Re: livepatch: reuse module loader code to write relocations

From	Petr Mladek <pmladek@suse.com>
Newsgroups	linux.kernel
Subject	Re: livepatch: reuse module loader code to write relocations
Date	2015-11-12 10:20 +0100
Message-ID	<qtWcW-71a-3@gated-at.bofh.it> (permalink)
References	<qt92x-kt-1@gated-at.bofh.it> <qt92y-kt-15@gated-at.bofh.it> <qtFvs-4xR-11@gated-at.bofh.it> <qtIjE-6mP-25@gated-at.bofh.it>
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On Wed 2015-11-11 13:27:18, Jessica Yu wrote:
> Basically, the patch module code is expected to build the reloc_secs
> list for each object that is being patched. For example in kpatch, the
> patch module generates this list in patch_init(). Like you guessed, it
> does go through all the elf sections of the patch module to find the
> reloc sections marked SHF_RELA_LIVEPATCH. We are able to access these
> sections through module->info, which is set up for livepatch modules
> before the module loader calls do_init_module() (and hence before
> patch_init(), See patch 2/5).
> See below for an example of how the reloc_secs list might be built: https://github.com/flaming-toast/kpatch/blob/no_dynrela_redux/kmod/patch/livepatch-patch-hook.c#L213

Thanks a lot for the link and explanation. I think that it would be nice to
incorporate this into the patchset. I would put it into a separate
function, e.g. klp_reloc_secs_init(). It can be called either from
klp_register_patch() or from klp_init_patch().

> Once the patch module has built this list, it is good to go for use in
> livepatch core. All livepatch has to do then is to iterate though the
> list, resolve any outstanding symbols, and call apply_relocate_add(),
> as shown in this patch.
>
> Miroslav mentioned in another email that we should start thinking
> about including documentation about this, including the expected patch
> module format. So perhaps v2 should include some documentation about
> this whole process somewhere.

That would be cool.

Thank you,
Petr
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Thread

[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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