On Tue, Jul 21, 2015 at 12:53:07PM +1000, Michael Ellerman wrote: > On Sun, 2015-07-19 at 11:21 +0900, Masami Hiramatsu wrote: > > On 2015/07/16 19:56, Ananth N Mavinakayanahalli wrote: > > > Kprobes uses a breakpoint instruction to trap into execution flow > > > and the probed instruction is single-stepped from an alternate location. > > > > > > On some architectures like x86, under certain conditions, the OPTPROBES > > > feature enables replacing the probed instruction with a jump instead, > > > resulting in a significant perfomance boost (one single-step exception > > > is bypassed for each kprobe). > > > > The OPTPROBE is not only for bypassing the single-step exception, but also > > the breakpoint exception. > > Please see commit 0dc016dbd820260b (ARM: kprobes: enable OPTPROBES for ARM > > 32) too, > > which shows how it is done on RISC processor. > > > > > Powerpc has an in-kernel instruction emulator. Kprobes on powerpc uses > > > this emulator already and bypasses the single-step exception, with a > > > lot less complexity. > > > > So, this might miss the point. Since it is impossible to do on some RISC > > processor, I agree with this change, but it should be committed with > > correct comments. > > I don't think it's impossible on powerpc. > > So we should leave it as a TODO for now.
OK. I put it on my TODO list. Ananth _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
