diff mbox series

lib/bitmap: waive const_eval test as it breaks the build

Message ID	20230717195813.29059-1-yury.norov@gmail.com
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; From: Yury Norov <yury.norov@gmail.com> To: linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Nick Desaulniers <ndesaulniers@google.com> Cc: Yury Norov <yury.norov@gmail.com>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Alexander Lobakin <alexandr.lobakin@intel.com>, Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Nathan Chancellor <nathan@kernel.org>, Tom Rix <trix@redhat.com>, oe-kbuild-all@lists.linux.dev Subject: [PATCH] lib/bitmap: waive const_eval test as it breaks the build Date: Mon, 17 Jul 2023 12:58:13 -0700 Message-Id: <20230717195813.29059-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	lib/bitmap: waive const_eval test as it breaks the build \| lib/bitmap: waive const_eval test as it breaks the build

Commit Message

Yury Norov July 17, 2023, 7:58 p.m. UTC

  When building with clang, and when KASAN and GCOV_PROFILE_ALL are both
enabled, the test fails to build [1]:

>> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
           BUILD_BUG_ON(!__builtin_constant_p(res));
           ^
   include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
           BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
           ^
   include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
   #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                       ^
   include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert'
           _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
           ^
   include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert'
           __compiletime_assert(condition, msg, prefix, suffix)
           ^
   include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert'
                           prefix ## suffix();                             \
                           ^
   <scratch space>:185:1: note: expanded from here
   __compiletime_assert_239

Originally it was attributed to s390, which now looks seemingly wrong. The
issue is also not related to bitmap code itself, but it breaks build for
a given configuration. So, disabling the test unless the compiler will
get fixed.

[1] https://github.com/ClangBuiltLinux/linux/issues/1874

Fixes: dc34d5036692 ("lib: test_bitmap: add compile-time optimization/evaluations assertions")
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 lib/test_bitmap.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

Comments

Nathan Chancellor July 17, 2023, 8:31 p.m. UTC | #1

Hi Yury,

On Mon, Jul 17, 2023 at 12:58:13PM -0700, Yury Norov wrote:
> When building with clang, and when KASAN and GCOV_PROFILE_ALL are both
> enabled, the test fails to build [1]:
> 
> >> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
>            BUILD_BUG_ON(!__builtin_constant_p(res));
>            ^
>    include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
>            BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>            ^
>    include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
>    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>                                        ^
>    include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert'
>            _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>            ^
>    include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert'
>            __compiletime_assert(condition, msg, prefix, suffix)
>            ^
>    include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert'
>                            prefix ## suffix();                             \
>                            ^
>    <scratch space>:185:1: note: expanded from here
>    __compiletime_assert_239
> 
> Originally it was attributed to s390, which now looks seemingly wrong. The
> issue is also not related to bitmap code itself, but it breaks build for
> a given configuration. So, disabling the test unless the compiler will
> get fixed.
> 
> [1] https://github.com/ClangBuiltLinux/linux/issues/1874
> 
> Fixes: dc34d5036692 ("lib: test_bitmap: add compile-time optimization/evaluations assertions")
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
>  lib/test_bitmap.c | 17 +++++------------
>  1 file changed, 5 insertions(+), 12 deletions(-)
> 
> diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
> index 187f5b2db4cf..a791fdb7a8c9 100644
> --- a/lib/test_bitmap.c
> +++ b/lib/test_bitmap.c
> @@ -1163,6 +1163,9 @@ static void __init test_bitmap_print_buf(void)
>  
>  static void __init test_bitmap_const_eval(void)
>  {
> +#if defined(CONFIG_CC_IS_CLANG) && defined(CONFIG_KASAN) && defined(CONFIG_GCOV_PROFILE_ALL)
> +#warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"

Making this a '#warning' will basically just replace the current error
with a different one in the face of CONFIG_WERROR, which seems pointless
to me:

  lib/test_bitmap.c:1167:2: error: "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" [-Werror,-W#warnings]
   1167 | #warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
        |  ^
  1 error generated.

