On Wed, Jan 27, 2016 at 09:51:12PM +1100, Balbir Singh wrote:
> On Mon, 25 Jan 2016 16:38:48 +0100
> Torsten Duwe <d...@lst.de> wrote:
>
> > Changes since v5:
> > * extra "std r0,LRSAVE(r1)" for gcc-6
> > This makes the code compiler-agnostic.
> > * Follow Petr Mladek's suggestion to avoid
> > redefinition of HAVE_LIVEPATCH
>
> I looked at the patches - well mostly patches 1 and 2, some quick questions
>
> 1. I know -mprofile-kernel is a big optimization win, do we need it or can
> we incrementally add it?
There's a reason why these are first ;-)
The following ones assume -mprofile-kernel is used.
The disadvantage is all relevant registers need to be saved before calling
further C code in between functions. On the Pro side, no stack frame has been
created at that point. These are assumptions made all over the ftrace-with-regs
and live patching code here.
> 2. Some of the hardcoded checks for opcode are hard to review, I know they've
> been there in similar forms for a while. May be as an iterative step we should
> give the numbers some meaning and use proper helpers for it.
Yes, Michael has already criticised that. No further literal hex constants, I
promise.
> I am going to give the patches a spin
Thanks! Make sure you use a compiler that can disable -mprofile-kernel with
"notrace".
Torsten
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