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// 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 (
"errors"
"runtime"
"runtime/pprof"
"runtime/trace"
"sync"
"gvisor.dev/gvisor/pkg/fd"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/urpc"
)
var errNoOutput = errors.New("no output writer provided")
// ProfileOpts contains options for the StartCPUProfile/Goroutine RPC call.
type ProfileOpts struct {
// File is the filesystem path for the profile.
File string `json:"path"`
// FilePayload is the destination for the profiling output.
urpc.FilePayload
}
// Profile includes profile-related RPC stubs. It provides a way to
// control the built-in pprof facility in sentry via sentryctl.
//
// The following options to sentryctl are added:
//
// - collect CPU profile on-demand.
// sentryctl -pid <pid> pprof-cpu-start
// sentryctl -pid <pid> pprof-cpu-stop
//
// - dump out the stack trace of current go routines.
// sentryctl -pid <pid> pprof-goroutine
type Profile struct {
// mu protects the fields below.
mu sync.Mutex
// cpuFile is the current CPU profile output file.
cpuFile *fd.FD
// traceFile is the current execution trace output file.
traceFile *fd.FD
// Kernel is the kernel under profile.
Kernel *kernel.Kernel
}
// StartCPUProfile is an RPC stub which starts recording the CPU profile in a
// file.
func (p *Profile) StartCPUProfile(o *ProfileOpts, _ *struct{}) error {
if len(o.FilePayload.Files) < 1 {
return errNoOutput
}
output, err := fd.NewFromFile(o.FilePayload.Files[0])
if err != nil {
return err
}
p.mu.Lock()
defer p.mu.Unlock()
// Returns an error if profiling is already started.
if err := pprof.StartCPUProfile(output); err != nil {
output.Close()
return err
}
p.cpuFile = output
return nil
}
// StopCPUProfile is an RPC stub which stops the CPU profiling and flush out the
// profile data. It takes no argument.
func (p *Profile) StopCPUProfile(_, _ *struct{}) error {
p.mu.Lock()
defer p.mu.Unlock()
if p.cpuFile == nil {
return errors.New("CPU profiling not started")
}
pprof.StopCPUProfile()
p.cpuFile.Close()
p.cpuFile = nil
return nil
}
// HeapProfile generates a heap profile for the sentry.
func (p *Profile) HeapProfile(o *ProfileOpts, _ *struct{}) error {
if len(o.FilePayload.Files) < 1 {
return errNoOutput
}
output := o.FilePayload.Files[0]
defer output.Close()
runtime.GC() // Get up-to-date statistics.
if err := pprof.WriteHeapProfile(output); err != nil {
return err
}
return nil
}
// Goroutine is an RPC stub which dumps out the stack trace for all running
// goroutines.
func (p *Profile) Goroutine(o *ProfileOpts, _ *struct{}) error {
if len(o.FilePayload.Files) < 1 {
return errNoOutput
}
output := o.FilePayload.Files[0]
defer output.Close()
if err := pprof.Lookup("goroutine").WriteTo(output, 2); err != nil {
return err
}
return nil
}
// StartTrace is an RPC stub which starts collection of an execution trace.
func (p *Profile) StartTrace(o *ProfileOpts, _ *struct{}) error {
if len(o.FilePayload.Files) < 1 {
return errNoOutput
}
output, err := fd.NewFromFile(o.FilePayload.Files[0])
if err != nil {
return err
}
p.mu.Lock()
defer p.mu.Unlock()
// Returns an error if profiling is already started.
if err := trace.Start(output); err != nil {
output.Close()
return err
}
// Ensure all trace contexts are registered.
p.Kernel.RebuildTraceContexts()
p.traceFile = output
return nil
}
// StopTrace is an RPC stub which stops collection of an ongoing execution
// trace and flushes the trace data. It takes no argument.
func (p *Profile) StopTrace(_, _ *struct{}) error {
p.mu.Lock()
defer p.mu.Unlock()
if p.traceFile == nil {
return errors.New("Execution tracing not started")
}
// Similarly to the case above, if tasks have not ended traces, we will
// lose information. Thus we need to rebuild the tasks in order to have
// complete information. This will not lose information if multiple
// traces are overlapping.
p.Kernel.RebuildTraceContexts()
trace.Stop()
p.traceFile.Close()
p.traceFile = nil
return nil
}
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