
  482                  * to lock page queues here as we know that the pages we got
  483                  * aren't on any queues.
  484                  */
  485                 if (m == NULL) {
  486                         if ((flags & M_NOWAIT) == 0)
  487                                 goto retry;
  488                         VM_OBJECT_WUNLOCK(object);
  489                         kmem_unback(object, addr, i);
  490                         return (KERN_NO_SPACE);
  491                 }
  492                 KASSERT(vm_phys_domain(m) == domain,
  493                     ("kmem_back_domain: Domain mismatch %d != %d",
  494                     vm_phys_domain(m), domain));
  495                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  496                         pmap_zero_page(m);
  497                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  498                     ("kmem_malloc: page %p is managed", m));
  499                 m->valid = VM_PAGE_BITS_ALL;
  500                 pmap_enter(kernel_pmap, addr + i, m, prot,
  501                     prot | PMAP_ENTER_WIRED, 0);
  502 #if VM_NRESERVLEVEL > 0
  503                 if (__predict_false((prot & VM_PROT_EXECUTE) != 0))
  504                         m->oflags |= VPO_KMEM_EXEC;
  505 #endif
  506         }
  507         VM_OBJECT_WUNLOCK(object);
  508 
  509         return (KERN_SUCCESS);
  510 }
  511 
  512 /*
  513  *      kmem_back:
  514  *
  515  *      Allocate physical pages for the specified virtual address range.
  516  */
  517 int
  518 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  519 {
  520         vm_offset_t end, next, start;
  521         int domain, rv;
  522 
  523         KASSERT(object == kernel_object,
  524             ("kmem_back: only supports kernel object."));
  525 
  526         for (start = addr, end = addr + size; addr < end; addr = next) {
  527                 /*
  528                  * We must ensure that pages backing a given large virtual page
  529                  * all come from the same physical domain.
  530                  */
  531                 if (vm_ndomains > 1) {
  532                         domain = (addr >> KVA_QUANTUM_SHIFT) % vm_ndomains;
  533                         while (VM_DOMAIN_EMPTY(domain))
  534                                 domain++;
  535                         next = roundup2(addr + 1, KVA_QUANTUM);
  536                         if (next > end || next < start)
  537                                 next = end;
  538                 } else {
  539                         domain = 0;
  540                         next = end;
  541                 }
  542                 rv = kmem_back_domain(domain, object, addr, next - addr, flags);
  543                 if (rv != KERN_SUCCESS) {
  544                         kmem_unback(object, start, addr - start);
  545                         break;
  546                 }
  547         }
  548         return (rv);
  549 }
  550 
  551 /*
  552  *      kmem_unback:
  553  *
  554  *      Unmap and free the physical pages underlying the specified virtual
  555  *      address range.
  556  *
  557  *      A physical page must exist within the specified object at each index
  558  *      that is being unmapped.
  559  */
  560 static struct vmem *
  561 _kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  562 {
  563         struct vmem *arena;
  564         vm_page_t m, next;
  565         vm_offset_t end, offset;
  566         int domain;
  567 
  568         KASSERT(object == kernel_object,
  569             ("kmem_unback: only supports kernel object."));
  570 
  571         if (size == 0)
  572                 return (NULL);
  573         pmap_remove(kernel_pmap, addr, addr + size);
  574         offset = addr - VM_MIN_KERNEL_ADDRESS;
  575         end = offset + size;
  576         VM_OBJECT_WLOCK(object);
  577         m = vm_page_lookup(object, atop(offset)); 
  578         domain = vm_phys_domain(m);
  579 #if VM_NRESERVLEVEL > 0
  580         if (__predict_true((m->oflags & VPO_KMEM_EXEC) == 0))
  581                 arena = vm_dom[domain].vmd_kernel_arena;
  582         else
  583                 arena = vm_dom[domain].vmd_kernel_rwx_arena;
  584 #else
  585         arena = vm_dom[domain].vmd_kernel_arena;
  586 #endif
  587         for (; offset < end; offset += PAGE_SIZE, m = next) {
  588                 next = vm_page_next(m);
  589                 vm_page_unwire(m, PQ_NONE);
  590                 vm_page_free(m);
  591         }
  592         VM_OBJECT_WUNLOCK(object);
  593 
  594         return (arena);
  595 }
  596 
  597 void
  598 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  599 {
  600 
  601         (void)_kmem_unback(object, addr, size);
  602 }
  603 
  604 /*
  605  *      kmem_free:
  606  *
  607  *      Free memory allocated with kmem_malloc.  The size must match the
  608  *      original allocation.