Could we just opt out of GCOV for test_bitmap.c if KASAN is enabled with
clang? That does not seem too bad of a workaround. I highly doubt there
are many people who are interested in debugging test_bitmap.c with KASAN
while profiling it with GCOV when building with clang, since they would
have hit this already and reported it already; as far as I can tell,
only the Intel robot has reported this with a randconfig.

diff --git a/lib/Makefile b/lib/Makefile
index 42d307ade225..c6f60ae42769 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -83,6 +83,10 @@ obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
 obj-$(CONFIG_TEST_PRINTF) += test_printf.o
 obj-$(CONFIG_TEST_SCANF) += test_scanf.o
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
+# https://github.com/ClangBuiltLinux/linux/issues/1874
+ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy)
+GCOV_PROFILE_test_bitmap.o := n
+endif
 obj-$(CONFIG_TEST_UUID) += test_uuid.o
 obj-$(CONFIG_TEST_XARRAY) += test_xarray.o
 obj-$(CONFIG_TEST_MAPLE_TREE) += test_maple_tree.o

Cheers,
Nathan

> +#else
>  	DECLARE_BITMAP(bitmap, BITS_PER_LONG);
>  	unsigned long initvar = BIT(2);
>  	unsigned long bitopvar = 0;
> @@ -1177,20 +1180,9 @@ static void __init test_bitmap_const_eval(void)
>  	 * in runtime.
>  	 */
>  
> -	/*
> -	 * Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }`.
> -	 * Clang on s390 optimizes bitops at compile-time as intended, but at
> -	 * the same time stops treating @bitmap and @bitopvar as compile-time
> -	 * constants after regular test_bit() is executed, thus triggering the
> -	 * build bugs below. So, call const_test_bit() there directly until
> -	 * the compiler is fixed.
> -	 */
> +	/* Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }` */
>  	bitmap_clear(bitmap, 0, BITS_PER_LONG);
> -#if defined(__s390__) && defined(__clang__)
> -	if (!const_test_bit(7, bitmap))
> -#else
>  	if (!test_bit(7, bitmap))
> -#endif
>  		bitmap_set(bitmap, 5, 2);
>  
>  	/* Equals to `unsigned long bitopvar = BIT(20)` */
> @@ -1220,6 +1212,7 @@ static void __init test_bitmap_const_eval(void)
>  	/* ~BIT(25) */
>  	BUILD_BUG_ON(!__builtin_constant_p(~var));
>  	BUILD_BUG_ON(~var != ~BIT(25));
> +#endif
>  }
>  
>  static void __init selftest(void)
> -- 
> 2.39.2
>

Nick Desaulniers July 17, 2023, 8:57 p.m. UTC | #2

On Mon, Jul 17, 2023 at 1:31 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Yury,
>
> On Mon, Jul 17, 2023 at 12:58:13PM -0700, Yury Norov wrote:
> > When building with clang, and when KASAN and GCOV_PROFILE_ALL are both
> > enabled, the test fails to build [1]:
> >
> > >> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
> >            BUILD_BUG_ON(!__builtin_constant_p(res));
> >            ^
> >    include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
> >            BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> >            ^
> >    include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
> >    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> >                                        ^
> >    include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert'
> >            _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> >            ^
> >    include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert'
> >            __compiletime_assert(condition, msg, prefix, suffix)
> >            ^
> >    include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert'
> >                            prefix ## suffix();                             \
> >                            ^
> >    <scratch space>:185:1: note: expanded from here
> >    __compiletime_assert_239
> >
> > Originally it was attributed to s390, which now looks seemingly wrong. The
> > issue is also not related to bitmap code itself, but it breaks build for
> > a given configuration. So, disabling the test unless the compiler will
> > get fixed.
> >
> > [1] https://github.com/ClangBuiltLinux/linux/issues/1874
> >
> > Fixes: dc34d5036692 ("lib: test_bitmap: add compile-time optimization/evaluations assertions")
> > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > ---
> >  lib/test_bitmap.c | 17 +++++------------
> >  1 file changed, 5 insertions(+), 12 deletions(-)
> >
> > diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
> > index 187f5b2db4cf..a791fdb7a8c9 100644
> > --- a/lib/test_bitmap.c
> > +++ b/lib/test_bitmap.c
> > @@ -1163,6 +1163,9 @@ static void __init test_bitmap_print_buf(void)
> >
> >  static void __init test_bitmap_const_eval(void)
> >  {
> > +#if defined(CONFIG_CC_IS_CLANG) && defined(CONFIG_KASAN) && defined(CONFIG_GCOV_PROFILE_ALL)
> > +#warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
>
> Making this a '#warning' will basically just replace the current error
> with a different one in the face of CONFIG_WERROR, which seems pointless
> to me:
>
>   lib/test_bitmap.c:1167:2: error: "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" [-Werror,-W#warnings]
>    1167 | #warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
>         |  ^
>   1 error generated.
>
> Could we just opt out of GCOV for test_bitmap.c if KASAN is enabled with
> clang? That does not seem too bad of a workaround. I highly doubt there
> are many people who are interested in debugging test_bitmap.c with KASAN
> while profiling it with GCOV when building with clang, since they would
> have hit this already and reported it already; as far as I can tell,
> only the Intel robot has reported this with a randconfig.

