linux-kernel - Re: [PATCH 2/3] powerpc/ppc-opcode: Define and use PPC_RAW_TRAP() and PPC_RAW

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Date:   Wed, 03 Aug 2022 20:38:48 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 2/3] powerpc/ppc-opcode: Define and use PPC_RAW_TRAP()
 and PPC_RAW_TW()

"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com> writes:
> Christophe Leroy wrote:
>> Add and use PPC_RAW_TRAP() instead of opencoding.
>> 
>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>> ---
>>  arch/powerpc/include/asm/ppc-opcode.h | 2 ++
>>  arch/powerpc/include/asm/probes.h     | 3 ++-
>>  arch/powerpc/xmon/xmon.c              | 2 +-
>>  3 files changed, 5 insertions(+), 2 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
>> index 89beabf5325c..5527a955fb4a 100644
>> --- a/arch/powerpc/include/asm/ppc-opcode.h
>> +++ b/arch/powerpc/include/asm/ppc-opcode.h
>> @@ -581,6 +581,8 @@
>>  
>>  #define PPC_RAW_BRANCH(offset)		(0x48000000 | PPC_LI(offset))
>>  #define PPC_RAW_BL(offset)		(0x48000001 | PPC_LI(offset))
>> +#define PPC_RAW_TW(t0, a, b)		(0x7f000008 | ___PPC_RS(t0) | ___PPC_RA(a) | ___PPC_RB(b))
>
> Shouldn't that be 0x7c000008 ?

Yes, my script agrees.

https://github.com/mpe/misc-scripts/blob/master/ppc/ppc-instruction-encode

$ ./ppc-instruction-encode 0:31 6:t0 11:ra 16:rb 21:4 31:
.long 0x7c000008
t0 << 21
ra << 16
rb << 11


I guess the only user is PPC_RAW_TRAP() which passes t0 = 31, so that's
why nothing has broken.

Send a fixup? :)

cheers