1 files changed, 58 insertions, 0 deletions
diff --git a/pkg/sentry/arch/signal_stack.go b/pkg/sentry/arch/signal_stack.go
new file mode 100644
index 000000000..7c6531d79
--- /dev/null
+++ b/pkg/sentry/arch/signal_stack.go
@@ -0,0 +1,58 @@
+// Copyright 2018 Google Inc.
+//
+// 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 i386 amd64
+
+package arch
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+const (
+	// SignalStackFlagOnStack is possible set on return from getaltstack,
+	// in order to indicate that the thread is currently on the alt stack.
+	SignalStackFlagOnStack = 1
+
+	// SignalStackFlagDisable is a flag to indicate the stack is disabled.
+	SignalStackFlagDisable = 2
+)
+
+// IsEnabled returns true iff this signal stack is marked as enabled.
+func (s SignalStack) IsEnabled() bool {
+	return s.Flags&SignalStackFlagDisable == 0
+}
+
+// Top returns the stack's top address.
+func (s SignalStack) Top() usermem.Addr {
+	return usermem.Addr(s.Addr + s.Size)
+}
+
+// SetOnStack marks this signal stack as in use. (This is only called on copies
+// sent to user applications, so there's no corresponding ClearOnStack.)
+func (s *SignalStack) SetOnStack() {
+	s.Flags |= SignalStackFlagOnStack
+}
+
+// NativeSignalStack is a type that is equivalent to stack_t in the guest
+// architecture.
+type NativeSignalStack interface {
+	// SerializeFrom copies the data in the host SignalStack s into this
+	// object.
+	SerializeFrom(s *SignalStack)
+
+	// DeserializeTo copies the data in this object into the host SignalStack
+	// s.
+	DeserializeTo(s *SignalStack)
+}