linux-kernel - Re: [RFC V3] mm: Generalize and rename notify_page_fault() as kprobe_page

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Message-ID: <6e095842-0f7f-f428-653d-2b6e98fea6b3@intel.com>
Date:   Fri, 7 Jun 2019 08:06:30 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        x86@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [RFC V3] mm: Generalize and rename notify_page_fault() as
 kprobe_page_fault()

On 6/7/19 3:34 AM, Anshuman Khandual wrote:
> +static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
> +					      unsigned int trap)
> +{
> +	int ret = 0;
> +
> +	/*
> +	 * To be potentially processing a kprobe fault and to be allowed
> +	 * to call kprobe_running(), we have to be non-preemptible.
> +	 */
> +	if (kprobes_built_in() && !preemptible() && !user_mode(regs)) {
> +		if (kprobe_running() && kprobe_fault_handler(regs, trap))
> +			ret = 1;
> +	}
> +	return ret;
> +}

Nits: Other that taking the nice, readable, x86 one and globbing it onto
a single line, looks OK to me.  It does seem a _bit_ silly to go to the
trouble of converting to 'bool' and then using 0/1 and an 'int'
internally instead of true/false and a bool, though.  It's also not a
horrible thing to add a single line comment to this sucker to say:

/* returns true if kprobes handled the fault */

In any case, and even if you don't clean any of this up:

Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>