linux-kernel - Re: [PATCH 1/2] elf loader support for auxvec base platform string

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Date:	Mon, 07 Jul 2008 15:48:13 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Roland McGrath <roland@...hat.com>
Cc:	Nathan Lynch <ntl@...ox.com>, linuxppc-dev@...abs.org,
	Paul Mackerras <paulus@...ba.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] elf loader support for auxvec base platform string

On Thu, 2008-07-03 at 19:19 -0700, Roland McGrath wrote:
> Why not just use ELF_HWCAP for this?  It looks like powerpc only has 3 bits
> left there (keeping it to 32), but 3 is not 0.  If not that, why not use
> dsocaps?  That is, some magic in the vDSO, which glibc already supports on
> all machines where it uses the vDSO.  (For how it works, see the use in
> arch/x86/vdso/vdso32/note.S for CONFIG_XEN.)

Well, we use strings to represent the platforms already (ie, the actual
CPU microarchitecture). Fitting those into bits would be annoying, it
makes sense to have AT_BASE_PLATFORM to be the "base" variant of
AT_PLATFORM.

_However_ there is a bug in that this patch adds an entry without
bumping the number of entries in the cached array (ie.
AT_VECTOR_SIZE_BASE needs to be updated).

Ben.


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