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/10.3/sys/vm/vm_kern.c 294283 2016-01-18 18:27:21Z jhb $");
   67 
   68 #include <sys/param.h>
   69 #include <sys/systm.h>
   70 #include <sys/kernel.h>         /* for ticks and hz */
   71 #include <sys/eventhandler.h>
   72 #include <sys/lock.h>
   73 #include <sys/proc.h>
   74 #include <sys/malloc.h>
   75 #include <sys/rwlock.h>
   76 #include <sys/sysctl.h>
   77 #include <sys/vmem.h>
   78 
   79 #include <vm/vm.h>
   80 #include <vm/vm_param.h>
   81 #include <vm/vm_kern.h>
   82 #include <vm/pmap.h>
   83 #include <vm/vm_map.h>
   84 #include <vm/vm_object.h>
   85 #include <vm/vm_page.h>
   86 #include <vm/vm_pageout.h>
   87 #include <vm/vm_extern.h>
   88 #include <vm/uma.h>
   89 
   90 vm_map_t kernel_map;
   91 vm_map_t exec_map;
   92 vm_map_t pipe_map;
   93 
   94 const void *zero_region;
   95 CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
   96 
   97 /* NB: Used by kernel debuggers. */
   98 const u_long vm_maxuser_address = VM_MAXUSER_ADDRESS;
   99 
  100 SYSCTL_ULONG(_vm, OID_AUTO, min_kernel_address, CTLFLAG_RD,
  101     SYSCTL_NULL_ULONG_PTR, VM_MIN_KERNEL_ADDRESS, "Min kernel address");
  102 
  103 SYSCTL_ULONG(_vm, OID_AUTO, max_kernel_address, CTLFLAG_RD,
  104 #if defined(__arm__) || defined(__sparc64__)
  105     &vm_max_kernel_address, 0,
  106 #else
  107     SYSCTL_NULL_ULONG_PTR, VM_MAX_KERNEL_ADDRESS,
  108 #endif
  109     "Max kernel address");
  110 
  111 /*
  112  *      kva_alloc:
  113  *
  114  *      Allocate a virtual address range with no underlying object and
  115  *      no initial mapping to physical memory.  Any mapping from this
  116  *      range to physical memory must be explicitly created prior to
  117  *      its use, typically with pmap_qenter().  Any attempt to create
  118  *      a mapping on demand through vm_fault() will result in a panic. 
  119  */
  120 vm_offset_t
  121 kva_alloc(size)
  122         vm_size_t size;
  123 {
  124         vm_offset_t addr;
  125 
  126         size = round_page(size);
  127         if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
  128                 return (0);
  129 
  130         return (addr);
  131 }
  132 
  133 /*
  134  *      kva_free:
  135  *
  136  *      Release a region of kernel virtual memory allocated
  137  *      with kva_alloc, and return the physical pages
  138  *      associated with that region.
  139  *
  140  *      This routine may not block on kernel maps.
  141  */
  142 void
  143 kva_free(addr, size)
  144         vm_offset_t addr;
  145         vm_size_t size;
  146 {
  147 
  148         size = round_page(size);
  149         vmem_free(kernel_arena, addr, size);
  150 }
  151 
  152 /*
  153  *      Allocates a region from the kernel address map and physical pages
  154  *      within the specified address range to the kernel object.  Creates a
  155  *      wired mapping from this region to these pages, and returns the
  156  *      region's starting virtual address.  The allocated pages are not
  157  *      necessarily physically contiguous.  If M_ZERO is specified through the
  158  *      given flags, then the pages are zeroed before they are mapped.
