Allow to specify a separate log for GO's runtime messages

GO's runtime calls the write system call twice to print "panic:"
and "the reason of this panic", so here is a race window when
other threads can print something to the log and we will see
something like this:

panic: log messages from another thread
The reason of the panic.

This confuses the syzkaller blacklist and dedup detection.

It also makes the logs generally difficult to read. e.g.,
data races often have one side of the race, followed by
a large "diagnosis" dump, finally followed by the other
side of the race.

PiperOrigin-RevId: 297887895

1 files changed, 18 insertions, 0 deletions

diff --git a/runsc/sandbox/sandbox.go b/runsc/sandbox/sandbox.go
index ec72bdbfd..67e27df4d 100644
--- a/runsc/sandbox/sandbox.go
+++ b/runsc/sandbox/sandbox.go
@@ -369,6 +369,24 @@ func (s *Sandbox) createSandboxProcess(conf *boot.Config, args *Args, startSyncF
 		cmd.Args = append(cmd.Args, "--debug-log-fd="+strconv.Itoa(nextFD))
 		nextFD++
 	}
+	if conf.PanicLog != "" {
+		test := ""
+		if len(conf.TestOnlyTestNameEnv) != 0 {
+			// Fetch test name if one is provided and the test only flag was set.
+			if t, ok := specutils.EnvVar(args.Spec.Process.Env, conf.TestOnlyTestNameEnv); ok {
+				test = t
+			}
+		}
+
+		panicLogFile, err := specutils.DebugLogFile(conf.PanicLog, "panic", test)
+		if err != nil {
+			return fmt.Errorf("opening debug log file in %q: %v", conf.PanicLog, err)
+		}
+		defer panicLogFile.Close()
+		cmd.ExtraFiles = append(cmd.ExtraFiles, panicLogFile)
+		cmd.Args = append(cmd.Args, "--panic-log-fd="+strconv.Itoa(nextFD))
+		nextFD++
+	}
 
 	cmd.Args = append(cmd.Args, "--panic-signal="+strconv.Itoa(int(syscall.SIGTERM)))