The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_kern.c

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    1 /*-
    2  * Copyright (c) 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * The Mach Operating System project at Carnegie-Mellon University.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      from: @(#)vm_kern.c     8.3 (Berkeley) 1/12/94
   33  *
   34  *
   35  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   36  * All rights reserved.
   37  *
   38  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   39  *
   40  * Permission to use, copy, modify and distribute this software and
   41  * its documentation is hereby granted, provided that both the copyright
   42  * notice and this permission notice appear in all copies of the
   43  * software, derivative works or modified versions, and any portions
   44  * thereof, and that both notices appear in supporting documentation.
   45  *
   46  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   47  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   48  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   49  *
   50  * Carnegie Mellon requests users of this software to return to
   51  *
   52  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   53  *  School of Computer Science
   54  *  Carnegie Mellon University
   55  *  Pittsburgh PA 15213-3890
   56  *
   57  * any improvements or extensions that they make and grant Carnegie the
   58  * rights to redistribute these changes.
   59  */
   60 
   61 /*
   62  *      Kernel memory management.
   63  */
   64 
   65 #include <sys/cdefs.h>
   66 __FBSDID("$FreeBSD: releng/11.2/sys/vm/vm_kern.c 331722 2018-03-29 02:50:57Z eadler $");
   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_radix.h>
   88 #include <vm/vm_extern.h>
   89 #include <vm/uma.h>
   90 
   91 vm_map_t kernel_map;
   92 vm_map_t exec_map;
   93 vm_map_t pipe_map;
   94 
   95 const void *zero_region;
   96 CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
   97 
   98 /* NB: Used by kernel debuggers. */
   99 const u_long vm_maxuser_address = VM_MAXUSER_ADDRESS;
  100 
  101 u_int exec_map_entry_size;
  102 u_int exec_map_entries;
  103 
  104 SYSCTL_ULONG(_vm, OID_AUTO, min_kernel_address, CTLFLAG_RD,
  105     SYSCTL_NULL_ULONG_PTR, VM_MIN_KERNEL_ADDRESS, "Min kernel address");
  106 
  107 SYSCTL_ULONG(_vm, OID_AUTO, max_kernel_address, CTLFLAG_RD,
  108 #if defined(__arm__) || defined(__sparc64__)
  109     &vm_max_kernel_address, 0,
  110 #else
  111     SYSCTL_NULL_ULONG_PTR, VM_MAX_KERNEL_ADDRESS,
  112 #endif
  113     "Max kernel address");
  114 
  115 /*
  116  *      kva_alloc:
  117  *
  118  *      Allocate a virtual address range with no underlying object and
  119  *      no initial mapping to physical memory.  Any mapping from this
  120  *      range to physical memory must be explicitly created prior to
  121  *      its use, typically with pmap_qenter().  Any attempt to create
  122  *      a mapping on demand through vm_fault() will result in a panic. 
  123  */
  124 vm_offset_t
  125 kva_alloc(vm_size_t size)
  126 {
  127         vm_offset_t addr;
  128 
  129         size = round_page(size);
  130         if (vmem_alloc(kernel_arena, size, M_BESTFIT | M_NOWAIT, &addr))
  131                 return (0);
  132 
  133         return (addr);
  134 }
  135 
  136 /*
  137  *      kva_free:
  138  *
  139  *      Release a region of kernel virtual memory allocated
  140  *      with kva_alloc, and return the physical pages
  141  *      associated with that region.
  142  *
  143  *      This routine may not block on kernel maps.
  144  */
  145 void
  146 kva_free(vm_offset_t addr, vm_size_t size)
  147 {
  148 
  149         size = round_page(size);
  150         vmem_free(kernel_arena, addr, size);
  151 }
  152 
  153 /*
  154  *      Allocates a region from the kernel address map and physical pages
  155  *      within the specified address range to the kernel object.  Creates a
  156  *      wired mapping from this region to these pages, and returns the
  157  *      region's starting virtual address.  The allocated pages are not
  158  *      necessarily physically contiguous.  If M_ZERO is specified through the
  159  *      given flags, then the pages are zeroed before they are mapped.