  159  */
  160 vm_offset_t
  161 kmem_alloc_attr(vmem_t *vmem, vm_size_t size, int flags, vm_paddr_t low,
  162     vm_paddr_t high, vm_memattr_t memattr)
  163 {
  164         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  165         vm_offset_t addr, i;
  166         vm_ooffset_t offset;
  167         vm_page_t m;
  168         int pflags, tries;
  169 
  170         size = round_page(size);
  171         if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
  172                 return (0);
  173         offset = addr - VM_MIN_KERNEL_ADDRESS;
  174         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  175         VM_OBJECT_WLOCK(object);
  176         for (i = 0; i < size; i += PAGE_SIZE) {
  177                 tries = 0;
  178 retry:
  179                 m = vm_page_alloc_contig(object, OFF_TO_IDX(offset + i),
  180                     pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  181                 if (m == NULL) {
  182                         VM_OBJECT_WUNLOCK(object);
  183                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  184                                 vm_pageout_grow_cache(tries, low, high);
  185                                 VM_OBJECT_WLOCK(object);
  186                                 tries++;
  187                                 goto retry;
  188                         }
  189                         kmem_unback(object, addr, i);
  190                         vmem_free(vmem, addr, size);
  191                         return (0);
  192                 }
  193                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  194                         pmap_zero_page(m);
  195                 m->valid = VM_PAGE_BITS_ALL;
  196                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  197                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  198         }
  199         VM_OBJECT_WUNLOCK(object);
  200         return (addr);
  201 }
  202 
  203 /*
  204  *      Allocates a region from the kernel address map and physically
  205  *      contiguous pages within the specified address range to the kernel
  206  *      object.  Creates a wired mapping from this region to these pages, and
  207  *      returns the region's starting virtual address.  If M_ZERO is specified
  208  *      through the given flags, then the pages are zeroed before they are
  209  *      mapped.
  210  */
  211 vm_offset_t
  212 kmem_alloc_contig(struct vmem *vmem, vm_size_t size, int flags, vm_paddr_t low,
  213     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  214     vm_memattr_t memattr)
  215 {
  216         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  217         vm_offset_t addr, tmp;
  218         vm_ooffset_t offset;
  219         vm_page_t end_m, m;
  220         int pflags, tries;
  221  
  222         size = round_page(size);
  223         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  224                 return (0);
  225         offset = addr - VM_MIN_KERNEL_ADDRESS;
  226         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  227         VM_OBJECT_WLOCK(object);
  228         tries = 0;
  229 retry:
  230         m = vm_page_alloc_contig(object, OFF_TO_IDX(offset), pflags,
  231             atop(size), low, high, alignment, boundary, memattr);
  232         if (m == NULL) {
  233                 VM_OBJECT_WUNLOCK(object);
  234                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  235                         vm_pageout_grow_cache(tries, low, high);
  236                         VM_OBJECT_WLOCK(object);
  237                         tries++;
  238                         goto retry;
  239                 }
  240                 vmem_free(vmem, addr, size);
  241                 return (0);
  242         }
  243         end_m = m + atop(size);
  244         tmp = addr;
  245         for (; m < end_m; m++) {
  246                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  247                         pmap_zero_page(m);
  248                 m->valid = VM_PAGE_BITS_ALL;
  249                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
  250                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  251                 tmp += PAGE_SIZE;
  252         }
  253         VM_OBJECT_WUNLOCK(object);
  254         return (addr);
  255 }
  256 
  257 /*
  258  *      kmem_suballoc:
  259  *
  260  *      Allocates a map to manage a subrange
  261  *      of the kernel virtual address space.
  262  *
  263  *      Arguments are as follows:
  264  *
  265  *      parent          Map to take range from
  266  *      min, max        Returned endpoints of map
  267  *      size            Size of range to find
  268  *      superpage_align Request that min is superpage aligned
  269  */
  270 vm_map_t
  271 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  272     vm_size_t size, boolean_t superpage_align)
  273 {
  274         int ret;
  275         vm_map_t result;
  276 
  277         size = round_page(size);
  278 
  279         *min = vm_map_min(parent);
  280         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  281             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  282             MAP_ACC_NO_CHARGE);
  283         if (ret != KERN_SUCCESS)
  284                 panic("kmem_suballoc: bad status return of %d", ret);
  285         *max = *min + size;
  286         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  287         if (result == NULL)
  288                 panic("kmem_suballoc: cannot create submap");
  289         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  290                 panic("kmem_suballoc: unable to change range to submap");
  291         return (result);
  292 }
  293 
  294 /*
  295  *      kmem_malloc:
  296  *
  297  *      Allocate wired-down pages in the kernel's address space.
