linux kernel printk syslog

最新推荐文章于 2025-12-27 15:35:24 发布

原创最新推荐文章于 2025-12-27 15:35:24 发布 · 819 阅读

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#linux #function #logging #each #user

本文介绍了Linux内核中用于日志记录的API及其使用方法。详细解释了不同日志级别对应的宏定义，并展示了如何根据不同配置条件选择合适的日志打印方式。此外，还介绍了syslog调用的工作原理及其在内核中的实现。

The kernel also provides some helper functions for logging that can simplify their use. Each log level has its own function, which expands as a macro for theprintk function. For example, when using printk with the KERN_EMERG log level, you can use the pr_emerg, instead. Each macro is listed in ./linux/include/linux/kernel.h.

/* If you are writing a driver, please use dev_dbg instead */

#if defined(DEBUG)

#define pr_debug(fmt, ...) /

printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)

#elif defined(CONFIG_DYNAMIC_DEBUG)

/* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */

#define pr_debug(fmt, ...) do { /

dynamic_pr_debug(fmt, ##__VA_ARGS__); /

} while (0)

#else

#define pr_debug(fmt, ...) /

({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; })

#endif

The syslog call (called do_syslog within the kernel in ./linux/kernel/printk.c) is a relatively small function that provides the ability to read and control the kernel ring buffer.

SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
{
return do_syslog(type, buf, len);
}

http://www.ibm.com/developerworks/linux/library/l-kernel-logging-apis/?ca=drs-