Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 10 Jun 2019 12:19:29 -0500
From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Nadav Amit <namit@vmware.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Andy Lutomirski <luto@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Jason Baron <jbaron@akamai.com>, Jiri Kosina <jkosina@suse.cz>,
        David Laight <David.Laight@ACULAB.COM>,
        Borislav Petkov <bp@alien8.de>,
        Julia Cartwright <julia@ni.com>, Jessica Yu <jeyu@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Edward Cree <ecree@solarflare.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: [PATCH 11/15] static_call: Add inline static call infrastructure
Message-ID: <20190610171929.3xemvsykvkswcvya@treble>
References: <20190605130753.327195108@infradead.org>
 <20190605131945.193241464@infradead.org>
 <37CFAEC1-6D36-4A6D-8C44-F85FCFA053AA@vmware.com>
 <20190607083756.GW3419@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20190607083756.GW3419@hirez.programming.kicks-ass.net>
User-Agent: NeoMutt/20180716
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Jun 07, 2019 at 10:37:56AM +0200, Peter Zijlstra wrote:
> > > +}
> > > +
> > > +static int static_call_module_notify(struct notifier_block *nb,
> > > +				     unsigned long val, void *data)
> > > +{
> > > +	struct module *mod = data;
> > > +	int ret = 0;
> > > +
> > > +	cpus_read_lock();
> > > +	static_call_lock();
> > > +
> > > +	switch (val) {
> > > +	case MODULE_STATE_COMING:
> > > +		module_disable_ro(mod);
> > > +		ret = static_call_add_module(mod);
> > > +		module_enable_ro(mod, false);
> > 
> > Doesn’t it cause some pages to be W+X ?

How so?

>> Can it be avoided?
> 
> I don't know why it does this, jump_labels doesn't seem to need this,
> and I'm not seeing what static_call needs differently.

I forgot why I did this, but it's probably for the case where there's a
static call site in module init code.  It deserves a comment.

Theoretically, jump labels need this to.

BTW, there's a change coming that will require the text_mutex before
calling module_{disable,enable}_ro().

-- 
Josh