FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_glue.c

     /*-
      * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
      *
      * Copyright (c) 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * The Mach Operating System project at Carnegie-Mellon University.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)vm_glue.c     8.6 (Berkeley) 1/5/94
     *
     *
     * Copyright (c) 1987, 1990 Carnegie-Mellon University.
     * All rights reserved.
     *
     * Permission to use, copy, modify and distribute this software and
     * its documentation is hereby granted, provided that both the copyright
     * notice and this permission notice appear in all copies of the
     * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     *
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     *
     * Carnegie Mellon requests users of this software to return to
     *
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     *
     * any improvements or extensions that they make and grant Carnegie the
     * rights to redistribute these changes.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/12.0/sys/vm/vm_glue.c 339998 2018-11-01 15:19:36Z markj $");
    
    #include "opt_vm.h"
    #include "opt_kstack_pages.h"
    #include "opt_kstack_max_pages.h"
    #include "opt_kstack_usage_prof.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/domainset.h>
    #include <sys/limits.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/racct.h>
    #include <sys/resourcevar.h>
    #include <sys/rwlock.h>
    #include <sys/sched.h>
    #include <sys/sf_buf.h>
    #include <sys/shm.h>
    #include <sys/vmmeter.h>
    #include <sys/vmem.h>
    #include <sys/sx.h>
    #include <sys/sysctl.h>
    #include <sys/_kstack_cache.h>
    #include <sys/eventhandler.h>
    #include <sys/kernel.h>
    #include <sys/ktr.h>
    #include <sys/unistd.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    #include <vm/vm_domainset.h>
    #include <vm/vm_map.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pageout.h>
   #include <vm/vm_object.h>
   #include <vm/vm_kern.h>
   #include <vm/vm_extern.h>
   #include <vm/vm_pager.h>
   #include <vm/swap_pager.h>
   
   #include <machine/cpu.h>
   
   /*
    * MPSAFE
    *
    * WARNING!  This code calls vm_map_check_protection() which only checks
    * the associated vm_map_entry range.  It does not determine whether the
    * contents of the memory is actually readable or writable.  In most cases
    * just checking the vm_map_entry is sufficient within the kernel's address
    * space.
    */
   int
   kernacc(void *addr, int len, int rw)
   {
           boolean_t rv;
           vm_offset_t saddr, eaddr;
           vm_prot_t prot;
   
           KASSERT((rw & ~VM_PROT_ALL) == 0,
               ("illegal ``rw'' argument to kernacc (%x)\n", rw));
   
           if ((vm_offset_t)addr + len > vm_map_max(kernel_map) ||
               (vm_offset_t)addr + len < (vm_offset_t)addr)
                   return (FALSE);
   
           prot = rw;
           saddr = trunc_page((vm_offset_t)addr);
           eaddr = round_page((vm_offset_t)addr + len);
           vm_map_lock_read(kernel_map);
           rv = vm_map_check_protection(kernel_map, saddr, eaddr, prot);
           vm_map_unlock_read(kernel_map);
           return (rv == TRUE);
   }
   
   /*
    * MPSAFE
    *
    * WARNING!  This code calls vm_map_check_protection() which only checks
    * the associated vm_map_entry range.  It does not determine whether the
    * contents of the memory is actually readable or writable.  vmapbuf(),
    * vm_fault_quick(), or copyin()/copout()/su*()/fu*() functions should be
    * used in conjunction with this call.
    */
   int
   useracc(void *addr, int len, int rw)
   {
           boolean_t rv;
           vm_prot_t prot;
           vm_map_t map;
   
           KASSERT((rw & ~VM_PROT_ALL) == 0,
               ("illegal ``rw'' argument to useracc (%x)\n", rw));
           prot = rw;
           map = &curproc->p_vmspace->vm_map;
           if ((vm_offset_t)addr + len > vm_map_max(map) ||
               (vm_offset_t)addr + len < (vm_offset_t)addr) {
                   return (FALSE);
           }
           vm_map_lock_read(map);
           rv = vm_map_check_protection(map, trunc_page((vm_offset_t)addr),
               round_page((vm_offset_t)addr + len), prot);
           vm_map_unlock_read(map);
           return (rv == TRUE);
   }
   
   int
   vslock(void *addr, size_t len)
   {
           vm_offset_t end, last, start;
           vm_size_t npages;
           int error;
   
           last = (vm_offset_t)addr + len;
           start = trunc_page((vm_offset_t)addr);
           end = round_page(last);
           if (last < (vm_offset_t)addr || end < (vm_offset_t)addr)
                   return (EINVAL);
           npages = atop(end - start);
           if (npages > vm_page_max_wired)
                   return (ENOMEM);
   #if 0
           /*
            * XXX - not yet
            *
            * The limit for transient usage of wired pages should be
            * larger than for "permanent" wired pages (mlock()).
            *
            * Also, the sysctl code, which is the only present user
            * of vslock(), does a hard loop on EAGAIN.
            */
           if (npages + vm_wire_count() > vm_page_max_wired)
                   return (EAGAIN);
   #endif
           error = vm_map_wire(&curproc->p_vmspace->vm_map, start, end,
               VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
           if (error == KERN_SUCCESS) {
                   curthread->td_vslock_sz += len;
                   return (0);
           }
   
