1 files changed, 148 insertions, 0 deletions
diff --git a/pkg/sentry/kernel/task_futex.go b/pkg/sentry/kernel/task_futex.go
new file mode 100644
index 000000000..62ebbcb0d
--- /dev/null
+++ b/pkg/sentry/kernel/task_futex.go
@@ -0,0 +1,148 @@
+// 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 kernel
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/futex"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// Futex returns t's futex manager.
+//
+// Preconditions: The caller must be running on the task goroutine, or t.mu
+// must be locked.
+func (t *Task) Futex() *futex.Manager {
+	return t.tc.fu
+}
+
+// FutexChecker returns a futex.Checker that interprets addresses in t's
+// address space.
+//
+// Preconditions: All uses of the returned futex.Checker must be on the task
+// goroutine.
+func (t *Task) FutexChecker() futex.Checker {
+	return futexChecker{t}
+}
+
+type futexChecker struct {
+	t *Task
+}
+
+// Check implements futex.Checker.Check.
+func (f futexChecker) Check(addr uintptr, val uint32) error {
+	// FIXME
+	in := f.t.CopyScratchBuffer(4)
+	_, err := f.t.CopyInBytes(usermem.Addr(addr), in)
+	if err != nil {
+		return err
+	}
+	nval := usermem.ByteOrder.Uint32(in)
+	if val != nval {
+		return syserror.EAGAIN
+	}
+	return nil
+}
+
+func (f futexChecker) atomicOp(addr uintptr, op func(uint32) uint32) (uint32, error) {
+	// FIXME
+	in := f.t.CopyScratchBuffer(4)
+	_, err := f.t.CopyInBytes(usermem.Addr(addr), in)
+	if err != nil {
+		return 0, err
+	}
+	o := usermem.ByteOrder.Uint32(in)
+	mm := f.t.MemoryManager()
+	for {
+		n := op(o)
+		r, err := mm.CompareAndSwapUint32(f.t, usermem.Addr(addr), o, n, usermem.IOOpts{
+			AddressSpaceActive: true,
+		})
+		if err != nil {
+			return 0, err
+		}
+
+		if r == o {
+			return o, nil
+		}
+		o = r
+	}
+}
+
+// Op implements futex.Checker.Op, interpreting opIn consistently with Linux.
+func (f futexChecker) Op(addr uintptr, opIn uint32) (bool, error) {
+	op := (opIn >> 28) & 0xf
+	cmp := (opIn >> 24) & 0xf
+	opArg := (opIn >> 12) & 0xfff
+	cmpArg := opIn & 0xfff
+
+	if op&linux.FUTEX_OP_OPARG_SHIFT != 0 {
+		opArg = 1 << opArg
+		op &^= linux.FUTEX_OP_OPARG_SHIFT // clear flag
+	}
+
+	var oldVal uint32
+	var err error
+	switch op {
+	case linux.FUTEX_OP_SET:
+		oldVal, err = f.t.MemoryManager().SwapUint32(f.t, usermem.Addr(addr), opArg, usermem.IOOpts{
+			AddressSpaceActive: true,
+		})
+	case linux.FUTEX_OP_ADD:
+		oldVal, err = f.atomicOp(addr, func(a uint32) uint32 {
+			return a + opArg
+		})
+	case linux.FUTEX_OP_OR:
+		oldVal, err = f.atomicOp(addr, func(a uint32) uint32 {
+			return a | opArg
+		})
+	case linux.FUTEX_OP_ANDN:
+		oldVal, err = f.atomicOp(addr, func(a uint32) uint32 {
+			return a &^ opArg
+		})
+	case linux.FUTEX_OP_XOR:
+		oldVal, err = f.atomicOp(addr, func(a uint32) uint32 {
+			return a ^ opArg
+		})
+	default:
+		return false, syserror.ENOSYS
+	}
+	if err != nil {
+		return false, err
+	}
+
+	switch cmp {
+	case linux.FUTEX_OP_CMP_EQ:
+		return oldVal == cmpArg, nil
+	case linux.FUTEX_OP_CMP_NE:
+		return oldVal != cmpArg, nil
+	case linux.FUTEX_OP_CMP_LT:
+		return oldVal < cmpArg, nil
+	case linux.FUTEX_OP_CMP_LE:
+		return oldVal <= cmpArg, nil
+	case linux.FUTEX_OP_CMP_GT:
+		return oldVal > cmpArg, nil
+	case linux.FUTEX_OP_CMP_GE:
+		return oldVal >= cmpArg, nil
+	default:
+		return false, syserror.ENOSYS
+	}
+}
+
+// GetSharedKey implements futex.Checker.GetSharedKey.
+func (f futexChecker) GetSharedKey(addr uintptr) (futex.Key, error) {
+	return f.t.MemoryManager().GetSharedFutexKey(f.t, usermem.Addr(addr))
+}