Re: [PATCH] dynamic_debug: Add an option to enable dynamic debug for modules only

From: Jason Baron
Date: Wed Apr 15 2020 - 15:27:58 EST

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On 4/15/20 12:31 PM, Orson Zhai wrote:
> Hi Jason,
>
> On Fri, Apr 10, 2020 at 8:33 PM Orson Zhai <orson.unisoc@xxxxxxxxx> wrote:
>>
>> From: Orson Zhai <orson.zhai@xxxxxxxxxx>
>>
>> Instead of enabling dynamic debug globally with CONFIG_DYNAMIC_DEBUG,
>> CONFIG_DYNAMIC_DEBUG_CORE will only enable core function of dynamic
>> debug. With the DEBUG_MODULE defined for any modules, dynamic debug
>> will be tied to them.
>>
>> This is useful for people who only want to enable dynamic debug for
>> kernel modules without worrying about kernel image size and memory
>> consumption is increasing too much.
>>
>
> Do you have any comments for this patch?
>

So I like that you added the 'DEBUG_MODULE', but I'm wondering if the
naming is too generic? Maybe DYNAMIC_DEBUG_MODULE?

There may also be other places where you want to have the per-module
dependency, for example netdev_dbg()? But perhaps further expansion
could wait for a user...

Thanks,

-Jason

> Best Regards,
> Orson
>
>> Signed-off-by: Orson Zhai <orson.zhai@xxxxxxxxxx>
>> ---
>> Documentation/admin-guide/dynamic-debug-howto.rst | 7 +++++--
>> include/linux/dev_printk.h | 6 ++++--
>> include/linux/dynamic_debug.h | 2 +-
>> include/linux/printk.h | 14 +++++++++-----
>> lib/Kconfig.debug | 12 ++++++++++++
>> lib/Makefile | 2 +-
>> lib/dynamic_debug.c | 9 +++++++--
>> 7 files changed, 39 insertions(+), 13 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
>> index 0dc2eb8..fa5b8d4 100644
>> --- a/Documentation/admin-guide/dynamic-debug-howto.rst
>> +++ b/Documentation/admin-guide/dynamic-debug-howto.rst
>> @@ -13,8 +13,11 @@ kernel code to obtain additional kernel information. Currently, if
>> ``print_hex_dump_debug()``/``print_hex_dump_bytes()`` calls can be dynamically
>> enabled per-callsite.
>>
>> -If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is just
>> -shortcut for ``print_hex_dump(KERN_DEBUG)``.
>> +If ``CONFIG_DYNAMIC_DEBUG_CORE`` is set, only the modules with ``DEBUG_MODULE``
>> +defined will be tied into dynamic debug.
>> +
>> +If ``CONFIG_DYNAMIC_DEBUG`` or ``CONFIG_DYNAMIC_DEBUG_CORE`` is not set,
>> +``print_hex_dump_debug()`` is just shortcut for ``print_hex_dump(KERN_DEBUG)``.
>>
>> For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is
>> its ``prefix_str`` argument, if it is constant string; or ``hexdump``
>> diff --git a/include/linux/dev_printk.h b/include/linux/dev_printk.h
>> index 5aad06b..2fb0671 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_DEBUG_CORE) && defined(DEBUG_MODULE))
>> #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_DEBUG_CORE) && defined(DEBUG_MODULE))
>> /* 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..77fab5b 100644
>> --- a/include/linux/printk.h
>> +++ b/include/linux/printk.h
>> @@ -291,8 +291,9 @@ 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.
>> + * and other debug macros are compiled out unless either DEBUG is defined,
>> + * CONFIG_DYNAMIC_DEBUG is set, or CONFIG_DYNAMIC_DEBUG_CORE is set when
>> + * DEBUG_MODULE being defined for any modules.
>> */
>> #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_DEBUG_CORE) && defined(DEBUG_MODULE))
>> #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_DEBUG_CORE) && defined(DEBUG_MODULE))
>> /* 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_DEBUG_CORE) && defined(DEBUG_MODULE))
>> #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 50c1f5f..25a1b9de 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 || PROC_FS)
>> + select DYNAMIC_DEBUG_CORE
>> help
>>
>> Compiles debug level messages into the kernel, which would not
>> @@ -165,6 +166,17 @@ config DYNAMIC_DEBUG
>> See Documentation/admin-guide/dynamic-debug-howto.rst for additional
>> information.
>>
>> +config DYNAMIC_DEBUG_CORE
>> + bool "Enable core function of dynamic debug support"
>> + depends on PRINTK
>> + depends on (DEBUG_FS || PROC_FS)
>> + help
>> + Enable core functional support of dynamic debug. It is useful
>> + when you want to tie dynamic debug to your kernel modules with
>> + DEBUG_MODULE defined for each of them, especially for the case
>> + of embedded system where the kernel image size is sensitive for
>> + people.
>> +
>> config SYMBOLIC_ERRNAME
>> bool "Support symbolic error names in printf"
>> default y if PRINTK
>> diff --git a/lib/Makefile b/lib/Makefile
>> index 685aee6..8952772 100644
>> --- a/lib/Makefile
>> +++ b/lib/Makefile
>> @@ -186,7 +186,7 @@ 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 8f199f4..321437b 100644
>> --- a/lib/dynamic_debug.c
>> +++ b/lib/dynamic_debug.c
>> @@ -1032,8 +1032,13 @@ 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 CONFIG_DYNAMIC_DEBUG_CORE build\n");
>> + ddebug_init_success = 1;
>> + return 0;
>> }
>> iter = __start___verbose;
>> modname = iter->modname;
>> --
>> 2.7.4
>>

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In reply to: Orson Zhai: "Re: [PATCH] dynamic_debug: Add an option to enable dynamic debug for modules only"
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