linux-kernel - Re: [PATCH v5] kernel/trace: Add DISALLOW_TRACE

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Date:   Mon, 24 Aug 2020 16:42:01 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     David Laight <David.Laight@...lab.com>,
        'Nicolas Boichat' <drinkcat@...omium.org>,
        "dianders@...omium.org" <dianders@...omium.org>,
        "groeck@...omium.org" <groeck@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        "Guilherme G. Piccoli" <gpiccoli@...onical.com>,
        Kars Mulder <kerneldev@...smulder.nl>,
        Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Will Deacon <will@...nel.org>, Yue Hu <huyue2@...ong.com>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5] kernel/trace: Add DISALLOW_TRACE_PRINTK make option

On Mon, Aug 24, 2020 at 09:28:28AM -0400, Steven Rostedt wrote:
> On Mon, 24 Aug 2020 08:26:13 +0000
> David Laight <David.Laight@...LAB.COM> wrote:
> 
> > Since the objective seems to be to ensure there are no
> > calls to trace_printk() in the git tree, but to allow
> > them in uncommitted sources. Why not use a config option
> > and rely on rand-config builds to detect any 'accidental'
> > commits?
> 
> Because we don't want distros to ship with disallowing trace_printk,
> where someone finds a bug, sends the config to a developer, who then
> adds trace_printk() just to find that they can't use it.
> 
> The point of avoiding a config was to keep the burden of having the
> developer needing it and having to then modify the config given to them.
> 
> Also, it would then prevent those developing modules from using
> trace_printk() in their module if they build against one of these
> kernels.
> 
> Finally, there's debug code in the kernel that legitimately uses
> trace_printk(), and those randconfigs will trigger on them.

How making it make's option prevent some "smart" distros to achieve the same?
AFAIU any compile-time knob will allow to build a kernel w/o a feature and you
are against of such kernel builds in distros. Catch-22?

-- 
With Best Regards,
Andy Shevchenko