           /*
            * Return EFAULT on error to match copy{in,out}() behaviour
            * rather than returning ENOMEM like mlock() would.
            */
           return (EFAULT);
   }
   
   void
   vsunlock(void *addr, size_t len)
   {
   
           /* Rely on the parameter sanity checks performed by vslock(). */
           MPASS(curthread->td_vslock_sz >= len);
           curthread->td_vslock_sz -= len;
           (void)vm_map_unwire(&curproc->p_vmspace->vm_map,
               trunc_page((vm_offset_t)addr), round_page((vm_offset_t)addr + len),
               VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
   }
   
   /*
    * Pin the page contained within the given object at the given offset.  If the
    * page is not resident, allocate and load it using the given object's pager.
    * Return the pinned page if successful; otherwise, return NULL.
    */
   static vm_page_t
   vm_imgact_hold_page(vm_object_t object, vm_ooffset_t offset)
   {
           vm_page_t m;
           vm_pindex_t pindex;
           int rv;
   
           VM_OBJECT_WLOCK(object);
           pindex = OFF_TO_IDX(offset);
           m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY);
           if (m->valid != VM_PAGE_BITS_ALL) {
                   vm_page_xbusy(m);
                   rv = vm_pager_get_pages(object, &m, 1, NULL, NULL);
                   if (rv != VM_PAGER_OK) {
                           vm_page_lock(m);
                           vm_page_free(m);
                           vm_page_unlock(m);
                           m = NULL;
                           goto out;
                   }
                   vm_page_xunbusy(m);
           }
           vm_page_lock(m);
           vm_page_hold(m);
           vm_page_activate(m);
           vm_page_unlock(m);
   out:
           VM_OBJECT_WUNLOCK(object);
           return (m);
   }
   
   /*
    * Return a CPU private mapping to the page at the given offset within the
    * given object.  The page is pinned before it is mapped.
    */
   struct sf_buf *
   vm_imgact_map_page(vm_object_t object, vm_ooffset_t offset)
   {
           vm_page_t m;
   
           m = vm_imgact_hold_page(object, offset);
           if (m == NULL)
                   return (NULL);
           sched_pin();
           return (sf_buf_alloc(m, SFB_CPUPRIVATE));
   }
   
   /*
    * Destroy the given CPU private mapping and unpin the page that it mapped.
    */
   void
   vm_imgact_unmap_page(struct sf_buf *sf)
   {
           vm_page_t m;
   
           m = sf_buf_page(sf);
           sf_buf_free(sf);
           sched_unpin();
           vm_page_lock(m);
           vm_page_unhold(m);
           vm_page_unlock(m);
   }
   
   void
   vm_sync_icache(vm_map_t map, vm_offset_t va, vm_offset_t sz)
   {
   
           pmap_sync_icache(map->pmap, va, sz);
   }
   
   struct kstack_cache_entry *kstack_cache;
   static int kstack_cache_size = 128;
   static int kstacks, kstack_domain_iter;
   static struct mtx kstack_cache_mtx;
   MTX_SYSINIT(kstack_cache, &kstack_cache_mtx, "kstkch", MTX_DEF);
   
   SYSCTL_INT(_vm, OID_AUTO, kstack_cache_size, CTLFLAG_RW, &kstack_cache_size, 0,
       "");
   SYSCTL_INT(_vm, OID_AUTO, kstacks, CTLFLAG_RD, &kstacks, 0,
       "");
   
   /*
    * Create the kernel stack (including pcb for i386) for a new thread.
    * This routine directly affects the fork perf for a process and
    * create performance for a thread.
    */
   int
   vm_thread_new(struct thread *td, int pages)
   {
           vm_object_t ksobj;
           vm_offset_t ks;
           vm_page_t ma[KSTACK_MAX_PAGES];
           struct kstack_cache_entry *ks_ce;
           int i;
   
           /* Bounds check */
           if (pages <= 1)
                   pages = kstack_pages;
           else if (pages > KSTACK_MAX_PAGES)
                   pages = KSTACK_MAX_PAGES;
   
           if (pages == kstack_pages && kstack_cache != NULL) {
                   mtx_lock(&kstack_cache_mtx);
                   if (kstack_cache != NULL) {
                           ks_ce = kstack_cache;
                           kstack_cache = ks_ce->next_ks_entry;
                           mtx_unlock(&kstack_cache_mtx);
   
