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probe.go
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probe.go
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package ftrace
import (
"errors"
"fmt"
"strings"
"sync"
)
const (
maxArguments = 16
enabledStatusFile = "/proc/sys/kernel/ftrace_enabled"
systemProbesFile = "/sys/kernel/debug/tracing/kprobe_events"
eventsPipeFile = "/sys/kernel/debug/tracing/trace_pipe"
probeFileFormat = "/sys/kernel/debug/tracing/events/kprobes/%s/enable"
eventFileFormat = "/sys/kernel/debug/tracing/events/%s/enable"
)
var errUnavailable = errors.New("FTRACE kernel framework not available on your system")
// Probe represents a FTRACE probe to a system call and optional sub events.
type Probe struct {
sync.RWMutex
// custom name of the probe
name string
// probe status file name
fileName string
// syscall to intercept
syscall string
// ftrace descriptor of the probe
descriptor string
// kernel sub events
events map[string]string
// probe status
enabled bool
// pipe file reader
pipe chan string
// channel used to signal from the worker
done chan bool
// channel where events are sent
bus chan Event
}
// NewProbe creates a new probe with a custom name for the given syscall and optional sub events.
func NewProbe(name string, syscall string, subEvents []string) *Probe {
return &Probe{
name: name,
fileName: fmt.Sprintf(probeFileFormat, name),
syscall: syscall,
descriptor: makeDescriptor(name, syscall),
events: mapSubevents(subEvents),
enabled: false,
pipe: nil,
done: make(chan bool),
bus: make(chan Event),
}
}
// Enabled return true if this probe is enabled and running, otherwise false.
func (p *Probe) Enabled() bool {
p.RLock()
defer p.RUnlock()
return p.enabled
}
// Events returns a channel where FTRACE events will be written by this Probe worker routine.
func (p *Probe) Events() <-chan Event {
return p.bus
}
func (p *Probe) selectEvent(event string) bool {
// main probe event
if strings.Contains(event, p.name) {
return true
}
// one of the sub events
for eventName := range p.events {
if strings.Contains(event, eventName) {
return true
}
}
return false
}
func (p *Probe) worker() {
// signal we're done when we exit
defer func() {
p.done <- true
}()
for eventLine := range p.pipe {
// our parent go routine is telling us to quit
if eventLine == "<quit>" {
break
}
// check if we're interested in this event
if p.selectEvent(eventLine) {
// parse the raw event data
if event, err := parseEvent(eventLine); err != nil {
fmt.Printf("Error while parsing event: %s\n", err)
} else {
p.bus <- event
}
}
}
}
// Enable enables this probe and starts its async worker routine in order to read FTRACE events.
func (p *Probe) Enable() (err error) {
p.Lock()
defer p.Unlock()
if p.enabled == true {
return nil
}
if Available() == false {
return errUnavailable
}
// enable all events
for eventName, eventFileName := range p.events {
if err = writeFile(eventFileName, "1"); err != nil {
return fmt.Errorf("Error while enabling event %s: %s", eventName, err)
}
}
// create the custom kprobe consumer
if err = writeFile(systemProbesFile, p.descriptor); err != nil {
return fmt.Errorf("Error while enabling probe descriptor for %s: %s", p.name, err)
}
// enable the probe
if err = writeFile(p.fileName, "1"); err != nil {
return fmt.Errorf("Error while enable probe %s: %s", p.name, err)
}
// create the handle to the pipe file
if p.pipe, err = asyncFileReader(eventsPipeFile); err != nil {
return fmt.Errorf("Error while opening %s: %s", eventsPipeFile, err)
}
p.enabled = true
// start the async worker that will read events from the
// pipe file and send them to the `bus` channel
go p.worker()
return nil
}
// Reset disables this probe.
func (p *Probe) Reset() error {
// disable all events
for eventName, eventFileName := range p.events {
if err := writeFile(eventFileName, "0"); err != nil {
return fmt.Errorf("Error while disabling event %s: %s", eventName, err)
}
}
// disable the probe itself
if err := writeFile(p.fileName, "0"); err != nil {
return fmt.Errorf("Error while disabling probe %s: %s", p.name, err)
}
// remove the probe from the system
if err := appendFile(systemProbesFile, fmt.Sprintf("-:%s", p.name)); err != nil {
return fmt.Errorf("Error while removing the probe %s: %s", p.name, err)
}
return nil
}
// Disable disables this probe and stops its async worker.
func (p *Probe) Disable() error {
p.Lock()
defer p.Unlock()
if p.enabled == false {
return nil
}
if err := p.Reset(); err != nil {
return err
}
p.enabled = false
p.pipe <- "<quit>"
// wait for the worker to finish
<-p.done
return nil
}