  609  */
  610 void
  611 kmem_free(vm_offset_t addr, vm_size_t size)
  612 {
  613         struct vmem *arena;
  614 
  615         size = round_page(size);
  616         arena = _kmem_unback(kernel_object, addr, size);
  617         if (arena != NULL)
  618                 vmem_free(arena, addr, size);
  619 }
  620 
  621 /*
  622  *      kmap_alloc_wait:
  623  *
  624  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  625  *      has no room, the caller sleeps waiting for more memory in the submap.
  626  *
  627  *      This routine may block.
  628  */
  629 vm_offset_t
  630 kmap_alloc_wait(vm_map_t map, vm_size_t size)
  631 {
  632         vm_offset_t addr;
  633 
  634         size = round_page(size);
  635         if (!swap_reserve(size))
  636                 return (0);
  637 
  638         for (;;) {
  639                 /*
  640                  * To make this work for more than one map, use the map's lock
  641                  * to lock out sleepers/wakers.
  642                  */
  643                 vm_map_lock(map);
  644                 addr = vm_map_findspace(map, vm_map_min(map), size);
  645                 if (addr + size <= vm_map_max(map))
  646                         break;
  647                 /* no space now; see if we can ever get space */
  648                 if (vm_map_max(map) - vm_map_min(map) < size) {
  649                         vm_map_unlock(map);
  650                         swap_release(size);
  651                         return (0);
  652                 }
  653                 map->needs_wakeup = TRUE;
  654                 vm_map_unlock_and_wait(map, 0);
  655         }
  656         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_RW, VM_PROT_RW,
  657             MAP_ACC_CHARGED);
  658         vm_map_unlock(map);
  659         return (addr);
  660 }
  661 
  662 /*
  663  *      kmap_free_wakeup:
  664  *
  665  *      Returns memory to a submap of the kernel, and wakes up any processes
  666  *      waiting for memory in that map.
  667  */
  668 void
  669 kmap_free_wakeup(vm_map_t map, vm_offset_t addr, vm_size_t size)
  670 {
  671 
  672         vm_map_lock(map);
  673         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  674         if (map->needs_wakeup) {
  675                 map->needs_wakeup = FALSE;
  676                 vm_map_wakeup(map);
  677         }
  678         vm_map_unlock(map);
  679 }
  680 
  681 void
  682 kmem_init_zero_region(void)
  683 {
  684         vm_offset_t addr, i;
  685         vm_page_t m;
  686 
  687         /*
  688          * Map a single physical page of zeros to a larger virtual range.
  689          * This requires less looping in places that want large amounts of
  690          * zeros, while not using much more physical resources.
  691          */
  692         addr = kva_alloc(ZERO_REGION_SIZE);
  693         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  694             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  695         if ((m->flags & PG_ZERO) == 0)
  696                 pmap_zero_page(m);
  697         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  698                 pmap_qenter(addr + i, &m, 1);
  699         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  700 
  701         zero_region = (const void *)addr;
  702 }
  703 
  704 /*
  705  * Import KVA from the kernel map into the kernel arena.
  706  */
  707 static int
  708 kva_import(void *unused, vmem_size_t size, int flags, vmem_addr_t *addrp)
  709 {
  710         vm_offset_t addr;
  711         int result;
  712 
  713         KASSERT((size % KVA_QUANTUM) == 0,
  714             ("kva_import: Size %jd is not a multiple of %d",
  715             (intmax_t)size, (int)KVA_QUANTUM));
  716         addr = vm_map_min(kernel_map);
  717         result = vm_map_find(kernel_map, NULL, 0, &addr, size, 0,
  718             VMFS_SUPER_SPACE, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  719         if (result != KERN_SUCCESS)
  720                 return (ENOMEM);
  721 
  722         *addrp = addr;
  723 
  724         return (0);
  725 }
  726 
  727 /*
  728  * Import KVA from a parent arena into a per-domain arena.  Imports must be
  729  * KVA_QUANTUM-aligned and a multiple of KVA_QUANTUM in size.
  730  */
  731 static int
  732 kva_import_domain(void *arena, vmem_size_t size, int flags, vmem_addr_t *addrp)
  733 {
  734 
  735         KASSERT((size % KVA_QUANTUM) == 0,
  736             ("kva_import_domain: Size %jd is not a multiple of %d",
  737             (intmax_t)size, (int)KVA_QUANTUM));
  738         return (vmem_xalloc(arena, size, KVA_QUANTUM, 0, 0, VMEM_ADDR_MIN,
  739             VMEM_ADDR_MAX, flags, addrp));
  740 }
  741 
  742 /*
  743  *      kmem_init:
  744  *
  745  *      Create the kernel map; insert a mapping covering kernel text, 
  746  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  747  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  748  *      `start' as allocated, and the range between `start' and `end' as free.
