Re: [PATCH v4 01/10] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()"

From: Jiri Kosina <jikos@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Nadav Amit <namit@vmware.com>, Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH v4 01/10] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()"
Date: Mon, 12 Nov 2018 11:59:11 +0100 (CET)	[thread overview]
Message-ID: <nycvar.YFH.7.76.1811121158340.27368@cbobk.fhfr.pm> (raw)
In-Reply-To: <20181112115419.3e86d8a522b6c7457c036dc9@kernel.org>

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@kernel.org>

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

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

Thanks.

-- 
Jiri Kosina
SUSE Labs