Allow to change logging options using 'runsc debug'

New options are:
  runsc debug --strace=off|all|function1,function2
  runsc debug --log-level=warning|info|debug
  runsc debug --log-packets=true|false

Updates #407

PiperOrigin-RevId: 254843128

2 files changed, 139 insertions, 0 deletions

diff --git a/pkg/sentry/control/BUILD b/pkg/sentry/control/BUILD
index 15a1fe8a9..5dccb8e3c 100644
--- a/pkg/sentry/control/BUILD
+++ b/pkg/sentry/control/BUILD
@@ -6,6 +6,7 @@ go_library(
     name = "control",
     srcs = [
         "control.go",
+        "logging.go",
         "pprof.go",
         "proc.go",
         "state.go",
@@ -26,8 +27,10 @@ go_library(
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/limits",
         "//pkg/sentry/state",
+        "//pkg/sentry/strace",
         "//pkg/sentry/usage",
         "//pkg/sentry/watchdog",
+        "//pkg/tcpip/link/sniffer",
         "//pkg/urpc",
     ],
 )
diff --git a/pkg/sentry/control/logging.go b/pkg/sentry/control/logging.go
new file mode 100644
index 000000000..811f24324
--- /dev/null
+++ b/pkg/sentry/control/logging.go
@@ -0,0 +1,136 @@
+// Copyright 2019 The gVisor Authors.
+//
+// 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 control
+
+import (
+	"fmt"
+	"sync/atomic"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sentry/strace"
+	"gvisor.dev/gvisor/pkg/tcpip/link/sniffer"
+)
+
+// LoggingArgs are the arguments to use for changing the logging
+// level and strace list.
+type LoggingArgs struct {
+	// SetLevel is a flag used to indicate that we should update
+	// the logging level. We should be able to change the strace
+	// list without affecting the logging level and vice versa.
+	SetLevel bool
+
+	// Level is the log level that will be set if SetLevel is true.
+	Level log.Level
+
+	// SetLogPackets indicates that we should update the log packets flag.
+	SetLogPackets bool
+
+	// LogPackets is the actual value to set for LogPackets.
+	// SetLogPackets must be enabled to indicate that we're changing
+	// the value.
+	LogPackets bool
+
+	// SetStrace is a flag used to indicate that strace related
+	// arguments were passed in.
+	SetStrace bool
+
+	// EnableStrace is a flag from the CLI that specifies whether to
+	// enable strace at all. If this flag is false then a completely
+	// pristine copy of the syscall table will be swapped in. This
+	// approach is used to remain consistent with an empty strace
+	// whitelist meaning trace all system calls.
+	EnableStrace bool
+
+	// Strace is the whitelist of syscalls to trace to log. If this
+	// and StraceEventWhitelist are empty trace all system calls.
+	StraceWhitelist []string
+
+	// SetEventStrace is a flag used to indicate that event strace
+	// related arguments were passed in.
+	SetEventStrace bool
+
+	// StraceEventWhitelist is the whitelist of syscalls to trace
+	// to event log.
+	StraceEventWhitelist []string
+}
+
+// Logging provides functions related to logging.
+type Logging struct{}
+
+// Change will change the log level and strace arguments. Although
+// this functions signature requires an error it never acctually
+// return san error. It's required by the URPC interface.
+// Additionally, it may look odd that this is the only method
+// attached to an empty struct but this is also part of how
+// URPC dispatches.
+func (l *Logging) Change(args *LoggingArgs, code *int) error {
+	if args.SetLevel {
+		// Logging uses an atomic for the level so this is thread safe.
+		log.SetLevel(args.Level)
+	}
+
+	if args.SetLogPackets {
+		if args.LogPackets {
+			atomic.StoreUint32(&sniffer.LogPackets, 1)
+		} else {
+			atomic.StoreUint32(&sniffer.LogPackets, 0)
+		}
+		log.Infof("LogPackets set to: %v", atomic.LoadUint32(&sniffer.LogPackets))
+	}
+
+	if args.SetStrace {
+		if err := l.configureStrace(args); err != nil {
+			return fmt.Errorf("error configuring strace: %v", err)
+		}
+	}
+
+	if args.SetEventStrace {
+		if err := l.configureEventStrace(args); err != nil {
+			return fmt.Errorf("error configuring event strace: %v", err)
+		}
+	}
+
+	return nil
+}
+
+func (l *Logging) configureStrace(args *LoggingArgs) error {
+	if args.EnableStrace {
+		// Install the whitelist specified.
+		if len(args.StraceWhitelist) > 0 {
+			if err := strace.Enable(args.StraceWhitelist, strace.SinkTypeLog); err != nil {
+				return err
+			}
+		} else {
+			// For convenience, if strace is enabled but whitelist
+			// is empty, enable everything to log.
+			strace.EnableAll(strace.SinkTypeLog)
+		}
+	} else {
+		// Uninstall all strace functions.
+		strace.Disable(strace.SinkTypeLog)
+	}
+	return nil
+}
+
+func (l *Logging) configureEventStrace(args *LoggingArgs) error {
+	if len(args.StraceEventWhitelist) > 0 {
+		if err := strace.Enable(args.StraceEventWhitelist, strace.SinkTypeEvent); err != nil {
+			return err
+		}
+	} else {
+		strace.Disable(strace.SinkTypeEvent)
+	}
+	return nil
+}