linux-kernel - Re: [PATCH v2 3/8] x86-64: Allow alternative patching in the vDSO

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Message-ID: <CAObL_7GZEQO1YUv2bco+2b=H98=pA-ZFUj1JZYZ_jG3KhSq8Fw@mail.gmail.com>
Date:	Mon, 11 Jul 2011 08:21:07 -0600
From:	Andrew Lutomirski <luto@....edu>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, John Stultz <johnstul@...ibm.com>,
	Borislav Petkov <bp@...64.org>
Subject: Re: [PATCH v2 3/8] x86-64: Allow alternative patching in the vDSO

On Mon, Jul 11, 2011 at 4:41 AM, Rakib Mullick <rakib.mullick@...il.com> wrote:
> On Sun, Jul 10, 2011 at 9:22 AM, Andy Lutomirski <luto@....edu> wrote:

>> +static void patch_vdso(void *vdso, size_t len)
>
> I think, patch_vdso should mark with __init. Since it's been only
> called from an __init function. We might hit a section mismatch, even
> if we don't hit section mismatch, the will function get removed after
> system boot - saves some .text size.

Sure.  It won't make any difference, because my compiler at least is
smart enough to inline the whole function into init_vdso_vars, but
it's the right thing to do anyway.

>> +       return;  /* nothing to patch */
>
> If there's nothing to patch, I think (perhaps) - it would be nice to
> let user know through printk.

Will do.  I verified it myself by dumping the vdso image from memory
and confirming that it got patched correctly, but if the code ever
bitrots it'll be nice to have the warning.

--Andy
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