लिनक्स/linux-0.01.tar/kernel/printk.c

/*
 * 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];

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;
} 

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