linux-kernel - Re: [PATCH v2] x86: Remove compat vdso support

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Date:	Tue, 11 Mar 2014 08:30:34 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Stefani Seibold <stefani@...bold.net>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Dave Jones <davej@...hat.com>,
	Martin Runge <Martin.Runge@...de-schwarz.com>,
	Andreas Brief <Andreas.Brief@...de-schwarz.com>
Subject: Re: [PATCH v2] x86: Remove compat vdso support

On Tue, Mar 11, 2014 at 7:53 AM, Andy Lutomirski <luto@...capital.net> wrote:
>
> I wonder if we can actually detect buggy glibc versions at runtime.

No, don't do that. That way lies madness.

What might be acceptable then is to just keep the old config name, and
if the COMPAT_VDSO config is enabled, you just disable the non-compat
vdso. At least that way, presumably any opensuse people would have
their kernel config continue working.

Then if people have that enabled but didn't  need it, you can enable
it at runtime with

    echo 1 > /proc/sys/abi/vsyscall32

which presumably would need to be exposed on 32-bit kernels too (it
looks like a x86-64-only thing right now)

The important thing is that we do *not* break user space. Not ever.
Not knowingly.

           Linus
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