linux-kernel - Re: [RFC V2] mm: Generalize notify_page

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Date:   Tue, 4 Jun 2019 08:54:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        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>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [RFC V2] mm: Generalize notify_page_fault()

On Tue, Jun 04, 2019 at 12:04:06PM +0530, Anshuman Khandual wrote:
> diff --git a/mm/memory.c b/mm/memory.c
> index ddf20bd..b6bae8f 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -52,6 +52,7 @@
>  #include <linux/pagemap.h>
>  #include <linux/memremap.h>
>  #include <linux/ksm.h>
> +#include <linux/kprobes.h>
>  #include <linux/rmap.h>
>  #include <linux/export.h>
>  #include <linux/delayacct.h>
> @@ -141,6 +142,21 @@ static int __init init_zero_pfn(void)
>  core_initcall(init_zero_pfn);
>  
>  
> +int __kprobes notify_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;
> +}

That thing should be called kprobe_page_fault() or something,
notify_page_fault() is a horribly crap name for this function.