Re: [RFC PATCH 0/5] Arch-independent livepatch

From	Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 0/5] Arch-independent livepatch
Date	2015-11-11 17:30 +0100
Message-ID	<qtGrx-592-35@gated-at.bofh.it> (permalink)
References	<qt92x-kt-1@gated-at.bofh.it> <qtEg3-3OD-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Nov 11, 2015 at 03:00:44PM +0100, Miroslav Benes wrote:
> > Background: Why does livepatch need to write its own relocations?
> > ==
> > A typical livepatch module contains patched versions of functions that can
> > reference non-exported global symbols and non-included local symbols.
> > Relocations referencing these types of symbols cannot be left in as-is
> > since the kernel module loader cannot resolve them and will therefore
> > reject the livepatch module. Furthermore, we cannot apply relocations that
> > affect modules not loaded yet at run time (e.g. a patch to a driver). The
> > current kpatch build system therefore solves this problem by embedding
> > special "dynrela" (dynamic reloc) sections in the resulting patch module
> > elf output. Using these dynrela sections, livepatch can correctly resolve
> > symbols while taking into account its scope and what module the symbol
> > belongs to, and then manually apply the dynamic relocations.
> 
> I'll only add that we solve the problem with kallsyms calls in kGraft. It 
> can get really cumbersome from time to time, so this work would simplify 
> our effort as well.

I haven't yet reviewed the code in-depth, but overall I think this patch
set is a good idea.  It simplifies livepatch itself as well as the patch
creation process (for both kGraft and kpatch-build), so it's a win-win.

-- 
Josh
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[RFC PATCH 0/5] Arch-independent livepatch Jessica Yu <jeyu@redhat.com> - 2015-11-10 05:50 +0100
  [RFC PATCH 2/5] module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-10 05:50 +0100
    Re: [RFC PATCH 2/5] module: save load_info for livepatch modules Minfei Huang <mnfhuang@gmail.com> - 2015-11-11 09:10 +0100
    Re: [RFC PATCH 2/5] module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-11 15:20 +0100
      Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-12 06:40 +0100
        Re: module: save load_info for livepatch modules Petr Mladek <pmladek@suse.com> - 2015-11-12 11:30 +0100
          Re: module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-12 14:30 +0100
            Re: module: save load_info for livepatch modules Petr Mladek <pmladek@suse.com> - 2015-11-12 16:10 +0100
              Re: module: save load_info for livepatch modules Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 18:10 +0100
                Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-12 23:20 +0100
                Re: module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-13 13:30 +0100
                Re: module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-13 13:50 +0100
                Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-14 01:40 +0100
                Re: module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-13 14:00 +0100
                Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-14 03:20 +0100
            Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-13 01:30 +0100
    Re: [RFC PATCH 2/5] module: save load_info for livepatch modules Petr Mladek <pmladek@suse.com> - 2015-11-11 15:40 +0100
      Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-12 05:50 +0100
        Re: module: save load_info for livepatch modules Petr Mladek <pmladek@suse.com> - 2015-11-12 11:10 +0100
          Re: module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-12 15:20 +0100
            Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-13 07:40 +0100
              Re: module: save load_info for livepatch modules Miroslav Benes <mbenes@suse.cz> - 2015-11-13 14:10 +0100
          Re: module: save load_info for livepatch modules Jessica Yu <jeyu@redhat.com> - 2015-11-13 09:30 +0100
    Re: [RFC PATCH 2/5] module: save load_info for livepatch modules Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 18:20 +0100
    Re: [RFC PATCH 2/5] module: save load_info for livepatch modules Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 18:30 +0100
  [RFC PATCH 1/5] elf: add livepatch-specific elf constants Jessica Yu <jeyu@redhat.com> - 2015-11-10 05:50 +0100
    Re: [RFC PATCH 1/5] elf: add livepatch-specific elf constants Petr Mladek <pmladek@suse.com> - 2015-11-11 15:00 +0100
    Re: [RFC PATCH 1/5] elf: add livepatch-specific elf constants Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 16:40 +0100
    Re: [RFC PATCH 1/5] elf: add livepatch-specific elf constants Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 16:50 +0100
      Re: elf: add livepatch-specific elf constants Jessica Yu <jeyu@redhat.com> - 2015-11-13 08:00 +0100
  [RFC PATCH 4/5] samples: livepatch: init reloc list and mark as klp module Jessica Yu <jeyu@redhat.com> - 2015-11-10 05:50 +0100
    Re: [RFC PATCH 4/5] samples: livepatch: init reloc list and mark as  klp module Jiri Slaby <jslaby@suse.cz> - 2015-11-10 09:20 +0100
      Re: [RFC PATCH 4/5] samples: livepatch: init reloc list and mark as  klp module Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-10 15:00 +0100
        Re: samples: livepatch: init reloc list and mark as klp module Jessica Yu <jeyu@redhat.com> - 2015-11-10 19:40 +0100
    Re: [RFC PATCH 4/5] samples: livepatch: init reloc list and mark as  klp module Petr Mladek <pmladek@suse.com> - 2015-11-11 16:50 +0100
      Re: samples: livepatch: init reloc list and mark as klp module Jessica Yu <jeyu@redhat.com> - 2015-11-12 07:10 +0100
        Re: samples: livepatch: init reloc list and mark as klp module Miroslav Benes <mbenes@suse.cz> - 2015-11-12 11:50 +0100
  [RFC PATCH 5/5] livepatch: x86: remove unused relocation code Jessica Yu <jeyu@redhat.com> - 2015-11-10 05:50 +0100
    Re: [RFC PATCH 5/5] livepatch: x86: remove unused relocation code Petr Mladek <pmladek@suse.com> - 2015-11-11 16:50 +0100
      Re: [RFC PATCH 5/5] livepatch: x86: remove unused relocation code Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 19:10 +0100
  [RFC PATCH 3/5] livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-10 05:50 +0100
    Re: [RFC PATCH 3/5] livepatch: reuse module loader code to write  relocations Jiri Slaby <jslaby@suse.cz> - 2015-11-10 09:20 +0100
    Re: [RFC PATCH 3/5] livepatch: reuse module loader code to write  relocations Miroslav Benes <mbenes@suse.cz> - 2015-11-11 15:40 +0100
      Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-11 21:10 +0100
        Re: livepatch: reuse module loader code to write relocations Miroslav Benes <mbenes@suse.cz> - 2015-11-12 16:30 +0100
          Re: livepatch: reuse module loader code to write relocations Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 18:50 +0100
            Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-12 21:30 +0100
              Re: livepatch: reuse module loader code to write relocations Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 21:40 +0100
                Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-13 08:20 +0100
                Re: livepatch: reuse module loader code to write relocations Miroslav Benes <mbenes@suse.cz> - 2015-11-13 15:00 +0100
          Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-12 20:20 +0100
            Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-12 21:40 +0100
    Re: [RFC PATCH 3/5] livepatch: reuse module loader code to write  relocations Petr Mladek <pmladek@suse.com> - 2015-11-11 16:30 +0100
      Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2015-11-11 19:30 +0100
        Re: livepatch: reuse module loader code to write relocations Petr Mladek <pmladek@suse.com> - 2015-11-12 10:20 +0100
    Re: [RFC PATCH 3/5] livepatch: reuse module loader code to write  relocations Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 19:00 +0100
  Re: [RFC PATCH 0/5] Arch-independent livepatch Miroslav Benes <mbenes@suse.cz> - 2015-11-11 15:10 +0100
    Re: [RFC PATCH 0/5] Arch-independent livepatch Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-11 17:30 +0100

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