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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Joe Perches <joe@perches.com>,
	Chenggang Wang <wangchenggang@vivo.com>,
	linux-kernel@vger.kernel.org, Petr Mladek <pmladek@suse.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [RFC PATCH 2/2] init: Allow multi-line output of kernel command line
Date: Thu, 21 May 2020 21:48:56 +0900	[thread overview]
Message-ID: <20200521124856.GC755@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <20200520214007.86f36f61e1fc0329b66758ed@linux-foundation.org>

On (20/05/20 21:40), Andrew Morton wrote:
> > On (20/05/20 18:00), Andrew Morton wrote:
> > [..]
> > > 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.
> > 
> > Can you point me at some examples?
> > 
> 
> ./arch/powerpc/kernel/udbg.c:           printk("%s", s);
> ./arch/powerpc/xmon/nonstdio.c:         printk("%s", xmon_outbuf);
> ./arch/um/os-Linux/drivers/ethertap_user.c:             printk("%s", output);
> ./arch/um/os-Linux/drivers/ethertap_user.c:             printk("%s", output);
> ./arch/um/os-Linux/drivers/tuntap_user.c:                       printk("%s", out

Hmm, interesting.

	output = uml_kmalloc(UM_KERN_PAGE_SIZE, UM_GFP_KERNEL);
	read_output(fd, output, UM_KERN_PAGE_SIZE);
	printk("%s", output);
	kfree(output);

> etc.
>
> My point is, if we created a length-unlimited puts() function for printing the
> kernel command line, it could be reused in such places

A function that prints the kernel command line is a bit different
in the way that we can split command line arguments - they are
space separated, which is very convenient - so we would pr_cont()
parts of command line individually. This has an advantage that we
won't \r\n in the middle of the parameter.

Looking at examples, it seems that most of them simply do a single
printk() with arbitrary sized buffers that contain random data,
not necessarily space separated. So same problem - we truncate
messages (maybe?), but needs a slightly different solution (?).

	-ss

  parent reply	other threads:[~2020-05-21 12:49 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19  3:29 [PATCH] init/main.c: Print all command line when boot 王程刚
2020-05-19  3:44 ` Andrew Morton
2020-05-19  5:09   ` Joe Perches
2020-05-19 14:34     ` Arvind Sankar
2020-05-19 19:42     ` [RFC PATCH 0/2] printk/init: multi-line kernel command line logging Joe Perches
2020-05-19 19:42       ` [RFC PATCH 1/2] printk: Move and rename maximum printk output line length defines Joe Perches
2020-05-21 13:49         ` Petr Mladek
2020-05-19 19:42       ` [RFC PATCH 2/2] init: Allow multi-line output of kernel command line Joe Perches
2020-05-20  4:41         ` Sergey Senozhatsky
2020-05-20  4:58           ` Joe Perches
2020-05-20 12:10             ` Sergey Senozhatsky
2020-05-20 20:36               ` Joe Perches
2020-05-21  1:00                 ` Andrew Morton
2020-05-21  2:09                   ` Joe Perches
2020-05-21  4:36                   ` Sergey Senozhatsky
2020-05-21  4:40                     ` Andrew Morton
2020-05-21 12:31                       ` Petr Mladek
2020-05-21 15:08                         ` Arvind Sankar
2020-05-21 12:48                       ` Sergey Senozhatsky [this message]
2020-05-21  4:32                 ` Sergey Senozhatsky
2020-05-21 13:46         ` Petr Mladek
2020-05-21 15:59         ` Arvind Sankar
2020-05-21 16:09           ` Joe Perches
2020-06-03  8:48         ` [init] d0bcc26c0d: BUG:kernel_hang_in_early-boot_stage,last_printk:early_console_in_setup_code kernel test robot
2020-05-21 18:40       ` [PATCH] printk: Move and rename maximum printk output line length defines Joe Perches
2020-05-25  8:38         ` Sergey Senozhatsky
2020-05-20 14:01 ` [PATCH] init/main.c: Print all command line when boot Masami Hiramatsu

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