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Date:   Thu, 15 Sep 2022 12:26:06 +0530
From:   "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 11/16] objtool: Add --mnop as an option to --mcount
To:     linuxppc-dev@lists.ozlabs.org, kernel test robot <lkp@intel.com>,
        Sathvika Vasireddy <sv@linux.ibm.com>
Cc:     aik@ozlabs.ru, chenzhongjin@huawei.com,
        christophe.leroy@csgroup.eu, jpoimboe@redhat.com,
        kbuild-all@lists.01.org, linux-kernel@vger.kernel.org,
        mbenes@suse.cz, mingo@redhat.com, mpe@ellerman.id.au,
        npiggin@gmail.com, peterz@infradead.org, rostedt@goodmis.org
References: <20220912082020.226755-12-sv@linux.ibm.com>
        <202209130240.GpGMxW7T-lkp@intel.com>
In-Reply-To: <202209130240.GpGMxW7T-lkp@intel.com>
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kernel test robot wrote:
> Hi Sathvika,
>=20
> Thank you for the patch! Yet something to improve:
>=20
> [auto build test ERROR on powerpc/topic/ppc-kvm]
> [also build test ERROR on linus/master v6.0-rc5]
> [cannot apply to powerpc/next masahiroy-kbuild/for-next next-20220912]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>=20
> url:    https://github.com/intel-lab-lkp/linux/commits/Sathvika-Vasireddy=
/objtool-Enable-and-implement-mcount-option-on-powerpc/20220912-163023
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git=
 topic/ppc-kvm
> config: x86_64-rhel-8.3 (https://download.01.org/0day-ci/archive/20220913=
/202209130240.GpGMxW7T-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.3.0-5) 11.3.0
> reproduce (this is a W=3D1 build):
>         # https://github.com/intel-lab-lkp/linux/commit/ca5e2b42c0d4438ba=
93623579b6860b98f3598f3
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Sathvika-Vasireddy/objtool-Enabl=
e-and-implement-mcount-option-on-powerpc/20220912-163023
>         git checkout ca5e2b42c0d4438ba93623579b6860b98f3598f3
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         make W=3D1 O=3Dbuild_dir ARCH=3Dx86_64 SHELL=3D/bin/bash
>=20
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>

Thanks.

>=20
> All errors (new ones prefixed by >>):
>=20
>>> cc1: error: '-mnop-mcount' is not implemented for '-fPIC'

CONFIG_NOP_MCOUNT is used for FTRACE_MCOUNT_USE_CC, so instead of:

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f9920f1341c8..a8dd138df637 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -189,6 +189,7 @@ config X86
        select HAVE_CONTEXT_TRACKING_USER_OFFSTACK      if HAVE_CONTEXT_TRA=
CKING_USER
        select HAVE_C_RECORDMCOUNT
        select HAVE_OBJTOOL_MCOUNT              if HAVE_OBJTOOL
+       select HAVE_NOP_MCOUNT                  if HAVE_OBJTOOL_MCOUNT
        select HAVE_BUILDTIME_MCOUNT_SORT
        select HAVE_DEBUG_KMEMLEAK
        select HAVE_DMA_CONTIGUOUS

I think you should do:

+       select HAVE_NOP_MCOUNT                  if FTRACE_MCOUNT_USE_OBJTOOL


I was hoping we could reuse CONFIG_NOP_MCOUNT seeing as it is only used=20
by s390, but I now wonder if it is better to just keep that separate. We=20
could introduce HAVE_OBJTOOL_NOP_MCOUNT for objtool instead.


- Naveen