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 (both the breakpoint and
single-step exception is bypassed for each kprobe).
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. There is a potential gain to be had with a direct
jump instead of a breakpoint, but the caveats need to be traded off
with the complexity it brings in.
For now, mark OPTPROBES na 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..73662f9 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: | na |
| s390: | TODO |
| score: | TODO |
| sh: | TODO |
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