On Fri, Feb 26, 2010 at 02:58:12AM +0100, Frederic Weisbecker wrote:
> On Mon, Feb 22, 2010 at 06:47:46PM +0530, K.Prasad wrote:
[snip]
> > > Oh, why does ptrace use a one-shot behaviour in ppc? Breakpoints
> > > only trigger once?
> > >
> >
> > Yes, ptrace breakpoints on PPC64 are designed to trigger once and this
> > patch retains that behaviour. It is very convenient to use one-shot
> > behaviour on archs where exceptions are triggered-before-execute.
>
> Ah, Why?
Because otherwise you have jump through some tricky hoops so that when
gdb (or whatever) resumes after the breakpoint, you don't immediately
retrap in the same place. I gather x86 has hardware assistance to do
this, but powerpc doesn't.
--
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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