From 0f47ac958bf6231f5a8f474ee0b096daaf06051c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Josef=20S=C3=B6ntgen?= <josef.soentgen@genode-labs.com>
Date: Thu, 12 Feb 2015 12:35:37 +0100
Subject: [PATCH] log/serial: handle spurious EOF

While booting up, some devices send garbage over the serial connection.
This can result in an unexpected EOF event within expect(1). A filter
program may be specified with '--log-serial-filter' to circumvent this
problem. Then, the output of the serial program is piped through
the filter, which may sanitize the character stream.

Fixes #1395.
---
 tool/run/log/serial | 38 +++++++++++++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 5 deletions(-)

diff --git a/tool/run/log/serial b/tool/run/log/serial
index e4ddf3eac4..02baa7ce11 100644
--- a/tool/run/log/serial
+++ b/tool/run/log/serial
@@ -1,7 +1,8 @@
 ##
 # Get the output of the target machine via serial connection
 #
-# \param --log-serial-cmd   Cmd that is executed to capture the output
+# \param --log-serial-cmd    Cmd that is executed to capture the output
+# \param --log-serial-filter Sanitize output by piping it through a filter
 #
 
 source [genode_dir]/tool/run/log.inc
@@ -16,6 +17,11 @@ proc log_serial_cmd { } {
 }
 
 
+proc log_serial_filter { } {
+	return [get_cmd_arg --log-serial-filter ""]
+}
+
+
 ##
 # Log output of the test machine via serial device
 #
@@ -24,14 +30,36 @@ proc run_log { wait_for_re timeout_value } {
 
 	set kernel_msg [run_boot_string]
 
-	eval spawn [log_serial_cmd]
+	#
+	# Certain devices send garbage through the serial connection that may
+	# result in an unexpected EOF in expect. This is caused by TCL using the
+	# terminal encoding for the channel to the spawned program and interpreting
+	# the input for conversion to UTF-8. In the case of the serial connection,
+	# this may not be valid with garbage bytes in the character stream. If any
+	# garbage coming from the serial connection is interpreted as the beginning
+	# of a UTF-8 multi-byte sequence but does not resemble the complete
+	# sequence (i.e., is truncated), parsing may result in EOF. To prevent this
+	# from happening one may use a filter that sanitizes the serial output,
+	# i.e., lets only ASCII characters through.
+	#
+	set serial_cmd_chain [log_serial_cmd]
+	if {[get_cmd_switch --log-serial-filter]} {
+		set serial_cmd_chain "$serial_cmd_chain | [log_serial_filter]"
+	}
+
+	#
+	# XXX the initial timeout was estimated by testing and is merely enough
+	#     to load large scenarios via TFTP.
+	#
+	set timeout 210
+
+	spawn /bin/sh -c "$serial_cmd_chain"
 	set output_spawn_id $spawn_id
 
-	set timeout 210
 	expect {
-		$kernel_msg { }
+		-i $output_spawn_id $kernel_msg { }
 		eof         {
-			puts stderr "Serial command process died unexpectedly"
+			puts stderr "Aborting, received EOF"
 			return false
 		}
 		timeout     {