Messages in this thread | | | Date | Wed, 26 Aug 2009 02:03:07 +0530 | From | "K.Prasad" <> | Subject | Re: [Patch 0/1] HW-BKPT: Allow per-cpu kernel-space Hardware Breakpoint requests |
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On Thu, Aug 20, 2009 at 10:57:19PM +0530, K.Prasad wrote: > On Wed, Aug 19, 2009 at 07:33:00PM +0200, Frederic Weisbecker wrote: > > On Wed, Aug 19, 2009 at 09:41:19PM +0530, K.Prasad wrote: > > > On Mon, Aug 17, 2009 at 06:16:41PM +0530, K.Prasad wrote: > > > > Hi All, > > > > Please find a patch that enables kernel-space breakpoints to be > > > > requested for a subset of the available CPUs in the system. This allows > > > > per-CPU breakpoints and comes with the associated benefit of reduced > > > > overhead during (un)registration. > > > > > > > > This enhancement allows exploitation of hardware breakpoint registers by > > > > 'perf' which produces a CPU-wise information. > > > > > [edited] > > > > > > Hi Frederic, > > > Do you find these patches, that provide the ability to restrict > > > kernel-space breakpoints to any given subset of CPUs, to bring the > > > requisite features for exploitation of hw-bkpt by 'perf tools'? > > > > > > Also of interest would be the reduced overhead associated with > > > (un)register_kernel_hw_breakpoint() operations (no IPI in case of > > > single-CPU breakpoint request). > > > [edited] > > - having a callback that quickly swap two breakpoints in order to support > > the hardware register multiplexing. I guess the pmu object would just need > > to call it when the multiplexing is decided. > > > > > > Are you suggesting something like a modify_kernel_hw_breakpoint() that > can quickly change a breakpoint address/characteristics? > > That's quite doable...it requires a quick validation through > arch_validate_hwbkpt_settings() and the requisite IPIs (depending on > what the new cpumask is). > > I will send a patch to that effect soon. >
Hi Frederic, I just sent a patchset that adds the ability to specify per-cpu kernel-space breakpoints + a (relatively) lightweight function to modify the characteristics of a kernel-space breakpoint that can be used to swap between two breakpoint requests.
Please pull them into -tip tree if you find them mature and ready.
With these new feature additions, I see the HW-Breakpoint infrastructure code ready to meet the needs for exploitation by perf-tools and I presume you would restart your effort on the same?
Thanks, K.Prasad
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