Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs directory

From	Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs directory
Date	2015-11-10 14:50 +0100
Message-ID	<qtht9-5IV-29@gated-at.bofh.it> (permalink)
References	(1 earlier) <qsXkK-i7-13@gated-at.bofh.it> <qt1HJ-2YW-19@gated-at.bofh.it> <qt3Jw-5gt-17@gated-at.bofh.it> <qt9cd-nP-7@gated-at.bofh.it> <qtcMO-2IH-13@gated-at.bofh.it>
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On Tue, Nov 10, 2015 at 09:49:09AM +0100, Miroslav Benes wrote:
> On Mon, 9 Nov 2015, Josh Poimboeuf wrote:
> 
> > On Mon, Nov 09, 2015 at 05:01:18PM -0600, Chris J Arges wrote:
> > > On 11/09/2015 02:56 PM, Josh Poimboeuf wrote:
> > > > I'd recommend splitting this up into two separate patches:
> > > > 
> > > > 1. introduce old_sympos
> > > > 2. change the sysfs interface
> > > > 
> > > > On Mon, Nov 09, 2015 at 10:16:05AM -0600, Chris J Arges wrote:
> > > >> In cases of duplicate symbols in vmlinux, old_sympos will be used to
> > > >> disambiguate instead of old_addr. Normally old_sympos will be 0, and
> > > >> default to only returning the first found instance of that symbol. If an
> > > >> incorrect symbol position is specified then livepatching will fail.
> > > > 
> > > > In the case of old_sympos == 0, instead of just returning the first
> > > > symbol it finds, I think it should ensure that the symbol is unique.  As
> > > > Miroslav suggested:
> > > > 
> > > >   0 - default, preserve more or less current behaviour. If the symbol is 
> > > >       unique there is no problem. If it is not the patching would fail.
> > > >   1, 2, ... - occurrence of the symbol in kallsyms.
> > > >   
> > > >   The advantage is that if the user does not care and is certain that the 
> > > >   symbol is unique he doesn't have to do anything. If the symbol is not 
> > > >   unique he still has means how to solve it.
> > > > 
> > > 
> > > So one part that will be confusing here is as follows.
> > > 
> > > If '0' is specified for old_sympos, should the symbol be 'func_name,0'
> > > or 'func_name,1' provided we have a unique symbol? We could also default
> > > to 'what the user provides', but this seems odd.
> > 
> > I don't feel strongly either way, but I think using the same number the
> > user provides is fine, since it makes the sysfs interface consistent
> > with the old_sympos usage.
> 
> I think it should be func_name,1 even if '0' is specified and the symbol 
> is unique. Because if we say that 1, 2, ... is the occurrence of the 
> symbol in kallsyms it should stay that way everywhere. Hence for 
> old_sympos == 0 it is func_name,1 in sysfs; for 1 it is still func_name,1; 
> for 2 it is func_name,2 and so on.
> 
> And I'd add this to sysfs documentation.

That makes sense, sounds fine to me.

-- 
Josh
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Thread

[PATCH] livepatch: old_name.number scheme in livepatch sysfs directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-02 19:00 +0100
  Re: livepatch: old_name.number scheme in livepatch sysfs directory Jessica Yu <jeyu@redhat.com> - 2015-11-02 20:20 +0100
  Re: [PATCH] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-02 21:00 +0100
    Re: [PATCH] livepatch: old_name.number scheme in livepatch sysfs  directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-02 21:20 +0100
      Re: [PATCH] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-02 21:40 +0100
        [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-03 00:10 +0100
          Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-03 11:00 +0100
            Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-03 16:10 +0100
          Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-03 12:00 +0100
            Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Petr Mladek <pmladek@suse.com> - 2015-11-03 13:50 +0100
              Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-03 16:10 +0100
              Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Jiri Kosina <jikos@kernel.org> - 2015-11-03 21:00 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-03 21:10 +0100
                [PATCH 1/3 v4] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges <chris.j.arges@canonical.com> - 2015-11-11 17:30 +0100
                Re: [PATCH 1/3 v4] livepatch: add old_sympos as disambiguator field  to klp_func Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-11 18:50 +0100
                Re: [PATCH 1/3 v4] livepatch: add old_sympos as disambiguator field  to klp_func Miroslav Benes <mbenes@suse.cz> - 2015-11-12 11:30 +0100
                [PATCH 3/3 v4] livepatch: old_name,number scheme in livepatch sysfs directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-11 17:40 +0100
                Re: [PATCH 3/3 v4] livepatch: old_name,number scheme in livepatch  sysfs directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-11 19:10 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Chris J Arges <chris.j.arges@canonical.com> - 2015-11-11 17:40 +0100
                [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field to klp_reloc Chris J Arges <chris.j.arges@canonical.com> - 2015-11-11 17:40 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-11 19:00 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Petr Mladek <pmladek@suse.com> - 2015-11-12 15:40 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-12 20:20 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Petr Mladek <pmladek@suse.com> - 2015-11-13 15:00 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-13 18:00 +0100
                Re: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field  to klp_reloc Miroslav Benes <mbenes@suse.cz> - 2015-11-12 11:30 +0100
            Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-03 16:00 +0100
              Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-03 17:20 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-03 18:00 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-03 21:50 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-04 11:00 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-04 17:10 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-04 17:20 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-05 16:20 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-05 17:00 +0100
                Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs  directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-05 17:10 +0100
                [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-09 17:20 +0100
                Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-09 22:00 +0100
                Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs  directory Chris J Arges <chris.j.arges@canonical.com> - 2015-11-10 00:10 +0100
                Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-10 06:00 +0100
                Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-10 09:50 +0100
                Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs  directory Josh Poimboeuf <jpoimboe@redhat.com> - 2015-11-10 14:50 +0100
                Re: [PATCH v3] livepatch: old_name,number scheme in livepatch sysfs  directory Miroslav Benes <mbenes@suse.cz> - 2015-11-10 10:10 +0100

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