Return better "error" values for UWX_BOTTOM and UWX_ABI_FRAME in

unw_step(). Both errors denote the end of a stack trace (i.e. no
prior frame), but are otherwise not error conditions.
Have db_trace() return 0 when the trace ends due to one of these
return codes as they are really normal termination conditions.

This change especially improves the output of the "show thread"
command in DDB when there are threads in fork_trampoline() and
previously db_trace() would return an error, causing the show
command to emit '***'.

2 files changed, 21 insertions, 6 deletions

diff --git a/sys/ia64/ia64/db_trace.c b/sys/ia64/ia64/db_trace.c
index f90e0e9..1dae4da 100644
--- a/sys/ia64/ia64/db_trace.c
+++ b/sys/ia64/ia64/db_trace.c
@@ -106,7 +106,7 @@ db_backtrace(struct thread *td, struct pcb *pcb, int count)
 		db_printsym(ip, DB_STGY_PROC);
 		db_printf("\n");
 
-		if (error != EOVERFLOW)
+		if (error != ERESTART)
 			continue;
 		if (sp < IA64_RR_BASE(5))
 			break;
@@ -123,7 +123,11 @@ db_backtrace(struct thread *td, struct pcb *pcb, int count)
 	}
 
 	unw_delete(&rs);
-	return (error);
+	/*
+	 * EJUSTRETURN and ERESTART signal the end of a trace and
+	 * are not really errors.
+	 */
+	return ((error > 0) ? error : 0);
 }
 
 void
diff --git a/sys/ia64/ia64/unwind.c b/sys/ia64/ia64/unwind.c
index 69a3fa2..6343ed8 100644
--- a/sys/ia64/ia64/unwind.c
+++ b/sys/ia64/ia64/unwind.c
@@ -380,10 +380,21 @@ unw_step(struct unw_regstate *rs)
 {
 	int err;
 
-	err = uwx_step(rs->env);
-	if (err == UWX_ABI_FRAME)
-		return (EOVERFLOW);
-	return ((err != 0) ? EINVAL : 0);	/* XXX */
+	switch (uwx_step(rs->env)) {
+	case UWX_ABI_FRAME:
+		err = ERESTART;
+		break;
+	case UWX_BOTTOM:
+		err = EJUSTRETURN;
+		break;
+	case UWX_OK:
+		err = 0;
+		break;
+	default:
+		err = EINVAL;		/* XXX */
+		break;
+	}
+	return (err);
 }
 
 int