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// 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))
}
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