linux-kernel - Re: [PATCH] arm64: lib: use C string functions with KASAN enabled.

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Message-ID: <20180907145605.GE12788@arm.com>
Date:   Fri, 7 Sep 2018 15:56:05 +0100
From:   Will Deacon <will.deacon@....com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kyeongdon Kim <kyeongdon.kim@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: lib: use C string functions with KASAN enabled.

On Thu, Sep 06, 2018 at 08:05:33PM +0300, Andrey Ryabinin wrote:
> ARM64 has asm implementations of memchr(), memcmp(), str[r]chr(),
> str[n]cmp(), str[n]len(). KASAN don't see memory accesses in asm
> code, thus it can potentially miss many bugs.
> 
> Ifdef out __HAVE_ARCH_* defines of these functions when KASAN is
> enabled, so the generic implementations from lib/string.c will be used.
> 
> Declare asm functions as weak instead of removing them because they
> still can be used by efistub.

I don't understand this bit: efistub uses the __pi_ prefixed versions of the
routines, so why do we need to declare them as weak?

Will