linux-kernel - Re: [PATCH 0/3][RESEND] add support for never printing hashed addresses

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Date:   Thu, 11 Feb 2021 02:41:29 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Timur Tabi <timur@...nel.org>, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        akpm@...ux-foundation.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        roman.fietze@...na.com, Kees Cook <keescook@...omium.org>,
        John Ogness <john.ogness@...utronix.de>,
        akinobu.mita@...il.com, glider@...gle.com,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 0/3][RESEND] add support for never printing hashed
 addresses

On 2021/02/11 1:54, Andy Shevchenko wrote:
> On Thu, Feb 11, 2021 at 01:39:41AM +0900, Tetsuo Handa wrote:
>> On 2021/02/11 1:18, Steven Rostedt wrote:
>>> The point of this exercise is to be able to debug the *same* kernel that
>>> someone is having issues with. And this is to facilitate that debugging.
>>
>> That's too difficult to use. If a problem is not reproducible, we will have
>> no choice but always specify "never hash pointers" command line option. If a
>> problem is reproducible, we can rebuild that kernel with "never hash pointers"
>> config option turned on.
> 
> I think what you are targeting is something like dynamic debug approach where
> you can choose which prints to enable/disable and what enable/disable in them.

What I'm targeting is "zero interaction from kernel command line options" like
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/usb/usbip?id=f1bdf414e7dd0cbc26460425719fc3ea479947a2 .

> 
> In that case you specifically apply a command line option and enable only files
> / lines in the files.

While there is boot-config feature for specifying very long kernel command line
options, I can't enforce syzkaller users (including syzbot) to switch what to
enable/disable via kernel command line options. Let alone defining a kernel
command line option for single-purpose debug printk() changes like shown above.