308 lines
8.8 KiB
Go
308 lines
8.8 KiB
Go
// Copyright 2018 The gVisor Authors.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
// +build amd64
|
|
|
|
package pagetables
|
|
|
|
// Visitor is a generic type.
|
|
type Visitor interface {
|
|
// visit is called on each PTE.
|
|
visit(start uintptr, pte *PTE, align uintptr)
|
|
|
|
// requiresAlloc indicates that new entries should be allocated within
|
|
// the walked range.
|
|
requiresAlloc() bool
|
|
|
|
// requiresSplit indicates that entries in the given range should be
|
|
// split if they are huge or jumbo pages.
|
|
requiresSplit() bool
|
|
}
|
|
|
|
// Walker walks page tables.
|
|
type Walker struct {
|
|
// pageTables are the tables to walk.
|
|
pageTables *PageTables
|
|
|
|
// Visitor is the set of arguments.
|
|
visitor Visitor
|
|
}
|
|
|
|
// iterateRange iterates over all appropriate levels of page tables for the given range.
|
|
//
|
|
// If requiresAlloc is true, then Set _must_ be called on all given PTEs. The
|
|
// exception is super pages. If a valid super page (huge or jumbo) cannot be
|
|
// installed, then the walk will continue to individual entries.
|
|
//
|
|
// This algorithm will attempt to maximize the use of super pages whenever
|
|
// possible. Whether a super page is provided will be clear through the range
|
|
// provided in the callback.
|
|
//
|
|
// Note that if requiresAlloc is true, then no gaps will be present. However,
|
|
// if alloc is not set, then the iteration will likely be full of gaps.
|
|
//
|
|
// Note that this function should generally be avoided in favor of Map, Unmap,
|
|
// etc. when not necessary.
|
|
//
|
|
// Precondition: start must be page-aligned.
|
|
//
|
|
// Precondition: start must be less than end.
|
|
//
|
|
// Precondition: If requiresAlloc is true, then start and end should not span
|
|
// non-canonical ranges. If they do, a panic will result.
|
|
//
|
|
//go:nosplit
|
|
func (w *Walker) iterateRange(start, end uintptr) {
|
|
if start%pteSize != 0 {
|
|
panic("unaligned start")
|
|
}
|
|
if end < start {
|
|
panic("start > end")
|
|
}
|
|
if start < lowerTop {
|
|
if end <= lowerTop {
|
|
w.iterateRangeCanonical(start, end)
|
|
} else if end > lowerTop && end <= upperBottom {
|
|
if w.visitor.requiresAlloc() {
|
|
panic("alloc spans non-canonical range")
|
|
}
|
|
w.iterateRangeCanonical(start, lowerTop)
|
|
} else {
|
|
if w.visitor.requiresAlloc() {
|
|
panic("alloc spans non-canonical range")
|
|
}
|
|
w.iterateRangeCanonical(start, lowerTop)
|
|
w.iterateRangeCanonical(upperBottom, end)
|
|
}
|
|
} else if start < upperBottom {
|
|
if end <= upperBottom {
|
|
if w.visitor.requiresAlloc() {
|
|
panic("alloc spans non-canonical range")
|
|
}
|
|
} else {
|
|
if w.visitor.requiresAlloc() {
|
|
panic("alloc spans non-canonical range")
|
|
}
|
|
w.iterateRangeCanonical(upperBottom, end)
|
|
}
|
|
} else {
|
|
w.iterateRangeCanonical(start, end)
|
|
}
|
|
}
|
|
|
|
// next returns the next address quantized by the given size.
|
|
//
|
|
//go:nosplit
|
|
func next(start uintptr, size uintptr) uintptr {
|
|
start &= ^(size - 1)
|
|
start += size
|
|
return start
|
|
}
|
|
|
|
// iterateRangeCanonical walks a canonical range.
