1 files changed, 72 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/syscalls.go b/pkg/sentry/syscalls/syscalls.go
new file mode 100644
index 000000000..1176f858d
--- /dev/null
+++ b/pkg/sentry/syscalls/syscalls.go
@@ -0,0 +1,72 @@
+// 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.
+
+// Package syscalls is the interface from the application to the kernel.
+// Traditionally, syscalls is the interface that is used by applications to
+// request services from the kernel of a operating system. We provide a
+// user-mode kernel that needs to handle those requests coming from unmodified
+// applications. Therefore, we still use the term "syscalls" to denote this
+// interface.
+//
+// Note that the stubs in this package may merely provide the interface, not
+// the actual implementation. It just makes writing syscall stubs
+// straightforward.
+package syscalls
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/eventchannel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	uspb "gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/unimplemented_syscall_go_proto"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// Error returns a syscall handler that will always give the passed error.
+func Error(err error) kernel.SyscallFn {
+	return func(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+		return 0, nil, err
+	}
+}
+
+// ErrorWithEvent gives a syscall function that sends an unimplemented
+// syscall event via the event channel and returns the passed error.
+func ErrorWithEvent(err error) kernel.SyscallFn {
+	return func(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+		UnimplementedEvent(t)
+		return 0, nil, err
+	}
+}
+
+// CapError gives a syscall function that checks for capability c.  If the task
+// has the capability, it returns ENOSYS, otherwise EPERM. To unprivileged
+// tasks, it will seem like there is an implementation.
+func CapError(c linux.Capability) kernel.SyscallFn {
+	return func(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+		if !t.HasCapability(c) {
+			return 0, nil, syserror.EPERM
+		}
+		UnimplementedEvent(t)
+		return 0, nil, syserror.ENOSYS
+	}
+}
+
+// UnimplementedEvent emits an UnimplementedSyscall event via the event
+// channel.
+func UnimplementedEvent(t *kernel.Task) {
+	eventchannel.Emit(&uspb.UnimplementedSyscall{
+		Tid:       int32(t.ThreadID()),
+		Registers: t.Arch().StateData().Proto(),
+	})
+}