Subject: Re: [PATCH 15/18] x86 vDSO: consolidate vdso32
From: Zachary Amsden <zach@vmware.com>
To: Roland McGrath <roland@redhat.com>, Ingo Molnar <mingo@elte.hu>,
       Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
       "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
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	 <20071119220644.F41CA26F8C1@magilla.localdomain>
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Date: Tue, 20 Nov 2007 16:13:30 -0800
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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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