Re: [PATCH] kernel/trace: Add TRACING_ALLOW_PRINTK config option

[Jason Gunthorpe]

On Wed, Jun 24, 2020 at 04:45:24PM +0800, Nicolas Boichat wrote:
> trace_printk is only meant as a debugging tool, and should never be
> compiled into production code without source code changes, as
> indicated by the warning that shows up on boot if any trace_printk
> is called:
>  **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
>  **                                                      **
>  ** trace_printk() being used. Allocating extra memory.  **
>  **                                                      **
>  ** This means that this is a DEBUG kernel and it is     **
>  ** unsafe for production use.                           **
> 
> If this option is set to n, the kernel will generate a build-time
> error if trace_printk is used.
> 
> Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
>  include/linux/kernel.h | 17 ++++++++++++++++-
>  kernel/trace/Kconfig   |  9 +++++++++
>  2 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 196607aaf653082..b6addc6ba669e85 100644
> +++ b/include/linux/kernel.h
> @@ -721,10 +721,15 @@ do {									\
>  #define trace_printk(fmt, ...)				\
>  do {							\
>  	char _______STR[] = __stringify((__VA_ARGS__));	\
> +							\
> +	__static_assert(				\
> +		IS_ENABLED(CONFIG_TRACING_ALLOW_PRINTK),\
> +		"trace_printk called, please enable CONFIG_TRACING_ALLOW_PRINTK."); \
> +							\

Why __static_assert not normal static_assert?

Jason