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. Thank you, > > Hence, mark OPTPROBES n/a for powerpc. > > Signed-off-by: Ananth N Mavinakayanahalli <ana...@in.ibm.com> > --- > .../features/debug/optprobes/arch-support.txt | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/Documentation/features/debug/optprobes/arch-support.txt > b/Documentation/features/debug/optprobes/arch-support.txt > index b8999d8..0a3ca33 100644 > --- a/Documentation/features/debug/optprobes/arch-support.txt > +++ b/Documentation/features/debug/optprobes/arch-support.txt > @@ -27,7 +27,7 @@ > | nios2: | TODO | > | openrisc: | TODO | > | parisc: | TODO | > - | powerpc: | TODO | > + | powerpc: | n/a | > | s390: | TODO | > | score: | TODO | > | sh: | TODO | > > -- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu...@hitachi.com _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
