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/* $NetBSD: uvm_fault.c,v 1.200 2017/07/09 20:53:09 christos Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* All rights reserved.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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: Id: uvm_fault.c,v 1.1.2.23 1998/02/06 05:29:05 chs Exp
*/
/*
* uvm_fault.c: fault handler
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.200 2017/07/09 20:53:09 christos Exp $");
#include "opt_uvmhist.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/mman.h>
#include <uvm/uvm.h>
/*
*
* a word on page faults:
*
* types of page faults we handle:
*
* CASE 1: upper layer faults CASE 2: lower layer faults
*
* CASE 1A CASE 1B CASE 2A CASE 2B
* read/write1 write>1 read/write +-cow_write/zero
* | | | |
* +--|--+ +--|--+ +-----+ + | + | +-----+
* amap | V | | ---------> new | | | | ^ |
* +-----+ +-----+ +-----+ + | + | +--|--+
* | | |
* +-----+ +-----+ +--|--+ | +--|--+
* uobj | d/c | | d/c | | V | +----+ |
* +-----+ +-----+ +-----+ +-----+
*
* d/c = don't care
*
* case [0]: layerless fault
* no amap or uobj is present. this is an error.
*
* case [1]: upper layer fault [anon active]
* 1A: [read] or [write with anon->an_ref == 1]
* I/O takes place in upper level anon and uobj is not touched.
* 1B: [write with anon->an_ref > 1]
* new anon is alloc'd and data is copied off ["COW"]
*
* case [2]: lower layer fault [uobj]
* 2A: [read on non-NULL uobj] or [write to non-copy_on_write area]
* I/O takes place directly in object.
* 2B: [write to copy_on_write] or [read on NULL uobj]
* data is "promoted" from uobj to a new anon.
* if uobj is null, then we zero fill.
*
* we follow the standard UVM locking protocol ordering:
*
* MAPS => AMAP => UOBJ => ANON => PAGE QUEUES (PQ)
* we hold a PG_BUSY page if we unlock for I/O
*
*
* the code is structured as follows:
*
* - init the "IN" params in the ufi structure
* ReFault: (ERESTART returned to the loop in uvm_fault_internal)
* - do lookups [locks maps], check protection, handle needs_copy
* - check for case 0 fault (error)
* - establish "range" of fault
* - if we have an amap lock it and extract the anons
* - if sequential advice deactivate pages behind us
* - at the same time check pmap for unmapped areas and anon for pages
* that we could map in (and do map it if found)
* - check object for resident pages that we could map in
* - if (case 2) goto Case2
* - >>> handle case 1
* - ensure source anon is resident in RAM
* - if case 1B alloc new anon and copy from source
* - map the correct page in
* Case2:
* - >>> handle case 2
* - ensure source page is resident (if uobj)
* - if case 2B alloc new anon and copy from source (could be zero
* fill if uobj == NULL)
* - map the correct page in
* - done!
*
* note on paging:
* if we have to do I/O we place a PG_BUSY page in the correct object,
* unlock everything, and do the I/O. when I/O is done we must reverify
* the state of the world before assuming that our data structures are
* valid. [because mappings could change while the map is unlocked]
*
* alternative 1: unbusy the page in question and restart the page fault
* from the top (ReFault). this is easy but does not take advantage
* of the information that we already have from our previous lookup,
* although it is possible that the "hints" in the vm_map will help here.
*
* alternative 2: the system already keeps track of a "version" number of
* a map. [i.e. every time you write-lock a map (e.g. to change a
* mapping) you bump the version number up by one...] so, we can save
* the version number of the map before we release the lock and start I/O.
* then when I/O is done we can relock and check the version numbers
* to see if anything changed. this might save us some over 1 because
* we don't have to unbusy the page and may be less compares(?).
*
* alternative 3: put in backpointers or a way to "hold" part of a map
* in place while I/O is in progress. this could be complex to
* implement (especially with structures like amap that can be referenced
* by multiple map entries, and figuring out what should wait could be
* complex as well...).
*
* we use alternative 2. given that we are multi-threaded now we may want
* to reconsider the choice.
*/
/*
* local data structures
*/
struct uvm_advice {
int advice;
int nback;
int nforw;
};
/*
* page range array:
* note: index in array must match "advice" value
* XXX: borrowed numbers from freebsd. do they work well for us?
*/
static const struct uvm_advice uvmadvice[] = {
{ UVM_ADV_NORMAL, 3, 4 },
{ UVM_ADV_RANDOM, 0, 0 },
{ UVM_ADV_SEQUENTIAL, 8, 7},
};
#define UVM_MAXRANGE 16 /* must be MAX() of nback+nforw+1 */
/*
* private prototypes
*/
/*
* externs from other modules
*/
extern int start_init_exec; /* Is init_main() done / init running? */
/*
* inline functions
*/
/*
* uvmfault_anonflush: try and deactivate pages in specified anons
*
* => does not have to deactivate page if it is busy
*/
static inline void
uvmfault_anonflush(struct vm_anon **anons, int n)
{
int lcv;
struct vm_page *pg;
for (lcv = 0; lcv < n; lcv++) {
if (anons[lcv] == NULL)
continue;
KASSERT(mutex_owned(anons[lcv]->an_lock));
pg = anons[lcv]->an_page;
if (pg && (pg->flags & PG_BUSY) == 0) {
mutex_enter(&uvm_pageqlock);
if (pg->wire_count == 0) {
uvm_pagedeactivate(pg);
}
mutex_exit(&uvm_pageqlock);
}
}
}
/*
* normal functions
*/
/*
* uvmfault_amapcopy: clear "needs_copy" in a map.
*
* => called with VM data structures unlocked (usually, see below)
* => we get a write lock on the maps and clear needs_copy for a VA
* => if we are out of RAM we sleep (waiting for more)
*/
static void
uvmfault_amapcopy(struct uvm_faultinfo *ufi)
{
for (;;) {
/*
* no mapping? give up.
*/
if (uvmfault_lookup(ufi, true) == false)
return;
/*
* copy if needed.
*/
if (UVM_ET_ISNEEDSCOPY(ufi->entry))
amap_copy(ufi->map, ufi->entry, AMAP_COPY_NOWAIT,
ufi->orig_rvaddr, ufi->orig_rvaddr + 1);
/*
* didn't work? must be out of RAM. unlock and sleep.
*/
if (UVM_ET_ISNEEDSCOPY(ufi->entry)) {
uvmfault_unlockmaps(ufi, true);
uvm_wait("fltamapcopy");
continue;
}
/*
* got it! unlock and return.
*/
uvmfault_unlockmaps(ufi, true);
return;
}
/*NOTREACHED*/
}
/*
* uvmfault_anonget: get data in an anon into a non-busy, non-released
* page in that anon.
*
* => Map, amap and thus anon should be locked by caller.
* => If we fail, we unlock everything and error is returned.
* => If we are successful, return with everything still locked.
* => We do not move the page on the queues [gets moved later]. If we
* allocate a new page [we_own], it gets put on the queues. Either way,
* the result is that the page is on the queues at return time
* => For pages which are on loan from a uvm_object (and thus are not owned
* by the anon): if successful, return with the owning object locked.
* The caller must unlock this object when it unlocks everything else.
*/
int
uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
struct vm_anon *anon)
{
struct vm_page *pg;
int error;
UVMHIST_FUNC("uvmfault_anonget"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(anon->an_lock));
KASSERT(anon->an_lock == amap->am_lock);
/* Increment the counters.*/
uvmexp.fltanget++;
if (anon->an_page) {
curlwp->l_ru.ru_minflt++;
} else {
curlwp->l_ru.ru_majflt++;
}
error = 0;
/*
* Loop until we get the anon data, or fail.
*/
for (;;) {
bool we_own, locked;
/*
* Note: 'we_own' will become true if we set PG_BUSY on a page.
*/
we_own = false;
pg = anon->an_page;
/*
* If there is a resident page and it is loaned, then anon
* may not own it. Call out to uvm_anon_lockloanpg() to
* identify and lock the real owner of the page.
*/
if (pg && pg->loan_count)
pg = uvm_anon_lockloanpg(anon);
/*
* Is page resident? Make sure it is not busy/released.
*/
if (pg) {
/*
* at this point, if the page has a uobject [meaning
* we have it on loan], then that uobject is locked
* by us! if the page is busy, we drop all the
* locks (including uobject) and try again.
*/
if ((pg->flags & PG_BUSY) == 0) {
UVMHIST_LOG(maphist, "<- OK",0,0,0,0);
return 0;
}
pg->flags |= PG_WANTED;
uvmexp.fltpgwait++;
/*
* The last unlock must be an atomic unlock and wait
* on the owner of page.
