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

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Date:	Fri, 10 Apr 2015 14:40:35 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Michael Neuling <mikey@...ling.org>
CC:	james.hogan@...tec.com, avagin@...nvz.org,
	Paul.Clothier@...tec.com, linuxppc-dev@...abs.org,
	peterz@...radead.org, palves@...hat.com, davem@...emloft.net,
	shuahkh@....samsung.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, dhowells@...hat.com,
	Ulrich Weigand <Ulrich.Weigand@...ibm.com>, kirjanov@...il.com,
	oleg@...hat.com, davej@...hat.com, tglx@...utronix.de,
	sukadev@...ux.vnet.ibm.com,
	Edjunior Barbosa Machado <emachado@...ux.vnet.ibm.com>,
	sam.bobroff@....ibm.com
Subject: Re: [V6,1/9] elf: Add new powerpc specifc core note sections

On 04/10/2015 08:33 AM, Michael Neuling wrote:
> On Thu, 2015-04-09 at 18:20 +0530, Anshuman Khandual wrote:
>> On 04/09/2015 04:41 AM, Michael Neuling wrote:
>>> On Wed, 2015-04-08 at 19:50 +0200, Ulrich Weigand wrote:
>>>> Anshuman Khandual <khandual@...ux.vnet.ibm.com> wrote on 23.03.2015
>>>> 11:34:30:
>>>>
>>>>>> With that in mind, do we have a way to set the top 32bits of the MSR
>>>>>> (which contain the TM bits) when ptracing 32 bit processes?  I can't
>>>>>> find anything like that in this patch set.
>>>>>
>>>>> No, we dont have that yet. When ptracing in 32-bit mode the MSR value
>>>>> which can be viewed or set from the user space through PTRACE_GETREGS
>>>>> PTRACE_SETREGS call is it's lower 32 bits only. Either we can club
>>>>> the upper 32 bits of MSR as part of one of the ELF core notes we are
>>>>> adding in the patch series or we can create one more separate ELF core
>>>>> note for that purpose. Let me know your opinion on this.
>>>>
>>>> I'm not sure I understand this.  I thought we had the following:
>>>>
>>>> - If the process calling ptrace is itself 64-bit (which is how GDB is
>>>>   built on all current Linux distributions), then PTRACE_GETREGS etc.
>>>>   will *always* operate on 64-bit register sets, even if the target
>>>>   process is 32-bit.
>>>>
>>>> - If the process calling ptrace is 32-bit, then PTRACE_GETREGS will
>>>>   operate on 32-bit register sets.   However, there is a separate
>>>>   PTRACE_GETREGS64 / PTRACE_SETREGS64 call that will also provide
>>>>   the opportunity to operate on the full 64-bit register set.  Both
>>>>   apply independently of whether the target process is 32-bit or
>>>>   64-bit.
>>>>
>>>> Is this not correct?
>>>
>>> I think you're correct.  We should be right.  I'd forgotten about the
>>> GET/SETREGS64 interfaces.
>>
>> In that case, is the patch series complete and okay ? Is there any thing
>> else we need to verify other than waiting for the GDB test results which
>> Edjunior has been working on. But I am not aware of the status on the GDB
>> test development front.
> 
> I think we are good.

I had posted a newer version [V7] of this patch series couple of months back
which got ignored while the discussion continued in this version.

V7: https://lkml.org/lkml/2015/1/14/19

Apart from the last gitignore related patch which already got merged into
mainline separately, all other patches should be as good even today. I will
try rebasing the series, running the base tests again and re post it in some
time.

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