linux-kernel - Re: [PATCH 15/18] x86 vDSO: consolidate vdso32

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Date:	Tue, 20 Nov 2007 16:13:30 -0800
From:	Zachary Amsden <zach@...are.com>
To:	Roland McGrath <roland@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <ak@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/18] x86 vDSO: consolidate vdso32

On Mon, 2007-11-19 at 14:06 -0800, Roland McGrath wrote:
> This makes x86_64's ia32 emulation support share the sources used in the
> 32-bit kernel for the 32-bit vDSO and much of its setup code.
> 
> The 32-bit vDSO mapping now behaves the same on x86_64 as on native 32-bit.
> The abi.syscall32 sysctl on x86_64 now takes the same values that
> vm.vdso_enabled takes on the 32-bit kernel.  That is, 1 means a randomized
> vDSO location, 2 means the fixed old address.  The CONFIG_COMPAT_VDSO
> option is now available to make this the default setting, the same meaning
> it has for the 32-bit kernel.  (This does not affect the 64-bit vDSO.)

I think you should drop CONFIG_COMPAT_VDSO support for 32-bit VDSO on
64-bit kernel.  This was only to hack around a broken version of glibc
that shipped with SUSE PRO 9.0, which had broken assertions based on
misinterpretation of ELF fields.  64-bit machines will never see this
glibc and the hack can die.

Perhaps it is finally time to remove the hack from 32-bit as well, and
eliminate COMPAT_VDSO entirely?  Or does it really have to live forever.

Zach

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