On Thu, Dec 22, 2011 at 03:04:47PM +0530, K.Prasad wrote:
> On Wed, Dec 21, 2011 at 11:55:02AM +1100, David Gibson wrote:
> > On Thu, Dec 08, 2011 at 04:53:30PM +0530, K.Prasad wrote:
> > > While PPC_PTRACE_SETHWDEBUG ptrace flag in PowerPC accepts
> > > PPC_BREAKPOINT_MODE_EXACT mode of breakpoint, the same is not intimated
> > > to the
> > > user-space debuggers (like GDB) who may want to use it. Hence we
> > > introduce a
> > > new PPC_DEBUG_FEATURE_DATA_BP_EXACT flag which will be populated on the
> > > "features" member of "struct ppc_debug_info" to advertise support for the
> > > same on Book3E PowerPC processors.
> >
> > Hrm. I had assumed the reason there wasn't a feature bit for EXACT
> > originally was that EXACT breakpoints were *always* supposed to be
> > supported by the new interface.
> >
>
> Okay. Although BookS doesn't support EXACT breakpoints, it is possible
> (after the introduction of new hw-breakpoint interfaces) to request for
> a breakpoint of length 1 Byte.
Hrm. An EXACT breakpoint is not exactly the same as a range
breakpoint of length 1 (consider unaligned accesses). But despite
that, it should be possible to implement exact breakpoints on Book3S
server hardware with some software filtering.
And since that leaves no hardware that *can't* implement exact
breakpoints (directly or indirectly), I'm not yet convinced of the
need for a flag bit.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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