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

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Message-ID: <55267595.9030202@linux.vnet.ibm.com>
Date:	Thu, 09 Apr 2015 18:20:29 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Michael Neuling <mikey@...ling.org>,
	Ulrich Weigand <Ulrich.Weigand@...ibm.com>
CC:	shuahkh@....samsung.com, james.hogan@...tec.com, avagin@...nvz.org,
	Paul.Clothier@...tec.com, peterz@...radead.org, palves@...hat.com,
	linux-kernel@...r.kernel.org,
	Edjunior Barbosa Machado <emachado@...ux.vnet.ibm.com>,
	dhowells@...hat.com, linuxppc-dev@...abs.org, kirjanov@...il.com,
	tglx@...utronix.de, oleg@...hat.com, davej@...hat.com,
	akpm@...ux-foundation.org, sukadev@...ux.vnet.ibm.com,
	davem@...emloft.net, sam.bobroff@....ibm.com
Subject: Re: [V6,1/9] elf: Add new powerpc specifc core note sections

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.

Edjunior,

Do you have any updates ?

Regards
Anshuman


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