1 files changed, 168 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_timer.go b/pkg/sentry/syscalls/linux/sys_timer.go
new file mode 100644
index 000000000..4ed077626
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_timer.go
@@ -0,0 +1,168 @@
+// 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 linux
+
+import (
+	"syscall"
+	"time"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// ItimerType denotes the type of interval timer.
+type ItimerType int
+
+// Interval timer types from <sys/time.h>.
+const (
+	// ItimerReal equals to ITIMER_REAL.
+	ItimerReal ItimerType = iota
+	// ItimerVirtual equals to ITIMER_VIRTUAL.
+	ItimerVirtual
+	// ItimerProf equals to ITIMER_PROF.
+	ItimerProf
+)
+
+const nsecPerSec = int64(time.Second)
+
+// copyItimerValIn copies an ItimerVal from the untrusted app range to the
+// kernel.  The ItimerVal may be either 32 or 64 bits.
+// A NULL address is allowed because because Linux allows
+// setitimer(which, NULL, &old_value) which disables the timer.
+// There is a KERN_WARN message saying this misfeature will be removed.
+// However, that hasn't happened as of 3.19, so we continue to support it.
+func copyItimerValIn(t *kernel.Task, addr usermem.Addr) (linux.ItimerVal, error) {
+	if addr == usermem.Addr(0) {
+		return linux.ItimerVal{}, nil
+	}
+
+	switch t.Arch().Width() {
+	case 8:
+		// Native size, just copy directly.
+		var itv linux.ItimerVal
+		if _, err := t.CopyIn(addr, &itv); err != nil {
+			return linux.ItimerVal{}, err
+		}
+
+		return itv, nil
+	default:
+		return linux.ItimerVal{}, syscall.ENOSYS
+	}
+}
+
+// copyItimerValOut copies an ItimerVal to the untrusted app range.
+// The ItimerVal may be either 32 or 64 bits.
+// A NULL address is allowed, in which case no copy takes place
+func copyItimerValOut(t *kernel.Task, addr usermem.Addr, itv *linux.ItimerVal) error {
+	if addr == usermem.Addr(0) {
+		return nil
+	}
+
+	switch t.Arch().Width() {
+	case 8:
+		// Native size, just copy directly.
+		_, err := t.CopyOut(addr, itv)
+		return err
+	default:
+		return syscall.ENOSYS
+	}
+}
+
+func findTimer(t *kernel.Task, w ItimerType) (*ktime.Timer, error) {
+	switch w {
+	case ItimerReal:
+		return t.ThreadGroup().Timer().RealTimer, nil
+	case ItimerVirtual:
+		return t.ThreadGroup().Timer().VirtualTimer, nil
+	case ItimerProf:
+		return t.ThreadGroup().Timer().ProfTimer, nil
+	default:
+		return nil, syscall.EINVAL
+	}
+}
+
+// Getitimer implements linux syscall getitimer(2).
+func Getitimer(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	timerID := ItimerType(args[0].Int())
+	val := args[1].Pointer()
+
+	timer, err := findTimer(t, timerID)
+	if err != nil {
+		return 0, nil, err
+	}
+	value, interval := ktime.SpecFromSetting(timer.Get())
+	olditv := linux.ItimerVal{
+		Value:    linux.DurationToTimeval(value),
+		Interval: linux.DurationToTimeval(interval),
+	}
+
+	return 0, nil, copyItimerValOut(t, val, &olditv)
+}
+
+// Setitimer implements linux syscall setitimer(2).
+func Setitimer(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	timerID := ItimerType(args[0].Int())
+	newVal := args[1].Pointer()
+	oldVal := args[2].Pointer()
+
+	timer, err := findTimer(t, timerID)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	itv, err := copyItimerValIn(t, newVal)
+	if err != nil {
+		return 0, nil, err
+	}
+	// Just like linux, we cap the timer value and interval with the max
+	// number that int64 can represent which is roughly 292 years.
+	s, err := ktime.SettingFromSpec(itv.Value.ToDuration(),
+		itv.Interval.ToDuration(), timer.Clock())
+	if err != nil {
+		return 0, nil, err
+	}
+
+	valueNS, intervalNS := ktime.SpecFromSetting(timer.Swap(s))
+	olditv := linux.ItimerVal{
+		Value:    linux.DurationToTimeval(valueNS),
+		Interval: linux.DurationToTimeval(intervalNS),
+	}
+
+	return 0, nil, copyItimerValOut(t, oldVal, &olditv)
+}
+
+// Alarm implements linux syscall alarm(2).
+func Alarm(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	duration := time.Duration(args[0].Uint()) * time.Second
+
+	timer := t.ThreadGroup().Timer().RealTimer
+	s, err := ktime.SettingFromSpec(duration, 0, timer.Clock())
+	if err != nil {
+		return 0, nil, err
+	}
+
+	value, _ := ktime.SpecFromSetting(timer.Swap(s))
+	sec := int64(value) / nsecPerSec
+	nsec := int64(value) % nsecPerSec
+	// We can't return 0 if we have an alarm pending ...
+	if (sec == 0 && nsec > 0) || nsec >= nsecPerSec/2 {
+		sec++
+	}
+
+	return uintptr(sec), nil, nil
+}