linux 0.11 ÄÚºËѧϰ fcntl.c
/*
* linux/fs/fcntl.c
*
* (C) 1991 Linus Torvalds
*/
#include <string.h>
#include <errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <asm/segment.h>
#include <fcntl.h>
#include <sys/stat.h>
extern int sys_close(int fd);
/* ¸´ÖÆÎļþ¾ä±ú£¬²ÎÊýfdÊÇÖ¸Óë¸´ÖÆµÄÎļþ¾ä±ú£¬argÊÇÖ¸¶¨ÐÂÎļþµÄ¾ä±úµÄ×îСֵ */
static int dupfd(unsigned int fd, unsigned int arg)
{
// Èç¹ûÎļþ¾ä±úÖµ´óÓÚÒ»¸ö³ÌÐò×î¶à´ò¿ªÎļþÊýNR_OPEN£¬»òÕ߸þä±úµÄÎļþ½á¹¹²»´æÔÚ£¬Ôò³ö´í£¬
// ·µ»Ø³ö´íÂë²¢Í˳ö
if (fd >= NR_OPEN || !current->filp[fd])
return -EBADF;
// Èç¹ûÖ¸¶¨µÄоä±úÖµarg ´óÓÚ×î¶à´ò¿ªÎļþÊý£¬Ôò³ö´í
if (arg >= NR_OPEN)
return -EINVAL;
// ÔÚµ±Ç°½ø³ÌµÄÎļþ½á¹¹Ö¸ÕëÊý×éÖÐѰÕÒË÷ÒýºÅ´óÓÚµÈÓÚarg µ«»¹Ã»ÓÐʹÓõÄÏî
while (arg < NR_OPEN)
if (current->filp[arg])
arg++;
else
break;
// Èç¹ûÕÒµ½µÄоä±úÖµarg ´óÓÚ×î¶à´ò¿ªÎļþÊý£¬Ôò³ö´í
if (arg >= NR_OPEN)
return -EMFILE;
// ÔÚÔËÐÐexec()ÀຯÊýʱ²»¹Ø±Õ¸Ã¾ä±ú
current->close_on_exec &= ~(1<<arg);
// Áî¸ÃÎļþ½á¹¹Ö¸ÕëµÈÓÚÔ¾ä±úfd µÄÖ¸Õ룬²¢½«ÎļþÒýÓüÆÊýÔö1
(current->filp[arg] = current->filp[fd])->f_count++;
return arg;
}
/* ¸´ÖÆÎļþ¾ä±úϵͳµ÷Óú¯Êý */
int sys_dup2(unsigned int oldfd, unsigned int newfd)
{
// Èô¾ä±únewfd ÒѾ´ò¿ª£¬ÔòÊ×ÏȹرÕÖ®
sys_close(newfd);
// ¸´ÖƲ¢·µ»ØÐ¾ä±ú
return dupfd(oldfd,newfd);
}
/* ¸´ÖÆÎļþ¾ä±úϵͳµ÷Óú¯Êý¡£Ð¾ä±úµÄÖµÊǵ±Ç°×îСµÄδÓþä±ú */
int sys_dup(unsigned int fildes)
{
return dupfd(fildes,0);
}
/* Îļþ¿ØÖÆÏµÍ³µ÷Óú¯Êý */
int sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
{
struct file * filp;
// Èç¹ûÎļþ¾ä±úÖµ´óÓÚÒ»¸ö½ø³Ì×î¶à´ò¿ªÎļþÊýNR_OPEN£¬»òÕ߸þä±úµÄÎļþ½á¹¹Ö¸ÕëΪ¿Õ£¬Ôò³ö´í£¬
// ·µ»Ø³ö´íÂë²¢Í˳ö
if (fd >= NR_OPEN || !(filp = current->filp[fd]))
return -EBADF;
switch (cmd)
{
case F_DUPFD: // ¸´ÖÆÎļþ¾ä±ú
return dupfd(fd,arg);
case F_GETFD: // È¡Îļþ¾ä±úµÄÖ
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