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

From: Michael Neuling
Date: Wed Apr 08 2015 - 19:11:42 EST

On Wed, 2015-04-08 at 19:50 +0200, Ulrich Weigand wrote:
> Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx> 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.


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