Re: module: save load_info for livepatch modules

From	Petr Mladek <pmladek@suse.com>
Newsgroups	linux.kernel
Subject	Re: module: save load_info for livepatch modules
Date	2015-11-12 16:10 +0100
Message-ID	<qu1FE-240-19@gated-at.bofh.it> (permalink)
References	(1 earlier) <qt92y-kt-5@gated-at.bofh.it> <qtEpH-3Sx-7@gated-at.bofh.it> <qtSM1-4Ly-1@gated-at.bofh.it> <qtXiH-7Fc-31@gated-at.bofh.it> <qu06R-ZA-7@gated-at.bofh.it>
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On Thu 2015-11-12 14:22:28, Miroslav Benes wrote:
> On Thu, 12 Nov 2015, Petr Mladek wrote:
> > > >Maybe I am missing something but isn't it necessary to call vfree() on
> > > >info somewhere in the end?
> > > 
> > > So free_copy() will call vfree(info->hdr), except in livepatch modules
> > > we want to keep all the elf section information stored there, so we
> > > avoid calling free_copy(), As for the info struct itself, if you look
> > > at the init_module and finit_module syscall definitions in
> > > kernel/module.c, you will see that info is actually a local function
> > > variable, simply passed in to the call to load_module(), and will be
> > > automatically deallocated when the syscall returns. :-) No need to
> > > explicitly free info.
> > 
> > We still have to free the copied or preserved structures when
> > the module is unloaded.
> 
> ...freeing what we allocated. We need to free info->hdr somewhere if not 
> here and also mod_arch_specific struct where the patch module is removed. 
> This would unfortunately lead to changes in arch-specific code in 
> module.c. For example in arch/s390/kernel/module.c there is vfree call on 
> part of mod_arch_specific in module_finalize. We would call it only if the 
> flag mentioned above is not set and at the same time we would need to call 
> it when the patch module is being removed.

Sigh, I am afraid that the flag is not enough. IMHO, we need to split
the load finalizing functions into two pieces. One will be always
called when the module load is finalized. The other part will free
the load_info. It will be called either when the load is finalized or
when the module is unloaded, depending on if we want to preserve
the load_info.

Sigh, it is getting complicated. But let's see how it looks in reality.

Best Regards,
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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