kdb: Avoid printing KERN_ levels to consoles

Currently when kdb traps printk messages then the raw log level prefix
(consisting of '\001' followed by a numeral) does not get stripped off
before the message is issued to the various I/O handlers supported by
kdb. This causes annoying visual noise as well as causing problems
grepping for ^. It is also a change of behaviour compared to normal usage
of printk() usage. For example <SysRq>-h ends up with different output to
that of kdb's "sr h".

This patch addresses the problem by stripping log levels from messages
before they are issued to the I/O handlers. printk() which can also
act as an i/o handler in some cases is special cased; if the caller
provided a log level then the prefix will be preserved when sent to
printk().

The addition of non-printable characters to the output of kdb commands is a
regression, albeit and extremely elderly one, introduced by commit
04d2c8c83d0e ("printk: convert the format for KERN_<LEVEL> to a 2 byte
pattern"). Note also that this patch does *not* restore the original
behaviour from v3.5. Instead it makes printk() from within a kdb command
display the message without any prefix (i.e. like printk() normally does).

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 02d6b6d..fae29e3 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1811,7 +1811,7 @@ int vprintk_default(const char *fmt, va_list args)
 
 #ifdef CONFIG_KGDB_KDB
 	if (unlikely(kdb_trap_printk)) {
-		r = vkdb_printf(fmt, args);
+		r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
 		return r;
 	}
 #endif