  749  *      Create the kernel vmem arena and its per-domain children.
  750  */
  751 void
  752 kmem_init(vm_offset_t start, vm_offset_t end)
  753 {
  754         vm_map_t m;
  755         int domain;
  756 
  757         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  758         m->system_map = 1;
  759         vm_map_lock(m);
  760         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  761         kernel_map = m;
  762         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  763 #ifdef __amd64__
  764             KERNBASE,
  765 #else                
  766             VM_MIN_KERNEL_ADDRESS,
  767 #endif
  768             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  769         /* ... and ending with the completion of the above `insert' */
  770         vm_map_unlock(m);
  771 
  772         /*
  773          * Initialize the kernel_arena.  This can grow on demand.
  774          */
  775         vmem_init(kernel_arena, "kernel arena", 0, 0, PAGE_SIZE, 0, 0);
  776         vmem_set_import(kernel_arena, kva_import, NULL, NULL, KVA_QUANTUM);
  777 
  778         for (domain = 0; domain < vm_ndomains; domain++) {
  779                 /*
  780                  * Initialize the per-domain arenas.  These are used to color
  781                  * the KVA space in a way that ensures that virtual large pages
  782                  * are backed by memory from the same physical domain,
  783                  * maximizing the potential for superpage promotion.
  784                  */
  785                 vm_dom[domain].vmd_kernel_arena = vmem_create(
  786                     "kernel arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
  787                 vmem_set_import(vm_dom[domain].vmd_kernel_arena,
  788                     kva_import_domain, NULL, kernel_arena, KVA_QUANTUM);
  789 
  790                 /*
  791                  * In architectures with superpages, maintain separate arenas
  792                  * for allocations with permissions that differ from the
  793                  * "standard" read/write permissions used for kernel memory,
  794                  * so as not to inhibit superpage promotion.
  795                  */
  796 #if VM_NRESERVLEVEL > 0
  797                 vm_dom[domain].vmd_kernel_rwx_arena = vmem_create(
  798                     "kernel rwx arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
  799                 vmem_set_import(vm_dom[domain].vmd_kernel_rwx_arena,
  800                     kva_import_domain, (vmem_release_t *)vmem_xfree,
  801                     kernel_arena, KVA_QUANTUM);
  802 #endif
  803         }
  804 }
  805 
  806 /*
  807  *      kmem_bootstrap_free:
  808  *
  809  *      Free pages backing preloaded data (e.g., kernel modules) to the
  810  *      system.  Currently only supported on platforms that create a
  811  *      vm_phys segment for preloaded data.
  812  */
  813 void
  814 kmem_bootstrap_free(vm_offset_t start, vm_size_t size)
  815 {
  816 #if defined(__i386__) || defined(__amd64__)
  817         struct vm_domain *vmd;
  818         vm_offset_t end, va;
  819         vm_paddr_t pa;
  820         vm_page_t m;
  821 
  822         end = trunc_page(start + size);
  823         start = round_page(start);
  824 
  825         for (va = start; va < end; va += PAGE_SIZE) {
  826                 pa = pmap_kextract(va);
  827                 m = PHYS_TO_VM_PAGE(pa);
  828 
  829                 vmd = vm_pagequeue_domain(m);
  830                 vm_domain_free_lock(vmd);
  831                 vm_phys_free_pages(m, 0);
  832                 vm_domain_free_unlock(vmd);
  833 
  834                 vm_domain_freecnt_inc(vmd, 1);
  835                 vm_cnt.v_page_count++;
  836         }
  837         pmap_remove(kernel_pmap, start, end);
  838         (void)vmem_add(kernel_arena, start, end - start, M_WAITOK);
  839 #endif
  840 }
  841 
  842 #ifdef DIAGNOSTIC
  843 /*
  844  * Allow userspace to directly trigger the VM drain routine for testing
  845  * purposes.
  846  */
  847 static int
  848 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  849 {
  850         int error, i;
  851 
  852         i = 0;
  853         error = sysctl_handle_int(oidp, &i, 0, req);
  854         if (error)
  855                 return (error);
  856         if ((i & ~(VM_LOW_KMEM | VM_LOW_PAGES)) != 0)
  857                 return (EINVAL);
  858         if (i != 0)
  859                 EVENTHANDLER_INVOKE(vm_lowmem, i);
  860         return (0);
  861 }
  862 
  863 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  864     debug_vm_lowmem, "I", "set to trigger vm_lowmem event with given flags");
  865 #endif

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