*/
if (pg->uobject) {
/* Owner of page is UVM object. */
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, " unlock+wait on uobj",0,
0,0,0);
UVM_UNLOCK_AND_WAIT(pg,
pg->uobject->vmobjlock,
false, "anonget1", 0);
} else {
/* Owner of page is anon. */
uvmfault_unlockall(ufi, NULL, NULL);
UVMHIST_LOG(maphist, " unlock+wait on anon",0,
0,0,0);
UVM_UNLOCK_AND_WAIT(pg, anon->an_lock,
false, "anonget2", 0);
}
} else {
#if defined(VMSWAP)
/*
* No page, therefore allocate one.
*/
pg = uvm_pagealloc(NULL,
ufi != NULL ? ufi->orig_rvaddr : 0,
anon, ufi != NULL ? UVM_FLAG_COLORMATCH : 0);
if (pg == NULL) {
/* Out of memory. Wait a little. */
uvmfault_unlockall(ufi, amap, NULL);
uvmexp.fltnoram++;
UVMHIST_LOG(maphist, " noram -- UVM_WAIT",0,
0,0,0);
if (!uvm_reclaimable()) {
return ENOMEM;
}
uvm_wait("flt_noram1");
} else {
/* PG_BUSY bit is set. */
we_own = true;
uvmfault_unlockall(ufi, amap, NULL);
/*
* Pass a PG_BUSY+PG_FAKE+PG_CLEAN page into
* the uvm_swap_get() function with all data
* structures unlocked. Note that it is OK
* to read an_swslot here, because we hold
* PG_BUSY on the page.
*/
uvmexp.pageins++;
error = uvm_swap_get(pg, anon->an_swslot,
PGO_SYNCIO);
/*
* We clean up after the I/O below in the
* 'we_own' case.
*/
}
#else
panic("%s: no page", __func__);
#endif /* defined(VMSWAP) */
}
/*
* Re-lock the map and anon.
*/
locked = uvmfault_relock(ufi);
if (locked || we_own) {
mutex_enter(anon->an_lock);
}
/*
* If we own the page (i.e. we set PG_BUSY), then we need
* to clean up after the I/O. There are three cases to
* consider:
*
* 1) Page was released during I/O: free anon and ReFault.
* 2) I/O not OK. Free the page and cause the fault to fail.
* 3) I/O OK! Activate the page and sync with the non-we_own
* case (i.e. drop anon lock if not locked).
*/
if (we_own) {
#if defined(VMSWAP)
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
if (error) {
/*
* Remove the swap slot from the anon and
* mark the anon as having no real slot.
* Do not free the swap slot, thus preventing
* it from being used again.
*/
if (anon->an_swslot > 0) {
uvm_swap_markbad(anon->an_swslot, 1);
}
anon->an_swslot = SWSLOT_BAD;
if ((pg->flags & PG_RELEASED) != 0) {
goto released;
}
/*
* Note: page was never !PG_BUSY, so it
* cannot be mapped and thus no need to
* pmap_page_protect() it.
*/
mutex_enter(&uvm_pageqlock);
uvm_pagefree(pg);
mutex_exit(&uvm_pageqlock);
if (locked) {
uvmfault_unlockall(ufi, NULL, NULL);
}
mutex_exit(anon->an_lock);
UVMHIST_LOG(maphist, "<- ERROR", 0,0,0,0);
return error;
}
if ((pg->flags & PG_RELEASED) != 0) {
released:
KASSERT(anon->an_ref == 0);
/*
* Released while we had unlocked amap.
*/
if (locked) {
uvmfault_unlockall(ufi, NULL, NULL);
}
uvm_anon_release(anon);
if (error) {
UVMHIST_LOG(maphist,
"<- ERROR/RELEASED", 0,0,0,0);
return error;
}
UVMHIST_LOG(maphist, "<- RELEASED", 0,0,0,0);
return ERESTART;
}
/*
* We have successfully read the page, activate it.
*/
mutex_enter(&uvm_pageqlock);
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE);
UVM_PAGE_OWN(pg, NULL);
#else
panic("%s: we_own", __func__);
#endif /* defined(VMSWAP) */
}
/*
* We were not able to re-lock the map - restart the fault.
*/
if (!locked) {
if (we_own) {
mutex_exit(anon->an_lock);
}
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
return ERESTART;
}
/*
* Verify that no one has touched the amap and moved
* the anon on us.
*/
if (ufi != NULL && amap_lookup(&ufi->entry->aref,
ufi->orig_rvaddr - ufi->entry->start) != anon) {
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
return ERESTART;
}
/*
* Retry..
*/
uvmexp.fltanretry++;
continue;
}
/*NOTREACHED*/
}
/*
* uvmfault_promote: promote data to a new anon. used for 1B and 2B.
*
* 1. allocate an anon and a page.
* 2. fill its contents.
* 3. put it into amap.
*
* => if we fail (result != 0) we unlock everything.
* => on success, return a new locked anon via 'nanon'.
* (*nanon)->an_page will be a resident, locked, dirty page.
* => it's caller's responsibility to put the promoted nanon->an_page to the
* page queue.
*/
static int
uvmfault_promote(struct uvm_faultinfo *ufi,
struct vm_anon *oanon,
struct vm_page *uobjpage,
struct vm_anon **nanon, /* OUT: allocated anon */
struct vm_anon **spare)
{
struct vm_amap *amap = ufi->entry->aref.ar_amap;
struct uvm_object *uobj;
struct vm_anon *anon;
struct vm_page *pg;
struct vm_page *opg;
int error;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
if (oanon) {
/* anon COW */
opg = oanon->an_page;
KASSERT(opg != NULL);
KASSERT(opg->uobject == NULL || opg->loan_count > 0);
} else if (uobjpage != PGO_DONTCARE) {
/* object-backed COW */
opg = uobjpage;
} else {
/* ZFOD */
opg = NULL;
}
if (opg != NULL) {
uobj = opg->uobject;
} else {
uobj = NULL;
}
KASSERT(amap != NULL);
KASSERT(uobjpage != NULL);
KASSERT(uobjpage == PGO_DONTCARE || (uobjpage->flags & PG_BUSY) != 0);
KASSERT(mutex_owned(amap->am_lock));
KASSERT(oanon == NULL || amap->am_lock == oanon->an_lock);
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
if (*spare != NULL) {
anon = *spare;
*spare = NULL;
} else {
anon = uvm_analloc();
}
if (anon) {
/*
* The new anon is locked.
*
* if opg == NULL, we want a zero'd, dirty page,
* so have uvm_pagealloc() do that for us.
*/
KASSERT(anon->an_lock == NULL);
anon->an_lock = amap->am_lock;
pg = uvm_pagealloc(NULL, ufi->orig_rvaddr, anon,
UVM_FLAG_COLORMATCH | (opg == NULL ? UVM_PGA_ZERO : 0));
if (pg == NULL) {
anon->an_lock = NULL;
}
} else {
pg = NULL;
}
/*
* out of memory resources?
*/
if (pg == NULL) {
/* save anon for the next try. */
if (anon != NULL) {
*spare = anon;
}
/* unlock and fail ... */
uvm_page_unbusy(&uobjpage, 1);
uvmfault_unlockall(ufi, amap, uobj);
if (!uvm_reclaimable()) {
UVMHIST_LOG(maphist, "out of VM", 0,0,0,0);
uvmexp.fltnoanon++;
error = ENOMEM;
goto done;
}
UVMHIST_LOG(maphist, "out of RAM, waiting for more", 0,0,0,0);
uvmexp.fltnoram++;
uvm_wait("flt_noram5");
error = ERESTART;
goto done;
}
/* copy page [pg now dirty] */
if (opg) {
uvm_pagecopy(opg, pg);
}
amap_add(&ufi->entry->aref, ufi->orig_rvaddr - ufi->entry->start, anon,
oanon != NULL);
*nanon = anon;
error = 0;
done:
return error;
}
/*
* F A U L T - m a i n e n t r y p o i n t
*/
/*
* uvm_fault: page fault handler
*
* => called from MD code to resolve a page fault
* => VM data structures usually should be unlocked. however, it is
* possible to call here with the main map locked if the caller
* gets a write lock, sets it recusive, and then calls us (c.f.
* uvm_map_pageable). this should be avoided because it keeps
* the map locked off during I/O.
