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

Simon Horman
2024-03-27T14:44:39Z

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@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Signed-off-by: Guenter Roeck <linux@roeck-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__ ( \

...