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

Guenter Roeck
2024-03-27T15:10:55Z

On 3/27/24 07:44, Simon Horman wrote:
> 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?
>

Thanks a lot for the feedback.

The definition block needs to be inside CONFIG_DEBUG_BUGVERBOSE,
so it would be a bit odd to move it above the documentation
just to make kerneldoc happy. I am not really sure that to do
about it.

I'll wait for comments from others before making any changes.

Thanks,
Guenter

>> #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__ ( \
>
> ...