* => MUST NEVER BE CALLED IN INTERRUPT CONTEXT
*/
#define MASK(entry) (UVM_ET_ISCOPYONWRITE(entry) ? \
~VM_PROT_WRITE : VM_PROT_ALL)
/* fault_flag values passed from uvm_fault_wire to uvm_fault_internal */
#define UVM_FAULT_WIRE (1 << 0)
#define UVM_FAULT_MAXPROT (1 << 1)
struct uvm_faultctx {
/*
* the following members are set up by uvm_fault_check() and
* read-only after that.
*
* note that narrow is used by uvm_fault_check() to change
* the behaviour after ERESTART.
*
* most of them might change after RESTART if the underlying
* map entry has been changed behind us. an exception is
* wire_paging, which does never change.
*/
vm_prot_t access_type;
vaddr_t startva;
int npages;
int centeridx;
bool narrow; /* work on a single requested page only */
bool wire_mapping; /* request a PMAP_WIRED mapping
(UVM_FAULT_WIRE or VM_MAPENT_ISWIRED) */
bool wire_paging; /* request uvm_pagewire
(true for UVM_FAULT_WIRE) */
bool cow_now; /* VM_PROT_WRITE is actually requested
(ie. should break COW and page loaning) */
/*
* enter_prot is set up by uvm_fault_check() and clamped
* (ie. drop the VM_PROT_WRITE bit) in various places in case
* of !cow_now.
*/
vm_prot_t enter_prot; /* prot at which we want to enter pages in */
/*
* the following member is for uvmfault_promote() and ERESTART.
*/
struct vm_anon *anon_spare;
/*
* the folloing is actually a uvm_fault_lower() internal.
* it's here merely for debugging.
* (or due to the mechanical separation of the function?)
*/
bool promote;
};
static inline int uvm_fault_check(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_anon ***, bool);
static int uvm_fault_upper(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_anon **);
static inline int uvm_fault_upper_lookup(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct vm_anon **, struct vm_page **);
static inline void uvm_fault_upper_neighbor(
struct uvm_faultinfo *, const struct uvm_faultctx *,
vaddr_t, struct vm_page *, bool);
static inline int uvm_fault_upper_loan(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_anon *, struct uvm_object **);
static inline int uvm_fault_upper_promote(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_anon *);
static inline int uvm_fault_upper_direct(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_anon *);
static int uvm_fault_upper_enter(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object *, struct vm_anon *,
struct vm_page *, struct vm_anon *);
static inline void uvm_fault_upper_done(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct vm_anon *, struct vm_page *);
static int uvm_fault_lower(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct vm_page **);
static inline void uvm_fault_lower_lookup(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct vm_page **);
static inline void uvm_fault_lower_neighbor(
struct uvm_faultinfo *, const struct uvm_faultctx *,
vaddr_t, struct vm_page *, bool);
static inline int uvm_fault_lower_io(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object **, struct vm_page **);
static inline int uvm_fault_lower_direct(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_page *);
static inline int uvm_fault_lower_direct_loan(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_page **,
struct vm_page **);
static inline int uvm_fault_lower_promote(
struct uvm_faultinfo *, struct uvm_faultctx *,
struct uvm_object *, struct vm_page *);
static int uvm_fault_lower_enter(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object *,
struct vm_anon *, struct vm_page *);
static inline void uvm_fault_lower_done(
struct uvm_faultinfo *, const struct uvm_faultctx *,
struct uvm_object *, struct vm_page *);
int
uvm_fault_internal(struct vm_map *orig_map, vaddr_t vaddr,
vm_prot_t access_type, int fault_flag)
{
struct cpu_data *cd;
struct uvm_cpu *ucpu;
struct uvm_faultinfo ufi;
struct uvm_faultctx flt = {
.access_type = access_type,
/* don't look for neighborhood * pages on "wire" fault */
.narrow = (fault_flag & UVM_FAULT_WIRE) != 0,
/* "wire" fault causes wiring of both mapping and paging */
.wire_mapping = (fault_flag & UVM_FAULT_WIRE) != 0,
.wire_paging = (fault_flag & UVM_FAULT_WIRE) != 0,
};
const bool maxprot = (fault_flag & UVM_FAULT_MAXPROT) != 0;
struct vm_anon *anons_store[UVM_MAXRANGE], **anons;
struct vm_page *pages_store[UVM_MAXRANGE], **pages;
int error;
UVMHIST_FUNC("uvm_fault"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, "(map=%p, vaddr=%#lx, at=%d, ff=%d)",
orig_map, vaddr, access_type, fault_flag);
cd = &(curcpu()->ci_data);
cd->cpu_nfault++;
ucpu = cd->cpu_uvm;
/* Don't flood RNG subsystem with samples. */
if (cd->cpu_nfault % 503)
goto norng;
/* Don't count anything until user interaction is possible */
if (__predict_true(start_init_exec)) {
kpreempt_disable();
rnd_add_uint32(&ucpu->rs,
sizeof(vaddr_t) == sizeof(uint32_t) ?
(uint32_t)vaddr : sizeof(vaddr_t) ==
sizeof(uint64_t) ?
(uint32_t)(vaddr & 0x00000000ffffffff) :
(uint32_t)(cd->cpu_nfault & 0x00000000ffffffff));
kpreempt_enable();
}
norng:
/*
* init the IN parameters in the ufi
*/
ufi.orig_map = orig_map;
ufi.orig_rvaddr = trunc_page(vaddr);
ufi.orig_size = PAGE_SIZE; /* can't get any smaller than this */
error = ERESTART;
while (error == ERESTART) { /* ReFault: */
anons = anons_store;
pages = pages_store;
error = uvm_fault_check(&ufi, &flt, &anons, maxprot);
if (error != 0)
continue;
error = uvm_fault_upper_lookup(&ufi, &flt, anons, pages);
if (error != 0)
continue;
if (pages[flt.centeridx] == PGO_DONTCARE)
error = uvm_fault_upper(&ufi, &flt, anons);
else {
struct uvm_object * const uobj =
ufi.entry->object.uvm_obj;
if (uobj && uobj->pgops->pgo_fault != NULL) {
/*
* invoke "special" fault routine.
*/
mutex_enter(uobj->vmobjlock);
/* locked: maps(read), amap(if there), uobj */
error = uobj->pgops->pgo_fault(&ufi,
flt.startva, pages, flt.npages,
flt.centeridx, flt.access_type,
PGO_LOCKED|PGO_SYNCIO);
/*
* locked: nothing, pgo_fault has unlocked
* everything
*/
/*
* object fault routine responsible for
* pmap_update().
*/
} else {
error = uvm_fault_lower(&ufi, &flt, pages);
}
}
}
if (flt.anon_spare != NULL) {
flt.anon_spare->an_ref--;
KASSERT(flt.anon_spare->an_ref == 0);
KASSERT(flt.anon_spare->an_lock == NULL);
uvm_anon_free(flt.anon_spare);
}
return error;
}
/*
* uvm_fault_check: check prot, handle needs-copy, etc.
*
* 1. lookup entry.
* 2. check protection.
* 3. adjust fault condition (mainly for simulated fault).
* 4. handle needs-copy (lazy amap copy).
* 5. establish range of interest for neighbor fault (aka pre-fault).
* 6. look up anons (if amap exists).
* 7. flush pages (if MADV_SEQUENTIAL)
*
* => called with nothing locked.
* => if we fail (result != 0) we unlock everything.
* => initialize/adjust many members of flt.
*/
static int
uvm_fault_check(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct vm_anon ***ranons, bool maxprot)
{
struct vm_amap *amap;
struct uvm_object *uobj;
vm_prot_t check_prot;
int nback, nforw;
UVMHIST_FUNC("uvm_fault_check"); UVMHIST_CALLED(maphist);
/*
* lookup and lock the maps
*/
if (uvmfault_lookup(ufi, false) == false) {
UVMHIST_LOG(maphist, "<- no mapping @ 0x%x", ufi->orig_rvaddr,
0,0,0);
return EFAULT;
}
/* locked: maps(read) */
#ifdef DIAGNOSTIC
if ((ufi->map->flags & VM_MAP_PAGEABLE) == 0) {
printf("Page fault on non-pageable map:\n");
printf("ufi->map = %p\n", ufi->map);
printf("ufi->orig_map = %p\n", ufi->orig_map);
printf("ufi->orig_rvaddr = 0x%lx\n", (u_long) ufi->orig_rvaddr);
panic("uvm_fault: (ufi->map->flags & VM_MAP_PAGEABLE) == 0");
}
#endif
/*
* check protection
*/
check_prot = maxprot ?
ufi->entry->max_protection : ufi->entry->protection;
if ((check_prot & flt->access_type) != flt->access_type) {
UVMHIST_LOG(maphist,
"<- protection failure (prot=%#x, access=%#x)",
ufi->entry->protection, flt->access_type, 0, 0);
uvmfault_unlockmaps(ufi, false);
return EFAULT;
}
/*
* "enter_prot" is the protection we want to enter the page in at.