  298  */
  299 vm_offset_t
  300 kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
  301 {
  302         vm_offset_t addr;
  303         int rv;
  304 
  305         size = round_page(size);
  306         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  307                 return (0);
  308 
  309         rv = kmem_back((vmem == kmem_arena) ? kmem_object : kernel_object,
  310             addr, size, flags);
  311         if (rv != KERN_SUCCESS) {
  312                 vmem_free(vmem, addr, size);
  313                 return (0);
  314         }
  315         return (addr);
  316 }
  317 
  318 /*
  319  *      kmem_back:
  320  *
  321  *      Allocate physical pages for the specified virtual address range.
  322  */
  323 int
  324 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  325 {
  326         vm_offset_t offset, i;
  327         vm_page_t m;
  328         int pflags;
  329 
  330         KASSERT(object == kmem_object || object == kernel_object,
  331             ("kmem_back: only supports kernel objects."));
  332 
  333         offset = addr - VM_MIN_KERNEL_ADDRESS;
  334         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  335 
  336         VM_OBJECT_WLOCK(object);
  337         for (i = 0; i < size; i += PAGE_SIZE) {
  338 retry:
  339                 m = vm_page_alloc(object, OFF_TO_IDX(offset + i), pflags);
  340 
  341                 /*
  342                  * Ran out of space, free everything up and return. Don't need
  343                  * to lock page queues here as we know that the pages we got
  344                  * aren't on any queues.
  345                  */
  346                 if (m == NULL) {
  347                         VM_OBJECT_WUNLOCK(object);
  348                         if ((flags & M_NOWAIT) == 0) {
  349                                 VM_WAIT;
  350                                 VM_OBJECT_WLOCK(object);
  351                                 goto retry;
  352                         }
  353                         kmem_unback(object, addr, i);
  354                         return (KERN_NO_SPACE);
  355                 }
  356                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  357                         pmap_zero_page(m);
  358                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  359                     ("kmem_malloc: page %p is managed", m));
  360                 m->valid = VM_PAGE_BITS_ALL;
  361                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  362                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  363         }
  364         VM_OBJECT_WUNLOCK(object);
  365 
  366         return (KERN_SUCCESS);
  367 }
  368 
  369 /*
  370  *      kmem_unback:
  371  *
  372  *      Unmap and free the physical pages underlying the specified virtual
  373  *      address range.
  374  *
  375  *      A physical page must exist within the specified object at each index
  376  *      that is being unmapped.
  377  */
  378 void
  379 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  380 {
  381         vm_page_t m;
  382         vm_offset_t i, offset;
  383 
  384         KASSERT(object == kmem_object || object == kernel_object,
  385             ("kmem_unback: only supports kernel objects."));
  386 
  387         pmap_remove(kernel_pmap, addr, addr + size);
  388         offset = addr - VM_MIN_KERNEL_ADDRESS;
  389         VM_OBJECT_WLOCK(object);
  390         for (i = 0; i < size; i += PAGE_SIZE) {
  391                 m = vm_page_lookup(object, OFF_TO_IDX(offset + i));
  392                 vm_page_unwire(m, 0);
  393                 vm_page_free(m);
  394         }
  395         VM_OBJECT_WUNLOCK(object);
  396 }
  397 
  398 /*
  399  *      kmem_free:
  400  *
  401  *      Free memory allocated with kmem_malloc.  The size must match the
  402  *      original allocation.
