linux-kernel - Re: [PATCH v3 19/25] powerpc/ftrace: Minimise number of #ifdefs

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Message-ID: <a7e47e3d-9b2b-ee12-d38c-3e6bbba83f7d@csgroup.eu>
Date:   Wed, 18 May 2022 12:12:47 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v3 19/25] powerpc/ftrace: Minimise number of #ifdefs



Le 18/05/2022 à 14:03, Michael Ellerman a écrit :
> Michael Ellerman <mpe@...erman.id.au> writes:
>> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> writes:
>>> Christophe Leroy wrote:
>>>> A lot of #ifdefs can be replaced by IS_ENABLED()
>>>>
>>>> Do so.
>>>>
>>>> This requires to have kernel_toc_addr() defined at all time
>>>> as well as PPC_INST_LD_TOC and PPC_INST_STD_LR.
>>>>
>>>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>>>> ---
>>>> v2: Moved the setup of pop outside of the big if()/else() in __ftrace_make_nop()
>>>> ---
>>>>   arch/powerpc/include/asm/code-patching.h |   2 -
>>>>   arch/powerpc/include/asm/module.h        |   2 -
>>>>   arch/powerpc/include/asm/sections.h      |  24 +--
>>>>   arch/powerpc/kernel/trace/ftrace.c       | 182 +++++++++++------------
>>>>   4 files changed, 103 insertions(+), 107 deletions(-)
>>>>
>>>
>>> <snip>
>>>
>>>> @@ -710,6 +707,9 @@ void arch_ftrace_update_code(int command)
>>>>
>>>>   #ifdef CONFIG_PPC64
>>>>   #define PACATOC offsetof(struct paca_struct, kernel_toc)
>>>> +#else
>>>> +#define PACATOC 0
>>>> +#endif
>>>
>>> This conflicts with my fix for the ftrace init tramp:
>>> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220516071422.463738-1-naveen.n.rao@linux.vnet.ibm.com/
>>>
>>> It probably makes sense to retain #ifdef CONFIG_PPC64, so that we can
>>> get rid of the PACATOC. Here is an incremental diff:
>>
>> Where is the incremental diff meant to apply?
>>
>> It doesn't apply on top of patch 19, or at the end of the series.
> 
> I think I worked out what you meant.
> 
> Can you check what's in next-test:
> 
>    https://github.com/linuxppc/linux/commits/next-test

Yes that looks fine.

As Naveen mentioned we can also get rid of PACATOC completely and use 
offsetof(struct paca_struct, kernel_toc) directly at the only place 
PACATOC is used.

Thanks
Christophe