* for certain pages (e.g. copy-on-write pages) this protection can
* be more strict than ufi->entry->protection. "wired" means either
* the entry is wired or we are fault-wiring the pg.
*/
flt->enter_prot = ufi->entry->protection;
if (VM_MAPENT_ISWIRED(ufi->entry))
flt->wire_mapping = true;
if (flt->wire_mapping) {
flt->access_type = flt->enter_prot; /* full access for wired */
flt->cow_now = (check_prot & VM_PROT_WRITE) != 0;
} else {
flt->cow_now = (flt->access_type & VM_PROT_WRITE) != 0;
}
flt->promote = false;
/*
* handle "needs_copy" case. if we need to copy the amap we will
* have to drop our readlock and relock it with a write lock. (we
* need a write lock to change anything in a map entry [e.g.
* needs_copy]).
*/
if (UVM_ET_ISNEEDSCOPY(ufi->entry)) {
if (flt->cow_now || (ufi->entry->object.uvm_obj == NULL)) {
KASSERT(!maxprot);
/* need to clear */
UVMHIST_LOG(maphist,
" need to clear needs_copy and refault",0,0,0,0);
uvmfault_unlockmaps(ufi, false);
uvmfault_amapcopy(ufi);
uvmexp.fltamcopy++;
return ERESTART;
} else {
/*
* ensure that we pmap_enter page R/O since
* needs_copy is still true
*/
flt->enter_prot &= ~VM_PROT_WRITE;
}
}
/*
* identify the players
*/
amap = ufi->entry->aref.ar_amap; /* upper layer */
uobj = ufi->entry->object.uvm_obj; /* lower layer */
/*
* check for a case 0 fault. if nothing backing the entry then
* error now.
*/
if (amap == NULL && uobj == NULL) {
uvmfault_unlockmaps(ufi, false);
UVMHIST_LOG(maphist,"<- no backing store, no overlay",0,0,0,0);
return EFAULT;
}
/*
* establish range of interest based on advice from mapper
* and then clip to fit map entry. note that we only want
* to do this the first time through the fault. if we
* ReFault we will disable this by setting "narrow" to true.
*/
if (flt->narrow == false) {
/* wide fault (!narrow) */
KASSERT(uvmadvice[ufi->entry->advice].advice ==
ufi->entry->advice);
nback = MIN(uvmadvice[ufi->entry->advice].nback,
(ufi->orig_rvaddr - ufi->entry->start) >> PAGE_SHIFT);
flt->startva = ufi->orig_rvaddr - (nback << PAGE_SHIFT);
/*
* note: "-1" because we don't want to count the
* faulting page as forw
*/
nforw = MIN(uvmadvice[ufi->entry->advice].nforw,
((ufi->entry->end - ufi->orig_rvaddr) >>
PAGE_SHIFT) - 1);
flt->npages = nback + nforw + 1;
flt->centeridx = nback;
flt->narrow = true; /* ensure only once per-fault */
} else {
/* narrow fault! */
nback = nforw = 0;
flt->startva = ufi->orig_rvaddr;
flt->npages = 1;
flt->centeridx = 0;
}
/* offset from entry's start to pgs' start */
const voff_t eoff = flt->startva - ufi->entry->start;
/* locked: maps(read) */
UVMHIST_LOG(maphist, " narrow=%d, back=%d, forw=%d, startva=%#lx",
flt->narrow, nback, nforw, flt->startva);
UVMHIST_LOG(maphist, " entry=%p, amap=%p, obj=%p", ufi->entry,
amap, uobj, 0);
/*
* if we've got an amap, lock it and extract current anons.
*/
if (amap) {
amap_lock(amap);
amap_lookups(&ufi->entry->aref, eoff, *ranons, flt->npages);
} else {
*ranons = NULL; /* to be safe */
}
/* locked: maps(read), amap(if there) */
KASSERT(amap == NULL || mutex_owned(amap->am_lock));
/*
* for MADV_SEQUENTIAL mappings we want to deactivate the back pages
* now and then forget about them (for the rest of the fault).
*/
if (ufi->entry->advice == MADV_SEQUENTIAL && nback != 0) {
UVMHIST_LOG(maphist, " MADV_SEQUENTIAL: flushing backpages",
0,0,0,0);
/* flush back-page anons? */
if (amap)
uvmfault_anonflush(*ranons, nback);
/* flush object? */
if (uobj) {
voff_t uoff;
uoff = ufi->entry->offset + eoff;
mutex_enter(uobj->vmobjlock);
(void) (uobj->pgops->pgo_put)(uobj, uoff, uoff +
(nback << PAGE_SHIFT), PGO_DEACTIVATE);
}
/* now forget about the backpages */
if (amap)
*ranons += nback;
flt->startva += (nback << PAGE_SHIFT);
flt->npages -= nback;
flt->centeridx = 0;
}
/*
* => startva is fixed
* => npages is fixed
*/
KASSERT(flt->startva <= ufi->orig_rvaddr);
KASSERT(ufi->orig_rvaddr + ufi->orig_size <=
flt->startva + (flt->npages << PAGE_SHIFT));
return 0;
}
/*
* uvm_fault_upper_lookup: look up existing h/w mapping and amap.
*
* iterate range of interest:
* 1. check if h/w mapping exists. if yes, we don't care
* 2. check if anon exists. if not, page is lower.
* 3. if anon exists, enter h/w mapping for neighbors.
*
* => called with amap locked (if exists).
*/
static int
uvm_fault_upper_lookup(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct vm_anon **anons, struct vm_page **pages)
{
struct vm_amap *amap = ufi->entry->aref.ar_amap;
int lcv;
vaddr_t currva;
bool shadowed __unused;
UVMHIST_FUNC("uvm_fault_upper_lookup"); UVMHIST_CALLED(maphist);
/* locked: maps(read), amap(if there) */
KASSERT(amap == NULL || mutex_owned(amap->am_lock));
/*
* map in the backpages and frontpages we found in the amap in hopes
* of preventing future faults. we also init the pages[] array as
* we go.
*/
currva = flt->startva;
shadowed = false;
for (lcv = 0; lcv < flt->npages; lcv++, currva += PAGE_SIZE) {
/*
* don't play with VAs that are already mapped
* (except for center)
*/
if (lcv != flt->centeridx &&
pmap_extract(ufi->orig_map->pmap, currva, NULL)) {
pages[lcv] = PGO_DONTCARE;
continue;
}
/*
* unmapped or center page. check if any anon at this level.
*/
if (amap == NULL || anons[lcv] == NULL) {
pages[lcv] = NULL;
continue;
}
/*
* check for present page and map if possible. re-activate it.
*/
pages[lcv] = PGO_DONTCARE;
if (lcv == flt->centeridx) { /* save center for later! */
shadowed = true;
continue;
}
struct vm_anon *anon = anons[lcv];
struct vm_page *pg = anon->an_page;
KASSERT(anon->an_lock == amap->am_lock);
/* Ignore loaned and busy pages. */
if (pg && pg->loan_count == 0 && (pg->flags & PG_BUSY) == 0) {
uvm_fault_upper_neighbor(ufi, flt, currva,
pg, anon->an_ref > 1);
}
}
/* locked: maps(read), amap(if there) */
KASSERT(amap == NULL || mutex_owned(amap->am_lock));
/* (shadowed == true) if there is an anon at the faulting address */
UVMHIST_LOG(maphist, " shadowed=%d, will_get=%d", shadowed,
(ufi->entry->object.uvm_obj && shadowed != false),0,0);
/*
* note that if we are really short of RAM we could sleep in the above
* call to pmap_enter with everything locked. bad?
*
* XXX Actually, that is bad; pmap_enter() should just fail in that
* XXX case. --thorpej
*/
return 0;
}
/*
* uvm_fault_upper_neighbor: enter single lower neighbor page.
*
* => called with amap and anon locked.
*/
static void
uvm_fault_upper_neighbor(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
vaddr_t currva, struct vm_page *pg, bool readonly)
{
UVMHIST_FUNC("uvm_fault_upper_neighbor"); UVMHIST_CALLED(maphist);
/* locked: amap, anon */
mutex_enter(&uvm_pageqlock);
uvm_pageenqueue(pg);
mutex_exit(&uvm_pageqlock);
UVMHIST_LOG(maphist,
" MAPPING: n anon: pm=%p, va=%#lx, pg=%p",
ufi->orig_map->pmap, currva, pg, 0);
uvmexp.fltnamap++;
/*
* Since this page isn't the page that's actually faulting,
* ignore pmap_enter() failures; it's not critical that we
* enter these right now.