  160  */
  161 vm_offset_t
  162 kmem_alloc_attr(vmem_t *vmem, vm_size_t size, int flags, vm_paddr_t low,
  163     vm_paddr_t high, vm_memattr_t memattr)
  164 {
  165         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  166         vm_offset_t addr, i, 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         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  176         pflags |= VM_ALLOC_NOWAIT;
  177         VM_OBJECT_WLOCK(object);
  178         for (i = 0; i < size; i += PAGE_SIZE) {
  179                 tries = 0;
  180 retry:
  181                 m = vm_page_alloc_contig(object, atop(offset + i),
  182                     pflags, 1, low, high, PAGE_SIZE, 0, memattr);
  183                 if (m == NULL) {
  184                         VM_OBJECT_WUNLOCK(object);
  185                         if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  186                                 if (!vm_page_reclaim_contig(pflags, 1,
  187                                     low, high, PAGE_SIZE, 0) &&
  188                                     (flags & M_WAITOK) != 0)
  189                                         VM_WAIT;
  190                                 VM_OBJECT_WLOCK(object);
  191                                 tries++;
  192                                 goto retry;
  193                         }
  194                         kmem_unback(object, addr, i);
  195                         vmem_free(vmem, addr, size);
  196                         return (0);
  197                 }
  198                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  199                         pmap_zero_page(m);
  200                 m->valid = VM_PAGE_BITS_ALL;
  201                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  202                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  203         }
  204         VM_OBJECT_WUNLOCK(object);
  205         return (addr);
  206 }
  207 
  208 /*
  209  *      Allocates a region from the kernel address map and physically
  210  *      contiguous pages within the specified address range to the kernel
  211  *      object.  Creates a wired mapping from this region to these pages, and
  212  *      returns the region's starting virtual address.  If M_ZERO is specified
  213  *      through the given flags, then the pages are zeroed before they are
  214  *      mapped.
  215  */
  216 vm_offset_t
  217 kmem_alloc_contig(struct vmem *vmem, vm_size_t size, int flags, vm_paddr_t low,
  218     vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
  219     vm_memattr_t memattr)
  220 {
  221         vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
  222         vm_offset_t addr, offset, tmp;
  223         vm_page_t end_m, m;
  224         u_long npages;
  225         int pflags, tries;
  226  
  227         size = round_page(size);
  228         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  229                 return (0);
  230         offset = addr - VM_MIN_KERNEL_ADDRESS;
  231         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  232         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  233         pflags |= VM_ALLOC_NOWAIT;
  234         npages = atop(size);
  235         VM_OBJECT_WLOCK(object);
  236         tries = 0;
  237 retry:
  238         m = vm_page_alloc_contig(object, atop(offset), pflags,
  239             npages, low, high, alignment, boundary, memattr);
  240         if (m == NULL) {
  241                 VM_OBJECT_WUNLOCK(object);
  242                 if (tries < ((flags & M_NOWAIT) != 0 ? 1 : 3)) {
  243                         if (!vm_page_reclaim_contig(pflags, npages, low, high,
  244                             alignment, boundary) && (flags & M_WAITOK) != 0)
  245                                 VM_WAIT;
  246                         VM_OBJECT_WLOCK(object);
  247                         tries++;
  248                         goto retry;
  249                 }
  250                 vmem_free(vmem, addr, size);
  251                 return (0);
  252         }
  253         end_m = m + npages;
  254         tmp = addr;
  255         for (; m < end_m; m++) {
  256                 if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
  257                         pmap_zero_page(m);
  258                 m->valid = VM_PAGE_BITS_ALL;
  259                 pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
  260                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  261                 tmp += PAGE_SIZE;
  262         }
  263         VM_OBJECT_WUNLOCK(object);
  264         return (addr);
  265 }
  266 
  267 /*
  268  *      kmem_suballoc:
  269  *
  270  *      Allocates a map to manage a subrange
  271  *      of the kernel virtual address space.
  272  *
  273  *      Arguments are as follows:
  274  *
  275  *      parent          Map to take range from
  276  *      min, max        Returned endpoints of map
  277  *      size            Size of range to find
  278  *      superpage_align Request that min is superpage aligned
  279  */
  280 vm_map_t
  281 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  282     vm_size_t size, boolean_t superpage_align)
  283 {
  284         int ret;
  285         vm_map_t result;
  286 
  287         size = round_page(size);
  288 
  289         *min = vm_map_min(parent);
  290         ret = vm_map_find(parent, NULL, 0, min, size, 0, superpage_align ?
