linux-kernel - Re: [PATCH] arm64: Stop printing the virtual memory layout

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Date:   Thu, 18 Jan 2018 20:20:53 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Laura Abbott <labbott@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] arm64: Stop printing the virtual memory layout

On Thu, Jan 18, 2018 at 12:01:31PM -0800, Florian Fainelli wrote:
> On 12/19/2017 11:28 AM, Laura Abbott wrote:
> > Printing kernel addresses should be done in limited circumstances, mostly
> > for debugging purposes. Printing out the virtual memory layout at every
> > kernel bootup doesn't really fall into this category so delete the prints.
> > There are other ways to get the same information.
> 
> This really has some value when debugging systems, could we possibly
> just hide that behind an appropriate configuration option instead of
> completely removing this?

I've already ended up having to revert the vsprintf() change nobbling
%p for that very reason when debugging the BPF code.  It's easier to
do that while debugging than remember about the %px thing - and lets
face it, probably less error prone if it leaks out.

Otherwise we'll just end up with everyone spelling %p as %px in their
debug statements... or using %lx and casting to unsigned long.

So yes, I do think a Kconfig option (defaulting to obscuring kernel
addresses of course) would have been very sensible for this.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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