*/
(void) pmap_enter(ufi->orig_map->pmap, currva,
VM_PAGE_TO_PHYS(pg),
readonly ? (flt->enter_prot & ~VM_PROT_WRITE) :
flt->enter_prot,
PMAP_CANFAIL | (flt->wire_mapping ? PMAP_WIRED : 0));
pmap_update(ufi->orig_map->pmap);
}
/*
* uvm_fault_upper: handle upper fault.
*
* 1. acquire anon lock.
* 2. get anon. let uvmfault_anonget do the dirty work.
* 3. handle loan.
* 4. dispatch direct or promote handlers.
*/
static int
uvm_fault_upper(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct vm_anon **anons)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
struct vm_anon * const anon = anons[flt->centeridx];
struct uvm_object *uobj;
int error;
UVMHIST_FUNC("uvm_fault_upper"); UVMHIST_CALLED(maphist);
/* locked: maps(read), amap, anon */
KASSERT(mutex_owned(amap->am_lock));
KASSERT(anon->an_lock == amap->am_lock);
/*
* handle case 1: fault on an anon in our amap
*/
UVMHIST_LOG(maphist, " case 1 fault: anon=%p", anon, 0,0,0);
/*
* no matter if we have case 1A or case 1B we are going to need to
* have the anon's memory resident. ensure that now.
*/
/*
* let uvmfault_anonget do the dirty work.
* if it fails (!OK) it will unlock everything for us.
* if it succeeds, locks are still valid and locked.
* also, if it is OK, then the anon's page is on the queues.
* if the page is on loan from a uvm_object, then anonget will
* lock that object for us if it does not fail.
*/
error = uvmfault_anonget(ufi, amap, anon);
switch (error) {
case 0:
break;
case ERESTART:
return ERESTART;
case EAGAIN:
kpause("fltagain1", false, hz/2, NULL);
return ERESTART;
default:
return error;
}
/*
* uobj is non null if the page is on loan from an object (i.e. uobj)
*/
uobj = anon->an_page->uobject; /* locked by anonget if !NULL */
/* locked: maps(read), amap, anon, uobj(if one) */
KASSERT(mutex_owned(amap->am_lock));
KASSERT(anon->an_lock == amap->am_lock);
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
/*
* special handling for loaned pages
*/
if (anon->an_page->loan_count) {
error = uvm_fault_upper_loan(ufi, flt, anon, &uobj);
if (error != 0)
return error;
}
/*
* if we are case 1B then we will need to allocate a new blank
* anon to transfer the data into. note that we have a lock
* on anon, so no one can busy or release the page until we are done.
* also note that the ref count can't drop to zero here because
* it is > 1 and we are only dropping one ref.
*
* in the (hopefully very rare) case that we are out of RAM we
* will unlock, wait for more RAM, and refault.
*
* if we are out of anon VM we kill the process (XXX: could wait?).
*/
if (flt->cow_now && anon->an_ref > 1) {
flt->promote = true;
error = uvm_fault_upper_promote(ufi, flt, uobj, anon);
} else {
error = uvm_fault_upper_direct(ufi, flt, uobj, anon);
}
return error;
}
/*
* uvm_fault_upper_loan: handle loaned upper page.
*
* 1. if not cow'ing now, simply adjust flt->enter_prot.
* 2. if cow'ing now, and if ref count is 1, break loan.
*/
static int
uvm_fault_upper_loan(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct vm_anon *anon, struct uvm_object **ruobj)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
int error = 0;
UVMHIST_FUNC("uvm_fault_upper_loan"); UVMHIST_CALLED(maphist);
if (!flt->cow_now) {
/*
* for read faults on loaned pages we just cap the
* protection at read-only.
*/
flt->enter_prot = flt->enter_prot & ~VM_PROT_WRITE;
} else {
/*
* note that we can't allow writes into a loaned page!
*
* if we have a write fault on a loaned page in an
* anon then we need to look at the anon's ref count.
* if it is greater than one then we are going to do
* a normal copy-on-write fault into a new anon (this
* is not a problem). however, if the reference count
* is one (a case where we would normally allow a
* write directly to the page) then we need to kill
* the loan before we continue.
*/
/* >1 case is already ok */
if (anon->an_ref == 1) {
error = uvm_loanbreak_anon(anon, *ruobj);
if (error != 0) {
uvmfault_unlockall(ufi, amap, *ruobj);
uvm_wait("flt_noram2");
return ERESTART;
}
/* if we were a loan reciever uobj is gone */
if (*ruobj)
*ruobj = NULL;
}
}
return error;
}
/*
* uvm_fault_upper_promote: promote upper page.
*
* 1. call uvmfault_promote.
* 2. enqueue page.
* 3. deref.
* 4. pass page to uvm_fault_upper_enter.
*/
static int
uvm_fault_upper_promote(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_anon *anon)
{
struct vm_anon * const oanon = anon;
struct vm_page *pg;
int error;
UVMHIST_FUNC("uvm_fault_upper_promote"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, " case 1B: COW fault",0,0,0,0);
uvmexp.flt_acow++;
error = uvmfault_promote(ufi, oanon, PGO_DONTCARE, &anon,
&flt->anon_spare);
switch (error) {
case 0:
break;
case ERESTART:
return ERESTART;
default:
return error;
}
KASSERT(anon == NULL || anon->an_lock == oanon->an_lock);
pg = anon->an_page;
mutex_enter(&uvm_pageqlock);
uvm_pageenqueue(pg); /* uvm_fault_upper_done will activate the page */
mutex_exit(&uvm_pageqlock);
pg->flags &= ~(PG_BUSY|PG_FAKE);
UVM_PAGE_OWN(pg, NULL);
/* deref: can not drop to zero here by defn! */
KASSERT(oanon->an_ref > 1);
oanon->an_ref--;
/*
* note: oanon is still locked, as is the new anon. we
* need to check for this later when we unlock oanon; if
* oanon != anon, we'll have to unlock anon, too.
*/
return uvm_fault_upper_enter(ufi, flt, uobj, anon, pg, oanon);
}
/*
* uvm_fault_upper_direct: handle direct fault.
*/
static int
uvm_fault_upper_direct(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_anon *anon)
{
struct vm_anon * const oanon = anon;
struct vm_page *pg;
UVMHIST_FUNC("uvm_fault_upper_direct"); UVMHIST_CALLED(maphist);
uvmexp.flt_anon++;
pg = anon->an_page;
if (anon->an_ref > 1) /* disallow writes to ref > 1 anons */
flt->enter_prot = flt->enter_prot & ~VM_PROT_WRITE;
return uvm_fault_upper_enter(ufi, flt, uobj, anon, pg, oanon);
}
/*
* uvm_fault_upper_enter: enter h/w mapping of upper page.
*/
static int
uvm_fault_upper_enter(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_anon *anon, struct vm_page *pg,
struct vm_anon *oanon)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
UVMHIST_FUNC("uvm_fault_upper_enter"); UVMHIST_CALLED(maphist);
/* locked: maps(read), amap, oanon, anon(if different from oanon) */
KASSERT(mutex_owned(amap->am_lock));
KASSERT(anon->an_lock == amap->am_lock);
KASSERT(oanon->an_lock == amap->am_lock);
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
/*
* now map the page in.
*/
UVMHIST_LOG(maphist,
" MAPPING: anon: pm=%p, va=%#lx, pg=%p, promote=%d",
ufi->orig_map->pmap, ufi->orig_rvaddr, pg, flt->promote);
if (pmap_enter(ufi->orig_map->pmap, ufi->orig_rvaddr,
VM_PAGE_TO_PHYS(pg),
flt->enter_prot, flt->access_type | PMAP_CANFAIL |
(flt->wire_mapping ? PMAP_WIRED : 0)) != 0) {
/*
* No need to undo what we did; we can simply think of
* this as the pmap throwing away the mapping information.
*
* We do, however, have to go through the ReFault path,
* as the map may change while we're asleep.
