Messages in this thread |  | | | Date | Thu, 31 Dec 2009 01:33:49 +0100 | | From | Frederic Weisbecker <> | | Subject | Re: [RFC Patch 2/2][Bugfix][x86][hw-breakpoint] Fix return-code to notifier chain in hw_breakpoint_handler |
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On Sat, Dec 26, 2009 at 11:58:33PM +0530, K.Prasad wrote: > The hw-breakpoint handler will return NOTIFY_DONE for user-space breakpoints > to generate SIGTRAP signal (and not for kernel-space addresses). > > Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com> > --- > arch/x86/kernel/hw_breakpoint.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > Index: linux-2.6-tip/arch/x86/kernel/hw_breakpoint.c > =================================================================== > --- linux-2.6-tip.orig/arch/x86/kernel/hw_breakpoint.c > +++ linux-2.6-tip/arch/x86/kernel/hw_breakpoint.c > @@ -502,8 +502,6 @@ static int __kprobes hw_breakpoint_handl > rcu_read_lock(); > > bp = per_cpu(bp_per_reg[i], cpu); > - if (bp) > - rc = NOTIFY_DONE; > /* > * Reset the 'i'th TRAP bit in dr6 to denote completion of > * exception handling > @@ -517,6 +515,13 @@ static int __kprobes hw_breakpoint_handl > rcu_read_unlock(); > break; > } > + /* > + * Further processing in do_debug() is needed for a) user-space > + * breakpoints (to generate signals) and b) when the system has > + * taken exception due to multiple causes > + */ > + if (bp->attr.bp_addr < TASK_SIZE) > + rc = NOTIFY_DONE; > > perf_bp_event(bp, args->regs); > >
Looks good. This stops any further checks though. This is fine in case we have the DR_STEP bit as we will toggle to NOTIFY_DONE. But what about vm86 case? Is it possible we might still have something to handle in this side? (although I don't quite understand how we can have a breakpoint triggered in vm86 mode).
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