all: start/stop flight recorder conditionally

Author: ignoramous

intra/core/dontpanic.go

@@ -65,7 +65,7 @@ func RecoverFn(aux string, fn Finally) (didpanic bool) {
 	msg := fmt.Sprintf("%s [%d] %v\n", aux, DontExit, recovered)
 	log.E2(parentCallerDepthAt+1, msg)
 
-	runtimelog()
+	recorderToConsole()
 	applog(DontExit, msg)
 	return didpanic
 }
@@ -86,8 +86,12 @@ func Record(start bool) (recording bool, err error) {
 	return
 }
 
+func recorderToConsole() (logged bool) {
+	return DumpRecorder(true /* onConsole */)
+}
+
 // Logs Cmsg using recoder.WriteTo
-func runtimelog() (logged bool) {
+func DumpRecorder(onConsole bool) (logged bool) {
 	if !recorder.Enabled() {
 		return
 	}
@@ -104,10 +108,14 @@ func runtimelog() (logged bool) {
 	}()
 
 	r := bytes.NewBuffer(lob)
-	n, err := recorder.WriteTo(r)
+	n, _ := recorder.WriteTo(r)
 
 	if logged = n > 0; logged {
-		log.Cmsg("%s\n%v", r.String(), err)
+		if onConsole {
+			log.Cmsg(r.String())
+		} else {
+			log.TALL(r.String(), nil /* no-stacktrace*/)
+		}
 	}
 
 	return
@@ -125,7 +133,7 @@ func Recover(code ExitCode, aux any) (didpanic bool) {
 	msg := fmt.Sprintf("%s [%d] %v [%s]\n", aux, code, recovered, stamp())
 	log.E2(parentCallerDepthAt, msg)
 
-	runtimelog()
+	recorderToConsole()
 	applog(code, msg)
 	return didpanic
 }

intra/log/log.go

@@ -190,7 +190,7 @@ func T(msg string, args ...any) {
 // TALL logs the stack trace of all active goroutines.
 func TALL(msg string, atleast64k []byte) {
 	E2(callerat, "----START----")
-	Glogger.Stack(callerat, msg, atleast64k)
+	Glogger.Stack(callerat, msg, atleast64k /*may be nil*/)
 	E2(callerat, "----STOPP----")
 }
 

intra/log/logger.go

@@ -34,6 +34,7 @@ package log
 import (
 	"context"
 	"fmt"
+	"hash/fnv"
 	golog "log"
 	"os"
 	"reflect"
@@ -73,7 +74,7 @@ type simpleLogger struct {
 	cskips atomic.Uint32 // number of dropped console msgs
 
 	stmu    sync.Mutex        // guards stcount
-	stcount map[string]uint32 // stack trace counter for identical traces
+	stcount map[uint64]uint32 // stack trace counter for identical traces
 
 	o *golog.Logger
 	e *golog.Logger
@@ -241,7 +242,7 @@ func defaultLogger() *simpleLogger {
 		level:   defaultLevel,
 		clevel:  defaultClevel,
 		cmsgC:   make(chan *conMsg, consoleChSize),
-		stcount: make(map[string]uint32),
+		stcount: make(map[uint64]uint32),
 		// gomobile pipes stderr & stdout to logcat
 		// github.com/golang/mobile/blob/fa72addaaa/internal/mobileinit/mobileinit_android.go#L74-L92
 		e: golog.New(os.Stderr, "", defaultFlags),
@@ -291,12 +292,23 @@ func (l *simpleLogger) clearStCounts() {
 	clear(l.stcount)
 }
 
+// xor fold fnv to 48 bits: www.isthe.com/chongo/tech/comp/fnv
+func fhash(b []byte) uint64 {
+	h := fnv.New64a()
+	_, _ = h.Write(b)
+	return h.Sum64()
+}
+
 func (l *simpleLogger) incrStCount(id string) (c uint32) {
 	l.stmu.Lock()
 	defer l.stmu.Unlock()
 
-	c = l.stcount[id]
-	l.stcount[id]++
+	if len(id) > 500 {
+		id = id[:500]
+	}
+	loc := fhash([]byte(id))
+	c = l.stcount[loc]
+	l.stcount[loc]++
 	return c
 }
 

intra/tun2socks.go

@@ -116,10 +116,15 @@ func LogLevel(gologLevel, consolelogLevel int32) {
 		debug.SetTraceback(one.s())
 	}
 
-	recording, recerr := core.Record(dbg)
+	log.I("tun: new levels; golog: %d, consolelog: %d; debug? %t",
+		dlvl, clvl, dbg)
+}
 
-	log.I("tun: new levels; golog: %d, consolelog: %d; debug? %t, recording? %t, recorder error: %v",
-		dlvl, clvl, dbg, recording, recerr)
+// FlightRecorder starts Go runtime's flight recorder if y is true,
+// and stops it if y is false. The contents of the flight recorder
+// (limited to 15s) is written to log.Console on panics.
+func FlightRecorder(y bool) (bool, error) {
+	return core.Record(y)
 }
 
 // LowMem triggers garbage collection cycle & allows for
@@ -202,6 +207,13 @@ func PrintStack(onConsole bool) {
 	}
 }
 
+// PrintFlightRecord dumps the contents of the flight recorder
+// to stdout if onConsole is false, otherwise to Console.
+// For testing only.
+func PrintFlightRecord(onConsole bool) (logged bool) {
+	return core.DumpRecorder(onConsole)
+}
+
 // PanicAtRandom instruct portions under test of the network engine
 // to panic at random.
 func PanicAtRandom(y bool) {