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

[Guenter Roeck]

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