linux-kernel - Re: [RFC PATCH] asm/generic: introduce if_nospec and nospec

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Message-ID: <alpine.LRH.2.00.1801040253410.27010@gjva.wvxbf.pm>
Date:   Thu, 4 Jan 2018 02:59:47 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Dan Williams <dan.j.williams@...el.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arch@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Alan Cox <alan@...ux.intel.com>
Subject: Re: [RFC PATCH] asm/generic: introduce if_nospec and
 nospec_barrier

On Wed, 3 Jan 2018, Dan Williams wrote:

> Speaking from a purely Linux kernel maintenance process perspective we
> play wack-a-mole with missed endian conversions and other bugs that
> coccinelle, sparse, etc help us catch. 

Fully agreed.

> So this is in that same category, but yes, it's inconvenient.

Disagreed, violently. CPU has to execute the instructions I ask it to 
execute, and if it executes *anything* else that reveals any information 
about the instructions that have *not* been executed, it's flawed.

> Elena has done the work of auditing static analysis reports to a dozen
> or so locations that need some 'nospec' handling.

How exactly is that related (especially in longer-term support terms) to 
BPF anyway?

Thanks,

-- 
Jiri Kosina
SUSE Labs