Add 'runsc debug' command

It prints sandbox stacks to the log to help debug stuckness. I expect
that many more options will be added in the future.

PiperOrigin-RevId: 201405931
Change-Id: I87e560800cd5a5a7b210dc25a5661363c8c3a16e

3 files changed, 35 insertions, 0 deletions

diff --git a/runsc/boot/BUILD b/runsc/boot/BUILD
index 8b3b09a22..924cc2b90 100644
--- a/runsc/boot/BUILD
+++ b/runsc/boot/BUILD
@@ -7,6 +7,7 @@ go_library(
     srcs = [
         "config.go",
         "controller.go",
+        "debug.go",
         "events.go",
         "fds.go",
         "fs.go",
diff --git a/runsc/boot/controller.go b/runsc/boot/controller.go
index 1a598199d..ec24c4dad 100644
--- a/runsc/boot/controller.go
+++ b/runsc/boot/controller.go
@@ -68,6 +68,9 @@ const (
 	// RootContainerStart is the URPC endpoint for starting a new sandbox
 	// with root container.
 	RootContainerStart = "containerManager.StartRoot"
+
+	// SandboxStacks collects sandbox stacks for debugging.
+	SandboxStacks = "debug.Stacks"
 )
 
 // ControlSocketAddr generates an abstract unix socket name for the given id.
@@ -107,6 +110,8 @@ func newController(fd int, k *kernel.Kernel, w *watchdog.Watchdog) (*controller,
 		srv.Register(net)
 	}
 
+	srv.Register(&debug{})
+
 	if err := srv.StartServing(); err != nil {
 		return nil, err
 	}
diff --git a/runsc/boot/debug.go b/runsc/boot/debug.go
new file mode 100644
index 000000000..971962c91
--- /dev/null
+++ b/runsc/boot/debug.go
@@ -0,0 +1,29 @@
+// 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 boot
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/log"
+)
+
+type debug struct {
+}
+
+// Stacks collects all sandbox stacks and copies them to 'stacks'.
+func (*debug) Stacks(_ *struct{}, stacks *string) error {
+	buf := log.Stacks(true)
+	*stacks = string(buf)
+	return nil
+}