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: stable/10/sys/vm/vm_kern.c 324782 2017-10-20 00:38:01Z emaste $");
   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(vm_size_t size)
  122 {
  123         vm_offset_t addr;
  124 
  125         size = round_page(size);
  126         if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
  127                 return (0);
  128 
  129         return (addr);
  130 }
  131 
  132 /*
  133  *      kva_free:
  134  *
  135  *      Release a region of kernel virtual memory allocated
  136  *      with kva_alloc, and return the physical pages
  137  *      associated with that region.
  138  *
  139  *      This routine may not block on kernel maps.
  140  */
  141 void
  142 kva_free(vm_offset_t addr, vm_size_t size)
  143 {
  144 
  145         size = round_page(size);
  146         vmem_free(kernel_arena, addr, size);
  147 }
  148 
  149 /*
  150  *      Allocates a region from the kernel address map and physical pages
  151  *      within the specified address range to the kernel object.  Creates a
  152  *      wired mapping from this region to these pages, and returns the
  153  *      region's starting virtual address.  The allocated pages are not
  154  *      necessarily physically contiguous.  If M_ZERO is specified through the
  155  *      given flags, then the pages are zeroed before they are mapped.
  156  */
  157 vm_offset_t
  158 kmem_alloc_attr(vmem_t *vmem, vm_size_t size, int flags, vm_paddr_t low,
  159     vm_paddr_t high, vm_memattr_t memattr)
  160 {
  161         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  162         vm_offset_t addr, i;
  163         vm_ooffset_t offset;
  164         vm_page_t m;
  165         int pflags, tries;
  166 
  167         size = round_page(size);
  168         if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
  169                 return (0);
  170         offset = addr - VM_MIN_KERNEL_ADDRESS;
  171         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  172         VM_OBJECT_WLOCK(object);
  173         for (i = 0; i < size; i += PAGE_SIZE) {
  174                 tries = 0;
  175 retry:
  176                 m = vm_page_alloc_contig(object, OFF_TO_IDX(offset + i),
  177                     pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  178                 if (m == NULL) {
  179                         VM_OBJECT_WUNLOCK(object);
  180                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  181                                 vm_pageout_grow_cache(tries, low, high);
  182                                 VM_OBJECT_WLOCK(object);
  183                                 tries++;
  184                                 goto retry;
  185                         }
  186                         kmem_unback(object, addr, i);
  187                         vmem_free(vmem, addr, size);
  188                         return (0);
  189                 }
  190                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  191                         pmap_zero_page(m);
  192                 m->valid = VM_PAGE_BITS_ALL;
  193                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  194                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  195         }
  196         VM_OBJECT_WUNLOCK(object);
  197         return (addr);
  198 }
  199 
  200 /*
  201  *      Allocates a region from the kernel address map and physically
  202  *      contiguous pages within the specified address range to the kernel
  203  *      object.  Creates a wired mapping from this region to these pages, and
  204  *      returns the region's starting virtual address.  If M_ZERO is specified
  205  *      through the given flags, then the pages are zeroed before they are
  206  *      mapped.
  207  */
  208 vm_offset_t
  209 kmem_alloc_contig(struct vmem *vmem, vm_size_t size, int flags, vm_paddr_t low,
  210     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  211     vm_memattr_t memattr)
  212 {
  213         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  214         vm_offset_t addr, tmp;
  215         vm_ooffset_t offset;
  216         vm_page_t end_m, m;
  217         int pflags, tries;
  218  
  219         size = round_page(size);
  220         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  221                 return (0);
  222         offset = addr - VM_MIN_KERNEL_ADDRESS;
  223         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  224         VM_OBJECT_WLOCK(object);
  225         tries = 0;
  226 retry:
  227         m = vm_page_alloc_contig(object, OFF_TO_IDX(offset), pflags,
  228             atop(size), low, high, alignment, boundary, memattr);
  229         if (m == NULL) {
  230                 VM_OBJECT_WUNLOCK(object);
  231                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  232                         vm_pageout_grow_cache(tries, low, high);
  233                         VM_OBJECT_WLOCK(object);
  234                         tries++;
  235                         goto retry;
  236                 }
  237                 vmem_free(vmem, addr, size);
  238                 return (0);
  239         }
  240         end_m = m + atop(size);
  241         tmp = addr;
  242         for (; m < end_m; m++) {
  243                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  244                         pmap_zero_page(m);
  245                 m->valid = VM_PAGE_BITS_ALL;
  246                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
  247                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  248                 tmp += PAGE_SIZE;
  249         }
  250         VM_OBJECT_WUNLOCK(object);
  251         return (addr);
  252 }
  253 
  254 /*
  255  *      kmem_suballoc:
  256  *
  257  *      Allocates a map to manage a subrange
  258  *      of the kernel virtual address space.
