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From: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr
Date: Fri, 17 May 2019 22:55:43 +0530
Message-ID: <1558113815.l84ajqay2l.naveen@linux.ibm.com> (raw)
In-Reply-To: <1558084179.fz93ts375u.astroid@bobo.none>

Nicholas Piggin wrote:
> Naveen N. Rao's on May 17, 2019 4:22 am:
> 
>> While enabling ftrace, we will first need to patch the preceding 'mflr 
>> r0' (which would now be a 'nop') with 'b +8', then use 
>> synchronize_rcu_tasks() and finally patch in 'bl _mcount()' followed by 
>> 'mflr r0'.
>> 
>> I think that's what you meant, just that my reference to patching 'mflr 
>> r0' with a 'b +8' should have called out that the mflr would have been 
>> nop'ed out.
> 
> I meant that we don't need the b +8 anywhere, because the mflr r0
> is harmless. Enabling ftrace just needs to patch in 'mflr r0', and
> then synchronize_rcu_tasks(), and then patch in 'bl _mcount'. I think?

Ah, that's a good point! That should be enough and it simplifies this 
further.


Thanks,
Naveen



      reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-13  1:59 Nicholas Piggin
2019-04-15  9:42 ` Naveen N. Rao
2019-05-13  3:25 ` Michael Ellerman
2019-05-13  6:47   ` Naveen N. Rao
2019-05-13 11:34     ` Michael Ellerman
2019-05-14  8:32       ` Naveen N. Rao
2019-05-15 12:20         ` Michael Ellerman
2019-05-16  5:49         ` Nicholas Piggin
2019-05-16 18:22           ` Naveen N. Rao
2019-05-17  9:12             ` Nicholas Piggin
2019-05-17 17:25               ` Naveen N. Rao [this message]

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