[PATCH] kprobes: Mark OPTPROBES n/a for powerpc
masami.hiramatsu.pt at hitachi.com
Sun Jul 19 12:21:50 AEST 2015
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
> Hence, mark OPTPROBES n/a for powerpc.
> Signed-off-by: Ananth N Mavinakayanahalli <ananth at 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 |
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt at hitachi.com
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