Move ring0 package.

This allows the package to serve as a general purpose ring0 support package, as
opposed to being bound to specific sentry platforms.

Updates #5039

PiperOrigin-RevId: 355220044

1 files changed, 71 insertions, 0 deletions

diff --git a/pkg/ring0/pagetables/pagetables_arm64.go b/pkg/ring0/pagetables/pagetables_arm64.go
new file mode 100644
index 000000000..fef7a0fd1
--- /dev/null
+++ b/pkg/ring0/pagetables/pagetables_arm64.go
@@ -0,0 +1,71 @@
+// Copyright 2019 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.
+
+package pagetables
+
+// Address constraints.
+//
+// The lowerTop and upperBottom currently apply to four-level pagetables;
+// additional refactoring would be necessary to support five-level pagetables.
+const (
+	lowerTop    = 0x0000ffffffffffff
+	upperBottom = 0xffff000000000000
+	pteShift    = 12
+	pmdShift    = 21
+	pudShift    = 30
+	pgdShift    = 39
+
+	pteMask = 0x1ff << pteShift
+	pmdMask = 0x1ff << pmdShift
+	pudMask = 0x1ff << pudShift
+	pgdMask = 0x1ff << pgdShift
+
+	pteSize = 1 << pteShift
+	pmdSize = 1 << pmdShift
+	pudSize = 1 << pudShift
+	pgdSize = 1 << pgdShift
+
+	ttbrASIDOffset = 48
+	ttbrASIDMask   = 0xff
+
+	entriesPerPage = 512
+)
+
+// InitArch does some additional initialization related to the architecture.
+//
+// +checkescape:hard,stack
+//go:nosplit
+func (p *PageTables) InitArch(allocator Allocator) {
+	if p.upperSharedPageTables != nil {
+		p.cloneUpperShared()
+	} else {
+		p.archPageTables.root = p.Allocator.NewPTEs()
+		p.archPageTables.rootPhysical = p.Allocator.PhysicalFor(p.archPageTables.root)
+	}
+}
+
+// cloneUpperShared clone the upper from the upper shared page tables.
+//
+//go:nosplit
+func (p *PageTables) cloneUpperShared() {
+	if p.upperStart != upperBottom {
+		panic("upperStart should be the same as upperBottom")
+	}
+
+	p.archPageTables.root = p.upperSharedPageTables.archPageTables.root
+	p.archPageTables.rootPhysical = p.upperSharedPageTables.archPageTables.rootPhysical
+}
+
+// PTEs is a collection of entries.
+type PTEs [entriesPerPage]PTE