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References: <202310080853.UhMe5iWa-lkp@intel.com>
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From:   Uros Bizjak <ubizjak@gmail.com>
Date:   Fri, 1 Dec 2023 14:57:29 +0100
Message-ID: <CAFULd4ZgT1dZFz36ZbPeqJa+U2NwusSTudg175sSarhpvEu-Zw@mail.gmail.com>
Subject: Re: [tip:x86/percpu 12/12] arch/x86/include/asm/preempt.h:27:55:
 sparse: sparse: incompatible types for operation (&):
To:     kernel test robot <lkp@intel.com>
Cc:     oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org,
        x86@kernel.org, Ingo Molnar <mingo@kernel.org>,
        Nadav Amit <namit@vmware.com>
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On Sun, Oct 8, 2023 at 2:43=E2=80=AFAM kernel test robot <lkp@intel.com> wr=
ote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/p=
ercpu
> head:   ca4256348660cb2162668ec3d13d1f921d05374a
> commit: ca4256348660cb2162668ec3d13d1f921d05374a [12/12] x86/percpu: Use =
C for percpu read/write accessors
> config: x86_64-randconfig-122-20231007 (https://download.01.org/0day-ci/a=
rchive/20231008/202310080853.UhMe5iWa-lkp@intel.com/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> reproduce (this is a W=3D1 build): (https://download.01.org/0day-ci/archi=
ve/20231008/202310080853.UhMe5iWa-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new vers=
ion of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202310080853.UhMe5iWa-lkp=
@intel.com/
>
> sparse warnings: (new ones prefixed by >>)
>    kernel/bpf/percpu_freelist.c: note: in included file (through arch/x86=
/include/asm/preempt.h, include/linux/preempt.h, include/linux/spinlock.h, =
...):
>    arch/x86/include/asm/percpu.h:550:49: sparse: sparse: Expected ) at en=
d of cast operator
>    arch/x86/include/asm/percpu.h:550:49: sparse: sparse: got __seg_gs
>    arch/x86/include/asm/percpu.h:564:33: sparse: sparse: Expected ) at en=
d of cast operator
>    arch/x86/include/asm/percpu.h:564:33: sparse: sparse: got __seg_gs

sparse is too strict here. The following code is perfectly legal:

--cut here--
int __seg_gs foo;

int bar (int *pcp)
{
  return *(typeof (*pcp) __seg_gs *)(unsigned long)(pcp);
}
--cut here--

$ gcc -O2 -S -Wextra -Wall test.c
$
$ sparse test.c
test.c:1:14: error: Expected ; at end of declaration
test.c:1:14: error: got foo
test.c:5:26: error: Expected ) at end of cast operator
test.c:5:26: error: got __seg_gs
$

Uros.