Kprobes Support for ARM arch

[rsmadhvesh@vsnl.net]

Patch is attached now..

----- Original Message -----
From: rsmadhvesh@vsnl.net
Date: Thursday, January 18, 2007 2:22 pm
Subject: Re: Kprobes Support for ARM arch
To: systemtap@sources.redhat.com
Cc: madhvesh.s@ap.sony.com, satish.v@ap.sony.com

> Hi All,
> 
> The attached patch addresses the branch instructions
> check for ARM kprobes last week release and avoids 
> unexpected crash when probe is placed for branch 
> type instructions. If any one finds issues, please let 
> me know.
> 
> Regards
> Madhvesh
> 
> ----- Original Message -----
> From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> Date: Friday, January 12, 2007 11:02 am
> Subject: Re: Kprobes Support for ARM arch
> To: rsmadhvesh@vsnl.net
> Cc: systemtap@sources.redhat.com, madhvesh.s@ap.sony.com, 
> lubna@ap.sony.com, satish.v@ap.sony.com
> 
> > On Thu, Jan 11, 2007 at 07:58:07PM +0500, rsmadhvesh@vsnl.net wrote:
> > 
> > Hi Madhvesh,
> > 
> > > Hi All,
> > > 
> > > Recently we completed the kprobes support for ARM architecture
> > > targetted at 2.6.16 kernel. I have uploaded these patches in the
> > > below CELF wiki page along with few test programs.
> > > This implementation is tested using 2.6.16-24 kernel for
> > > OMAP5912 OSK reference platform.
> > 
> > I am not familiar with the ARM architecture details... the following
> > comments are from a quick glance at the patch.
> > 
> > > The patch is available in the below CELF wiki page
> > > http://tree.celinuxforum.org/CelfPubWiki/PatchArchive
> > > 
> > > The patch can be downloaded directly from here
> > > 
> > 
> http://tree.celinuxforum.org/CelfPubWiki/PatchArchive?action=AttachFile&do=get&target=kprobes-arm-patches-2.6.16.24.tgz
> > > 
> > > This implementation supports only kprobes and doesnot
> > > support any other variants like jprobes, kretprobes etc.
> > > Also it doesnot support branch/jump instructions probing.
> > 
> > How are you ensuring that a kprobe register request on a branch/jump
> > instruction fails? I don't see any profiling done to verify what the
> > underlying instruction is.
> > 
> > See arch_prepare_kprobe() from the powerpc port as to how we fail 
> > kproberegistration on certain instructions.
> > 
> > > I noticed some discussions regarding ARM kprobes in the
> > > archive. We are open to suggestions and how this implementation 
> can> > be improved.
> > 
> > Given that quite a bit of the kprobes code for any platform is
> > architecture specific, its important that your code gets reviewed 
> > by the
> > ARM kernel gurus/maintainers, if you intend that the patch be 
> included> in the mainline Linux kernels.
> > 
> > Also, you may want to port the patch to the latest kernel. There 
> have> been some interface changes:
> > - kprobe modules are more portable with the addition of in-kernel 
> > symbol  lookup.
> > - The page fault case gets its own notifier so there isn't a 
> > penalty paid
> >  when kprobes aren't in use.
> > 
> > Good work!
> > 
> > Ananth
> > 
> 
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