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SubjectRe: [RFC PATCH] dynamic_debug: Add config option of DYNAMIC_DEBUG_CORE
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On 3/18/20 3:03 PM, Orson Zhai wrote:
> There is the requirement from new Android that kernel image (GKI) and
> kernel modules are supposed to be built at differnet places. Some people
> want to enable dynamic debug for kernel modules only but not for kernel
> image itself with the consideration of binary size increased or more
> memory being used.
>
> By this patch, dynamic debug is divided into core part (the defination of
> functions) and macro replacement part. We can only have the core part to
> be built-in and do not have to activate the debug output from kenrel image.
>
> Signed-off-by: Orson Zhai <orson.unisoc@gmail.com>

Hi Orson,

I think this is a nice feature. Is the idea then that driver can do
something like:

#if defined(CONFIG_DRIVER_FOO_DEBUG)
#define driver_foo_debug(fmt, ...) \
dynamic_pr_debug(fmt, ##__VA_ARGS__)
#else
no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#enif

And then the Kconfig:

config DYNAMIC_DRIVER_FOO_DEBUG
bool "Enable dynamic driver foo printk() support"
select DYNAMIC_DEBUG_CORE


Or did you have something else in mind? Do you have an example
code for the drivers that you mention?

Thanks,

-Jason


> ---
> include/linux/dynamic_debug.h | 2 +-
> lib/Kconfig.debug | 18 ++++++++++++++++--
> lib/Makefile | 2 +-
> 3 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> index 4cf02ec..abcd5fd 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -48,7 +48,7 @@ struct _ddebug {
>
>
>
> -#if defined(CONFIG_DYNAMIC_DEBUG)
> +#if defined(CONFIG_DYNAMIC_DEBUG_CORE)
> int ddebug_add_module(struct _ddebug *tab, unsigned int n,
> const char *modname);
> extern int ddebug_remove_module(const char *mod_name);
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 69def4a..78a7256 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -97,8 +97,7 @@ config BOOT_PRINTK_DELAY
> config DYNAMIC_DEBUG
> bool "Enable dynamic printk() support"
> default n
> - depends on PRINTK
> - depends on DEBUG_FS
> + select DYNAMIC_DEBUG_CORE
> help
>
> Compiles debug level messages into the kernel, which would not
> @@ -164,6 +163,21 @@ config DYNAMIC_DEBUG
> See Documentation/admin-guide/dynamic-debug-howto.rst for additional
> information.
>
> +config DYNAMIC_DEBUG_CORE
> + bool "Enable core functions of dynamic debug support"
> + depends on PRINTK
> + depends on DEBUG_FS
> + help
> + Enable this option to build ddebug_* and __dynamic_* routines
> + into kernel. If you want enable whole dynamic debug features,
> + select CONFIG_DYNAMIC_DEBUG directly and this option will be
> + automatically selected.
> +
> + This option is selected when you want to enable dynamic debug
> + for kernel modules only but not for the kernel base. Especailly
> + in the case that kernel modules are built out of the place where
> + kernel base is built.
> +
> config SYMBOLIC_ERRNAME
> bool "Support symbolic error names in printf"
> default y if PRINTK
> diff --git a/lib/Makefile b/lib/Makefile
> index 611872c..2096d83 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -183,7 +183,7 @@ lib-$(CONFIG_GENERIC_BUG) += bug.o
>
> obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
>
> -obj-$(CONFIG_DYNAMIC_DEBUG) += dynamic_debug.o
> +obj-$(CONFIG_DYNAMIC_DEBUG_CORE) += dynamic_debug.o
> obj-$(CONFIG_SYMBOLIC_ERRNAME) += errname.o
>
> obj-$(CONFIG_NLATTR) += nlattr.o
>

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