linux-kernel - Re: [PATCH 11/14] s390: Add support for suppressing warning backtraces

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Date: Thu, 14 Mar 2024 08:57:45 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: linux-kselftest@...r.kernel.org, David Airlie <airlied@...il.com>, 
	Arnd Bergmann <arnd@...db.de>, Maíra Canal <mcanal@...lia.com>, 
	Dan Carpenter <dan.carpenter@...aro.org>, Kees Cook <keescook@...omium.org>, 
	Daniel Diaz <daniel.diaz@...aro.org>, David Gow <davidgow@...gle.com>, 
	Arthur Grillo <arthurgrillo@...eup.net>, Brendan Higgins <brendan.higgins@...ux.dev>, 
	Naresh Kamboju <naresh.kamboju@...aro.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Maxime Ripard <mripard@...nel.org>, 
	Ville Syrjälä <ville.syrjala@...ux.intel.com>, 
	Daniel Vetter <daniel@...ll.ch>, Thomas Zimmermann <tzimmermann@...e.de>, dri-devel@...ts.freedesktop.org, 
	kunit-dev@...glegroups.com, linux-arch@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org, 
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org, 
	loongarch@...ts.linux.dev, netdev@...ts.linux.dev
Subject: Re: [PATCH 11/14] s390: Add support for suppressing warning backtraces

Hi Günter,

On Tue, Mar 12, 2024 at 6:06 PM Guenter Roeck <linux@...ck-us.net> wrote:
> Add name of functions triggering warning backtraces to the __bug_table
> object section to enable support for suppressing WARNING backtraces.
>
> To limit image size impact, the pointer to the function name is only added
> to the __bug_table section if both CONFIG_KUNIT and CONFIG_DEBUG_BUGVERBOSE
> are enabled. Otherwise, the __func__ assembly parameter is replaced with a
> (dummy) NULL parameter to avoid an image size increase due to unused
> __func__ entries (this is necessary because __func__ is not a define but a
> virtual variable).
>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Thanks for your patch!

> --- a/arch/s390/include/asm/bug.h
> +++ b/arch/s390/include/asm/bug.h
> @@ -8,19 +8,30 @@
>
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
>
> +#if IS_ENABLED(CONFIG_KUNIT)
> +# define HAVE_BUG_FUNCTION
> +# define __BUG_FUNC_PTR        "       .long   %0-.\n"
> +# define __BUG_FUNC    __func__
> +#else
> +# define __BUG_FUNC_PTR
> +# define __BUG_FUNC    NULL
> +#endif /* IS_ENABLED(CONFIG_KUNIT) */
> +
>  #define __EMIT_BUG(x) do {                                     \
>         asm_inline volatile(                                    \
>                 "0:     mc      0,0\n"                          \
>                 ".section .rodata.str,\"aMS\",@progbits,1\n"    \
>                 "1:     .asciz  \""__FILE__"\"\n"               \
>                 ".previous\n"                                   \
> -               ".section __bug_table,\"awM\",@progbits,%2\n"   \
> +               ".section __bug_table,\"awM\",@progbits,%3\n"   \

This change conflicts with commit 3938490e78f443fb ("s390/bug:
remove entry size from __bug_table section") in linus/master.
I guess it should just be dropped?

>                 "2:     .long   0b-.\n"                         \
>                 "       .long   1b-.\n"                         \
> -               "       .short  %0,%1\n"                        \
> -               "       .org    2b+%2\n"                        \
> +               __BUG_FUNC_PTR                                  \
> +               "       .short  %1,%2\n"                        \
> +               "       .org    2b+%3\n"                        \
>                 ".previous\n"                                   \
> -               : : "i" (__LINE__),                             \
> +               : : "i" (__BUG_FUNC),                           \
> +                   "i" (__LINE__),                             \
>                     "i" (x),                                    \
>                     "i" (sizeof(struct bug_entry)));            \
>  } while (0)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

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