Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc

From	Torsten Duwe <duwe@lst.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc
Date	2016-03-17 16:50 +0100
Message-ID	<rdIlr-MU-1@gated-at.bofh.it> (permalink)
References	<raGpQ-4vx-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Mar 09, 2016 at 05:59:40PM +1100, Balbir Singh wrote:
> 
> Changelog v6:
> 	1. Experimental changes -- need loads of testing
> 	   Based on the assumption that very far TOC and LR values
> 	   indicate the call happened through a stub and the
> 	   stub return works differently from a local call which
> 	   uses klp_return_helper.

Well, this is true, but the inverse is not.
Less than 2GiB between LR and TOC is a necessary but not a sufficient
condition for a local call.

I see the problem with your code that it hardly detects calls from one module
to another nearby. It will fail iff you mistake a global call to a module loaded
earlier to be local while patching AND you access global data / 64-bit constants
after that call before the TOC is sanitised again.

	Torsten

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[PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Balbir Singh <bsingharora@gmail.com> - 2016-03-09 08:10 +0100
  Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Torsten Duwe <duwe@lst.de> - 2016-03-09 10:20 +0100
    Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Petr Mladek <pmladek@suse.com> - 2016-03-09 10:50 +0100
      Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Torsten Duwe <duwe@lst.de> - 2016-03-09 11:10 +0100
        Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Jiri Kosina <jikos@kernel.org> - 2016-03-09 11:20 +0100
          Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Torsten Duwe <duwe@lst.de> - 2016-03-09 12:20 +0100
            Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Petr Mladek <pmladek@suse.com> - 2016-03-09 14:00 +0100
        Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Michael Ellerman <mpe@ellerman.id.au> - 2016-03-09 11:30 +0100
    Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Balbir Singh <bsingharora@gmail.com> - 2016-03-10 01:50 +0100
  Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Miroslav Benes <mbenes@suse.cz> - 2016-03-15 11:30 +0100
  Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Torsten Duwe <duwe@lst.de> - 2016-03-17 16:50 +0100

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