linux-kernel - Re: Avoid speculative indirect calls in kernel

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Message-ID: <20180104004034.wouy454tjmitkm5g@two.firstfloor.org>
Date:   Wed, 3 Jan 2018 16:40:35 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Andi Kleen <andi@...stfloor.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        dwmw@...zon.co.uk, Tim Chen <tim.c.chen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: Avoid speculative indirect calls in kernel

> So you say, that we finally need a perl interpreter in the kernel to do
> alternative patching?

I don't think perl or objtool makes sense. That would be just incredibly
fragile because compilers can reorder and mix code. 

It could be done with a gcc change I suppose. That should be reliable.

But that would need to be developed first. We don't have it right now.

As the first step a compile time approach should be sufficient.
We can add a CONFIG option so people can chose at compile time.

Then later we can investigate run time patching.

-Andi