linux-kernel - Re: [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and lm

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Message-ID: <2f3ac043-c4cc-5c5a-8ac7-1396b6bb193f@virtuozzo.com>
Date:   Thu, 1 Dec 2016 14:36:05 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Laura Abbott <labbott@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        <kasan-dev@...glegroups.com>
Subject: Re: [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and
 lm_alias

On 11/29/2016 09:55 PM, Laura Abbott wrote:
> __pa_symbol is the correct API to find the physical address of symbols.
> Switch to it to allow for debugging APIs to work correctly.

But __pa() is correct for symbols. I see how __pa_symbol() might be a little
faster than __pa(), but there is nothing wrong in using __pa() on symbols.

> Other
> functions such as p*d_populate may call __pa internally. Ensure that the
> address passed is in the linear region by calling lm_alias.

Why it should be linear mapping address? __pa() translates kernel image address just fine.
This lm_alias() only obfuscates source code. Generated code is probably worse too.