  259  *
  260  *      Arguments are as follows:
  261  *
  262  *      parent          Map to take range from
  263  *      min, max        Returned endpoints of map
  264  *      size            Size of range to find
  265  *      superpage_align Request that min is superpage aligned
  266  */
  267 vm_map_t
  268 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  269     vm_size_t size, boolean_t superpage_align)
  270 {
  271         int ret;
  272         vm_map_t result;
  273 
  274         size = round_page(size);
  275 
  276         *min = vm_map_min(parent);
  277         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  278             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  279             MAP_ACC_NO_CHARGE);
  280         if (ret != KERN_SUCCESS)
  281                 panic("kmem_suballoc: bad status return of %d", ret);
  282         *max = *min + size;
  283         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  284         if (result == NULL)
  285                 panic("kmem_suballoc: cannot create submap");
  286         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  287                 panic("kmem_suballoc: unable to change range to submap");
  288         return (result);
  289 }
  290 
  291 /*
  292  *      kmem_malloc:
  293  *
  294  *      Allocate wired-down pages in the kernel's address space.
  295  */
  296 vm_offset_t
  297 kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
  298 {
  299         vm_offset_t addr;
  300         int rv;
  301 
  302         size = round_page(size);
  303         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  304                 return (0);
  305 
  306         rv = kmem_back((vmem == kmem_arena) ? kmem_object : kernel_object,
  307             addr, size, flags);
  308         if (rv != KERN_SUCCESS) {
  309                 vmem_free(vmem, addr, size);
  310                 return (0);
  311         }
  312         return (addr);
  313 }
  314 
  315 /*
  316  *      kmem_back:
  317  *
  318  *      Allocate physical pages for the specified virtual address range.
  319  */
  320 int
  321 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  322 {
  323         vm_offset_t offset, i;
  324         vm_page_t m;
  325         int pflags;
  326 
  327         KASSERT(object == kmem_object || object == kernel_object,
  328             ("kmem_back: only supports kernel objects."));
  329 
  330         offset = addr - VM_MIN_KERNEL_ADDRESS;
  331         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  332 
  333         VM_OBJECT_WLOCK(object);
  334         for (i = 0; i < size; i += PAGE_SIZE) {
  335 retry:
  336                 m = vm_page_alloc(object, OFF_TO_IDX(offset + i), pflags);
  337 
  338                 /*
  339                  * Ran out of space, free everything up and return. Don't need
  340                  * to lock page queues here as we know that the pages we got
  341                  * aren't on any queues.
  342                  */
  343                 if (m == NULL) {
  344                         VM_OBJECT_WUNLOCK(object);
  345                         if ((flags & M_NOWAIT) == 0) {
  346                                 VM_WAIT;
  347                                 VM_OBJECT_WLOCK(object);
  348                                 goto retry;
  349                         }
  350                         kmem_unback(object, addr, i);
  351                         return (KERN_NO_SPACE);
  352                 }
  353                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  354                         pmap_zero_page(m);
  355                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  356                     ("kmem_malloc: page %p is managed", m));
  357                 m->valid = VM_PAGE_BITS_ALL;
  358                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  359                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  360         }
  361         VM_OBJECT_WUNLOCK(object);
  362 
  363         return (KERN_SUCCESS);
  364 }
  365 
  366 /*
  367  *      kmem_unback:
  368  *
  369  *      Unmap and free the physical pages underlying the specified virtual
  370  *      address range.
  371  *
  372  *      A physical page must exist within the specified object at each index
  373  *      that is being unmapped.
  374  */
  375 void
  376 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  377 {
  378         vm_page_t m;
  379         vm_offset_t i, offset;
  380 
  381         KASSERT(object == kmem_object || object == kernel_object,
  382             ("kmem_unback: only supports kernel objects."));
  383 
  384         pmap_remove(kernel_pmap, addr, addr + size);
  385         offset = addr - VM_MIN_KERNEL_ADDRESS;
  386         VM_OBJECT_WLOCK(object);
  387         for (i = 0; i < size; i += PAGE_SIZE) {
  388                 m = vm_page_lookup(object, OFF_TO_IDX(offset + i));
  389                 vm_page_unwire(m, 0);
  390                 vm_page_free(m);
  391         }
  392         VM_OBJECT_WUNLOCK(object);
  393 }
  394 
  395 /*
  396  *      kmem_free:
  397  *
  398  *      Free memory allocated with kmem_malloc.  The size must match the
  399  *      original allocation.
