linux-kernel - Re: [RFC PATCH 2/2] init: Allow multi-line output of kernel command line

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Date:   Wed, 20 May 2020 18:00:28 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Chenggang Wang <wangchenggang@...o.com>,
        linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC PATCH 2/2] init: Allow multi-line output of kernel command
 line

On Wed, 20 May 2020 13:36:45 -0700 Joe Perches <joe@...ches.com> wrote:

> On Wed, 2020-05-20 at 21:10 +0900, Sergey Senozhatsky wrote:
> > On (20/05/19 21:58), Joe Perches wrote:
> > [..]
> > > >  Maybe we can
> > > > use here something rather random and much shorter instead. E.g.
> > > > 256 chars. Hmm. How 
> > > 
> > > 	min(some_max like 132/256, PRINTK_LOG_LINE_MAX)
> > > 
> > > would work.
> > 
> > An alternative approach would be to do what we do in the
> > print_modules() (the list of modules which can definitely
> > be longer than 1K chars).
> > 
> > We can split command line in a loop - memchr(pos, ' ') - and
> > pr_cont() parts of the command line. pr_cont() has overflow
> > control and it flushes cont buffer before it overflows, so
> > we should not lose anything.
> 
> It doesn't matter much here, but I believe
> there's an 8k max buffer for pr_cont output.
> 
> include/linux/printk.h:#define CONSOLE_EXT_LOG_MAX      8192
> 
> Anyway, no worries, it simplifies the loop if
> done that way.

I'm wondering if we shold add a kernel puts() (putsk()?  yuk) which can
puts() a string of any length.

I'm counting around 150 instances of printk("%s", ...) and pr_foo("%s",
...) which could perhaps be converted, thus saving an argument.