netdev - Re: [PATCH v2 12/14] sh: Add support for suppressing warning backtraces

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Date: Wed, 27 Mar 2024 14:44:31 +0000
From: Simon Horman <horms@...nel.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@...r.kernel.org,
	Linux Kernel Functional Testing <lkft@...aro.org>
Subject: Re: [PATCH v2 12/14] sh: Add support for suppressing warning
 backtraces

On Mon, Mar 25, 2024 at 10:52:46AM -0700, Guenter Roeck 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_SUPPRESS_BACKTRACE 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).
> 
> Tested-by: Linux Kernel Functional Testing <lkft@...aro.org>
> Acked-by: Dan Carpenter <dan.carpenter@...aro.org>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
> - Introduced KUNIT_SUPPRESS_BACKTRACE configuration option
> 
>  arch/sh/include/asm/bug.h | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
> index 05a485c4fabc..470ce6567d20 100644
> --- a/arch/sh/include/asm/bug.h
> +++ b/arch/sh/include/asm/bug.h
> @@ -24,21 +24,36 @@
>   * The offending file and line are encoded in the __bug_table section.
>   */
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
> +
> +#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> +# define HAVE_BUG_FUNCTION
> +# define __BUG_FUNC_PTR	"\t.long %O2\n"
> +#else
> +# define __BUG_FUNC_PTR
> +#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +

Hi Guenter,

a minor nit from my side: this change results in a Kernel doc warning.

     .../bug.h:29: warning: expecting prototype for _EMIT_BUG_ENTRY(). Prototype was for HAVE_BUG_FUNCTION() instead

Perhaps either the new code should be placed above the Kernel doc,
or scripts/kernel-doc should be enhanced?

>  #define _EMIT_BUG_ENTRY				\
>  	"\t.pushsection __bug_table,\"aw\"\n"	\
>  	"2:\t.long 1b, %O1\n"			\
> -	"\t.short %O2, %O3\n"			\
> -	"\t.org 2b+%O4\n"			\
> +	__BUG_FUNC_PTR				\
> +	"\t.short %O3, %O4\n"			\
> +	"\t.org 2b+%O5\n"			\
>  	"\t.popsection\n"
>  #else
>  #define _EMIT_BUG_ENTRY				\
>  	"\t.pushsection __bug_table,\"aw\"\n"	\
>  	"2:\t.long 1b\n"			\
> -	"\t.short %O3\n"			\
> -	"\t.org 2b+%O4\n"			\
> +	"\t.short %O4\n"			\
> +	"\t.org 2b+%O5\n"			\
>  	"\t.popsection\n"
>  #endif
>  
> +#ifdef HAVE_BUG_FUNCTION
> +# define __BUG_FUNC	__func__
> +#else
> +# define __BUG_FUNC	NULL
> +#endif
> +
>  #define BUG()						\
>  do {							\
>  	__asm__ __volatile__ (				\

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