diff options
| -rw-r--r-- | pkg/sentry/sighandling/sighandling.go | 50 |
1 files changed, 35 insertions, 15 deletions
diff --git a/pkg/sentry/sighandling/sighandling.go b/pkg/sentry/sighandling/sighandling.go index 1a94b535b..0c3a14da5 100644 --- a/pkg/sentry/sighandling/sighandling.go +++ b/pkg/sentry/sighandling/sighandling.go @@ -29,23 +29,31 @@ import ( // numSignals is the number of normal (non-realtime) signals on Linux. const numSignals = 32 -// forwardSignals listens for incoming signals and delivers them to k. It stops -// when the stop channel is closed. -func forwardSignals(k *kernel.Kernel, sigchans []chan os.Signal, stop chan struct{}) { +// forwardSignals listens for incoming signals and delivers them to k. It starts +// when the start channel is closed and stops when the stop channel is closed. +func forwardSignals(k *kernel.Kernel, sigchans []chan os.Signal, start, stop chan struct{}) { // Build a select case. - sc := []reflect.SelectCase{{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(stop)}} + sc := []reflect.SelectCase{{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(start)}} for _, sigchan := range sigchans { sc = append(sc, reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(sigchan)}) } + started := false for { // Wait for a notification. index, _, ok := reflect.Select(sc) - // Was it the stop channel? + // Was it the start / stop channel? if index == 0 { if !ok { - break + if started { + // stop channel + break + } else { + // start channel + started = true + sc[0] = reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(stop)} + } } continue } @@ -57,18 +65,18 @@ func forwardSignals(k *kernel.Kernel, sigchans []chan os.Signal, stop chan struc // Otherwise, it was a signal on channel N. Index 0 represents the stop // channel, so index N represents the channel for signal N. - if !k.SendExternalSignal(&arch.SignalInfo{Signo: int32(index)}, "sentry") { + if !started || !k.SendExternalSignal(&arch.SignalInfo{Signo: int32(index)}, "sentry") { // Kernel is not ready to receive signals. // // Kill ourselves if this signal would have killed the - // process before StartForwarding was called. i.e., all + // process before PrepareForwarding was called. i.e., all // _SigKill signals; see Go // src/runtime/sigtab_linux_generic.go. // // Otherwise ignore the signal. // // TODO: Convert Go's runtime.raise from - // tkill to tgkill so StartForwarding doesn't need to + // tkill to tgkill so PrepareForwarding doesn't need to // be called until after filter installation. switch linux.Signal(index) { case linux.SIGHUP, linux.SIGINT, linux.SIGTERM: @@ -84,9 +92,11 @@ func forwardSignals(k *kernel.Kernel, sigchans []chan os.Signal, stop chan struc } } -// StartForwarding ensures that synchronous signals are forwarded to k and -// returns a callback that stops signal forwarding. -func StartForwarding(k *kernel.Kernel) func() { +// PrepareForwarding ensures that synchronous signals are forwarded to k and +// returns a callback that starts signal delivery, which itself returns a +// callback that stops signal forwarding. +func PrepareForwarding(k *kernel.Kernel) func() func() { + start := make(chan struct{}) stop := make(chan struct{}) // Register individual channels. One channel per standard signal is @@ -109,8 +119,18 @@ func StartForwarding(k *kernel.Kernel) func() { signal.Notify(sigchan, syscall.Signal(sig)) } // Start up our listener. - go forwardSignals(k, sigchans, stop) // S/R-SAFE: synchronized by Kernel.extMu + go forwardSignals(k, sigchans, start, stop) // S/R-SAFE: synchronized by Kernel.extMu + + return func() func() { + close(start) + return func() { + close(stop) + } + } +} - // ... shouldn't this wait until the forwardSignals goroutine returns? - return func() { close(stop) } +// StartForwarding ensures that synchronous signals are forwarded to k and +// returns a callback that stops signal forwarding. +func StartForwarding(k *kernel.Kernel) func() { + return PrepareForwarding(k)() } |