linux-kernel - Re: [PATCH 2/2] xen64: disable 32-bit syscall/sysenter if not supported.

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Date:	Fri, 11 Jul 2008 15:47:06 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] xen64: disable 32-bit syscall/sysenter if not
	supported.


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Old versions of Xen (3.1 and before) don't support sysenter or syscall 
> from 32-bit compat userspaces.  If we can't set the appropriate 
> syscall callback, then disable the corresponding feature bit, which 
> will cause the vdso32 setup to fall back appropriately.
>
> Linux assumes that syscall is always available to 32-bit userspace, 
> and installs it by default if sysenter isn't available.  In that case, 
> we just disable vdso altogether, forcing userspace libc to fall back 
> to int $0x80.

merged the latest version of tip/x86/core to tip/xen-64bit and then 
added this patch to tip/xen-64bit - thanks Jeremy.

	Ingo
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