linux-kernel - Re: [PATCH] uprobes/x86: allow to probe a "nop" insn with 0x66 prefix

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Date:   Sun, 4 Dec 2022 18:34:36 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Seiji Nishikawa <snishika@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uprobes/x86: allow to probe a "nop" insn with 0x66 prefix

On 12/02, Oleg Nesterov wrote:
>
> On 12/02, Thomas Gleixner wrote:
> >
> > On Thu, Dec 01 2022 at 15:26, Oleg Nesterov wrote:
> >
> > > From: Denys Vlasenko <dvlasenk@...hat.com>
> > >
> > > Intel icc -hotpatch inserts 2-byte "0x66 0x90" NOP at the start of each
> > > function to reserve extra space for hot-patching, and currently it is not
> > > possible to probe these functions because branch_setup_xol_ops() wrongly
> > > nacks NOP with REP prefix.
> > >
> > > Fixes: 250bbd12c2fe ("uprobes/x86: Refuse to attach uprobe to "word-sized" branch insns")
> > > Reported-by: Seiji Nishikawa <snishika@...hat.com>
> > > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> >
> > The SOB chain is invalid as it lacks the author's signoff.
>
> Denys, can we have your signed-off-by?

OK, let me turn "From" into "Suggested-by" if this can help to merge this fix.

After all, the patch is really simple, I don't think Denys will object when he
returns.

I am sending v2 with Masami's ack applied.

Oleg.