  291             VMFS_SUPER_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  292             MAP_ACC_NO_CHARGE);
  293         if (ret != KERN_SUCCESS)
  294                 panic("kmem_suballoc: bad status return of %d", ret);
  295         *max = *min + size;
  296         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  297         if (result == NULL)
  298                 panic("kmem_suballoc: cannot create submap");
  299         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  300                 panic("kmem_suballoc: unable to change range to submap");
  301         return (result);
  302 }
  303 
  304 /*
  305  *      kmem_malloc:
  306  *
  307  *      Allocate wired-down pages in the kernel's address space.
  308  */
  309 vm_offset_t
  310 kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
  311 {
  312         vm_offset_t addr;
  313         int rv;
  314 
  315         size = round_page(size);
  316         if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
  317                 return (0);
  318 
  319         rv = kmem_back((vmem == kmem_arena) ? kmem_object : kernel_object,
  320             addr, size, flags);
  321         if (rv != KERN_SUCCESS) {
  322                 vmem_free(vmem, addr, size);
  323                 return (0);
  324         }
  325         return (addr);
  326 }
  327 
  328 /*
  329  *      kmem_back:
  330  *
  331  *      Allocate physical pages for the specified virtual address range.
  332  */
  333 int
  334 kmem_back(vm_object_t object, vm_offset_t addr, vm_size_t size, int flags)
  335 {
  336         vm_offset_t offset, i;
  337         vm_page_t m, mpred;
  338         int pflags;
  339 
  340         KASSERT(object == kmem_object || object == kernel_object,
  341             ("kmem_back: only supports kernel objects."));
  342 
  343         offset = addr - VM_MIN_KERNEL_ADDRESS;
  344         pflags = malloc2vm_flags(flags) | VM_ALLOC_NOBUSY | VM_ALLOC_WIRED;
  345         pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
  346         if (flags & M_WAITOK)
  347                 pflags |= VM_ALLOC_WAITFAIL;
  348 
  349         i = 0;
  350         VM_OBJECT_WLOCK(object);
  351 retry:
  352         mpred = vm_radix_lookup_le(&object->rtree, atop(offset + i));
  353         for (; i < size; i += PAGE_SIZE, mpred = m) {
  354                 m = vm_page_alloc_after(object, atop(offset + i), pflags,
  355                     mpred);
  356 
  357                 /*
  358                  * Ran out of space, free everything up and return. Don't need
  359                  * to lock page queues here as we know that the pages we got
  360                  * aren't on any queues.
  361                  */
  362                 if (m == NULL) {
  363                         if ((flags & M_NOWAIT) == 0)
  364                                 goto retry;
  365                         VM_OBJECT_WUNLOCK(object);
  366                         kmem_unback(object, addr, i);
  367                         return (KERN_NO_SPACE);
  368                 }
  369                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  370                         pmap_zero_page(m);
  371                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  372                     ("kmem_malloc: page %p is managed", m));
  373                 m->valid = VM_PAGE_BITS_ALL;
  374                 pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
  375                     VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
  376         }
  377         VM_OBJECT_WUNLOCK(object);
  378 
  379         return (KERN_SUCCESS);
  380 }
  381 
  382 /*
  383  *      kmem_unback:
  384  *
  385  *      Unmap and free the physical pages underlying the specified virtual
  386  *      address range.
  387  *
  388  *      A physical page must exist within the specified object at each index
  389  *      that is being unmapped.
  390  */
  391 void
  392 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
  393 {
  394         vm_page_t m, next;
  395         vm_offset_t end, offset;
  396 
  397         KASSERT(object == kmem_object || object == kernel_object,
  398             ("kmem_unback: only supports kernel objects."));
  399 
  400         pmap_remove(kernel_pmap, addr, addr + size);
  401         offset = addr - VM_MIN_KERNEL_ADDRESS;
  402         end = offset + size;
  403         VM_OBJECT_WLOCK(object);
  404         for (m = vm_page_lookup(object, atop(offset)); offset < end;
  405             offset += PAGE_SIZE, m = next) {
  406                 next = vm_page_next(m);
  407                 vm_page_unwire(m, PQ_NONE);
  408                 vm_page_free(m);
  409         }
  410         VM_OBJECT_WUNLOCK(object);
  411 }
  412 
  413 /*
  414  *      kmem_free:
  415  *
  416  *      Free memory allocated with kmem_malloc.  The size must match the
  417  *      original allocation.
