From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk1-f196.google.com ([209.85.221.196]:42753 "EHLO mail-vk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726159AbeJHVxR (ORCPT ); Mon, 8 Oct 2018 17:53:17 -0400 MIME-Version: 1.0 References: <20180921142234.16882-1-kieran.bingham+renesas@ideasonboard.com> <20181005083313.2088252-1-arnd@arndb.de> <5cbb504c-0506-cec8-d51b-00928cdb27fe@ideasonboard.com> In-Reply-To: From: Geert Uytterhoeven Date: Mon, 8 Oct 2018 16:41:01 +0200 Message-ID: Subject: Re: [PATCH] kbuild: fix kernel/bounds.c 'W=1' warning To: Masahiro Yamada Cc: Kieran Bingham , Miguel Ojeda Sandonis , Arnd Bergmann , Andrew Morton , Linux-Renesas , stable , Linux Kernel Mailing List , linux-kbuild Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Sender: linux-renesas-soc-owner@vger.kernel.org List-ID: On Mon, Oct 8, 2018 at 4:33 PM Masahiro Yamada wrote: > On Mon, Oct 8, 2018 at 7:01 PM Kieran Bingham > wrote: > > On 06/10/18 23:06, Masahiro Yamada wrote: > > > On Sun, Oct 7, 2018 at 6:58 AM Masahiro Yamada > > > wrote: > > >> > > >> Hi Miguel, > > >> > > >> > > >> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda > > >> wrote: > > >>> > > >>> On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann wrote: > > >>>> > > >>>> Building any configuration with 'make W=1' produces a warning: > > >>>> > > >>>> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes] > > >>>> > > >>>> When also passing -Werror, this prevents us from building any > > >>>> other files. Nobody ever calls the function, but we can't make > > >>>> it 'static' either since we want the compiler output. > > >>>> > > >>>> Calling it 'main' instead however avoids the warning, because gcc > > >>>> does not insist on having a declaration for main. > > >>> > > >>> I think marking the function as static __used should do the trick and > > >>> would be less confusing. > > >> > > >> > > >> > > >> > > >> I tried __used, but I still see the warning. > > >> > > >> > > >> masahiro@grover:~/ref/linux$ git diff > > >> diff --git a/kernel/bounds.c b/kernel/bounds.c > > >> index c373e88..aee0101 100644 > > >> --- a/kernel/bounds.c > > >> +++ b/kernel/bounds.c > > >> @@ -13,7 +13,7 @@ > > >> #include > > >> #include > > >> > > >> -void foo(void) > > >> +void __used foo(void) > > >> { > > >> /* The enum constants to put into include/generated/bounds.h */ > > >> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS); > > >> masahiro@grover:~/ref/linux$ make W=1 prepare > > >> CC kernel/bounds.s > > >> kernel/bounds.c:16:13: warning: no previous prototype for ‘foo’ > > >> [-Wmissing-prototypes] > > >> void __used foo(void) > > >> ^ > > >> CC arch/x86/kernel/asm-offsets.s > > > > > > > > > > > > Sorry, I forgot to add 'static'. > > > > > > Adding both static and __used worked for me, > > > and I like the idea. > > > > > > > Aha - I'd also tried converting to static in my earlier attempts, but > > didn't realise we had __used! > > > > updating as "static __used" causes the following diff: > > > > diff -Nurp bounds.s.foo bounds.s.static-used > > --- bounds.s.foo 2018-10-05 10:20:53.269941404 +0100 > > +++ bounds.s.static-used 2018-10-08 10:51:18.079309049 +0100 > > @@ -110,7 +110,6 @@ > > #NO_APP > > .align 2 > > .p2align 3,,7 > > - .global foo > > .type foo, %function > > foo: > > stp x29, x30, [sp, -16]! //,,, > > > > > > I'd say this is a pretty good alternative fix - however I see Arnd's > > version is already on it's way though akpm's tree... > > > > https://ozlabs.org/~akpm/mmots/broken-out/kbuild-fix-kernel-boundsc-w%3D1-warning.patch > > > > Anyway, as long as one of the variants gets there I'll be happy :) > > > I will leave it to Arnd. > > > When we fix arch/{mips,sparc}/kernel/asm-offsets.c, > 'static __used' is just additions. > > The 'main(void)' solution would require a little bit restructuring. > > > > FWIW, with my quick analysis, the following should be fixed as well: > > arch/alpha/kernel/asm-offsets.c > arch/c6x/kernel/asm-offsets.c > arch/ia64/kernel/asm-offsets.c > arch/ia64/kernel/nr-irqs.c > arch/mips/kernel/asm-offsets.c > arch/riscv/kernel/asm-offsets.c > arch/sparc/kernel/asm-offsets.c > arch/x86/kernel/asm-offsets.c > arch/x86/um/shared/sysdep/kernel-offsets.h > samples/bpf/syscall_nrs.c All the other asm-offsets.c files already use "int main(void)" ;-) Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds