internal/trace: fix int overflow in timestamps

Fixes #15102

Change-Id: I7fdb6464afd0b7af9b6652051416f0fddd34dc9a
Reviewed-on: https://go-review.googlesource.com/21730
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/internal/trace/parser.go b/src/internal/trace/parser.go
index 82ddb8b6c8fdf758d3cdade8ea727d2ca8fbc0b7..3099b0ffebc6be4c2bccae4607df9140b7ac3d70 100644 (file)
--- a/src/internal/trace/parser.go
+++ b/src/internal/trace/parser.go
@@ -372,8 +372,10 @@ func parseEvents(ver int, rawEvents []rawEvent, strings map[uint64]string) (even
                return
        }
        minTs := events[0].Ts
+       // Use floating point to avoid integer overflows.
+       freq := 1e9 / float64(ticksPerSec)
        for _, ev := range events {
-               ev.Ts = (ev.Ts - minTs) * 1e9 / ticksPerSec
+               ev.Ts = int64(float64(ev.Ts-minTs) * freq)
                // Move timers and syscalls to separate fake Ps.
                if timerGoid != 0 && ev.G == timerGoid && ev.Type == EvGoUnblock {
                        ev.P = TimerP

diff --git a/src/internal/trace/parser_test.go b/src/internal/trace/parser_test.go
index db8d2a30cec5887037c2d979b85577b555cacd4e..337d5a85d74e1a33c23f33a5f03563f133ab025e 100644 (file)
--- a/src/internal/trace/parser_test.go
+++ b/src/internal/trace/parser_test.go
@@ -85,3 +85,55 @@ func TestParseVersion(t *testing.T) {
                }
        }
 }
+
+func TestTimestampOverflow(t *testing.T) {
+       // Test that parser correctly handles large timestamps (long tracing).
+       w := newWriter()
+       w.emit(EvBatch, 0, 0, 0)
+       w.emit(EvFrequency, 1e9, 0)
+       for ts := uint64(1); ts < 1e16; ts *= 2 {
+               w.emit(EvGoCreate, 1, ts, ts, 1, 0)
+       }
+       if _, err := Parse(w, ""); err != nil {
+               t.Fatalf("failed to parse: %v", err)
+       }
+}
+
+type writer struct {
+       bytes.Buffer
+}
+
+func newWriter() *writer {
+       w := new(writer)
+       w.Write([]byte("go 1.7 trace\x00\x00\x00\x00"))
+       return w
+}
+
+func (w *writer) emit(typ byte, args ...uint64) {
+       nargs := byte(len(args)) - 2
+       if nargs > 3 {
+               nargs = 3
+       }
+       buf := []byte{typ | nargs<<6}
+       if nargs == 3 {
+               buf = append(buf, 0)
+       }
+       for _, a := range args {
+               buf = appendVarint(buf, a)
+       }
+       if nargs == 3 {
+               buf[1] = byte(len(buf) - 2)
+       }
+       n, err := w.Write(buf)
+       if n != len(buf) || err != nil {
+               panic("failed to write")
+       }
+}
+
+func appendVarint(buf []byte, v uint64) []byte {
+       for ; v >= 0x80; v >>= 7 {
+               buf = append(buf, 0x80|byte(v))
+       }
+       buf = append(buf, byte(v))
+       return buf
+}