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Re: hot patching
Thanks a lot.
U have painted exactly what i am thinking of. I agree the points. But the line
>> * Whenever possible, compile your code as a kernel module. You can load/unload
>> your code without rebooting.
confuses me. I havnt understood the micro kernel architechture in full. How far the kernel
part can be modularised ?!!! any way i will have a study on that.
Once again thanks.
Raja Subramanian wrote:
> Pratap Chakravarthy wrote (pratap.chakravarthy@xxxxxxxxx):
> > Can you please tell me the feasibility of hot patching in an operating
> > system like linux and if possible please provide me with any details or
> > pointers on that. I saw in the sun's web site that they have provided
> > hot patching in their solaris 8. How far it is reliable.
> Reliability of hot patching is questionable. I've seen solaris "panic" after a
> hotpatch. I would not hotfix a busy running system, planned downtime sounds
> safer. But that does not mean that hot patching is a bad idea anyway.
> > what is hot patching ?
> > It is nothing but replacing a function present in the memory "on fly".In
> > usual cases suppose there is a bug in the kernel code, that bug has to be
> > removed and then compiled and linked to get the image [kernel image],which
> > is then booted. Here in hot patching the debuged function has to be
> > compiled. Then it is linked with the kernel without rebooting the system,
> > on the fly.
> > I dont know whether this facility is really required for linux. But for any
> > OS developer, this tool is a required one.
> Possible solutions for an OS developer who does not want to reboot -
> * Whenever possible, compile your code as a kernel module. You can load/unload
> your code without rebooting.
> * Run/debug the kernel you're developing in user mode. See "use mode linux".
> * Rewrite the linux kernel in erlang (just kidding...)
> The closest linux ever came to restarting without rebooting (in the
> Ctrl+Alt+Del sense) was with the "two kernel monte". This invloves restarting
> with a new kernel without rebooting the machine.
> Note: You will kill all processes as a result, so this is probably not what
> you want.
> Due to its modular design, hotpatching is easier with micro-kernel
> implementations like the Hurd. Even then, there may be seveal bugs which
> cannot be hotpatched.
> - Raja
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