Oldlinux Cross Reference
Linux/kernel/printk.c

   /*
    *  linux/kernel/printk.c
    *
    *  (C) 1991  Linus Torvalds
    */
   
   /*
    * When in kernel-mode, we cannot use printf, as fs is liable to
    * point to 'interesting' things. Make a printf with fs-saving, and
   * all is well.
   */
  #include <stdarg.h>
  #include <stddef.h>
  
  #include <linux/kernel.h>
  
  static char buf[1024];
  
  extern int vsprintf(char * buf, const char * fmt, va_list args);
  
  int printk(const char *fmt, ...)
  {
          va_list args;
          int i;
  
          va_start(args, fmt);
          i=vsprintf(buf,fmt,args);
          va_end(args);
          __asm__("push %%fs\n\t"
                  "push %%ds\n\t"
                  "pop %%fs\n\t"
                  "pushl %0\n\t"
                  "pushl $_buf\n\t"
                  "pushl $0\n\t"
                  "call _tty_write\n\t"
                  "addl $8,%%esp\n\t"
                  "popl %0\n\t"
                  "pop %%fs"
                  ::"r" (i):"ax","cx","dx");
          return i;
  }