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From:   Kaiwan N Billimoria <kaiwan@kaiwantech.com>
Date:   Sun, 8 Mar 2020 17:47:50 +0530
Message-ID: <CAPDLWs-b0NjDx4A=wdd6aJu84Wrc2wk6QZAf6EYGbqWyy-4ZFw@mail.gmail.com>
Subject: Re: [PATCH] sh: Stop printing the virtual memory layout
To:     John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc:     Arvind Sankar <nivedita@alum.mit.edu>,
        Kees Cook <keescook@chromium.org>,
        "Tobin C . Harding" <me@tobin.cc>, Tycho Andersen <tycho@tycho.ws>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, linux-sh@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Mar 5, 2020 at 8:48 PM John Paul Adrian Glaubitz
<glaubitz@physik.fu-berlin.de> wrote:
>
> On 3/5/20 4:10 PM, Arvind Sankar wrote:
> > For security, don't display the kernel's virtual memory layout.
> >
> > Kees Cook points out:
> > "These have been entirely removed on other architectures, so let's
> > just do the same for ia32 and remove it unconditionally."
> >
> > 071929dbdd86 ("arm64: Stop printing the virtual memory layout")
> > 1c31d4e96b8c ("ARM: 8820/1: mm: Stop printing the virtual memory layout")
> > 31833332f798 ("m68k/mm: Stop printing the virtual memory layout")
> > fd8d0ca25631 ("parisc: Hide virtual kernel memory layout")
> > adb1fe9ae2ee ("mm/page_alloc: Remove kernel address exposure in free_reserved_area()")
> Aww, why wasn't this made configurable? I found these memory map printouts
> very useful for development.

Same here! IMO, the kernel segment layout is useful for devs/debug purposes.
Perhaps:
a) all these printk's could be gathered into one function and invoked
only when DEBUG (or equivalent) is defined?
b) else, the s/pr_info/pr_devel approach with %pK should be good?
-Kaiwan.