linux-kernel - Re: [PATCH v7 2/4] lib/test_bitmap.c: Add for_each_set

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Date:   Sun, 7 Jun 2020 04:45:19 +0530
From:   Syed Nayyar Waris <syednwaris@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     kbuild test robot <lkp@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kbuild-all@...ts.01.org,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/4] lib/test_bitmap.c: Add for_each_set_clump test cases

On Fri, Jun 5, 2020 at 5:54 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Fri, Jun 05, 2020 at 02:12:54AM +0530, Syed Nayyar Waris wrote:
> > On Sun, May 31, 2020 at 12:50 AM kbuild test robot <lkp@...el.com> wrote:
>
> > > >> WARNING: modpost: lib/test_bitmap.o(.data+0xe80): Section mismatch in reference from the variable clump_test_data to the variable .init.rodata:clump_exp1
> > > The variable clump_test_data references
> > > the variable __initconst clump_exp1
> > > If the reference is valid then annotate the
> > > variable with or __refdata (see linux/init.h) or name the variable:
> > >
> > > --
> > > >> WARNING: modpost: lib/test_bitmap.o(.data+0xec8): Section mismatch in reference from the variable clump_test_data to the variable .init.rodata:clump_exp2
> > > The variable clump_test_data references
> > > the variable __initconst clump_exp2
> > > If the reference is valid then annotate the
> > > variable with or __refdata (see linux/init.h) or name the variable:
> > >
> > > --
> > > >> WARNING: modpost: lib/test_bitmap.o(.data+0xf10): Section mismatch in reference from the variable clump_test_data to the variable .init.rodata:clump_exp3
> > > The variable clump_test_data references
> > > the variable __initconst clump_exp3
> > > If the reference is valid then annotate the
> > > variable with or __refdata (see linux/init.h) or name the variable:
> > >
> > > --
> > > >> WARNING: modpost: lib/test_bitmap.o(.data+0xf58): Section mismatch in reference from the variable clump_test_data to the variable .init.rodata:clump_exp4
> > > The variable clump_test_data references
> > > the variable __initconst clump_exp4
> > > If the reference is valid then annotate the
> > > variable with or __refdata (see linux/init.h) or name the variable:
>
> > I am unable to reproduce the compilation warning.
>
> You have to enable section mismatch checker.
>
> > I ran the command:
> > make W=1 C=1 ARCH=x86_64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'  lib/
> >
> > But the compilation warning didn't show up. Can anyone please point to me
> > what I am doing wrong here? How shall I reproduce the warning? Thanks !
>
> You put some data into init section of the object, while you are trying to
> access it from non-init one. It's easy-to-fix issue.
>
> --
> With Best Regards,
> Andy Shevchenko

Thanks! I have made code changes for the above warning. Actually I am
still unable to reproduce the compilation warning. But I believe the
following code fix will fix the compilation warning:

In file lib/test_bitmap.c

@@ -692,7 +692,7 @@ struct clump_test_data_params {
        unsigned long const *exp;
 };

-struct clump_test_data_params clump_test_data[] =
+static struct clump_test_data_params clump_test_data[] __initdata =
                                        { {{0}, 2, 0, 64, 8, clump_exp1},
                                        {{0}, 8, 2, 240, 24, clump_exp2},
                                        {{0}, 8, 10, 240, 30, clump_exp3},



Let me know if I should submit a new patchset (v8) for
'for_each_set_clump' including above code fix.

Just to share how I attempted to reproduce the warning (but unsuccessful):

Step 1: Use the config file in attachment. Download, extract, rename
file to .config at the root of the tree.
Step 2: '$ make lib/'
No warning reproduced after above step 2.
Step 3: '$ make W=1 C=1 ARCH=x86_64 CF='-fdiagnostic-prefix
-D__CHECK_ENDIAN__' lib/'
After step 3 I got error in build:
scripts/kconfig/conf  --syncconfig Kconfig
  CHECK   scripts/mod/empty.c
No such file: asan-globals=1
scripts/Makefile.build:266: recipe for target 'scripts/mod/empty.o' failed
make[1]: *** [scripts/mod/empty.o] Error 1
Makefile:1147: recipe for target 'prepare0' failed
make: *** [prepare0] Error 2

The command in above step 3 was mentioned in the bot mail.

Regards
Syed Nayyar Waris