Re: kernel CI: printk loglevels in kernel boot logs?

[Fengguang Wu]

On Thu, Nov 23, 2017 at 11:59:57AM +0900, Sergey Senozhatsky wrote:
> On (11/22/17 20:52), Fengguang Wu wrote:
> [..]
> > > well, I think that that "consoles_format=syslog" command line parameter
> > > will be enabled only by those who actually want to have it - Fengguang's
> > > build robot and kernelCI (+ may be more setups).  so I'd probably assume
> > > there are low risks here. may be I'm wrong.
> >
> > Yes, since it needs explicit enabling, local parsers should stay
> > working. Unless we send dmesg to other developers, but then they
> > might also receive $(dmesg --raw) outputs and need to handle <%u>
> > prefixes, too.
> >
> > > I think it makes sense to have syslog's format "<%u>[timestamp] text\n"
> > > on serial consoles (time stamp when PRINTK_TIME set; <%u> when
> > > consoles_format=syslog set).
> >
> > Thanks. Since the 0day scripts can already parse that format (code
> > is listed below), we should quickly benefit from that feature when
> > it's mainlined.
>
> okay... who's going to send the patch? kernelCI folks?
>
> I have some sort of a patch. added console_msg_format= with the only

The patch looks good to me. Perhaps you can send it out after getting
review comments from kernelci folks?

Reviewed-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>

Thanks,
Fengguang

> available option so far - "syslog". may be people would want to have
> boot time, etc. on their consoles. who knows. may be msg_format will
> be extended someday in the future or may be not, and we can do
> something like "console_format_syslog" (or any better name).
>
> Not-yet-signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++
> kernel/printk/printk.c                          | 21 ++++++++++++++++++++-
> 2 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 62436bd5f34a..42113e5181b2 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -640,6 +640,17 @@
> 			console=brl,ttyS0
> 		For now, only VisioBraille is supported.
>
> +	console_msg_format=
> +			[KNL] Control message format
> +			By default we print messages 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 (similar to "dmesg --raw" or
> +			reading from /proc/kmsg): "<%u>[time stamp] text\n"
> +			IOW, each message is getting prepended with the
> +			facility and loglevel prefix.
> +
> 	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 5d81206a572d..034f3ad85f5b 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 = 1,
> +	MSG_FORMAT_SYSLOG = 2,
> +};
> +
> +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 +1920,15 @@ 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;
> +	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 +2231,10 @@ 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),
> --
> 2.15.0