linux-kernel - Re: [RFCv2 2/4] Documentation: document nospec helpers

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Message-ID: <f7a88365-8936-0d5e-0764-8664429e6305@infradead.org>
Date:   Sat, 6 Jan 2018 21:20:59 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org
Cc:     dan.j.williams@...el.com, elena.reshetova@...el.com,
        corbet@....net, alan@...ux.intel.com, peterz@...radead.org,
        will.deacon@....com, gregkh@...uxfoundation.org,
        tglx@...utronix.de, Paul Turner <pjt@...gle.com>
Subject: Re: [RFCv2 2/4] Documentation: document nospec helpers

On 01/05/18 06:57, Mark Rutland wrote:
> Document the rationale and usage of the new nospec*() helpers.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Will Deacon <will.deacon@....com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Jonathan Corbet <corbet@....net>
> Cc: Peter Zijlstra <peterz@...radead.org>
> ---
>  Documentation/speculation.txt | 166 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 166 insertions(+)
>  create mode 100644 Documentation/speculation.txt
> 
> diff --git a/Documentation/speculation.txt b/Documentation/speculation.txt
> new file mode 100644
> index 000000000000..748fcd4dcda4
> --- /dev/null
> +++ b/Documentation/speculation.txt
> @@ -0,0 +1,166 @@
> +
> +Typically speculative execution cannot be observed from architectural state,
> +such as the contents of registers. However, in some cases it is possible to
> +observe its impact on microarchitectural state, such as the presence or
> +absence of data in caches. Such state may form side-channels which can be
> +observed to extract secret information.

I'm curious about what it takes to observe this...

or is that covered in the exploit papers?

thanks,
-- 
~Randy