From: Michael Ellerman <mpe@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Cc: Diana Craciun <diana.craciun@nxp.com>,
Scott Wood <oss@buserror.net>, Nick Piggin <npiggin@au1.ibm.com>,
Laurentiu Tudor <laurentiu.tudor@nxp.com>
Subject: Re: [RFC/WIP] powerpc: Fix 32-bit handling of MSR_EE on exceptions
Date: Tue, 05 Feb 2019 21:10:01 +1100 [thread overview]
Message-ID: <87pns6mtqe.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <5a97253c-0ec4-d61f-fa9e-ea5da8590f32@c-s.fr>
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Le 20/12/2018 à 23:35, Benjamin Herrenschmidt a écrit :
>>
>>>> /*
>>>> * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE.
>>>> @@ -205,20 +208,46 @@ transfer_to_handler_cont:
>>>> mflr r9
>>>> lwz r11,0(r9) /* virtual address of handler */
>>>> lwz r9,4(r9) /* where to go when done */
>>>> +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
>>>> + mtspr SPRN_NRI, r0
>>>> +#endif
>>>
>>> That's not part of your patch, it's already in the tree.
>>
>> Yup rebase glitch.
>>
>> .../...
>>
>>> I tested it on the 8xx with the below changes in addition. No issue seen
>>> so far.
>>
>> Thanks !
>>
>> I'll merge that in.
>
> I'm currently working on a refactorisation and simplification of
> exception and syscall entry on ppc32.
>
> I plan to take your patch in my serie as it helps quite a bit. I hope
> you don't mind. I expect to come out with a series this week.
Ben's AFK so go ahead and pull it in to your series if that helps you.
>> The main obscure area is that business with the irqsoff tracer and thus
>> the need to create stack frames around calls to trace_hardirqs_* ... we
>> do it in some places and not others, but I've not managed to make it
>> crash either. I need to get to the bottom of that, and possibly provide
>> proper macro helpers like ppc64 has to do it.
>
> I can't see anything special around this in ppc32 code. As far as I
> understand, a stack frame is put in place when there is a need to
> save and restore some volatile registers. At the places where nothing
> needs to be saved, nothing is done. I think that's the normal way for
> any function call, isn't it ?
The concern was that the irqsoff tracer was doing
__builtin_return_address(1) (or some number > 0) and that crashes if
there aren't sufficiently many stack frames available.
See ftrace_return_address.
Possibly the answer is that we don't have CONFIG_FRAME_POINTER and so we
get the empty version of that.
cheers
next prev parent reply other threads:[~2019-02-05 10:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-20 5:40 [RFC/WIP] powerpc: Fix 32-bit handling of MSR_EE on exceptions Benjamin Herrenschmidt
2018-12-20 16:33 ` Christophe Leroy
2018-12-20 22:35 ` Benjamin Herrenschmidt
2019-02-05 9:45 ` Christophe Leroy
2019-02-05 10:10 ` Michael Ellerman [this message]
2019-03-15 17:10 ` Christophe Leroy
2019-02-05 12:19 ` Benjamin Herrenschmidt
2019-01-27 18:56 ` christophe leroy
2019-01-27 19:26 ` christophe leroy
2019-02-05 12:14 ` Christophe Leroy
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