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

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Date:   Tue, 18 Jun 2019 08:56:33 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
CC:     Anshuman Khandual <anshuman.khandual@....com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        arcml <linux-snps-arc@...ts.infradead.org>,
        "Masami Hiramatsu" <mhiramat@...nel.org>
Subject: Re: [PATCH] mm: Generalize and rename notify_page_fault() as
 kprobe_page_fault()

+CC Masami San, Eugeniy

On 6/13/19 10:57 AM, Vineet Gupta wrote:


> On 6/13/19 3:07 AM, Anshuman Khandual wrote:
>> Questions:
>>
>> AFAICT there is no equivalent of erstwhile notify_page_fault() during page
>> fault handling in arc and mips archs which can call this generic function.
>> Please let me know if that is not the case.
> 
> For ARC do_page_fault() is entered for MMU exceptions (TLB Miss, access violations
> r/w/x etc). kprobes uses a combination of UNIMP_S and TRAP_S instructions which
> don't funnel into do_page_fault().
> 
> UINMP_S leads to
> 
> instr_service
>    do_insterror_or_kprobe
>       notify_die(DIE_IERR)
>          kprobe_exceptions_notify
>             arc_kprobe_handler
> 
> 
> TRAP_S 2 leads to
> 
> EV_Trap
>    do_non_swi_trap
>       trap_is_kprobe
>          notify_die(DIE_TRAP)
>             kprobe_exceptions_notify
>                arc_post_kprobe_handler
> 
> But indeed we are *not* calling into kprobe_fault_handler() - from eithet of those
> paths and not sure if the existing arc*_kprobe_handler() combination does the
> equivalent in tandem.

@Eugeniy can you please investigate this - do we have krpobes bit rot in ARC port.

-Vineet