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 <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Kevin Hilman <khilman@baylibre.com> Cc: Mark Brown <broonie@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: LKML <linux-kernel@vger.kernel.org> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Reviewed-by: Kevin Hilman <khilman@baylibre.com> Tested-by: Kevin Hilman <khilman@baylibre.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
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@ -640,6 +640,20 @@
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console=brl,ttyS0
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console=brl,ttyS0
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For now, only VisioBraille is supported.
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For now, only VisioBraille is supported.
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console_msg_format=
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[KNL] Change console messages format
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default
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By default we print messages on consoles in
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"[time stamp] text\n" format (time stamp may not be
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printed, depending on CONFIG_PRINTK_TIME or
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`printk_time' param).
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syslog
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Switch to syslog format: "<%u>[time stamp] text\n"
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IOW, each message will have a facility and loglevel
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prefix. The format is similar to one used by syslog()
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syscall, or to executing "dmesg -S --raw" or to reading
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from /proc/kmsg.
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consoleblank= [KNL] The console blank (screen saver) timeout in
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consoleblank= [KNL] The console blank (screen saver) timeout in
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seconds. A value of 0 disables the blank timer.
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seconds. A value of 0 disables the blank timer.
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Defaults to 0.
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Defaults to 0.
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@ -277,6 +277,13 @@ EXPORT_SYMBOL(console_set_on_cmdline);
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/* Flag: console code may call schedule() */
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/* Flag: console code may call schedule() */
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static int console_may_schedule;
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static int console_may_schedule;
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enum con_msg_format_flags {
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MSG_FORMAT_DEFAULT = 0,
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MSG_FORMAT_SYSLOG = (1 << 0),
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};
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static int console_msg_format = MSG_FORMAT_DEFAULT;
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/*
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/*
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* The printk log buffer consists of a chain of concatenated variable
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* The printk log buffer consists of a chain of concatenated variable
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* length records. Every record starts with a record header, containing
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* length records. Every record starts with a record header, containing
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@ -1913,6 +1920,17 @@ static int __add_preferred_console(char *name, int idx, char *options,
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c->index = idx;
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c->index = idx;
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return 0;
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return 0;
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}
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}
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static int __init console_msg_format_setup(char *str)
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{
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if (!strcmp(str, "syslog"))
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console_msg_format = MSG_FORMAT_SYSLOG;
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if (!strcmp(str, "default"))
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console_msg_format = MSG_FORMAT_DEFAULT;
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return 1;
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}
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__setup("console_msg_format=", console_msg_format_setup);
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/*
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/*
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* Set up a console. Called via do_early_param() in init/main.c
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* Set up a console. Called via do_early_param() in init/main.c
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* for each "console=" parameter in the boot command line.
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* for each "console=" parameter in the boot command line.
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@ -2215,7 +2233,10 @@ skip:
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goto skip;
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goto skip;
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}
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}
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len += msg_print_text(msg, false, text + len, sizeof(text) - len);
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len += msg_print_text(msg,
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console_msg_format & MSG_FORMAT_SYSLOG,
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text + len,
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sizeof(text) - len);
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if (nr_ext_console_drivers) {
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if (nr_ext_console_drivers) {
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ext_len = msg_print_ext_header(ext_text,
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ext_len = msg_print_ext_header(ext_text,
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sizeof(ext_text),
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sizeof(ext_text),
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