app: improve shim process management

This ensures a signal gets delivered to the process instead of relying on parent death behaviour.

SIGCONT was chosen as it is the only signal an unprivileged process is allowed to send to processes with different credentials.

A custom signal handler is installed because the Go runtime does not expose signal information other than which signal was received, and shim must check pid to ensure reasonable behaviour.

Signed-off-by: Ophestra <cat@gensokyo.uk>

1 files changed, 5 insertions, 5 deletions

diff --git a/cmd/fpkg/proc.go b/cmd/fpkg/proc.go
index 311ae4f2..677ddb75 100644
--- a/cmd/fpkg/proc.go
+++ b/cmd/fpkg/proc.go
@@ -13,16 +13,16 @@ func mustRunApp(ctx context.Context, config *fst.Config, beforeFail func()) {
 	rs := new(fst.RunState)
 	a := app.MustNew(ctx, std)
 
+	var code int
 	if sa, err := a.Seal(config); err != nil {
 		fmsg.PrintBaseError(err, "cannot seal app:")
-		rs.ExitCode = 1
+		code = 1
 	} else {
-		// this updates ExitCode
-		app.PrintRunStateErr(rs, sa.Run(rs))
+		code = app.PrintRunStateErr(rs, sa.Run(rs))
 	}
 
-	if rs.ExitCode != 0 {
+	if code != 0 {
 		beforeFail()
-		os.Exit(rs.ExitCode)
+		os.Exit(code)
 	}
 }