linux-kernel - Re: [RFC PATCH next-20200930] treewide: Convert macro and uses of __section(foo) to _

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Message-ID: <CAKwvOd=P+j0RaQfHsXPfB0EL3oRgAu8Q0+spUOn_v-p2+3=3pw@mail.gmail.com>
Date:   Wed, 30 Sep 2020 15:20:55 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Sedat Dilek <sedat.dilek@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, rcu@...r.kernel.org,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [RFC PATCH next-20200930] treewide: Convert macro and uses of
 __section(foo) to __section("foo")

On Wed, Sep 30, 2020 at 3:06 PM Joe Perches <joe@...ches.com> wrote:
>
> On Wed, 2020-09-30 at 14:40 -0700, Nick Desaulniers wrote:
> > On Wed, Sep 30, 2020 at 12:16 PM Joe Perches <joe@...ches.com> wrote:
> > > Use a more generic form for __section that requires quotes to avoid
> > > complications with clang and gcc differences.
> > >
> > > Remove the quote operator # from compiler_attributes.h __section macro.
> > >
> > > Convert all unquoted __section(foo) uses to quoted __section("foo").
> > > Also convert __attribute__((section("foo"))) uses to __section("foo")
> > > even if the __attribute__ has multiple list entry forms.
> > >
> > > Signed-off-by: Joe Perches <joe@...ches.com>
> > > ---
> > >
> > > This is the current output from the script against next-20200930
> > > attached in this link:
> > >
> > > https://lore.kernel.org/lkml/0e582a7f5144a33f465978d97701f9b3dcc377f3.camel@perches.com/
> > >
> > > It might be useful to run the script immediately before
> > > the next -rc1.
> >
> > $ ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- make CC=clang -j71
> > powernv_defconfig
> > $ ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- make CC=clang -j71
> > ...
> > arch/powerpc/boot/main.c:193:44: error: expected ';' after top level declarator
> > static char cmdline[BOOT_COMMAND_LINE_SIZE]
>
> The script does not convert files in
>
>         scripts/
>         tools/
>         uapi/
>         and include/linux/compiler_attributes.h
>
> It otherwise assumes that any __attribute__((__section__
> use should be converted to __section.
>
> If this ppc file is the only file outside of the
> listed exclusions, I can either exclude it directly
> or add compiler.h to it.
>
> You have a preference?

If compiler_types.h which includes compiler_attributes.h is being
implicitly including by Kbuild add `-include` flags to most
translation units in the kernel, it would be nice to be able to use it
everywhere.  I consider open coded __attribute__'s a portability bug.
So including the header in arch/powerpc/boot/*.c would be my
preference.

>
> Perhaps these are also possible files that need exclusions:
>
> ./arch/x86/boot/video.h:#define __videocard struct card_info __section(".videocards") __attribute__((used))
> ./arch/x86/boot/compressed/pgtable_64.c:unsigned long *trampoline_32bit __section(".data");
> ./arch/x86/boot/tty.c:static void __section(".inittext") serial_putchar(int ch)
> ./arch/x86/boot/tty.c:static void __section(".inittext") bios_putchar(int ch)
> ./arch/x86/boot/tty.c:void __section(".inittext") putchar(int ch)
> ./arch/x86/boot/tty.c:void __section(".inittext") puts(const char *str)
> ./arch/s390/boot/startup.c:static struct diag210 _diag210_tmp_dma __section(".dma.data");
> ./arch/powerpc/boot/main.c:     __section("__builtin_cmdline");
> ./arch/powerpc/boot/ps3.c:      __section("__builtin_cmdline");
>
>


-- 
Thanks,
~Nick Desaulniers