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Date: Sat, 28 Mar 2020 14:17:43 +0800
From: Orson Zhai <orsonzhai@...il.com>
To: Jason Baron <jbaron@...mai.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Randy Dunlap <rdunlap@...radead.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Shuah Khan <skhan@...uxfoundation.org>,
Krzysztof Kozlowski <krzk@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Brendan Higgins <brendanhiggins@...gle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
Ard Biesheuvel <ardb@...nel.org>,
Andy Shevchenko <andy.shevchenko@...il.com>,
David Gow <davidgow@...gle.com>,
Mark Rutland <mark.rutland@....com>, joe@...ches.com,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Android Kernel Team <kernel-team@...roid.com>,
Orson Zhai <orson.unisoc@...il.com>
Subject: Re: [RFC PATCH V2] dynamic_debug: Add config option of DYNAMIC_DEBUG_CORE
Hi Jason,
On Thu, Mar 26, 2020 at 1:13 AM Orson Zhai <orson.unisoc@...il.com> wrote:
>
> Instead of enabling whole kernel with CONFIG_DYNAMIC_DEBUG, CONFIG_
> DYNAMIC_DEBUG_CORE will only make the basic function definition and
> exported symbols to be built without replacing pr_debug or dev_dbg
> to dynamic version unless DEBUG is defined for any desired modules
How do you think about this idea?
Optionally enable dynamic debug of modules by the DEBUG macro.
Best Regards,
-Orson
> together by users.
>
> This is useful for people who only want to enable dynamic debug for some
> specific kernel modules without worrying about whole kernel image size will
> be significantly increased and more memory consumption caused by CONFIG_
> DYNAMIC_DEBUG.
>
> Signed-off-by: Orson Zhai <orson.unisoc@...il.com>
> ---
> Changes from V1:
> - Rewrite commit message for more generic usage.
> - Add combination use of CONFIG_DYNAMIC_DEBUG_CORE and DEBUG to enable
> dynamic debug seperately.
> - Ignore empty _ddtable and return success when only the core is enabled.
> - Fix all typoes.
>
> include/linux/dev_printk.h | 6 ++++--
> include/linux/dynamic_debug.h | 2 +-
> include/linux/printk.h | 12 ++++++++----
> lib/Kconfig.debug | 18 ++++++++++++++++++
> lib/Makefile | 2 +-
> lib/dynamic_debug.c | 9 +++++++--
> 6 files changed, 39 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/dev_printk.h b/include/linux/dev_printk.h
> index 5aad06b..ed40030 100644
> --- a/include/linux/dev_printk.h
> +++ b/include/linux/dev_printk.h
> @@ -109,7 +109,8 @@ void _dev_info(const struct device *dev, const char *fmt, ...)
> #define dev_info(dev, fmt, ...) \
> _dev_info(dev, dev_fmt(fmt), ##__VA_ARGS__)
>
> -#if defined(CONFIG_DYNAMIC_DEBUG)
> +#if defined(CONFIG_DYNAMIC_DEBUG) || \
> + (defined(CONFIG_DYNAMIC_CORE) && defined(DEBUG))
> #define dev_dbg(dev, fmt, ...) \
> dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
> #elif defined(DEBUG)
> @@ -181,7 +182,8 @@ do { \
> dev_level_ratelimited(dev_notice, dev, fmt, ##__VA_ARGS__)
> #define dev_info_ratelimited(dev, fmt, ...) \
> dev_level_ratelimited(dev_info, dev, fmt, ##__VA_ARGS__)
> -#if defined(CONFIG_DYNAMIC_DEBUG)
> +#if defined(CONFIG_DYNAMIC_DEBUG) || \
> + (defined(CONFIG_DYNAMIC_CORE) && defined(DEBUG))
> /* descriptor check is first to prevent flooding with "callbacks suppressed" */
> #define dev_dbg_ratelimited(dev, fmt, ...) \
> do { \
> 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/include/linux/printk.h b/include/linux/printk.h
> index 1e6108b..44d5378 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -292,7 +292,8 @@ extern int kptr_restrict;
> * These can be used to print at the various log levels.
> * All of these will print unconditionally, although note that pr_debug()
> * and other debug macros are compiled out unless either DEBUG is defined
> - * or CONFIG_DYNAMIC_DEBUG is set.
> + * or CONFIG_DYNAMIC_DEBUG is set, or both CONFIG_DYNAMIC_DEBUG_CORE and
> + * DEBUG is defined.
> */
> #define pr_emerg(fmt, ...) \
> printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
> @@ -327,7 +328,8 @@ extern int kptr_restrict;
>
>
> /* If you are writing a driver, please use dev_dbg instead */
> -#if defined(CONFIG_DYNAMIC_DEBUG)
> +#if defined(CONFIG_DYNAMIC_DEBUG) || \
> + (defined(CONFIG_DYNAMIC_CORE) && defined(DEBUG))
> #include <linux/dynamic_debug.h>
>
> /* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */
> @@ -453,7 +455,8 @@ extern int kptr_restrict;
> #endif
>
> /* If you are writing a driver, please use dev_dbg instead */
> -#if defined(CONFIG_DYNAMIC_DEBUG)
> +#if defined(CONFIG_DYNAMIC_DEBUG) || \
> + (defined(CONFIG_DYNAMIC_CORE) && defined(DEBUG))
> /* descriptor check is first to prevent flooding with "callbacks suppressed" */
> #define pr_debug_ratelimited(fmt, ...) \
> do { \
> @@ -500,7 +503,8 @@ static inline void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
>
> #endif
>
> -#if defined(CONFIG_DYNAMIC_DEBUG)
> +#if defined(CONFIG_DYNAMIC_DEBUG) || \
> + (defined(CONFIG_DYNAMIC_CORE) && defined(DEBUG))
> #define print_hex_dump_debug(prefix_str, prefix_type, rowsize, \
> groupsize, buf, len, ascii) \
> dynamic_hex_dump(prefix_str, prefix_type, rowsize, \
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 69def4a..8381b19 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -99,6 +99,7 @@ config DYNAMIC_DEBUG
> 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 +165,23 @@ 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 as well.
> +
> + This option can be selected with DEBUG together which could be
> + defined for desired kernel modules to enable dynamic debug
> + features instead for whole kernel. Especially being used in
> + the case that kernel modules are built out of kernel tree to
> + have dynamic debug capabilities without affecting the kernel
> + base.
> +
> 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
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index c604091..34f303a 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -1014,8 +1014,13 @@ static int __init dynamic_debug_init(void)
> int verbose_bytes = 0;
>
> if (__start___verbose == __stop___verbose) {
> - pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
> - return 1;
> + if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
> + pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
> + return 1;
> + }
> + pr_info("Ignore empty _ddebug table in a core only build\n");
> + ddebug_init_success = 1;
> + return 0;
> }
> iter = __start___verbose;
> modname = iter->modname;
> --
> 2.7.4
>
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