Date: Fri, 18 Jun 2004 21:53:55 +0100
From: matthew-lkml@newtoncomputing.co.uk
To: linux-kernel@vger.kernel.org
Cc: torvalds@osdl.org
Subject: [PATCH] Stop printk printing non-printable chars
Message-ID: <20040618205355.GA5286@newtoncomputing.co.uk>
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Hi,

I have had problems recently with the output from dmesg. Somewhere in
the depths of ACPI (drivers/acpi/tables.c:104) the
header->asl_compiler_id contained non-printable characters, and it made
xterm stop displaying any more output. dmesg|less had to be used as less
filters out the duff chars.

The main problem seems to be in ACPI, but I don't see any reason for
printk to even consider printing _any_ non-printable characters at all.
It makes all characters out of the range 32..126 (except for newline)
print as a '?'.

Patch is for 2.6.7.

Matthew


--- linux-2.6.7/kernel/printk.c.orig	2004-06-18 20:44:28.000000000 +0100
+++ linux-2.6.7/kernel/printk.c	2004-06-18 20:53:36.000000000 +0100
@@ -14,6 +14,8 @@
  *     manfreds@colorfullife.com
  * Rewrote bits to get rid of console_lock
  *	01Mar01 Andrew Morton <andrewm@uow.edu.au>
+ * Stop emit_log_char from emitting non-ASCII chars.
+ *  Matthew Newton, 18 June 2004 <matthew-lkml@newtoncomputing.co.uk>
  */
 
 #include <linux/kernel.h>
@@ -538,7 +540,11 @@
 			}
 			log_level_unknown = 0;
 		}
-		emit_log_char(*p);
+		if (p[0] != '\n' && (p[0] < 32 || p[0] > 126)) {
+			emit_log_char('?');
+		} else {
+			emit_log_char(*p);
+		}
 		if (*p == '\n')
 			log_level_unknown = 1;
 	}


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