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SubjectRe: kernel CI: printk loglevels in kernel boot logs?
Date
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> writes:

> 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
> 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@gmail.com>

For kernelCI (part of how this thread got started):

Acked-by: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>

I also tested it on an arm64 platform with the new command-line arg:

Tested-by: Kevin Hilman <khilman@baylibre.com>

Thanks,

Kevin

> ---
> 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),

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