Merge release-20210125.0-61-gf884ea13b (automated)

1 files changed, 183 insertions, 0 deletions

diff --git a/pkg/ring0/pagetables/pagetables_x86.go b/pkg/ring0/pagetables/pagetables_x86.go
new file mode 100644
index 000000000..32edd2f0a
--- /dev/null
+++ b/pkg/ring0/pagetables/pagetables_x86.go
@@ -0,0 +1,183 @@
+// 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 386 amd64
+
+package pagetables
+
+import (
+	"sync/atomic"
+
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// archPageTables is architecture-specific data.
+type archPageTables struct {
+	// pcid is the value assigned by PCIDs.Assign.
+	//
+	// Note that zero is a valid PCID.
+	pcid uint16
+}
+
+// CR3 returns the CR3 value for these tables.
+//
+// This may be called in interrupt contexts. A PCID of zero always implies a
+// flush and should be passed when PCIDs are not enabled. See pcids_x86.go for
+// more information.
+//
+//go:nosplit
+func (p *PageTables) CR3(noFlush bool, pcid uint16) uint64 {
+	// Bit 63 is set to avoid flushing the PCID (per SDM 4.10.4.1).
+	const noFlushBit uint64 = 0x8000000000000000
+	if noFlush && pcid != 0 {
+		return noFlushBit | uint64(p.rootPhysical) | uint64(pcid)
+	}
+	return uint64(p.rootPhysical) | uint64(pcid)
+}
+
+// Bits in page table entries.
+const (
+	present      = 0x001
+	writable     = 0x002
+	user         = 0x004
+	writeThrough = 0x008
+	cacheDisable = 0x010
+	accessed     = 0x020
+	dirty        = 0x040
+	super        = 0x080
+	global       = 0x100
+	optionMask   = executeDisable | 0xfff
+)
+
+// MapOpts are x86 options.
+type MapOpts struct {
+	// AccessType defines permissions.
+	AccessType usermem.AccessType
+
+	// Global indicates the page is globally accessible.
+	Global bool
+
+	// User indicates the page is a user page.
+	User bool
+}
+
+// PTE is a page table entry.
+type PTE uintptr
+
+// Clear clears this PTE, including super page information.
+//
+//go:nosplit
+func (p *PTE) Clear() {
+	atomic.StoreUintptr((*uintptr)(p), 0)
+}
+
+// Valid returns true iff this entry is valid.
+//
+//go:nosplit
+func (p *PTE) Valid() bool {
+	return atomic.LoadUintptr((*uintptr)(p))&present != 0
+}
+
+// Opts returns the PTE options.
+//
+// These are all options except Valid and Super.
+//
+//go:nosplit
+func (p *PTE) Opts() MapOpts {
+	v := atomic.LoadUintptr((*uintptr)(p))
+	return MapOpts{
+		AccessType: usermem.AccessType{
+			Read:    v&present != 0,
+			Write:   v&writable != 0,
+			Execute: v&executeDisable == 0,
+		},
+		Global: v&global != 0,
+		User:   v&user != 0,
+	}
+}
+
+// SetSuper sets this page as a super page.
+//
+// The page must not be valid or a panic will result.
+//
+//go:nosplit
+func (p *PTE) SetSuper() {
+	if p.Valid() {
+		// This is not allowed.
+		panic("SetSuper called on valid page!")
+	}
+	atomic.StoreUintptr((*uintptr)(p), super)
+}
+
+// IsSuper returns true iff this page is a super page.
+//
+//go:nosplit
+func (p *PTE) IsSuper() bool {
+	return atomic.LoadUintptr((*uintptr)(p))&super != 0
+}
+
+// Set sets this PTE value.
+//
+// This does not change the super page property.
+//
+//go:nosplit
+func (p *PTE) Set(addr uintptr, opts MapOpts) {
+	if !opts.AccessType.Any() {
+		p.Clear()
+		return
+	}
+	v := (addr &^ optionMask)
+	if opts.AccessType.Any() {
+		v |= present | accessed
+	}
+	if opts.User {
+		v |= user
+	}
+	if opts.Global {
+		v |= global
+	}
+	if !opts.AccessType.Execute {
+		v |= executeDisable
+	}
+	if opts.AccessType.Write {
+		v |= writable | dirty
+	}
+	if p.IsSuper() {
+		// Note that this is inherited from the previous instance. Set
+		// does not change the value of Super. See above.
+		v |= super
+	}
+	atomic.StoreUintptr((*uintptr)(p), v)
+}
+
+// setPageTable sets this PTE value and forces the write bit and super bit to
+// be cleared. This is used explicitly for breaking super pages.
+//
+//go:nosplit
+func (p *PTE) setPageTable(pt *PageTables, ptes *PTEs) {
+	addr := pt.Allocator.PhysicalFor(ptes)
+	if addr&^optionMask != addr {
+		// This should never happen.
+		panic("unaligned physical address!")
+	}
+	v := addr | present | user | writable | accessed | dirty
+	atomic.StoreUintptr((*uintptr)(p), v)
+}
+
+// Address extracts the address. This should only be used if Valid returns true.
+//
+//go:nosplit
+func (p *PTE) Address() uintptr {
+	return atomic.LoadUintptr((*uintptr)(p)) &^ optionMask
+}