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

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Date:	Fri, 10 Apr 2015 13:03:53 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:	Ulrich Weigand <Ulrich.Weigand@...ibm.com>,
	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 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.

Mikey

> 
> Edjunior,
> 
> Do you have any updates ?
> 
> Regards
> Anshuman
> 
> 

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