Messages in this thread | | | Subject | Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN_DEBUG) | From | Tetsuo Handa <> | Date | Thu, 28 May 2020 08:33:37 +0900 |
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On 2020/05/28 0:55, Petr Mladek wrote: >>> Well, it would be possible to call vsprintf() with NULL buffer. It is >>> normally used to calculate the length of the message before it is >>> printed. But it also does all the accesses without printing anything. >> >> OK. I think that redirecting pr_debug() to vsnprintf(NULL, 0) will be >> better than modifying dynamic_debug path, for > > It might get more complicated if you would actually want to see > pr_debug() messages for a selected module in the fuzzer.
I don't expect that automated testing can afford selectively enabling DYNAMIC_DEBUG_BRANCH(id) conditions. But we could evaluate all arguments by calling snprintf(NULL, 0) if the condition to call printk() is false.
> vsprintf(NULL, ) can be called for pr_debug() messages in > vprintk_store(). It will be again only a single place for > all printk() wrappers.
I couldn't catch what you mean. The problem of pr_debug() is that vprintk_store() might not be called because of
#define no_printk(fmt, ...) \ ({ \ if (0) \ printk(fmt, ##__VA_ARGS__); \ 0; \ })
#define pr_debug(fmt, ...) \ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
or
#define __dynamic_func_call(id, fmt, func, ...) do { \ DEFINE_DYNAMIC_DEBUG_METADATA(id, fmt); \ if (DYNAMIC_DEBUG_BRANCH(id)) \ func(&id, ##__VA_ARGS__); \ } while (0)
#define _dynamic_func_call(fmt, func, ...) \ __dynamic_func_call(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)
#define dynamic_pr_debug(fmt, ...) \ _dynamic_func_call(fmt, __dynamic_pr_debug, \ pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug(fmt, ...) \ dynamic_pr_debug(fmt, ##__VA_ARGS__)
. Maybe we can append
else if (IS_BUILTIN(CONFIG_TWIST_ALWAYS_EVALUATE_DEBUG_PRINTK)) \ snprintf(NULL, 0, fmt, ##__VA_ARGS__); \
to no_printk() and __dynamic_func_call().
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