linux-kernel - Re: [PATCH v3 14/15] riscv: Add support for suppressing warning backtraces

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Date: Mon, 22 Apr 2024 13:40:53 -0400
From: Charlie Jenkins <charlie@...osinc.com>
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, x86@...nel.org,
	Linux Kernel Functional Testing <lkft@...aro.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>
Subject: Re: [PATCH v3 14/15] riscv: Add support for suppressing warning
 backtraces

On Wed, Apr 03, 2024 at 06:19:35AM -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).
> 
> To simplify the implementation, unify the __BUG_ENTRY_ADDR and
> __BUG_ENTRY_FILE macros into a single macro named __BUG_REL() which takes
> the address, file, or function reference as parameter.
> 
> Tested-by: Linux Kernel Functional Testing <lkft@...aro.org>
> Acked-by: Dan Carpenter <dan.carpenter@...aro.org>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Albert Ou <aou@...s.berkeley.edu>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
> v2:
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
> - Introduced KUNIT_SUPPRESS_BACKTRACE configuration option
> v3:
> - Rebased to v6.9-rc2
> 
>  arch/riscv/include/asm/bug.h | 38 ++++++++++++++++++++++++------------
>  1 file changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
> index 1aaea81fb141..79f360af4ad8 100644
> --- a/arch/riscv/include/asm/bug.h
> +++ b/arch/riscv/include/asm/bug.h
> @@ -30,26 +30,39 @@
>  typedef u32 bug_insn_t;
>  
>  #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
> -#define __BUG_ENTRY_ADDR	RISCV_INT " 1b - ."
> -#define __BUG_ENTRY_FILE	RISCV_INT " %0 - ."
> +#define __BUG_REL(val)	RISCV_INT " " __stringify(val) " - ."
>  #else
> -#define __BUG_ENTRY_ADDR	RISCV_PTR " 1b"
> -#define __BUG_ENTRY_FILE	RISCV_PTR " %0"
> +#define __BUG_REL(val)	RISCV_PTR " " __stringify(val)
>  #endif
>  
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
> +
> +#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> +# define HAVE_BUG_FUNCTION
> +# define __BUG_FUNC_PTR	__BUG_REL(%1)
> +#else
> +# define __BUG_FUNC_PTR
> +#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +
>  #define __BUG_ENTRY			\
> -	__BUG_ENTRY_ADDR "\n\t"		\
> -	__BUG_ENTRY_FILE "\n\t"		\
> -	RISCV_SHORT " %1\n\t"		\
> -	RISCV_SHORT " %2"
> +	__BUG_REL(1b) "\n\t"		\
> +	__BUG_REL(%0) "\n\t"		\
> +	__BUG_FUNC_PTR "\n\t"		\
> +	RISCV_SHORT " %2\n\t"		\
> +	RISCV_SHORT " %3"
>  #else
>  #define __BUG_ENTRY			\
> -	__BUG_ENTRY_ADDR "\n\t"		\
> -	RISCV_SHORT " %2"
> +	__BUG_REL(1b) "\n\t"		\
> +	RISCV_SHORT " %3"
>  #endif
>  
>  #ifdef CONFIG_GENERIC_BUG
> +#ifdef HAVE_BUG_FUNCTION
> +# define __BUG_FUNC	__func__
> +#else
> +# define __BUG_FUNC	NULL
> +#endif
> +
>  #define __BUG_FLAGS(flags)					\
>  do {								\
>  	__asm__ __volatile__ (					\
> @@ -58,10 +71,11 @@ do {								\
>  			".pushsection __bug_table,\"aw\"\n\t"	\
>  		"2:\n\t"					\
>  			__BUG_ENTRY "\n\t"			\
> -			".org 2b + %3\n\t"                      \
> +			".org 2b + %4\n\t"                      \
>  			".popsection"				\
>  		:						\
> -		: "i" (__FILE__), "i" (__LINE__),		\
> +		: "i" (__FILE__), "i" (__BUG_FUNC),		\
> +		  "i" (__LINE__),				\
>  		  "i" (flags),					\
>  		  "i" (sizeof(struct bug_entry)));              \
>  } while (0)
> -- 
> 2.39.2
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Reviewed-by: Charlie Jenkins <charlie@...osinc.com>

- Charlie

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