*/
uvmfault_unlockall(ufi, amap, uobj);
if (!uvm_reclaimable()) {
UVMHIST_LOG(maphist,
"<- failed. out of VM",0,0,0,0);
/* XXX instrumentation */
return ENOMEM;
}
/* XXX instrumentation */
uvm_wait("flt_pmfail1");
return ERESTART;
}
uvm_fault_upper_done(ufi, flt, anon, pg);
/*
* done case 1! finish up by unlocking everything and returning success
*/
pmap_update(ufi->orig_map->pmap);
uvmfault_unlockall(ufi, amap, uobj);
return 0;
}
/*
* uvm_fault_upper_done: queue upper center page.
*/
static void
uvm_fault_upper_done(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct vm_anon *anon, struct vm_page *pg)
{
const bool wire_paging = flt->wire_paging;
UVMHIST_FUNC("uvm_fault_upper_done"); UVMHIST_CALLED(maphist);
/*
* ... update the page queues.
*/
mutex_enter(&uvm_pageqlock);
if (wire_paging) {
uvm_pagewire(pg);
/*
* since the now-wired page cannot be paged out,
* release its swap resources for others to use.
* since an anon with no swap cannot be PG_CLEAN,
* clear its clean flag now.
*/
pg->flags &= ~(PG_CLEAN);
} else {
uvm_pageactivate(pg);
}
mutex_exit(&uvm_pageqlock);
if (wire_paging) {
uvm_anon_dropswap(anon);
}
}
/*
* uvm_fault_lower: handle lower fault.
*
* 1. check uobj
* 1.1. if null, ZFOD.
* 1.2. if not null, look up unnmapped neighbor pages.
* 2. for center page, check if promote.
* 2.1. ZFOD always needs promotion.
* 2.2. other uobjs, when entry is marked COW (usually MAP_PRIVATE vnode).
* 3. if uobj is not ZFOD and page is not found, do i/o.
* 4. dispatch either direct / promote fault.
*/
static int
uvm_fault_lower(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct vm_page **pages)
{
struct vm_amap *amap __diagused = ufi->entry->aref.ar_amap;
struct uvm_object *uobj = ufi->entry->object.uvm_obj;
struct vm_page *uobjpage;
int error;
UVMHIST_FUNC("uvm_fault_lower"); UVMHIST_CALLED(maphist);
/*
* now, if the desired page is not shadowed by the amap and we have
* a backing object that does not have a special fault routine, then
* we ask (with pgo_get) the object for resident pages that we care
* about and attempt to map them in. we do not let pgo_get block
* (PGO_LOCKED).
*/
if (uobj == NULL) {
/* zero fill; don't care neighbor pages */
uobjpage = NULL;
} else {
uvm_fault_lower_lookup(ufi, flt, pages);
uobjpage = pages[flt->centeridx];
}
/*
* note that at this point we are done with any front or back pages.
* we are now going to focus on the center page (i.e. the one we've
* faulted on). if we have faulted on the upper (anon) layer
* [i.e. case 1], then the anon we want is anons[centeridx] (we have
* not touched it yet). if we have faulted on the bottom (uobj)
* layer [i.e. case 2] and the page was both present and available,
* then we've got a pointer to it as "uobjpage" and we've already
* made it BUSY.
*/
/*
* locked:
* maps(read), amap(if there), uobj(if !null), uobjpage(if !null)
*/
KASSERT(amap == NULL || mutex_owned(amap->am_lock));
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
KASSERT(uobjpage == NULL || (uobjpage->flags & PG_BUSY) != 0);
/*
* note that uobjpage can not be PGO_DONTCARE at this point. we now
* set uobjpage to PGO_DONTCARE if we are doing a zero fill. if we
* have a backing object, check and see if we are going to promote
* the data up to an anon during the fault.
*/
if (uobj == NULL) {
uobjpage = PGO_DONTCARE;
flt->promote = true; /* always need anon here */
} else {
KASSERT(uobjpage != PGO_DONTCARE);
flt->promote = flt->cow_now && UVM_ET_ISCOPYONWRITE(ufi->entry);
}
UVMHIST_LOG(maphist, " case 2 fault: promote=%d, zfill=%d",
flt->promote, (uobj == NULL), 0,0);
/*
* if uobjpage is not null then we do not need to do I/O to get the
* uobjpage.
*
* if uobjpage is null, then we need to unlock and ask the pager to
* get the data for us. once we have the data, we need to reverify
* the state the world. we are currently not holding any resources.
*/
if (uobjpage) {
/* update rusage counters */
curlwp->l_ru.ru_minflt++;
} else {
error = uvm_fault_lower_io(ufi, flt, &uobj, &uobjpage);
if (error != 0)
return error;
}
/*
* locked:
* maps(read), amap(if !null), uobj(if !null), uobjpage(if uobj)
*/
KASSERT(amap == NULL || mutex_owned(amap->am_lock));
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
KASSERT(uobj == NULL || (uobjpage->flags & PG_BUSY) != 0);
/*
* notes:
* - at this point uobjpage can not be NULL
* - at this point uobjpage can not be PG_RELEASED (since we checked
* for it above)
* - at this point uobjpage could be PG_WANTED (handle later)
*/
KASSERT(uobjpage != NULL);
KASSERT(uobj == NULL || uobj == uobjpage->uobject);
KASSERT(uobj == NULL || !UVM_OBJ_IS_CLEAN(uobjpage->uobject) ||
(uobjpage->flags & PG_CLEAN) != 0);
if (!flt->promote) {
error = uvm_fault_lower_direct(ufi, flt, uobj, uobjpage);
} else {
error = uvm_fault_lower_promote(ufi, flt, uobj, uobjpage);
}
return error;
}
/*
* uvm_fault_lower_lookup: look up on-memory uobj pages.
*
* 1. get on-memory pages.
* 2. if failed, give up (get only center page later).
* 3. if succeeded, enter h/w mapping of neighbor pages.
*/
static void
uvm_fault_lower_lookup(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct vm_page **pages)
{
struct uvm_object *uobj = ufi->entry->object.uvm_obj;
int lcv, gotpages;
vaddr_t currva;
UVMHIST_FUNC("uvm_fault_lower_lookup"); UVMHIST_CALLED(maphist);
mutex_enter(uobj->vmobjlock);
/* Locked: maps(read), amap(if there), uobj */
uvmexp.fltlget++;
gotpages = flt->npages;
(void) uobj->pgops->pgo_get(uobj,
ufi->entry->offset + flt->startva - ufi->entry->start,
pages, &gotpages, flt->centeridx,
flt->access_type & MASK(ufi->entry), ufi->entry->advice, PGO_LOCKED);
KASSERT(mutex_owned(uobj->vmobjlock));
/*
* check for pages to map, if we got any
*/
if (gotpages == 0) {
pages[flt->centeridx] = NULL;
return;
}
currva = flt->startva;
for (lcv = 0; lcv < flt->npages; lcv++, currva += PAGE_SIZE) {
struct vm_page *curpg;
curpg = pages[lcv];
if (curpg == NULL || curpg == PGO_DONTCARE) {
continue;
}
KASSERT(curpg->uobject == uobj);
/*
* if center page is resident and not PG_BUSY|PG_RELEASED
* then pgo_get made it PG_BUSY for us and gave us a handle
* to it.
*/
if (lcv == flt->centeridx) {
UVMHIST_LOG(maphist, " got uobjpage "
"(0x%x) with locked get",
curpg, 0,0,0);
} else {
bool readonly = (curpg->flags & PG_RDONLY)
|| (curpg->loan_count > 0)
|| UVM_OBJ_NEEDS_WRITEFAULT(curpg->uobject);
uvm_fault_lower_neighbor(ufi, flt,
currva, curpg, readonly);
}
}
pmap_update(ufi->orig_map->pmap);
}
/*
* uvm_fault_lower_neighbor: enter h/w mapping of lower neighbor page.
*/
static void
uvm_fault_lower_neighbor(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
vaddr_t currva, struct vm_page *pg, bool readonly)
{
UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
/* locked: maps(read), amap(if there), uobj */
/*
* calling pgo_get with PGO_LOCKED returns us pages which
* are neither busy nor released, so we don't need to check
* for this. we can just directly enter the pages.
*/
mutex_enter(&uvm_pageqlock);
uvm_pageenqueue(pg);
mutex_exit(&uvm_pageqlock);
UVMHIST_LOG(maphist,
" MAPPING: n obj: pm=%p, va=%#lx, pg=%p",
ufi->orig_map->pmap, currva, pg, 0);
uvmexp.fltnomap++;
/*
* Since this page isn't the page that's actually faulting,
* ignore pmap_enter() failures; it's not critical that we
* enter these right now.
* NOTE: page can't be PG_WANTED or PG_RELEASED because we've
* held the lock the whole time we've had the handle.
