[cgl_discussion] RE: [cgl_specs] Use case - Live patching

Cress, Andrew R andrew.r.cress at intel.com
Mon Mar 28 08:06:42 PST 2005

Hmmm.  I see a clear difference between "Live Updates" (updating the
kernel and other base files via binary rpms, while live), and "Live
Patching" (source patch updates, while live).  

In the first case, support can be maintained through rpm versions, and
the binaries are a constant for integration testing.  

In the second case, there might not be as much rigor in versioning, and
there are lots more potential issues in re-building a kernel from
source, especially for the uninitiated system admin.  

Other Unixes do the first, but not the second, so the rules are less
Both are doable, but the second involves more risk.


-----Original Message-----
From: Corey Minyard [mailto:cminyard at mvista.com] 
Sent: Monday, March 28, 2005 10:06 AM
To: Ralf Flaxa
Cc: Takashi Ikebe; cgl_tech_board at groups.osdl.org;
cgl_specs at groups.osdl.org; cgl_discussion at lists.osdl.org
Subject: Re: [cgl_specs] Use case - Live patching

Why do you think it is evil?  It is standard practice in most large 
telecom systems as it improves availability.


Ralf Flaxa wrote:

>Speaking for SUSE/Novell I can at least say that live patching is evil
>and would never be considered supported. How shall you guarantee
>or certification with such a mechanism in place?
>	Ralf
>On Mon, Mar 28, 2005 at 11:14:50AM +0900, Takashi Ikebe wrote:
>>The following is a use case for a Live patching.  This
>>addresses AVL10.0 Live patching on CGL Specification 3.0.
>>Please feel free to comment / suggestion.
>>OSDL CGL specifies that carrier grade Linux shall provide the
>>for dynamically replacing the symbols of a running process without
>>restarting. Dynamic replacement of symbols allows a process to access
>>patched functions or values without restarting and can improve process
>>Desired Outcome
>>Mainline kernel acceptance or distro acceptance
>>System administrators setup the requirements on installations. On
>>operation, system administrators apply patch with the requirement.
>>On operation, system administrators apply patch with the requirement
>>following scenario;
>>1.System administrators make patch file from diff file or new
>>source code.
>>2.System administrators load patch to the process with provided live
>>patch tool.
>>3.System administrators activate patch to the process with provided
>>patch tool.
>>4.Confirm that the patch is correctly applied or not.
>>Implementation Notes
>>The requirement need to have following functions;
>>- The function which loads the patch file to target process's memory
>>- The function which overwrites the branch operation code to the
>>on the entry point of  target process's functions which wants to fix
>>- The function which restores overwritten branch code.
>>- The function which unload the patch files.
>>Through above functions, the requirement realize on-line patch to
>>The requirement need to provide on-line patch even if the process is
>>multi-thread model process, or environment is SMP, and stop time of
>>target process should not over  100 milliseconds.
>>Pannus project: http://pannus.sourceforge.net/
>>Live patching implementation:
>>Takashi Ikebe
>>NTT Network Service Systems Laboratories
>>9-11, Midori-Cho 3-Chome Musashino-Shi,
>>Tokyo 180-8585 Japan
>>Tel : +81 422 59 4246, Fax : +81 422 60 4012
>>e-mail : ikebe.takashi at lab.ntt.co.jp

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