linux-kernel - Re: [PATCH RFC] mm: Add debug_virt_to

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Message-ID: <20161112054318.GB24127@arm.com>
Date:   Sat, 12 Nov 2016 05:43:19 +0000
From:   Will Deacon <will.deacon@....com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Chris Brandt <chris.brandt@...esas.com>,
        Pratyush Anand <panand@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Laura Abbott <labbott@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Jerome Marchand <jmarchan@...hat.com>,
        Konstantin Khlebnikov <koct9i@...il.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        "open list:GENERIC INCLUDE/ASM HEADER FILES" 
        <linux-arch@...r.kernel.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>
Subject: Re: [PATCH RFC] mm: Add debug_virt_to_phys()

On Fri, Nov 11, 2016 at 04:44:43PM -0800, Florian Fainelli wrote:
> When CONFIG_DEBUG_VM is turned on, virt_to_phys() maps to
> debug_virt_to_phys() which helps catch vmalloc space addresses being
> passed. This is helpful in debugging bogus drivers that just assume
> linear mappings all over the place.
> 
> For ARM, ARM64, Unicore32 and Microblaze, the architectures define
> __virt_to_phys() as being the functional implementation of the address
> translation, so we special case the debug stub to call into
> __virt_to_phys directly.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  arch/arm/include/asm/memory.h      |  4 ++++
>  arch/arm64/include/asm/memory.h    |  4 ++++
>  include/asm-generic/memory_model.h |  4 ++++
>  mm/debug.c                         | 15 +++++++++++++++
>  4 files changed, 27 insertions(+)

What's the interaction between this and the DEBUG_VIRTUAL patches from Laura?

http://lkml.kernel.org/r/20161102210054.16621-7-labbott@redhat.com

They seem to be tackling the exact same problem afaict.

Will