Re: [PATCH v5 3.1.0-rc4-tip 8/26] x86: analyze instruction anddetermine fixups.

[Stefan Hajnoczi]

On Tue, Sep 20, 2011 at 05:31:27PM +0530, Srikar Dronamraju wrote:
> 
> The instruction analysis is based on x86 instruction decoder and
> determines if an instruction can be probed and determines the necessary
> fixups after singlestep.  Instruction analysis is done at probe
> insertion time so that we avoid having to repeat the same analysis every
> time a probe is hit.
> 
> Signed-off-by: Jim Keniston <jkenisto@xxxxxxxxxx>
> Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/Kconfig               |    3 
>  arch/x86/include/asm/uprobes.h |   42 ++++
>  arch/x86/kernel/Makefile       |    1 
>  arch/x86/kernel/uprobes.c      |  385 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 431 insertions(+), 0 deletions(-)
>  create mode 100644 arch/x86/include/asm/uprobes.h
>  create mode 100644 arch/x86/kernel/uprobes.c

You've probably thought of this but it would be nice to skip XOL for
nops.  This would be a common case with static probes (e.g. sdt.h) where
the probe template includes a nop where we can easily plant int $0x3.

Perhaps a check can be added to the analysis so that after calling the
filter/handler we can immediately continue the process instead of
executing the (useless) nop out-of-line.

Stefan
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