linux-kernel - Re: [PATCH v2 resend 1/5] ARM: add support for AT

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Message-ID: <CAKv+Gu-dZZ4yzkDoHoHVRgW1KQ7H3PLy-OV731Es8BNmpkYqLQ@mail.gmail.com>
Date:	Fri, 17 Jan 2014 16:26:50 +0100
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	Will Deacon <will.deacon@....com>
Cc:	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	Dave P Martin <Dave.Martin@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"peter.maydell@...aro.org" <peter.maydell@...aro.org>
Subject: Re: [PATCH v2 resend 1/5] ARM: add support for AT_HWCAP2 ELF auxv entry

On 17 January 2014 16:07, Will Deacon <will.deacon@....com> wrote:
> Hi Ard,
>
> On Fri, Jan 17, 2014 at 09:23:07AM +0000, Ard Biesheuvel wrote:
>> This enables AT_HWCAP2 for ARM. The generic support for this
>> new ELF auxv entry was added in commit 2171364d1a9 (powerpc:
>> Add HWCAP2 aux entry)
>
> Does this require a corresponding change in libc so that the entry is
> actually used by the dynamic linker?
>

The auxv entry itself is already wired up [this includes getauxval()]

https://sourceware.org/git/?p=glibc.git;a=commit;h=1ae8bfe07c1a

The only thing that is lacking is a way to hook up ifunc relocation,
as the current prototype passes a single 32-bit quantity.
So either we change the prototype to (hwcap, hwcap2) or we need to
rely on getauxval() in ifunc selectors if they need to inspect hwcap2

-- 
Ard.
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