Yury, Nathan,
Thanks for the patches and discussion.  Yes, I think a combo of:

1. Nathan's lib/Makefile change plus
2. Yury's removal of the current preprocessor guards in lib/test_bitmap.c

make most sense.


>
> diff --git a/lib/Makefile b/lib/Makefile
> index 42d307ade225..c6f60ae42769 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -83,6 +83,10 @@ obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
>  obj-$(CONFIG_TEST_PRINTF) += test_printf.o
>  obj-$(CONFIG_TEST_SCANF) += test_scanf.o
>  obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
> +# https://github.com/ClangBuiltLinux/linux/issues/1874
> +ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy)
> +GCOV_PROFILE_test_bitmap.o := n
> +endif
>  obj-$(CONFIG_TEST_UUID) += test_uuid.o
>  obj-$(CONFIG_TEST_XARRAY) += test_xarray.o
>  obj-$(CONFIG_TEST_MAPLE_TREE) += test_maple_tree.o
>
> Cheers,
> Nathan
>
> > +#else
> >       DECLARE_BITMAP(bitmap, BITS_PER_LONG);
> >       unsigned long initvar = BIT(2);
> >       unsigned long bitopvar = 0;
> > @@ -1177,20 +1180,9 @@ static void __init test_bitmap_const_eval(void)
> >        * in runtime.
> >        */
> >
> > -     /*
> > -      * Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }`.
> > -      * Clang on s390 optimizes bitops at compile-time as intended, but at
> > -      * the same time stops treating @bitmap and @bitopvar as compile-time
> > -      * constants after regular test_bit() is executed, thus triggering the
> > -      * build bugs below. So, call const_test_bit() there directly until
> > -      * the compiler is fixed.
> > -      */
> > +     /* Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }` */
> >       bitmap_clear(bitmap, 0, BITS_PER_LONG);
> > -#if defined(__s390__) && defined(__clang__)
> > -     if (!const_test_bit(7, bitmap))
> > -#else
> >       if (!test_bit(7, bitmap))
> > -#endif
> >               bitmap_set(bitmap, 5, 2);
> >
> >       /* Equals to `unsigned long bitopvar = BIT(20)` */
> > @@ -1220,6 +1212,7 @@ static void __init test_bitmap_const_eval(void)
> >       /* ~BIT(25) */
> >       BUILD_BUG_ON(!__builtin_constant_p(~var));
> >       BUILD_BUG_ON(~var != ~BIT(25));
> > +#endif
> >  }
> >
> >  static void __init selftest(void)
> > --
> > 2.39.2
> >
>

