linux-kernel - Re: [V6,1/9] elf: Add new powerpc specifc core note sections

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Date:	Wed, 03 Dec 2014 12:18:51 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
CC:	shuahkh@....samsung.com, mikey@...ling.org, james.hogan@...tec.com,
	avagin@...nvz.org, Paul.Clothier@...tec.com, peterz@...radead.org,
	palves@...hat.com, oleg@...hat.com, davem@...emloft.net,
	dhowells@...hat.com, kirjanov@...il.com, davej@...hat.com,
	akpm@...ux-foundation.org, sukadev@...ux.vnet.ibm.com,
	tglx@...utronix.de, sam.bobroff@....ibm.com
Subject: Re: [V6,1/9] elf: Add new powerpc specifc core note sections

On 12/03/2014 10:52 AM, Michael Ellerman wrote:
> On Tue, 2014-02-12 at 07:56:45 UTC, Anshuman Khandual wrote:
>> This patch adds four new ELF core note sections for powerpc
>> transactional memory and one new ELF core note section for
>> powerpc general miscellaneous debug registers. These addition
>> of new ELF core note sections extends the existing ELF ABI
>> without affecting it in any manner.
>>
>> Acked-by: Andrew Morton <akpm@...ux-foundation.org>
>> Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
>> ---
>>  include/uapi/linux/elf.h | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
>> index ea9bf25..2260fc0 100644
>> --- a/include/uapi/linux/elf.h
>> +++ b/include/uapi/linux/elf.h
>> @@ -379,6 +379,11 @@ typedef struct elf64_shdr {
>>  #define NT_PPC_VMX	0x100		/* PowerPC Altivec/VMX registers */
>>  #define NT_PPC_SPE	0x101		/* PowerPC SPE/EVR registers */
>>  #define NT_PPC_VSX	0x102		/* PowerPC VSX registers */
>> +#define NT_PPC_TM_SPR	0x103		/* PowerPC TM special registers */
>> +#define NT_PPC_TM_CGPR	0x104		/* PowerpC TM checkpointed GPR */
>> +#define NT_PPC_TM_CFPR	0x105		/* PowerPC TM checkpointed FPR */
>> +#define NT_PPC_TM_CVMX	0x106		/* PowerPC TM checkpointed VMX */
>> +#define NT_PPC_MISC	0x107		/* PowerPC miscellaneous registers */
> 
> This is a really terrible name, "MISC".
> 
> Having said that, I guess it's accurate. We have a whole bunch of regs that
> have accrued over recent years that aren't accessible via ptrace.
> 
> It seems to me if we're adding a misc regset we should be adding everything we
> might want to it that is currenty architected.

But I believe they also need to be part of the thread_struct structure to be
accessible from ptrace.
 
> 
> But currently you only include the PPR, TAR & DSCR.

Yeah, thats what we started with.

> 
> Looking at Power ISA v2.07, I see the following that could be included:
> 
>   MMCR2
>   MMCRA
>   PMC1
>   PMC2
>   PMC3
>   PMC4
>   PMC5
>   PMC6
>   MMCR0
>   EBBHR
>   EBBRR
>   BESCR
>   SIAR
>   SDAR
>   CFAR?

MMCRA, PMC[1..6], EBBHR, BESCR, EBBRR, CFAR are not part of the thread struct.

> 
> Those are all new in 2.07 except for CFAR.
> 
> There might be more I missed, that was just a quick scan.
> 
> Some are only accessible when EBB is in use, maybe those could be a separate
> regset.

Yeah we can have one more regset for EBB specific registers.

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