                           td->td_kstack_obj = ks_ce->ksobj;
                           td->td_kstack = (vm_offset_t)ks_ce;
                           td->td_kstack_pages = kstack_pages;
                           return (1);
                   }
                   mtx_unlock(&kstack_cache_mtx);
           }
   
           /*
            * Allocate an object for the kstack.
            */
           ksobj = vm_object_allocate(OBJT_DEFAULT, pages);
           
           /*
            * Get a kernel virtual address for this thread's kstack.
            */
   #if defined(__mips__)
           /*
            * We need to align the kstack's mapped address to fit within
            * a single TLB entry.
            */
           if (vmem_xalloc(kernel_arena, (pages + KSTACK_GUARD_PAGES) * PAGE_SIZE,
               PAGE_SIZE * 2, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX,
               M_BESTFIT | M_NOWAIT, &ks)) {
                   ks = 0;
           }
   #else
           ks = kva_alloc((pages + KSTACK_GUARD_PAGES) * PAGE_SIZE);
   #endif
           if (ks == 0) {
                   printf("vm_thread_new: kstack allocation failed\n");
                   vm_object_deallocate(ksobj);
                   return (0);
           }
   
           /*
            * Ensure that kstack objects can draw pages from any memory
            * domain.  Otherwise a local memory shortage can block a process
            * swap-in.
            */
           if (vm_ndomains > 1) {
                   ksobj->domain.dr_policy = DOMAINSET_RR();
                   ksobj->domain.dr_iter =
                       atomic_fetchadd_int(&kstack_domain_iter, 1);
           }
   
           atomic_add_int(&kstacks, 1);
           if (KSTACK_GUARD_PAGES != 0) {
                   pmap_qremove(ks, KSTACK_GUARD_PAGES);
                   ks += KSTACK_GUARD_PAGES * PAGE_SIZE;
           }
           td->td_kstack_obj = ksobj;
           td->td_kstack = ks;
           /*
            * Knowing the number of pages allocated is useful when you
            * want to deallocate them.
            */
           td->td_kstack_pages = pages;
           /* 
            * For the length of the stack, link in a real page of ram for each
            * page of stack.
            */
           VM_OBJECT_WLOCK(ksobj);
           (void)vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY |
               VM_ALLOC_WIRED, ma, pages);
           for (i = 0; i < pages; i++)
                   ma[i]->valid = VM_PAGE_BITS_ALL;
           VM_OBJECT_WUNLOCK(ksobj);
           pmap_qenter(ks, ma, pages);
           return (1);
   }
   
   static void
   vm_thread_stack_dispose(vm_object_t ksobj, vm_offset_t ks, int pages)
   {
           vm_page_t m;
           int i;
   
           atomic_add_int(&kstacks, -1);
           pmap_qremove(ks, pages);
           VM_OBJECT_WLOCK(ksobj);
           for (i = 0; i < pages; i++) {
                   m = vm_page_lookup(ksobj, i);
                   if (m == NULL)
                           panic("vm_thread_dispose: kstack already missing?");
                   vm_page_lock(m);
                   vm_page_unwire(m, PQ_NONE);
                   vm_page_free(m);
                   vm_page_unlock(m);
           }
           VM_OBJECT_WUNLOCK(ksobj);
           vm_object_deallocate(ksobj);
           kva_free(ks - (KSTACK_GUARD_PAGES * PAGE_SIZE),
               (pages + KSTACK_GUARD_PAGES) * PAGE_SIZE);
   }
   
   /*
    * Dispose of a thread's kernel stack.
    */
   void
   vm_thread_dispose(struct thread *td)
   {
           vm_object_t ksobj;
           vm_offset_t ks;
           struct kstack_cache_entry *ks_ce;
           int pages;
   
           pages = td->td_kstack_pages;
           ksobj = td->td_kstack_obj;
           ks = td->td_kstack;
           td->td_kstack = 0;
           td->td_kstack_pages = 0;
           if (pages == kstack_pages && kstacks <= kstack_cache_size) {
                   ks_ce = (struct kstack_cache_entry *)ks;
                   ks_ce->ksobj = ksobj;
                   mtx_lock(&kstack_cache_mtx);
                   ks_ce->next_ks_entry = kstack_cache;
                   kstack_cache = ks_ce;
                   mtx_unlock(&kstack_cache_mtx);
                   return;
           }
           vm_thread_stack_dispose(ksobj, ks, pages);
   }
   
