[v2] Add support for suppressing warning backtraces

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

Posted by Guenter Roeck 1 year, 10 months ago

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 */
+
 #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__ (				\
@@ -47,6 +62,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__), "i" (0),		\
 		   "i" (sizeof(struct bug_entry)));	\
 	unreachable();					\
@@ -60,6 +76,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__),			\
 		   "i" (BUGFLAG_WARNING|(flags)),	\
 		   "i" (sizeof(struct bug_entry)));	\
@@ -85,6 +102,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__),			\
 		   "i" (BUGFLAG_UNWINDER),		\
 		   "i" (sizeof(struct bug_entry)));	\
-- 
2.39.2

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

Posted by Simon Horman 1 year, 10 months ago

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__ (				\

...

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

Posted by Guenter Roeck 1 year, 10 months ago

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__ (				\
> 
> ...

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

Posted by Simon Horman 1 year, 10 months ago

On Wed, Mar 27, 2024 at 08:10:51AM -0700, Guenter Roeck wrote:
> 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.

FWIIW, I agree that would be odd.
But perhaps the #ifdef could also move above the Kernel doc?
Maybe not a great idea, but the best one I've had so far.

> 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__ (				\
> > 
> > ...
>

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

Posted by Guenter Roeck 1 year, 10 months ago

On Wed, Mar 27, 2024 at 07:39:20PM +0000, Simon Horman wrote:
[ ... ]
> > > 
> > > 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.
> 
> FWIIW, I agree that would be odd.
> But perhaps the #ifdef could also move above the Kernel doc?
> Maybe not a great idea, but the best one I've had so far.
> 

I did that for the next version of the patch series. It is a bit more
clumsy, so I left it as separate patch on top of this patch. I'd
still like to get input from others before making the change final.

Thanks,
Guenter