From cca10d58d25d271f05e1115132b4c2d913bb652e Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Thu, 21 Dec 2017 14:41:49 +0900 Subject: printk: add console_msg_format command line option 0day and kernelCI automatically parse kernel log - basically some sort of grepping using the pre-defined text patterns - in order to detect and report regressions/errors. There are several sources they get the kernel logs from: a) dmesg or /proc/ksmg This is the preferred way. Because `dmesg --raw' (see later Note) and /proc/kmsg output contains facility and log level, which greatly simplifies grepping for EMERG/ALERT/CRIT/ERR messages. b) serial consoles This option is harder to maintain, because serial console messages don't contain facility and log level. This patch introduces a `console_msg_format=' command line option, to switch between different message formatting on serial consoles. For the time being we have just two options - default and syslog. The "default" option just keeps the existing format. While the "syslog" option makes serial console messages to appear in syslog format [syslog() syscall], matching the `dmesg -S --raw' and `cat /proc/kmsg' output formats: - facility and log level - time stamp (depends on printk_time/PRINTK_TIME) - message <%u>[time stamp] text\n NOTE: while Kevin and Fengguang talk about "dmesg --raw", it's actually "dmesg -S --raw" that always prints messages in syslog format [per Petr Mladek]. Running "dmesg --raw" may produce output in non-syslog format sometimes. console_msg_format=syslog enables syslog format, thus in documentation we mention "dmesg -S --raw", not "dmesg --raw". Per Kevin Hilman: : Right now we can get this info from a "dmesg --raw" after bootup, : but it would be really nice in certain automation frameworks to : have a kernel command-line option to enable printing of loglevels : in default boot log. : : This is especially useful when ingesting kernel logs into advanced : search/analytics frameworks (I'm playing with and ELK stack: Elastic : Search, Logstash, Kibana). : : The other important reason for having this on the command line is that : for testing linux-next (and other bleeding edge developer branches), : it's common that we never make it to userspace, so can't even run : "dmesg --raw" (or equivalent.) So we really want this on the primary : boot (serial) console. Per Fengguang Wu, 0day scripts should quickly benefit from that feature, because they will be able to switch to a more reliable parsing, based on messages' facility and log levels [1]: `#{grep} -a -E -e '^<[0123]>' -e '^kern :(err |crit |alert |emerg )' instead of doing text pattern matching `#{grep} -a -F -f /lkp/printk-error-messages #{kmsg_file} | grep -a -v -E -f #{LKP_SRC}/etc/oops-pattern | grep -a -v -F -f #{LKP_SRC}/etc/kmsg-blacklist` [1] https://github.com/fengguang/lkp-tests/blob/master/lib/dmesg.rb Link: http://lkml.kernel.org/r/20171221054149.4398-1-sergey.senozhatsky@gmail.com To: Steven Rostedt Cc: Linus Torvalds Cc: Fengguang Wu Cc: Kevin Hilman Cc: Mark Brown Cc: Greg Kroah-Hartman Cc: Andrew Morton Cc: LKML Signed-off-by: Sergey Senozhatsky Reviewed-by: Fengguang Wu Reviewed-by: Kevin Hilman Tested-by: Kevin Hilman Signed-off-by: Petr Mladek --- Documentation/admin-guide/kernel-parameters.txt | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'Documentation/admin-guide/kernel-parameters.txt') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 62436bd5f34a..af614995b71d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -640,6 +640,20 @@ console=brl,ttyS0 For now, only VisioBraille is supported. + console_msg_format= + [KNL] Change console messages format + default + By default we print messages on consoles in + "[time stamp] text\n" format (time stamp may not be + printed, depending on CONFIG_PRINTK_TIME or + `printk_time' param). + syslog + Switch to syslog format: "<%u>[time stamp] text\n" + IOW, each message will have a facility and loglevel + prefix. The format is similar to one used by syslog() + syscall, or to executing "dmesg -S --raw" or to reading + from /proc/kmsg. + consoleblank= [KNL] The console blank (screen saver) timeout in seconds. A value of 0 disables the blank timer. Defaults to 0. -- cgit