   static void
   vm_thread_stack_lowmem(void *nulll)
   {
           struct kstack_cache_entry *ks_ce, *ks_ce1;
   
           mtx_lock(&kstack_cache_mtx);
           ks_ce = kstack_cache;
           kstack_cache = NULL;
           mtx_unlock(&kstack_cache_mtx);
   
           while (ks_ce != NULL) {
                   ks_ce1 = ks_ce;
                   ks_ce = ks_ce->next_ks_entry;
   
                   vm_thread_stack_dispose(ks_ce1->ksobj, (vm_offset_t)ks_ce1,
                       kstack_pages);
           }
   }
   
   static void
   kstack_cache_init(void *nulll)
   {
   
           EVENTHANDLER_REGISTER(vm_lowmem, vm_thread_stack_lowmem, NULL,
               EVENTHANDLER_PRI_ANY);
   }
   
   SYSINIT(vm_kstacks, SI_SUB_KTHREAD_INIT, SI_ORDER_ANY, kstack_cache_init, NULL);
   
   #ifdef KSTACK_USAGE_PROF
   /*
    * Track maximum stack used by a thread in kernel.
    */
   static int max_kstack_used;
   
   SYSCTL_INT(_debug, OID_AUTO, max_kstack_used, CTLFLAG_RD,
       &max_kstack_used, 0,
       "Maxiumum stack depth used by a thread in kernel");
   
   void
   intr_prof_stack_use(struct thread *td, struct trapframe *frame)
   {
           vm_offset_t stack_top;
           vm_offset_t current;
           int used, prev_used;
   
           /*
            * Testing for interrupted kernel mode isn't strictly
            * needed. It optimizes the execution, since interrupts from
            * usermode will have only the trap frame on the stack.
            */
           if (TRAPF_USERMODE(frame))
                   return;
   
           stack_top = td->td_kstack + td->td_kstack_pages * PAGE_SIZE;
           current = (vm_offset_t)(uintptr_t)&stack_top;
   
           /*
            * Try to detect if interrupt is using kernel thread stack.
            * Hardware could use a dedicated stack for interrupt handling.
            */
           if (stack_top <= current || current < td->td_kstack)
                   return;
   
           used = stack_top - current;
           for (;;) {
                   prev_used = max_kstack_used;
                   if (prev_used >= used)
                           break;
                   if (atomic_cmpset_int(&max_kstack_used, prev_used, used))
                           break;
           }
   }
   #endif /* KSTACK_USAGE_PROF */
   
   /*
    * Implement fork's actions on an address space.
    * Here we arrange for the address space to be copied or referenced,
    * allocate a user struct (pcb and kernel stack), then call the
    * machine-dependent layer to fill those in and make the new process
    * ready to run.  The new process is set up so that it returns directly
    * to user mode to avoid stack copying and relocation problems.
    */
   int
   vm_forkproc(struct thread *td, struct proc *p2, struct thread *td2,
       struct vmspace *vm2, int flags)
   {
           struct proc *p1 = td->td_proc;
           struct domainset *dset;
           int error;
   
           if ((flags & RFPROC) == 0) {
                   /*
                    * Divorce the memory, if it is shared, essentially
                    * this changes shared memory amongst threads, into
                    * COW locally.
                    */
                   if ((flags & RFMEM) == 0) {
                           if (p1->p_vmspace->vm_refcnt > 1) {
                                   error = vmspace_unshare(p1);
                                   if (error)
                                           return (error);
                           }
                   }
                   cpu_fork(td, p2, td2, flags);
                   return (0);
           }
   
           if (flags & RFMEM) {
                   p2->p_vmspace = p1->p_vmspace;
                   atomic_add_int(&p1->p_vmspace->vm_refcnt, 1);
           }
           dset = td2->td_domain.dr_policy;
           while (vm_page_count_severe_set(&dset->ds_mask)) {
                   vm_wait_doms(&dset->ds_mask);
           }
   
           if ((flags & RFMEM) == 0) {
                   p2->p_vmspace = vm2;
                   if (p1->p_vmspace->vm_shm)
                           shmfork(p1, p2);
           }
   
           /*
            * cpu_fork will copy and update the pcb, set up the kernel stack,
            * and make the child ready to run.
            */
           cpu_fork(td, p2, td2, flags);
           return (0);
   }
   
   /*
    * Called after process has been wait(2)'ed upon and is being reaped.
    * The idea is to reclaim resources that we could not reclaim while
    * the process was still executing.
    */
   void
   vm_waitproc(p)
           struct proc *p;
   {
   
           vmspace_exitfree(p);            /* and clean-out the vmspace */
   }
   
   void
   kick_proc0(void)
   {
   
           wakeup(&proc0);
   }

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