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Date:   Fri, 22 Mar 2019 14:29:29 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Joao Moreira <jmoreira@...e.de>
Cc:     live-patching@...r.kernel.org, mbenes@...e.cz, pmladek@...e.cz,
        jikos@...e.cz, nstange@...e.de, jpoimboe@...hat.com,
        khlebnikov@...dex-team.ru, jeyu@...nel.org, matz@...e.de,
        linux-kernel@...r.kernel.org, yamada.masahiro@...ionext.com,
        linux-kbuild@...r.kernel.org, michal.lkml@...kovi.net,
        live-patching-owner@...r.kernel.org
Subject: Re: [PATCH v2 5/8] modpost: Integrate klp-convert

On 3/22/19 12:37 PM, Joao Moreira wrote:
> On 2019-03-22 11:54, Joe Lawrence wrote:
>> On Fri, Mar 01, 2019 at 11:13:10AM -0300, Joao Moreira wrote:
>>> From: Josh Poimboeuf <jpoimboe@...hat.com>
>>>
>>> Create cmd_klp_convert and hook it into scripts/Makefile.modpost.
>>> cmd_klp_convert invokes klp-convert with the right arguments for the
>>> conversion of unresolved symbols inside a livepatch.
>>>
>>> [khlebnikov:
>>> * save cmd_ld_ko_o into .module.cmd, if_changed_rule doesn't do that
>>> * fix bashisms for debian where /bin/sh is a symlink to /bin/dash
>>> * rename rule_link_module to rule_ld_ko_o, otherwise arg-check inside
>>>    if_changed_rule compares cmd_link_module and cmd_ld_ko_o
>>> * check modinfo -F livepatch only if CONFIG_LIVEPATCH is true
>>> ]
>>>
>>> [mbenes:
>>> * remove modinfo call. LIVEPATCH_ in Makefiled
>>> ]
>>>
>>> [jmoreira:
>>> * split up: move the .livepatch file-based scheme for identifying
>>> livepatches to a previous patch, as it was required for correctly
>>> building Symbols.list there.
>>> ]
>>>
>>> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
>>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
>>> Signed-off-by: Miroslav Benes <mbenes@...e.cz>
>>> Signed-off-by: Joao Moreira <jmoreira@...e.de>
>>> ---
>>>   scripts/Kbuild.include   |  4 +++-
>>>   scripts/Makefile.modpost | 16 +++++++++++++++-
>>>   scripts/mod/modpost.c    |  6 +++++-
>>>   scripts/mod/modpost.h    |  1 +
>>>   4 files changed, 24 insertions(+), 3 deletions(-)
>>>
>>>
>>> [ ... snip ... ]
>>>
>>> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
>>> index 7d4af0d0accb..da779a185218 100644
>>> --- a/scripts/Makefile.modpost
>>> +++ b/scripts/Makefile.modpost
>>> @@ -125,8 +125,22 @@ quiet_cmd_ld_ko_o = LD [M]  $@
>>>                    -o $@ $(filter-out FORCE,$^) ;
>>>    \
>>>   	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
>>>
>>> +SLIST = $(objtree)/Symbols.list
>>> +KLP_CONVERT = scripts/livepatch/klp-convert
>>> +quiet_cmd_klp_convert = KLP $@
>>> +      cmd_klp_convert = mv $@ $(@:.ko=.klp.o);				\
>>> +			$(KLP_CONVERT) $(SLIST) $(@:.ko=.klp.o) $@
>>> +
>>> +define rule_ld_ko_o
>>> +	$(call cmd,ld_ko_o) $(cmd_ld_ko_o) ;				\
>>                             ^
>> Should there be a ';' semicolon here (and maybe a line-break) between
>> $(call cmd,ld_ko_o) and $(cmd_ld_ko_o)?
>>
>> I didn't see this in my x86_64 VM, but on a ppc64le box, I kept getting
>> really strange build errors that I traced to this line.  Without a
>> semicolon, the build was trying to run a make command with a linker
>> command smashed onto the end of it:
>>
>>    make -f ./arch/powerpc/Makefile.postlink crypto/xts.ko ld -r  -EL -m
>> elf64lppc -T ./scripts/module-common.lds -T
>> ./arch/powerpc/kernel/module.lds --save-restore-funcs  --build-id  -o
>> crypto/xts.ko crypto/xts.o crypto/xts.mod.o
>>
>>
>> Now, klp-convert looks like will need some ppc64le work as well, as
>> it's
>> confused about .TOC. symbols:
>>
>>      CC      samples/livepatch/livepatch-annotated-sample.mod.o
>>      CC      samples/livepatch/livepatch-callbacks-busymod.mod.o
>>      CC      samples/livepatch/livepatch-callbacks-demo.mod.o
>>      CC      samples/livepatch/livepatch-callbacks-mod.mod.o
>>      CC      samples/livepatch/livepatch-sample.mod.o
>>      CC      samples/livepatch/livepatch-shadow-fix1.mod.o
>>      CC      samples/livepatch/livepatch-shadow-fix2.mod.o
>>      CC      samples/livepatch/livepatch-shadow-mod.mod.o
>>      LD [M]  samples/livepatch/livepatch-annotated-sample.ko
>>      LD [M]  samples/livepatch/livepatch-callbacks-demo.ko
>>      KLP     samples/livepatch/livepatch-annotated-sample.ko
>>      LD [M]  samples/livepatch/livepatch-callbacks-mod.ko
>>      KLP     samples/livepatch/livepatch-callbacks-demo.ko
>>      LD [M]  samples/livepatch/livepatch-sample.ko
>>      LD [M]  samples/livepatch/livepatch-shadow-fix1.ko
>>    klp-convert: Define KLP_SYMPOS for the symbol: .TOC.
>>    Valid KLP_SYMPOS for symbol .TOC.:
>>
>>    [ ... snip listing of all .TOC's across the kernel ... ]
>>
>> but we can save that for another day.
>>
> 
> Hi Joe, first of all, thank you for you in-depth review. I did not have
> the time to go through everything yet, and I'll reply properly to the
> other comments soon. Yet, I would like to add a quick note here, since
> you are testing ppc64le. ppc64le is exactly one of the things I have
> been dealing with in the last two days, specifically the .TOC. symbols
> (there is also another bug related to converting relocations of symbols
> with index 0, but this one is architecture agnostic).
> 
> If you would like to take a look, the fix is in the latest commit here:
> - https://github.com/SUSE/klp-convert/tree/fixppc64le
> 
> I would be very glad if you have any comment or input on that, and I
> guess that if the fix is that simple, I can manage to squash it into v3.

Hi João,

I added https://github.com/SUSE/klp-convert/commit/69b89ef5c366 on top 
of my 
https://github.com/joe-lawrence/linux/tree/klp-convert-v2-rebase-review 
branch with positive results:

(No build klp-convert build complaints)

   % uname -r
   Linux ibm-p9z-21-lp26.mpc.lab.eng.bos.redhat.com 5.1.0-rc1+ #6 SMP 
Thu Mar 21 11:40:24 EDT 2019 ppc64le ppc64le ppc64le GNU/Linux

   % insmod samples/livepatch/livepatch-annotated-sample.ko
   % grep -o 'livepatch.*' /proc/cmdline
   livepatch=1

   % ./tools/testing/selftests/livepatch/test-livepatch.sh
   TEST: basic function patching ... ok
   TEST: multiple livepatches ... ok
   TEST: atomic replace livepatch ... ok
   TEST: klp-convert symbols ... ok

There may be more ppc64le specifics lurking, but if we could get samples 
and self-tests working, I think we'd be in good shape for v3.

-- Joe

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