|
|
//
|
|
//go:nosplit
|
|
func (w *Walker) iterateRangeCanonical(start, end uintptr) {
|
|
for pgdIndex := uint16((start & pgdMask) >> pgdShift); start < end && pgdIndex < entriesPerPage; pgdIndex++ {
|
|
var (
|
|
pgdEntry = &w.pageTables.root[pgdIndex]
|
|
pudEntries *PTEs
|
|
)
|
|
if !pgdEntry.Valid() {
|
|
if !w.visitor.requiresAlloc() {
|
|
// Skip over this entry.
|
|
start = next(start, pgdSize)
|
|
continue
|
|
}
|
|
|
|
// Allocate a new pgd.
|
|
pudEntries = w.pageTables.Allocator.NewPTEs()
|
|
pgdEntry.setPageTable(w.pageTables, pudEntries)
|
|
} else {
|
|
pudEntries = w.pageTables.Allocator.LookupPTEs(pgdEntry.Address())
|
|
}
|
|
|
|
// Map the next level.
|
|
clearPUDEntries := uint16(0)
|
|
|
|
for pudIndex := uint16((start & pudMask) >> pudShift); start < end && pudIndex < entriesPerPage; pudIndex++ {
|
|
var (
|
|
pudEntry = &pudEntries[pudIndex]
|
|
pmdEntries *PTEs
|
|
)
|
|
if !pudEntry.Valid() {
|
|
if !w.visitor.requiresAlloc() {
|
|
// Skip over this entry.
|
|
clearPUDEntries++
|
|
start = next(start, pudSize)
|
|
continue
|
|
}
|
|
|
|
// This level has 1-GB super pages. Is this
|
|
// entire region at least as large as a single
|
|
// PUD entry? If so, we can skip allocating a
|
|
// new page for the pmd.
|
|
if start&(pudSize-1) == 0 && end-start >= pudSize {
|
|
pudEntry.SetSuper()
|
|
w.visitor.visit(uintptr(start), pudEntry, pudSize-1)
|
|
if pudEntry.Valid() {
|
|
start = next(start, pudSize)
|
|
continue
|
|
}
|
|
}
|
|
|
|
// Allocate a new pud.
|
|
pmdEntries = w.pageTables.Allocator.NewPTEs()
|
|
pudEntry.setPageTable(w.pageTables, pmdEntries)
|
|
|
|
} else if pudEntry.IsSuper() {
|
|
// Does this page need to be split?
|
|
if w.visitor.requiresSplit() && (start&(pudSize-1) != 0 || end < next(start, pudSize)) {
|
|
// Install the relevant entries.
|
|
pmdEntries = w.pageTables.Allocator.NewPTEs()
|
|
for index := uint16(0); index < entriesPerPage; index++ {
|
|
pmdEntries[index].SetSuper()
|
|
pmdEntries[index].Set(
|
|
pudEntry.Address()+(pmdSize*uintptr(index)),
|
|
pudEntry.Opts())
|
|
}
|
|
pudEntry.setPageTable(w.pageTables, pmdEntries)
|
|
} else {
|
|
// A super page to be checked directly.
|
|
w.visitor.visit(uintptr(start), pudEntry, pudSize-1)
|
|
|
|
// Might have been cleared.
|
|
if !pudEntry.Valid() {
|
|
clearPUDEntries++
|
|
}
|
|
|
|
// Note that the super page was changed.
|
|
start = next(start, pudSize)
|
|
continue
|
|
}
|
|
} else {
|
|
pmdEntries = w.pageTables.Allocator.LookupPTEs(pudEntry.Address())
|
|
}
|
|
|
|
// Map the next level, since this is valid.
|
|
clearPMDEntries := uint16(0)
|
|
|
|
for pmdIndex := uint16((start & pmdMask) >> pmdShift); start < end && pmdIndex < entriesPerPage; pmdIndex++ {
|
|
var (
|
|
pmdEntry = &pmdEntries[pmdIndex]
|
|
pteEntries *PTEs
|
|
)
|
|
if !pmdEntry.Valid() {
|
|
if !w.visitor.requiresAlloc() {
|
|
// Skip over this entry.
