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authorSergey Senozhatsky <sergey.senozhatsky.work@gmail.com>2017-12-21 08:41:49 +0300
committerPetr Mladek <pmladek@suse.com>2018-01-04 16:51:27 +0300
commitcca10d58d25d271f05e1115132b4c2d913bb652e (patch)
tree2059453edfde11b30d3da83871024ebccf7aa0cd /kernel/printk
parent11ca75d2d6d18d5a7ee4d7ec1da6f864f5c8c8be (diff)
downloadlinux-cca10d58d25d271f05e1115132b4c2d913bb652e.tar.xz
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>
Diffstat (limited to 'kernel/printk')
-rw-r--r--kernel/printk/printk.c23
1 files changed, 22 insertions, 1 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5d81206a572d..568729e0dc2c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -277,6 +277,13 @@ EXPORT_SYMBOL(console_set_on_cmdline);
/* Flag: console code may call schedule() */
static int console_may_schedule;
+enum con_msg_format_flags {
+ MSG_FORMAT_DEFAULT = 0,
+ MSG_FORMAT_SYSLOG = (1 << 0),
+};
+
+static int console_msg_format = MSG_FORMAT_DEFAULT;
+
/*
* The printk log buffer consists of a chain of concatenated variable
* length records. Every record starts with a record header, containing
@@ -1913,6 +1920,17 @@ static int __add_preferred_console(char *name, int idx, char *options,
c->index = idx;
return 0;
}
+
+static int __init console_msg_format_setup(char *str)
+{
+ if (!strcmp(str, "syslog"))
+ console_msg_format = MSG_FORMAT_SYSLOG;
+ if (!strcmp(str, "default"))
+ console_msg_format = MSG_FORMAT_DEFAULT;
+ return 1;
+}
+__setup("console_msg_format=", console_msg_format_setup);
+
/*
* Set up a console. Called via do_early_param() in init/main.c
* for each "console=" parameter in the boot command line.
@@ -2215,7 +2233,10 @@ skip:
goto skip;
}
- len += msg_print_text(msg, false, text + len, sizeof(text) - len);
+ len += msg_print_text(msg,
+ console_msg_format & MSG_FORMAT_SYSLOG,
+ text + len,
+ sizeof(text) - len);
if (nr_ext_console_drivers) {
ext_len = msg_print_ext_header(ext_text,
sizeof(ext_text),