*/
KASSERT((pg->flags & PG_PAGEOUT) == 0);
KASSERT((pg->flags & PG_RELEASED) == 0);
KASSERT((pg->flags & PG_WANTED) == 0);
KASSERT(!UVM_OBJ_IS_CLEAN(pg->uobject) || (pg->flags & PG_CLEAN) != 0);
pg->flags &= ~(PG_BUSY);
UVM_PAGE_OWN(pg, NULL);
KASSERT(mutex_owned(pg->uobject->vmobjlock));
const vm_prot_t mapprot =
readonly ? (flt->enter_prot & ~VM_PROT_WRITE) :
flt->enter_prot & MASK(ufi->entry);
const u_int mapflags =
PMAP_CANFAIL | (flt->wire_mapping ? (mapprot | PMAP_WIRED) : 0);
(void) pmap_enter(ufi->orig_map->pmap, currva,
VM_PAGE_TO_PHYS(pg), mapprot, mapflags);
}
/*
* uvm_fault_lower_io: get lower page from backing store.
*
* 1. unlock everything, because i/o will block.
* 2. call pgo_get.
* 3. if failed, recover.
* 4. if succeeded, relock everything and verify things.
*/
static int
uvm_fault_lower_io(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct uvm_object **ruobj, struct vm_page **ruobjpage)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
struct uvm_object *uobj = *ruobj;
struct vm_page *pg;
bool locked;
int gotpages;
int error;
voff_t uoff;
UVMHIST_FUNC("uvm_fault_lower_io"); UVMHIST_CALLED(maphist);
/* update rusage counters */
curlwp->l_ru.ru_majflt++;
/* Locked: maps(read), amap(if there), uobj */
uvmfault_unlockall(ufi, amap, NULL);
/* Locked: uobj */
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
uvmexp.fltget++;
gotpages = 1;
pg = NULL;
uoff = (ufi->orig_rvaddr - ufi->entry->start) + ufi->entry->offset;
error = uobj->pgops->pgo_get(uobj, uoff, &pg, &gotpages,
0, flt->access_type & MASK(ufi->entry), ufi->entry->advice,
PGO_SYNCIO);
/* locked: pg(if no error) */
/*
* recover from I/O
*/
if (error) {
if (error == EAGAIN) {
UVMHIST_LOG(maphist,
" pgo_get says TRY AGAIN!",0,0,0,0);
kpause("fltagain2", false, hz/2, NULL);
return ERESTART;
}
#if 0
KASSERT(error != ERESTART);
#else
/* XXXUEBS don't re-fault? */
if (error == ERESTART)
error = EIO;
#endif
UVMHIST_LOG(maphist, "<- pgo_get failed (code %d)",
error, 0,0,0);
return error;
}
/*
* re-verify the state of the world by first trying to relock
* the maps. always relock the object.
*/
locked = uvmfault_relock(ufi);
if (locked && amap)
amap_lock(amap);
/* might be changed */
uobj = pg->uobject;
mutex_enter(uobj->vmobjlock);
KASSERT((pg->flags & PG_BUSY) != 0);
mutex_enter(&uvm_pageqlock);
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
/* locked(locked): maps(read), amap(if !null), uobj, pg */
/* locked(!locked): uobj, pg */
/*
* verify that the page has not be released and re-verify
* that amap slot is still free. if there is a problem,
* we unlock and clean up.
*/
if ((pg->flags & PG_RELEASED) != 0 ||
(locked && amap && amap_lookup(&ufi->entry->aref,
ufi->orig_rvaddr - ufi->entry->start))) {
if (locked)
uvmfault_unlockall(ufi, amap, NULL);
locked = false;
}
/*
* didn't get the lock? release the page and retry.
*/
if (locked == false) {
UVMHIST_LOG(maphist,
" wasn't able to relock after fault: retry",
0,0,0,0);
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
if ((pg->flags & PG_RELEASED) == 0) {
pg->flags &= ~(PG_BUSY | PG_WANTED);
UVM_PAGE_OWN(pg, NULL);
} else {
uvmexp.fltpgrele++;
uvm_pagefree(pg);
}
mutex_exit(uobj->vmobjlock);
return ERESTART;
}
/*
* we have the data in pg which is busy and
* not released. we are holding object lock (so the page
* can't be released on us).
*/
/* locked: maps(read), amap(if !null), uobj, pg */
*ruobj = uobj;
*ruobjpage = pg;
return 0;
}
/*
* uvm_fault_lower_direct: fault lower center page
*
* 1. adjust flt->enter_prot.
* 2. if page is loaned, resolve.
*/
int
uvm_fault_lower_direct(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_page *uobjpage)
{
struct vm_page *pg;
UVMHIST_FUNC("uvm_fault_lower_direct"); UVMHIST_CALLED(maphist);
/*
* we are not promoting. if the mapping is COW ensure that we
* don't give more access than we should (e.g. when doing a read
* fault on a COPYONWRITE mapping we want to map the COW page in
* R/O even though the entry protection could be R/W).
*
* set "pg" to the page we want to map in (uobjpage, usually)
*/
uvmexp.flt_obj++;
if (UVM_ET_ISCOPYONWRITE(ufi->entry) ||
UVM_OBJ_NEEDS_WRITEFAULT(uobjpage->uobject))
flt->enter_prot &= ~VM_PROT_WRITE;
pg = uobjpage; /* map in the actual object */
KASSERT(uobjpage != PGO_DONTCARE);
/*
* we are faulting directly on the page. be careful
* about writing to loaned pages...
*/
if (uobjpage->loan_count) {
uvm_fault_lower_direct_loan(ufi, flt, uobj, &pg, &uobjpage);
}
KASSERT(pg == uobjpage);
KASSERT(uobj == NULL || (uobjpage->flags & PG_BUSY) != 0);
return uvm_fault_lower_enter(ufi, flt, uobj, NULL, pg);
}
/*
* uvm_fault_lower_direct_loan: resolve loaned page.
*
* 1. if not cow'ing, adjust flt->enter_prot.
* 2. if cow'ing, break loan.
*/
static int
uvm_fault_lower_direct_loan(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_page **rpg,
struct vm_page **ruobjpage)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
struct vm_page *pg;
struct vm_page *uobjpage = *ruobjpage;
UVMHIST_FUNC("uvm_fault_lower_direct_loan"); UVMHIST_CALLED(maphist);
if (!flt->cow_now) {
/* read fault: cap the protection at readonly */
/* cap! */
flt->enter_prot = flt->enter_prot & ~VM_PROT_WRITE;
} else {
/* write fault: must break the loan here */
pg = uvm_loanbreak(uobjpage);
if (pg == NULL) {
/*
* drop ownership of page, it can't be released
*/
if (uobjpage->flags & PG_WANTED)
wakeup(uobjpage);
uobjpage->flags &= ~(PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(uobjpage, NULL);
uvmfault_unlockall(ufi, amap, uobj);
UVMHIST_LOG(maphist,
" out of RAM breaking loan, waiting",
0,0,0,0);
uvmexp.fltnoram++;
uvm_wait("flt_noram4");
return ERESTART;
}
*rpg = pg;
*ruobjpage = pg;
}
return 0;
}
/*
* uvm_fault_lower_promote: promote lower page.
*
* 1. call uvmfault_promote.
* 2. fill in data.
* 3. if not ZFOD, dispose old page.
*/
int
uvm_fault_lower_promote(
struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_page *uobjpage)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
struct vm_anon *anon;
struct vm_page *pg;
int error;
UVMHIST_FUNC("uvm_fault_lower_promote"); UVMHIST_CALLED(maphist);
KASSERT(amap != NULL);
/*
* If we are going to promote the data to an anon we
* allocate a blank anon here and plug it into our amap.
*/
error = uvmfault_promote(ufi, NULL, uobjpage,
&anon, &flt->anon_spare);
switch (error) {
case 0:
break;
case ERESTART:
return ERESTART;
default:
return error;
}
pg = anon->an_page;
/*
* Fill in the data.
*/
KASSERT(uobj == NULL || (uobjpage->flags & PG_BUSY) != 0);
if (uobjpage != PGO_DONTCARE) {
uvmexp.flt_prcopy++;
/*
* promote to shared amap? make sure all sharing
* procs see it
*/
if ((amap_flags(amap) & AMAP_SHARED) != 0) {
pmap_page_protect(uobjpage, VM_PROT_NONE);
/*
* XXX: PAGE MIGHT BE WIRED!
*/
}
/*
* dispose of uobjpage. it can't be PG_RELEASED
* since we still hold the object lock.
