printk: guard the amount written per line by devkmsg_read()

This patchset updates netconsole so that it can emit messages with the
same header as used in /dev/kmsg which gives neconsole receiver full log
information which enables things like structured logging and detection
of lost messages.

This patch (of 7):

devkmsg_read() uses 8k buffer and assumes that the formatted output
message won't overrun which seems safe given LOG_LINE_MAX, the current use
of dict and the escaping method being used; however, we're planning to use
devkmsg formatting wider and accounting for the buffer size properly isn't
that complicated.

This patch defines CONSOLE_EXT_LOG_MAX as 8192 and updates devkmsg_read()
so that it limits output accordingly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David Miller <davem@davemloft.net>
Cc: Kay Sievers <kay@vrfy.org>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 9b30871c9149..58b1fec40d37 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -30,6 +30,8 @@ static inline const char *printk_skip_level(const char *buffer)
 	return buffer;
 }
 
+#define CONSOLE_EXT_LOG_MAX	8192
+
 /* printk's without a loglevel use this.. */
 #define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT