[PATCHv2] printk: add console_msg_format command line option

[PATCHv2] printk: add console_msg_format command line option

[Sergey Senozhatsky]

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
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>
---

v2: addressed comments made by Petr Mladek

 Documentation/admin-guide/kernel-parameters.txt | 14 ++++++++++++++
 kernel/printk/printk.c                          | 23 ++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8a61d1eda677..543de386e01e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -642,6 +642,20 @@
 			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.
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c2e713f6ae2e..16dd91260273 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 {
+	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 (!strncmp(str, "syslog", 6))
+		console_msg_format = MSG_FORMAT_SYSLOG;
+	if (!strncmp(str, "default", 7))
+		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 @@ void console_unlock(void)
 			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),
-- 
2.15.1

Re: [PATCHv2] printk: add console_msg_format command line option

[Steven Rostedt]

On Tue, 19 Dec 2017 17:42:43 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:

> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 8a61d1eda677..543de386e01e 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -642,6 +642,20 @@
>  			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.

Just to clarify. This affects all consoles, not just serial?

> +
>  	consoleblank=	[KNL] The console blank (screen saver) timeout in
>  			seconds. A value of 0 disables the blank timer.
>                         Defaults to 0.
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index c2e713f6ae2e..16dd91260273 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 {
> +	MSG_FORMAT_DEFAULT	= 0,
> +	MSG_FORMAT_SYSLOG	= (1 << 0),
> +};

So the con_msg_format will be a flag (as denoted with the (1<<0)).
Should we call it "con_msg_format_flags" to make it more obvious that
these are treated as flags and not a simple number.


> +
> +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 (!strncmp(str, "syslog", 6))
> +		console_msg_format = MSG_FORMAT_SYSLOG;
> +	if (!strncmp(str, "default", 7))

You can use strcmp() instead of strncmp(), the init code will nul
terminate the string for you before calling this function. Otherwise if
we add "syslog_special" or "default_extra" they will be confused with
the above.

-- Steve

> +		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 @@ void console_unlock(void)
>  			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),

Re: [PATCHv2] printk: add console_msg_format command line option

[Sergey Senozhatsky]

Hi,

On (12/19/17 10:17), Steven Rostedt wrote:
[..]
> > +	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.
> 
> Just to clarify. This affects all consoles, not just serial?

yes.

just like printk_time param/config option affects all the consoles,
console_msg_format affects all of them. we msg_print_text() once, that
makes messages look the same on every console. so I kept the existing
behaviour.

[..]
> > +enum con_msg_format {
> > +	MSG_FORMAT_DEFAULT	= 0,
> > +	MSG_FORMAT_SYSLOG	= (1 << 0),
> > +};
> 
> So the con_msg_format will be a flag (as denoted with the (1<<0)).
> Should we call it "con_msg_format_flags" to make it more obvious that
> these are treated as flags and not a simple number.

ok, can do.

[..]
> > +static int __init console_msg_format_setup(char *str)
> > +{
> > +	if (!strncmp(str, "syslog", 6))
> > +		console_msg_format = MSG_FORMAT_SYSLOG;
> > +	if (!strncmp(str, "default", 7))
> 
> You can use strcmp() instead of strncmp(), the init code will nul
> terminate the string for you before calling this function. Otherwise if
> we add "syslog_special" or "default_extra" they will be confused with
> the above.

ok, that's a minor thing, but can change.

	-ss

[PATCHv3] printk: add console_msg_format command line option

[Sergey Senozhatsky]

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
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>
---

v3: addressed comments made by Steven Rostedt
v2: addressed comments made by Petr Mladek

 Documentation/admin-guide/kernel-parameters.txt | 14 ++++++++++++++
 kernel/printk/printk.c                          | 23 ++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8a61d1eda677..543de386e01e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -642,6 +642,20 @@
 			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.
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c2e713f6ae2e..a214759b0fc1 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 @@ void console_unlock(void)
 			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),
-- 
2.15.1

Re: [PATCHv3] printk: add console_msg_format command line option

[Petr Mladek]

On Thu 2017-12-21 14:41:49, Sergey Senozhatsky wrote:
> 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
> 

> 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>

The patch looks and works good for me.

Reviewed-by: Petr Mladek <pmladek@suse.com>

I am going to add it into for-4.16 branch when I am back in January.
The patch is basically innocent. But I do not want to eventually
screw up printk.git with a last minute commit.

Best Regards,
Petr