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Subject: Re: [PATCH] mm: Generalize and rename notify_page_fault() as
 kprobe_page_fault()
To:     Anshuman Khandual <anshuman.khandual@arm.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
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        Thomas Gleixner <tglx@synopsys.com>,
        "Masami Hiramatsu" <masami.hiramatsu.pt@hitachi.com>
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From:   Vineet Gupta <Vineet.Gupta1@synopsys.com>
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Date:   Thu, 13 Jun 2019 10:57:45 -0700
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+CC Masami San

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.

-Vineet