Yury Norov July 17, 2023, 9:31 p.m. UTC | #3

On Mon, Jul 17, 2023 at 01:57:40PM -0700, Nick Desaulniers wrote:
> On Mon, Jul 17, 2023 at 1:31 PM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > Hi Yury,
> >
> > On Mon, Jul 17, 2023 at 12:58:13PM -0700, Yury Norov wrote:
> > > When building with clang, and when KASAN and GCOV_PROFILE_ALL are both
> > > enabled, the test fails to build [1]:
> > >
> > > >> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
> > >            BUILD_BUG_ON(!__builtin_constant_p(res));
> > >            ^
> > >    include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
> > >            BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> > >            ^
> > >    include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
> > >    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > >                                        ^
> > >    include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert'
> > >            _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > >            ^
> > >    include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert'
> > >            __compiletime_assert(condition, msg, prefix, suffix)
> > >            ^
> > >    include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert'
> > >                            prefix ## suffix();                             \
> > >                            ^
> > >    <scratch space>:185:1: note: expanded from here
> > >    __compiletime_assert_239
> > >
> > > Originally it was attributed to s390, which now looks seemingly wrong. The
> > > issue is also not related to bitmap code itself, but it breaks build for
> > > a given configuration. So, disabling the test unless the compiler will
> > > get fixed.
> > >
> > > [1] https://github.com/ClangBuiltLinux/linux/issues/1874
> > >
> > > Fixes: dc34d5036692 ("lib: test_bitmap: add compile-time optimization/evaluations assertions")
> > > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > > ---
> > >  lib/test_bitmap.c | 17 +++++------------
> > >  1 file changed, 5 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
> > > index 187f5b2db4cf..a791fdb7a8c9 100644
> > > --- a/lib/test_bitmap.c
> > > +++ b/lib/test_bitmap.c
> > > @@ -1163,6 +1163,9 @@ static void __init test_bitmap_print_buf(void)
> > >
> > >  static void __init test_bitmap_const_eval(void)
> > >  {
> > > +#if defined(CONFIG_CC_IS_CLANG) && defined(CONFIG_KASAN) && defined(CONFIG_GCOV_PROFILE_ALL)
> > > +#warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
> >
> > Making this a '#warning' will basically just replace the current error
> > with a different one in the face of CONFIG_WERROR, which seems pointless
> > to me:
> >
> >   lib/test_bitmap.c:1167:2: error: "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" [-Werror,-W#warnings]
> >    1167 | #warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
> >         |  ^
> >   1 error generated.
> >
> > Could we just opt out of GCOV for test_bitmap.c if KASAN is enabled with
> > clang? That does not seem too bad of a workaround. I highly doubt there
> > are many people who are interested in debugging test_bitmap.c with KASAN
> > while profiling it with GCOV when building with clang, since they would
> > have hit this already and reported it already; as far as I can tell,
> > only the Intel robot has reported this with a randconfig.
> 
> Yury, Nathan,
> Thanks for the patches and discussion.  Yes, I think a combo of:
> 
> 1. Nathan's lib/Makefile change plus
> 2. Yury's removal of the current preprocessor guards in lib/test_bitmap.c
> 
> make most sense.

OK, then I'll send a v2 shortly. Nathan, don't you mind if I add your
co-developed-by for this?