*/
if (uobjpage->flags & PG_WANTED) {
/* still have the obj lock */
wakeup(uobjpage);
}
uobjpage->flags &= ~(PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(uobjpage, NULL);
UVMHIST_LOG(maphist,
" promote uobjpage 0x%x to anon/page 0x%x/0x%x",
uobjpage, anon, pg, 0);
} else {
uvmexp.flt_przero++;
/*
* Page is zero'd and marked dirty by
* uvmfault_promote().
*/
UVMHIST_LOG(maphist," zero fill anon/page 0x%x/0%x",
anon, pg, 0, 0);
}
return uvm_fault_lower_enter(ufi, flt, uobj, anon, pg);
}
/*
* uvm_fault_lower_enter: enter h/w mapping of lower page or anon page promoted
* from the lower page.
*/
int
uvm_fault_lower_enter(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct uvm_object *uobj,
struct vm_anon *anon, struct vm_page *pg)
{
struct vm_amap * const amap = ufi->entry->aref.ar_amap;
int error;
UVMHIST_FUNC("uvm_fault_lower_enter"); UVMHIST_CALLED(maphist);
/*
* Locked:
*
* maps(read), amap(if !null), uobj(if !null),
* anon(if !null), pg(if anon), unlock_uobj(if !null)
*
* Note: pg is either the uobjpage or the new page in the new anon.
*/
KASSERT(amap == NULL || mutex_owned(amap->am_lock));
KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock));
KASSERT(anon == NULL || anon->an_lock == amap->am_lock);
KASSERT((pg->flags & PG_BUSY) != 0);
/*
* all resources are present. we can now map it in and free our
* resources.
*/
UVMHIST_LOG(maphist,
" MAPPING: case2: pm=%p, va=%#lx, pg=%#x, promote=%d",
ufi->orig_map->pmap, ufi->orig_rvaddr, pg, flt->promote);
KASSERT((flt->access_type & VM_PROT_WRITE) == 0 ||
(pg->flags & PG_RDONLY) == 0);
if (pmap_enter(ufi->orig_map->pmap, ufi->orig_rvaddr,
VM_PAGE_TO_PHYS(pg),
(pg->flags & PG_RDONLY) != 0 ?
flt->enter_prot & ~VM_PROT_WRITE : flt->enter_prot,
flt->access_type | PMAP_CANFAIL |
(flt->wire_mapping ? PMAP_WIRED : 0)) != 0) {
/*
* No need to undo what we did; we can simply think of
* this as the pmap throwing away the mapping information.
*
* We do, however, have to go through the ReFault path,
* as the map may change while we're asleep.
*/
/*
* ensure that the page is queued in the case that
* we just promoted the page.
*/
mutex_enter(&uvm_pageqlock);
uvm_pageenqueue(pg);
mutex_exit(&uvm_pageqlock);
if (pg->flags & PG_WANTED)
wakeup(pg);
/*
* note that pg can't be PG_RELEASED since we did not drop
* the object lock since the last time we checked.
*/
KASSERT((pg->flags & PG_RELEASED) == 0);
pg->flags &= ~(PG_BUSY|PG_FAKE|PG_WANTED);
UVM_PAGE_OWN(pg, NULL);
uvmfault_unlockall(ufi, amap, uobj);
if (!uvm_reclaimable()) {
UVMHIST_LOG(maphist,
"<- failed. out of VM",0,0,0,0);
/* XXX instrumentation */
error = ENOMEM;
return error;
}
/* XXX instrumentation */
uvm_wait("flt_pmfail2");
return ERESTART;
}
uvm_fault_lower_done(ufi, flt, uobj, pg);
/*
* note that pg can't be PG_RELEASED since we did not drop the object
* lock since the last time we checked.
*/
KASSERT((pg->flags & PG_RELEASED) == 0);
if (pg->flags & PG_WANTED)
wakeup(pg);
pg->flags &= ~(PG_BUSY|PG_FAKE|PG_WANTED);
UVM_PAGE_OWN(pg, NULL);
pmap_update(ufi->orig_map->pmap);
uvmfault_unlockall(ufi, amap, uobj);
UVMHIST_LOG(maphist, "<- done (SUCCESS!)",0,0,0,0);
return 0;
}
/*
* uvm_fault_lower_done: queue lower center page.
*/
void
uvm_fault_lower_done(
struct uvm_faultinfo *ufi, const struct uvm_faultctx *flt,
struct uvm_object *uobj, struct vm_page *pg)
{
bool dropswap = false;
UVMHIST_FUNC("uvm_fault_lower_done"); UVMHIST_CALLED(maphist);
mutex_enter(&uvm_pageqlock);
if (flt->wire_paging) {
uvm_pagewire(pg);
if (pg->pqflags & PQ_AOBJ) {
/*
* since the now-wired page cannot be paged out,
* release its swap resources for others to use.
* since an aobj page with no swap cannot be PG_CLEAN,
* clear its clean flag now.
*/
KASSERT(uobj != NULL);
pg->flags &= ~(PG_CLEAN);
dropswap = true;
}
} else {
uvm_pageactivate(pg);
}
mutex_exit(&uvm_pageqlock);
if (dropswap) {
uao_dropswap(uobj, pg->offset >> PAGE_SHIFT);
}
}
/*
* uvm_fault_wire: wire down a range of virtual addresses in a map.
*
* => map may be read-locked by caller, but MUST NOT be write-locked.
* => if map is read-locked, any operations which may cause map to
* be write-locked in uvm_fault() must be taken care of by
* the caller. See uvm_map_pageable().
*/
int
uvm_fault_wire(struct vm_map *map, vaddr_t start, vaddr_t end,
vm_prot_t access_type, int maxprot)
{
vaddr_t va;
int error;
/*
* now fault it in a page at a time. if the fault fails then we have
* to undo what we have done. note that in uvm_fault VM_PROT_NONE
* is replaced with the max protection if fault_type is VM_FAULT_WIRE.
*/
/*
* XXX work around overflowing a vaddr_t. this prevents us from
* wiring the last page in the address space, though.
*/
if (start > end) {
return EFAULT;
}
for (va = start; va < end; va += PAGE_SIZE) {
error = uvm_fault_internal(map, va, access_type,
(maxprot ? UVM_FAULT_MAXPROT : 0) | UVM_FAULT_WIRE);
if (error) {
if (va != start) {
uvm_fault_unwire(map, start, va);
}
return error;
}
}
return 0;
}
/*
* uvm_fault_unwire(): unwire range of virtual space.
*/
void
uvm_fault_unwire(struct vm_map *map, vaddr_t start, vaddr_t end)
{
vm_map_lock_read(map);
uvm_fault_unwire_locked(map, start, end);
vm_map_unlock_read(map);
}
/*
* uvm_fault_unwire_locked(): the guts of uvm_fault_unwire().
*
* => map must be at least read-locked.
*/
void
uvm_fault_unwire_locked(struct vm_map *map, vaddr_t start, vaddr_t end)
{
struct vm_map_entry *entry, *oentry;
pmap_t pmap = vm_map_pmap(map);
vaddr_t va;
paddr_t pa;
struct vm_page *pg;
/*
* we assume that the area we are unwiring has actually been wired
* in the first place. this means that we should be able to extract
* the PAs from the pmap. we also lock out the page daemon so that
* we can call uvm_pageunwire.
*/
/*
* find the beginning map entry for the region.
*/
KASSERT(start >= vm_map_min(map) && end <= vm_map_max(map));
if (uvm_map_lookup_entry(map, start, &entry) == false)
panic("uvm_fault_unwire_locked: address not in map");
oentry = NULL;
for (va = start; va < end; va += PAGE_SIZE) {
if (pmap_extract(pmap, va, &pa) == false)
continue;
/*
* find the map entry for the current address.
*/
KASSERT(va >= entry->start);
while (va >= entry->end) {
KASSERT(entry->next != &map->header &&
entry->next->start <= entry->end);
entry = entry->next;
}
/*
* lock it.
*/
if (entry != oentry) {
if (oentry != NULL) {
mutex_exit(&uvm_pageqlock);
uvm_map_unlock_entry(oentry);
}
uvm_map_lock_entry(entry);
mutex_enter(&uvm_pageqlock);
oentry = entry;
}
/*
* if the entry is no longer wired, tell the pmap.
*/
if (VM_MAPENT_ISWIRED(entry) == 0)
pmap_unwire(pmap, va);
pg = PHYS_TO_VM_PAGE(pa);
if (pg)
uvm_pageunwire(pg);
}
if (oentry != NULL) {
mutex_exit(&uvm_pageqlock);
uvm_map_unlock_entry(entry);
}
}
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