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Message-ID: <807b3a220811251848w384298dp393691173e603fc2@mail.gmail.com>
Date: Wed, 26 Nov 2008 08:18:02 +0530
From: "Nikanth K" <nikanth@gmail.com>
To: "Masami Hiramatsu" <mhiramat@redhat.com>
Subject: Re: [RFC] kreplace: Rebootless kernel updates
Cc: "Nikanth Karthikesan" <knikanth@suse.de>, linux-kernel@vger.kernel.org,
       ananth@in.ibm.com, davem@davemloft.net, contact@ksplice.com,
       jbarnold@ksplice.com, tabbott@ksplice.com, wdaher@ksplice.com,
       andersk@ksplice.com
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References: <200811211720.26394.knikanth@suse.de> <4926C838.8080105@redhat.com>
	 <200811241637.33329.knikanth@suse.de> <492AC522.4020202@redhat.com>
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Hi Masami

On Mon, Nov 24, 2008 at 8:45 PM, Masami Hiramatsu <mhiramat@redhat.com> wrote:
> Nikanth Karthikesan wrote:
>> On Friday 21 November 2008 20:09:52 Masami Hiramatsu wrote:
>>> Hi Nikanth,
>>>
>>> Nikanth Karthikesan wrote:
>>
>>> Hmm,
>>> Would you like to replace a function to another function?
>>> If so, AFAIK, you can do that with kprobe and below pre_handler.
>>> (see booster enabled path in setup_singlestep())
>>>
>>> pre_handler(...)
>>> {
>>>      reset_current_kprobe(); /* this kprobe doesn't need any more */
>>>      regs->ip = new_function;        /* change IP to new function */
>>>      preempt_enable_no_resched();    /* recover preempt count */
>>>      return 1;       /* No need to setup singlestep */
>>> }
>>>
>>>
>>
>> So, am I seeing worries to enable something, which is already possible, but
>> just not documented?
>
> Actually, you can do this with kprobes, but not documented,
> because the regs->ip setup depends on arch. (above code is only for
> x86/x86-64).
>
> I think it's easier to just provide above pre_handler for each arch than
> jprobe-based kreplace approach.
>

I thought jprobes would provide easy access to function parameters.

Thanks
Nikanth
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