include/linux/file.h

   1 /*
   2  * Wrapper functions for accessing the file_struct fd array.
   3  */
   4
   5 #ifndef __LINUX_FILE_H
   6 #define __LINUX_FILE_H
   7
   8 extern void FASTCALL(fput(struct file *));
   9 extern struct file * FASTCALL(fget(unsigned int fd));
  10
  11 static inline int get_close_on_exec(unsigned int fd)
  12 {
  13         struct files_struct *files = current->files;
  14         int res;
  15         read_lock(&files->file_lock);
  16         res = FD_ISSET(fd, files->close_on_exec);
  17         read_unlock(&files->file_lock);
  18         return res;
  19 }
  20
  21 static inline void set_close_on_exec(unsigned int fd, int flag)
  22 {
  23         struct files_struct *files = current->files;
  24         write_lock(&files->file_lock);
  25         if (flag)
  26                 FD_SET(fd, files->close_on_exec);
  27         else
  28                 FD_CLR(fd, files->close_on_exec);
  29         write_unlock(&files->file_lock);
  30 }
  31
  32 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  33 {
  34         struct file * file = NULL;
  35
  36         if (fd < files->max_fds)
  37                 file = files->fd[fd];
  38         return file;
  39 }
  40
  41 /*
  42  * Check whether the specified fd has an open file.
  43  */
  44 static inline struct file * fcheck(unsigned int fd)
  45 {
  46         struct file * file = NULL;
  47         struct files_struct *files = current->files;
  48
  49         if (fd < files->max_fds)
  50                 file = files->fd[fd];
  51         return file;
  52 }
  53
  54 extern void put_filp(struct file *);
  55
  56 extern int get_unused_fd(void);
  57
  58 static inline void __put_unused_fd(struct files_struct *files, unsigned int fd)
  59 {
  60         FD_CLR(fd, files->open_fds);
  61         if (fd < files->next_fd)
  62                 files->next_fd = fd;
  63 }
  64
  65 static inline void put_unused_fd(unsigned int fd)
  66 {
  67         struct files_struct *files = current->files;
  68
  69         write_lock(&files->file_lock);
  70         __put_unused_fd(files, fd);
  71         write_unlock(&files->file_lock);
  72 }
  73
  74 /*
  75  * Install a file pointer in the fd array.
  76  *
  77  * The VFS is full of places where we drop the files lock between
  78  * setting the open_fds bitmap and installing the file in the file
  79  * array.  At any such point, we are vulnerable to a dup2() race
  80  * installing a file in the array before us.  We need to detect this and
  81  * fput() the struct file we are about to overwrite in this case.
  82  *
  83  * It should never happen - if we allow dup2() do it, _really_ bad things
  84  * will follow.
  85  */
  86
  87 static inline void fd_install(unsigned int fd, struct file * file)
  88 {
  89         struct files_struct *files = current->files;
  90
  91         write_lock(&files->file_lock);
  92         if (files->fd[fd])
  93                 BUG();
  94         files->fd[fd] = file;
  95         write_unlock(&files->file_lock);
  96 }
  97
  98 void put_files_struct(struct files_struct *fs);
  99
 100 #endif /* __LINUX_FILE_H */