Nathan Chancellor July 17, 2023, 9:53 p.m. UTC | #4

On Mon, Jul 17, 2023 at 02:31:24PM -0700, Yury Norov wrote:
> On Mon, Jul 17, 2023 at 01:57:40PM -0700, Nick Desaulniers wrote:
> > On Mon, Jul 17, 2023 at 1:31 PM Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > Hi Yury,
> > >
> > > On Mon, Jul 17, 2023 at 12:58:13PM -0700, Yury Norov wrote:
> > > > When building with clang, and when KASAN and GCOV_PROFILE_ALL are both
> > > > enabled, the test fails to build [1]:
> > > >
> > > > >> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
> > > >            BUILD_BUG_ON(!__builtin_constant_p(res));
> > > >            ^
> > > >    include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
> > > >            BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> > > >            ^
> > > >    include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
> > > >    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > > >                                        ^
> > > >    include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert'
> > > >            _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > > >            ^
> > > >    include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert'
> > > >            __compiletime_assert(condition, msg, prefix, suffix)
> > > >            ^
> > > >    include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert'
> > > >                            prefix ## suffix();                             \
> > > >                            ^
> > > >    <scratch space>:185:1: note: expanded from here
> > > >    __compiletime_assert_239
> > > >
> > > > Originally it was attributed to s390, which now looks seemingly wrong. The
> > > > issue is also not related to bitmap code itself, but it breaks build for
> > > > a given configuration. So, disabling the test unless the compiler will
> > > > get fixed.
> > > >
> > > > [1] https://github.com/ClangBuiltLinux/linux/issues/1874
> > > >
> > > > Fixes: dc34d5036692 ("lib: test_bitmap: add compile-time optimization/evaluations assertions")
> > > > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > > > ---
> > > >  lib/test_bitmap.c | 17 +++++------------
> > > >  1 file changed, 5 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
> > > > index 187f5b2db4cf..a791fdb7a8c9 100644
> > > > --- a/lib/test_bitmap.c
> > > > +++ b/lib/test_bitmap.c
> > > > @@ -1163,6 +1163,9 @@ static void __init test_bitmap_print_buf(void)
> > > >
> > > >  static void __init test_bitmap_const_eval(void)
> > > >  {
> > > > +#if defined(CONFIG_CC_IS_CLANG) && defined(CONFIG_KASAN) && defined(CONFIG_GCOV_PROFILE_ALL)
> > > > +#warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
> > >
> > > Making this a '#warning' will basically just replace the current error
> > > with a different one in the face of CONFIG_WERROR, which seems pointless
> > > to me:
> > >
> > >   lib/test_bitmap.c:1167:2: error: "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" [-Werror,-W#warnings]
> > >    1167 | #warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
> > >         |  ^
> > >   1 error generated.
> > >
> > > Could we just opt out of GCOV for test_bitmap.c if KASAN is enabled with
> > > clang? That does not seem too bad of a workaround. I highly doubt there
> > > are many people who are interested in debugging test_bitmap.c with KASAN
> > > while profiling it with GCOV when building with clang, since they would
> > > have hit this already and reported it already; as far as I can tell,
> > > only the Intel robot has reported this with a randconfig.
> > 
> > Yury, Nathan,
> > Thanks for the patches and discussion.  Yes, I think a combo of:
> > 
> > 1. Nathan's lib/Makefile change plus
> > 2. Yury's removal of the current preprocessor guards in lib/test_bitmap.c
> > 
> > make most sense.
> 
> OK, then I'll send a v2 shortly. Nathan, don't you mind if I add your
> co-developed-by for this?

Sure, no worries!

Co-developed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Yury Norov July 17, 2023, 10:06 p.m. UTC | #5

> > > Yury, Nathan,
> > > Thanks for the patches and discussion.  Yes, I think a combo of:
> > > 
> > > 1. Nathan's lib/Makefile change plus
> > > 2. Yury's removal of the current preprocessor guards in lib/test_bitmap.c
> > > 
> > > make most sense.
> > 
> > OK, then I'll send a v2 shortly. Nathan, don't you mind if I add your
> > co-developed-by for this?
> 
> Sure, no worries!
> 
> Co-developed-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Done. Just removed external link from Makefile. We've got it in commit
message anyways, so better to not pollute sources.

diff mbox series

Patch

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 187f5b2db4cf..a791fdb7a8c9 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -1163,6 +1163,9 @@  static void __init test_bitmap_print_buf(void)
 
 static void __init test_bitmap_const_eval(void)
 {
+#if defined(CONFIG_CC_IS_CLANG) && defined(CONFIG_KASAN) && defined(CONFIG_GCOV_PROFILE_ALL)
+#warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled"
+#else
 	DECLARE_BITMAP(bitmap, BITS_PER_LONG);
 	unsigned long initvar = BIT(2);
 	unsigned long bitopvar = 0;
@@ -1177,20 +1180,9 @@  static void __init test_bitmap_const_eval(void)
 	 * in runtime.
 	 */
 
-	/*
-	 * Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }`.
-	 * Clang on s390 optimizes bitops at compile-time as intended, but at
-	 * the same time stops treating @bitmap and @bitopvar as compile-time
-	 * constants after regular test_bit() is executed, thus triggering the
-	 * build bugs below. So, call const_test_bit() there directly until
-	 * the compiler is fixed.
-	 */
+	/* Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }` */
 	bitmap_clear(bitmap, 0, BITS_PER_LONG);
-#if defined(__s390__) && defined(__clang__)
-	if (!const_test_bit(7, bitmap))
-#else
 	if (!test_bit(7, bitmap))
-#endif
 		bitmap_set(bitmap, 5, 2);
 
 	/* Equals to `unsigned long bitopvar = BIT(20)` */
@@ -1220,6 +1212,7 @@  static void __init test_bitmap_const_eval(void)
 	/* ~BIT(25) */
 	BUILD_BUG_ON(!__builtin_constant_p(~var));
 	BUILD_BUG_ON(~var != ~BIT(25));
+#endif
 }
 
 static void __init selftest(void)