  403  */
  404 void
  405 kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
  406 {
  407 
  408         size = round_page(size);
  409         kmem_unback((vmem == kmem_arena) ? kmem_object : kernel_object,
  410             addr, size);
  411         vmem_free(vmem, addr, size);
  412 }
  413 
  414 /*
  415  *      kmap_alloc_wait:
  416  *
  417  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  418  *      has no room, the caller sleeps waiting for more memory in the submap.
  419  *
  420  *      This routine may block.
  421  */
  422 vm_offset_t
  423 kmap_alloc_wait(map, size)
  424         vm_map_t map;
  425         vm_size_t size;
  426 {
  427         vm_offset_t addr;
  428 
  429         size = round_page(size);
  430         if (!swap_reserve(size))
  431                 return (0);
  432 
  433         for (;;) {
  434                 /*
  435                  * To make this work for more than one map, use the map's lock
  436                  * to lock out sleepers/wakers.
  437                  */
  438                 vm_map_lock(map);
  439                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  440                         break;
  441                 /* no space now; see if we can ever get space */
  442                 if (vm_map_max(map) - vm_map_min(map) < size) {
  443                         vm_map_unlock(map);
  444                         swap_release(size);
  445                         return (0);
  446                 }
  447                 map->needs_wakeup = TRUE;
  448                 vm_map_unlock_and_wait(map, 0);
  449         }
  450         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  451             VM_PROT_ALL, MAP_ACC_CHARGED);
  452         vm_map_unlock(map);
  453         return (addr);
  454 }
  455 
  456 /*
  457  *      kmap_free_wakeup:
  458  *
  459  *      Returns memory to a submap of the kernel, and wakes up any processes
  460  *      waiting for memory in that map.
  461  */
  462 void
  463 kmap_free_wakeup(map, addr, size)
  464         vm_map_t map;
  465         vm_offset_t addr;
  466         vm_size_t size;
  467 {
  468 
  469         vm_map_lock(map);
  470         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  471         if (map->needs_wakeup) {
  472                 map->needs_wakeup = FALSE;
  473                 vm_map_wakeup(map);
  474         }
  475         vm_map_unlock(map);
  476 }
  477 
  478 void
  479 kmem_init_zero_region(void)
  480 {
  481         vm_offset_t addr, i;
  482         vm_page_t m;
  483 
  484         /*
  485          * Map a single physical page of zeros to a larger virtual range.
  486          * This requires less looping in places that want large amounts of
  487          * zeros, while not using much more physical resources.
  488          */
  489         addr = kva_alloc(ZERO_REGION_SIZE);
  490         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  491             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  492         if ((m->flags & PG_ZERO) == 0)
  493                 pmap_zero_page(m);
  494         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  495                 pmap_qenter(addr + i, &m, 1);
  496         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  497 
  498         zero_region = (const void *)addr;
  499 }
  500 
  501 /*
  502  *      kmem_init:
  503  *
  504  *      Create the kernel map; insert a mapping covering kernel text, 
  505  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  506  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  507  *      `start' as allocated, and the range between `start' and `end' as free.
  508  */
  509 void
  510 kmem_init(start, end)
  511         vm_offset_t start, end;
  512 {
  513         vm_map_t m;
  514 
  515         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  516         m->system_map = 1;
  517         vm_map_lock(m);
  518         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  519         kernel_map = m;
  520         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  521 #ifdef __amd64__
  522             KERNBASE,
  523 #else                
  524             VM_MIN_KERNEL_ADDRESS,
  525 #endif
  526             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  527         /* ... and ending with the completion of the above `insert' */
  528         vm_map_unlock(m);
  529 }
  530 
  531 #ifdef DIAGNOSTIC
  532 /*
  533  * Allow userspace to directly trigger the VM drain routine for testing
  534  * purposes.
  535  */
  536 static int
  537 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  538 {
  539         int error, i;
  540 
  541         i = 0;
  542         error = sysctl_handle_int(oidp, &i, 0, req);
  543         if (error)
  544                 return (error);
  545         if (i)   
  546                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  547         return (0);
  548 }
  549 
  550 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  551     debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
  552 #endif

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