On Mon, May 18, 2009 at 12:30:41PM -0400, Alan Stern wrote:
> On Mon, 18 May 2009, K.Prasad wrote:
>
> > > > > > +int __kprobes hw_breakpoint_handler(struct die_args *args)
> > > > > > +{
> > > > > > + int rc = NOTIFY_STOP;
> > > > > > + struct hw_breakpoint *bp;
> > > > > > + struct pt_regs *regs = args->regs;
> > > > > > + unsigned long dar;
> > > > > > + int cpu, stepped, is_kernel;
> > > > > > +
> > > > > > + /* Disable breakpoints during exception handling */
> > > > > > + set_dabr(0);
> > > > > > +
> > > > > > + dar = regs->dar & (~HW_BREAKPOINT_ALIGN);
> > > > > > + is_kernel = (dar >= TASK_SIZE) ? 1 : 0;
> > > > >
> > > > > is_kernel_addr() ?
> > > > >
> > > >
> > > > Ok.
> > >
> > > Shouldn't this test hbp_kernel_pos instead?
> > >
> >
> > Testing hbp_kernel_pos should be sufficient for PPC64 with just one
> > breakpoint register. However the above code is more extensible to other
> > PowerPC implementations which have more than one breakpoint register.
>
> Then maybe you don't want to test this at all. Just compare the dar
> value with each of the breakpoint addresses. That's more like what the
> x86 code does.
>
> Alan Stern
>
Comparing the DAR register value with each breakpoint address is
required to determine if the exception is the cause of a breakpoint hit
and I've added the code to hw_breakpoint_handler(). With this check in
place, I find that using hbp_kernel_pos to determine kernel/user space
origin is much easier (as you suggested) and the code is modified
accordingly.
Please find the changes in the new patchset being sent.
Thanks,
K.Prasad
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