Re: [PATCH] kprobes: Mark OPTPROBES n/a for powerpc
From: Masami Hiramatsu <hidden>
Date: 2015-07-19 02:21:57
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,
quoted hunk ↗ jump to hunk
Hence, mark OPTPROBES n/a for powerpc. Signed-off-by: Ananth N Mavinakayanahalli <redacted> --- .../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.pt@hitachi.com