Linux下类FreeBSD uprintf实现

uprintf是FreeBSD下内核函数, 作用是将内核信息输出到当前的tty给用户显示, 非常方便. 而linux下无此函数, 不过可以通过借用tty设备来达到目的.

以下是代码实现.

Kernel version: 2.6.28

gcc Version: 4.3.3

#include <linux/module.h>       /* Needed by all modules */
#include <linux/kernel.h>       /* Needed for KERN_INFO */
#include <linux/init.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>

#include <linux/sched.h>    /* For current */
#include <linux/tty.h>      /* For the tty declarations */


static void tty_print(const char *str)
{
    struct tty_struct *cur_tty;

    // 取得当前的tty
    if ( current->signal )
        cur_tty = current->signal->tty;
    else
        cur_tty = NULL;

    // 调用当前tty设备驱动write操作
    if ( cur_tty ) {
        if ( cur_tty->driver ) {
            cur_tty->driver->ops->write(
                cur_tty,
                str,
                strlen( str )
                );
/*
            cur_tty->driver->ops->write(
                cur_tty,
                "\015\012",
                2
                );
*/
        }

    }

}

int uprintf(const char *fmt, ...)
{
    char printf_buf[1024];
    va_list args;
    int printed;

    va_start(args, fmt);
    printed = vsprintf(printf_buf, fmt, args);
    va_end(args);

    tty_print( printf_buf );
    return 0;
}

EXPORT_SYMBOL( uprintf );
static int __init uprintf_init(void)
{
    uprintf( "hello init\n" );
    return 0;
}

static void __exit uprintf_fini(void)
{
    uprintf( "hello end\n" );
}

module_init(uprintf_init);
module_exit(uprintf_fini);

Makefile

obj-m = uprintf.o
uprintf-objs = main.o

KVERSION = $(shell uname -r)
all:
            make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
            make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean
            rm -f Module.markers  modules.order

参考:

Replacing printk's