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

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Message-ID: <20180104155307.ouazlqdczqkgd76e@two.firstfloor.org>
Date:   Thu, 4 Jan 2018 07:53:07 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     "Woodhouse, David" <dwmw@...zon.co.uk>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "andi@...stfloor.org" <andi@...stfloor.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gregkh@...ux-foundation.org" <gregkh@...ux-foundation.org>,
        "gnomes@...rguk.ukuu.org.uk" <gnomes@...rguk.ukuu.org.uk>,
        "tim.c.chen@...ux.intel.com" <tim.c.chen@...ux.intel.com>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>
Subject: Re: Avoid speculative indirect calls in kernel

> +.macro JMP_THUNK reg:req
> +#ifdef RETPOLINE
> +       ALTERNATIVE __stringify(jmp __x86.indirect_thunk.\reg), __stringify(jmp *%\reg), X86_FEATURE_IBRS_ATT
> +#else
> +       jmp *\reg
> +#endif
> +.endm

I remove that because what you're testing for doesn't exist in the tree yet. 

Yes it can be added later.

Right now we just want a basic static version to work reliably.

-Andi