linux-kernel - Re: [tip: x86/urgent] x86/uprobes: Do not use prefixes.nbytes when looping over prefixes.bytes

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Message-ID: <20201210103607.GA26633@zn.tnic>
Date:   Thu, 10 Dec 2020 11:36:07 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org,
        tip-bot2 for Masami Hiramatsu <tip-bot2@...utronix.de>,
        linux-tip-commits@...r.kernel.org,
        syzbot+9b64b619f10f19d19a7c@...kaller.appspotmail.com,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, x86@...nel.org
Subject: Re: [tip: x86/urgent] x86/uprobes: Do not use prefixes.nbytes when
 looping over prefixes.bytes

On Wed, Dec 09, 2020 at 03:01:47PM -0300, Arnaldo Carvalho de Melo wrote:
> Trying to swap this back into my brain...

I know *exactly* what you mean. :)

> 
> Humm, if I'm building this on, say, aarch64 then asm/ will not be
> pointing to x86, right? Intel PT needs the x86 instruction decoder,
> right?

Yeah.

> I should've have wrote in the cset comment log if this was related to
> cross build failures I encountered, can't remember now :-\

I think that is it. There's inat.h in tools/arch/x86/include/asm/ too so
it needs to be exactly that one that gets included on other arches.

> And also it would be interesting to avoid updating both the kernel and
> the tools/ copy, otherwise one would have to test the tools build, which
> may break with such updates.
>
> The whole point of the copy is to avoid that, otherwise we could just
> use the kernel files directly.

Well, there's this diff -u thing which makes sure both copies are in sync.

Why did we ever copy the insn decoder to tools/?

There must've been some reason because otherwise we could probably use
the one in arch/x86/lib/, in tools/.

Yeah, this whole copying of headers back'n'forth is turning out to be
kinda hairy...

-- 
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg