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

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Message-ID: <016a4808-527d-7164-b8a0-3173a4ecfa25@arm.com>
Date:   Thu, 6 Jun 2019 07:33:52 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Matthew Wilcox <willy@...radead.org>
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>,
        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 V2] mm: Generalize notify_page_fault()



On 06/05/2019 03:23 AM, Matthew Wilcox wrote:
> On Tue, Jun 04, 2019 at 12:04:06PM +0530, Anshuman Khandual wrote:
>> +++ b/arch/x86/mm/fault.c
>> @@ -46,23 +46,6 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)
>>  	return 0;
>>  }
>>  
>> -static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
>> -{
> ...
>> -}
> 
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 0e8834a..c5a8dcf 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1778,6 +1778,7 @@ static inline int pte_devmap(pte_t pte)
>>  }
>>  #endif
>>  
>> +int notify_page_fault(struct pt_regs *regs, unsigned int trap);
> 
> Why is it now out-of-line?  

Did not get it. AFAICS it is the same from last version and does not cross
80 characters limit on that line.

> 
>> +++ b/mm/memory.c
>> +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;
>> +}
>> +
> 
> I would argue this should be in kprobes.h as a static nokprobe_inline.

We can do that. Though it will be a stand alone (not inside #ifdef) as it
already takes care of CONFIG_KPROBES via kprobes_built_in(). Will change
it and in which case the above declaration in mm.h would not be required.