从用户态open到内核驱动实现

 

 

man 2 open

 

int open(const char *pathname, int flags, mode_t mode);

 

SEE ALSO
       read(2), write(2), fcntl(2), close(2), link(2),  mknod(2),  mount(2),  stat(2),
       umask(2), unlink(2), socket(2), fopen(3), fifo(4)

Linux                                 1999-06-03                               OPEN(2)

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 open函数用于打开、创建文件         POSIX 标准系统调用

 

#include <fcntl.h>  ///usr/include/fcntl.h

 

返回值：成功则返回文件描述符，否则返回-1

 

对于open函数，第三个参数（…），仅当创建新文件时 才使用。

 

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理解从应用层到我们自己所写的驱动层的调用过程

asmlinkage long sys_readlink(const char __user *path,
    char __user *buf, int bufsiz);
asmlinkage long sys_creat(const char __user *pathname, int mode);
asmlinkage long sys_open(const char __user *filename,
    int flags, int mode);
asmlinkage long sys_close(unsigned int fd);
asmlinkage long sys_access(const char __user *filename, int mode);
asmlinkage long sys_vhangup(void);
asmlinkage long sys_chown(const char __user *filename,
    uid_t user, gid_t group);
asmlinkage long sys_lchown(const char __user *filename,

 

sys_open()

定义：

fs/open.c

SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, int, mode)
{
    long ret;

    if (force_o_largefile())
        flags |= O_LARGEFILE;

    ret = do_sys_open(AT_FDCWD, filename, flags, mode);
    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(3, ret, filename, flags, mode);
    return ret;
}