  400  */
  401 void
  402 kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
  403 {
  404 
  405         size = round_page(size);
  406         kmem_unback((vmem == kmem_arena) ? kmem_object : kernel_object,
  407             addr, size);
  408         vmem_free(vmem, addr, size);
  409 }
  410 
  411 /*
  412  *      kmap_alloc_wait:
  413  *
  414  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  415  *      has no room, the caller sleeps waiting for more memory in the submap.
  416  *
  417  *      This routine may block.
  418  */
  419 vm_offset_t
  420 kmap_alloc_wait(vm_map_t map, vm_size_t size)
  421 {
  422         vm_offset_t addr;
  423 
  424         size = round_page(size);
  425         if (!swap_reserve(size))
  426                 return (0);
  427 
  428         for (;;) {
  429                 /*
  430                  * To make this work for more than one map, use the map's lock
  431                  * to lock out sleepers/wakers.
  432                  */
  433                 vm_map_lock(map);
  434                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  435                         break;
  436                 /* no space now; see if we can ever get space */
  437                 if (vm_map_max(map) - vm_map_min(map) < size) {
  438                         vm_map_unlock(map);
  439                         swap_release(size);
  440                         return (0);
  441                 }
  442                 map->needs_wakeup = TRUE;
  443                 vm_map_unlock_and_wait(map, 0);
  444         }
  445         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  446             VM_PROT_ALL, MAP_ACC_CHARGED);
  447         vm_map_unlock(map);
  448         return (addr);
  449 }
  450 
  451 /*
  452  *      kmap_free_wakeup:
  453  *
  454  *      Returns memory to a submap of the kernel, and wakes up any processes
  455  *      waiting for memory in that map.
  456  */
  457 void
  458 kmap_free_wakeup(vm_map_t map, vm_offset_t addr, vm_size_t size)
  459 {
  460 
  461         vm_map_lock(map);
  462         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  463         if (map->needs_wakeup) {
  464                 map->needs_wakeup = FALSE;
  465                 vm_map_wakeup(map);
  466         }
  467         vm_map_unlock(map);
  468 }
  469 
  470 void
  471 kmem_init_zero_region(void)
  472 {
  473         vm_offset_t addr, i;
  474         vm_page_t m;
  475 
  476         /*
  477          * Map a single physical page of zeros to a larger virtual range.
  478          * This requires less looping in places that want large amounts of
  479          * zeros, while not using much more physical resources.
  480          */
  481         addr = kva_alloc(ZERO_REGION_SIZE);
  482         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  483             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  484         if ((m->flags & PG_ZERO) == 0)
  485                 pmap_zero_page(m);
  486         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  487                 pmap_qenter(addr + i, &m, 1);
  488         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  489 
  490         zero_region = (const void *)addr;
  491 }
  492 
  493 /*
  494  *      kmem_init:
  495  *
  496  *      Create the kernel map; insert a mapping covering kernel text, 
  497  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  498  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  499  *      `start' as allocated, and the range between `start' and `end' as free.
  500  */
  501 void
  502 kmem_init(vm_offset_t start, vm_offset_t end)
  503 {
  504         vm_map_t m;
  505 
  506         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  507         m->system_map = 1;
  508         vm_map_lock(m);
  509         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  510         kernel_map = m;
  511         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  512 #ifdef __amd64__
  513             KERNBASE,
  514 #else                
  515             VM_MIN_KERNEL_ADDRESS,
  516 #endif
  517             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  518         /* ... and ending with the completion of the above `insert' */
  519         vm_map_unlock(m);
  520 }
  521 
  522 #ifdef DIAGNOSTIC
  523 /*
  524  * Allow userspace to directly trigger the VM drain routine for testing
  525  * purposes.
  526  */
  527 static int
  528 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  529 {
  530         int error, i;
  531 
  532         i = 0;
  533         error = sysctl_handle_int(oidp, &i, 0, req);
  534         if (error)
  535                 return (error);
  536         if ((i & ~(VM_LOW_KMEM | VM_LOW_PAGES)) != 0)
  537                 return (EINVAL);
  538         if (i != 0)
  539                 EVENTHANDLER_INVOKE(vm_lowmem, i);
  540         return (0);
  541 }
  542 
  543 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  544     debug_vm_lowmem, "I", "set to trigger vm_lowmem event with given flags");
  545 #endif

Cache object: de190e7f95deae6a48c7f4443e873f3c


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