  418  */
  419 void
  420 kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
  421 {
  422 
  423         size = round_page(size);
  424         kmem_unback((vmem == kmem_arena) ? kmem_object : kernel_object,
  425             addr, size);
  426         vmem_free(vmem, addr, size);
  427 }
  428 
  429 /*
  430  *      kmap_alloc_wait:
  431  *
  432  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  433  *      has no room, the caller sleeps waiting for more memory in the submap.
  434  *
  435  *      This routine may block.
  436  */
  437 vm_offset_t
  438 kmap_alloc_wait(vm_map_t map, vm_size_t size)
  439 {
  440         vm_offset_t addr;
  441 
  442         size = round_page(size);
  443         if (!swap_reserve(size))
  444                 return (0);
  445 
  446         for (;;) {
  447                 /*
  448                  * To make this work for more than one map, use the map's lock
  449                  * to lock out sleepers/wakers.
  450                  */
  451                 vm_map_lock(map);
  452                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  453                         break;
  454                 /* no space now; see if we can ever get space */
  455                 if (vm_map_max(map) - vm_map_min(map) < size) {
  456                         vm_map_unlock(map);
  457                         swap_release(size);
  458                         return (0);
  459                 }
  460                 map->needs_wakeup = TRUE;
  461                 vm_map_unlock_and_wait(map, 0);
  462         }
  463         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  464             VM_PROT_ALL, MAP_ACC_CHARGED);
  465         vm_map_unlock(map);
  466         return (addr);
  467 }
  468 
  469 /*
  470  *      kmap_free_wakeup:
  471  *
  472  *      Returns memory to a submap of the kernel, and wakes up any processes
  473  *      waiting for memory in that map.
  474  */
  475 void
  476 kmap_free_wakeup(vm_map_t map, vm_offset_t addr, vm_size_t size)
  477 {
  478 
  479         vm_map_lock(map);
  480         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  481         if (map->needs_wakeup) {
  482                 map->needs_wakeup = FALSE;
  483                 vm_map_wakeup(map);
  484         }
  485         vm_map_unlock(map);
  486 }
  487 
  488 void
  489 kmem_init_zero_region(void)
  490 {
  491         vm_offset_t addr, i;
  492         vm_page_t m;
  493 
  494         /*
  495          * Map a single physical page of zeros to a larger virtual range.
  496          * This requires less looping in places that want large amounts of
  497          * zeros, while not using much more physical resources.
  498          */
  499         addr = kva_alloc(ZERO_REGION_SIZE);
  500         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  501             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  502         if ((m->flags & PG_ZERO) == 0)
  503                 pmap_zero_page(m);
  504         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  505                 pmap_qenter(addr + i, &m, 1);
  506         pmap_protect(kernel_pmap, addr, addr + ZERO_REGION_SIZE, VM_PROT_READ);
  507 
  508         zero_region = (const void *)addr;
  509 }
  510 
  511 /*
  512  *      kmem_init:
  513  *
  514  *      Create the kernel map; insert a mapping covering kernel text, 
  515  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  516  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  517  *      `start' as allocated, and the range between `start' and `end' as free.
  518  */
  519 void
  520 kmem_init(vm_offset_t start, vm_offset_t end)
  521 {
  522         vm_map_t m;
  523 
  524         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  525         m->system_map = 1;
  526         vm_map_lock(m);
  527         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  528         kernel_map = m;
  529         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  530 #ifdef __amd64__
  531             KERNBASE,
  532 #else                
  533             VM_MIN_KERNEL_ADDRESS,
  534 #endif
  535             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  536         /* ... and ending with the completion of the above `insert' */
  537         vm_map_unlock(m);
  538 }
  539 
  540 #ifdef DIAGNOSTIC
  541 /*
  542  * Allow userspace to directly trigger the VM drain routine for testing
  543  * purposes.
  544  */
  545 static int
  546 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  547 {
  548         int error, i;
  549 
  550         i = 0;
  551         error = sysctl_handle_int(oidp, &i, 0, req);
  552         if (error)
  553                 return (error);
  554         if ((i & ~(VM_LOW_KMEM | VM_LOW_PAGES)) != 0)
  555                 return (EINVAL);
  556         if (i != 0)
  557                 EVENTHANDLER_INVOKE(vm_lowmem, i);
  558         return (0);
  559 }
  560 
  561 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  562     debug_vm_lowmem, "I", "set to trigger vm_lowmem event with given flags");
  563 #endif

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