linux-kernel - Re: [PATCH v4 01/10] Fix "x86/alternatives: Lockdep-enforce text_mutex in text

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Message-ID: <nycvar.YFH.7.76.1811121158340.27368@cbobk.fhfr.pm>
Date:   Mon, 12 Nov 2018 11:59:11 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
cc:     Nadav Amit <namit@...are.com>, Ingo Molnar <mingo@...hat.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH v4 01/10] Fix "x86/alternatives: Lockdep-enforce text_mutex
 in text_poke*()"

On Mon, 12 Nov 2018, Masami Hiramatsu wrote:

> > text_mutex is currently expected to be held before text_poke() is 
> > called, but we kgdb does not take the mutex, and instead *supposedly* 
> > ensures the lock is not taken and will not be acquired by any other 
> > core while text_poke() is running.
> > 
> > The reason for the "supposedly" comment is that it is not entirely clear
> > that this would be the case if gdb_do_roundup is zero.
> > 
> > This patch creates two wrapper functions, text_poke() and
> > text_poke_kgdb() which do or do not run the lockdep assertion
> > respectively.
> > 
> > While we are at it, change the return code of text_poke() to something
> > meaningful. One day, callers might actually respect it and the existing
> > BUG_ON() when patching fails could be removed. For kgdb, the return
> > value can actually be used.
> 
> Hm, this looks reasonable and good to me.
> 
> Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Yes, I guess this is much better than putting the 'enforcement by comment' 
back in place :)

	Acked-by: Jiri Kosina <jkosina@...e.cz>

Thanks.

-- 
Jiri Kosina
SUSE Labs