|
|
clearPMDEntries++
|
|
start = next(start, pmdSize)
|
|
continue
|
|
}
|
|
|
|
// This level has 2-MB huge pages. If this
|
|
// region is contined in a single PMD entry?
|
|
// As above, we can skip allocating a new page.
|
|
if start&(pmdSize-1) == 0 && end-start >= pmdSize {
|
|
pmdEntry.SetSuper()
|
|
w.visitor.visit(uintptr(start), pmdEntry, pmdSize-1)
|
|
if pmdEntry.Valid() {
|
|
start = next(start, pmdSize)
|
|
continue
|
|
}
|
|
}
|
|
|
|
// Allocate a new pmd.
|
|
pteEntries = w.pageTables.Allocator.NewPTEs()
|
|
pmdEntry.setPageTable(w.pageTables, pteEntries)
|
|
|
|
} else if pmdEntry.IsSuper() {
|
|
// Does this page need to be split?
|
|
if w.visitor.requiresSplit() && (start&(pmdSize-1) != 0 || end < next(start, pmdSize)) {
|
|
// Install the relevant entries.
|
|
pteEntries = w.pageTables.Allocator.NewPTEs()
|
|
for index := uint16(0); index < entriesPerPage; index++ {
|
|
pteEntries[index].Set(
|
|
pmdEntry.Address()+(pteSize*uintptr(index)),
|
|
pmdEntry.Opts())
|
|
}
|
|
pmdEntry.setPageTable(w.pageTables, pteEntries)
|
|
} else {
|
|
// A huge page to be checked directly.
|
|
w.visitor.visit(uintptr(start), pmdEntry, pmdSize-1)
|
|
|
|
// Might have been cleared.
|
|
if !pmdEntry.Valid() {
|
|
clearPMDEntries++
|
|
}
|
|
|
|
// Note that the huge page was changed.
|
|
start = next(start, pmdSize)
|
|
continue
|
|
}
|
|
} else {
|
|
pteEntries = w.pageTables.Allocator.LookupPTEs(pmdEntry.Address())
|
|
}
|
|
|
|
// Map the next level, since this is valid.
|
|
clearPTEEntries := uint16(0)
|
|
|
|
for pteIndex := uint16((start & pteMask) >> pteShift); start < end && pteIndex < entriesPerPage; pteIndex++ {
|
|
var (
|
|
pteEntry = &pteEntries[pteIndex]
|
|
)
|
|
if !pteEntry.Valid() && !w.visitor.requiresAlloc() {
|
|
clearPTEEntries++
|
|
start += pteSize
|
|
continue
|
|
}
|
|
|
|
// At this point, we are guaranteed that start%pteSize == 0.
|
|
w.visitor.visit(uintptr(start), pteEntry, pteSize-1)
|
|
if !pteEntry.Valid() {
|
|
if w.visitor.requiresAlloc() {
|
|
panic("PTE not set after iteration with requiresAlloc!")
|
|
}
|
|
clearPTEEntries++
|
|
}
|
|
|
|
// Note that the pte was changed.
|
|
start += pteSize
|
|
continue
|
|
}
|
|
|
|
// Check if we no longer need this page.
|
|
if clearPTEEntries == entriesPerPage {
|
|
pmdEntry.Clear()
|
|
w.pageTables.Allocator.FreePTEs(pteEntries)
|
|
clearPMDEntries++
|
|
}
|
|
}
|
|
|
|
// Check if we no longer need this page.
|
|
if clearPMDEntries == entriesPerPage {
|
|
pudEntry.Clear()
|
|
w.pageTables.Allocator.FreePTEs(pmdEntries)
|
|
clearPUDEntries++
|
|
}
|
|
}
|
|
|
|
// Check if we no longer need this page.
|
|
if clearPUDEntries == entriesPerPage {
|
|
pgdEntry.Clear()
|
|
w.pageTables.Allocator.FreePTEs(pudEntries)
|
|
}
|
|
}
|
|
}
|