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TOMOYO Linux Cross Reference
Linux/include/linux/fdtable.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 /*
  3  * descriptor table internals; you almost certainly want file.h instead.
  4  */
  5 
  6 #ifndef __LINUX_FDTABLE_H
  7 #define __LINUX_FDTABLE_H
  8 
  9 #include <linux/posix_types.h>
 10 #include <linux/compiler.h>
 11 #include <linux/spinlock.h>
 12 #include <linux/rcupdate.h>
 13 #include <linux/nospec.h>
 14 #include <linux/types.h>
 15 #include <linux/init.h>
 16 #include <linux/fs.h>
 17 
 18 #include <linux/atomic.h>
 19 
 20 /*
 21  * The default fd array needs to be at least BITS_PER_LONG,
 22  * as this is the granularity returned by copy_fdset().
 23  */
 24 #define NR_OPEN_DEFAULT BITS_PER_LONG
 25 
 26 struct fdtable {
 27         unsigned int max_fds;
 28         struct file __rcu **fd;      /* current fd array */
 29         unsigned long *close_on_exec;
 30         unsigned long *open_fds;
 31         unsigned long *full_fds_bits;
 32         struct rcu_head rcu;
 33 };
 34 
 35 static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
 36 {
 37         return test_bit(fd, fdt->close_on_exec);
 38 }
 39 
 40 static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
 41 {
 42         return test_bit(fd, fdt->open_fds);
 43 }
 44 
 45 /*
 46  * Open file table structure
 47  */
 48 struct files_struct {
 49   /*
 50    * read mostly part
 51    */
 52         atomic_t count;
 53         bool resize_in_progress;
 54         wait_queue_head_t resize_wait;
 55 
 56         struct fdtable __rcu *fdt;
 57         struct fdtable fdtab;
 58   /*
 59    * written part on a separate cache line in SMP
 60    */
 61         spinlock_t file_lock ____cacheline_aligned_in_smp;
 62         unsigned int next_fd;
 63         unsigned long close_on_exec_init[1];
 64         unsigned long open_fds_init[1];
 65         unsigned long full_fds_bits_init[1];
 66         struct file __rcu * fd_array[NR_OPEN_DEFAULT];
 67 };
 68 
 69 struct file_operations;
 70 struct vfsmount;
 71 struct dentry;
 72 
 73 #define rcu_dereference_check_fdtable(files, fdtfd) \
 74         rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
 75 
 76 #define files_fdtable(files) \
 77         rcu_dereference_check_fdtable((files), (files)->fdt)
 78 
 79 /*
 80  * The caller must ensure that fd table isn't shared or hold rcu or file lock
 81  */
 82 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
 83 {
 84         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
 85 
 86         if (fd < fdt->max_fds) {
 87                 fd = array_index_nospec(fd, fdt->max_fds);
 88                 return rcu_dereference_raw(fdt->fd[fd]);
 89         }
 90         return NULL;
 91 }
 92 
 93 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
 94 {
 95         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
 96                            !lockdep_is_held(&files->file_lock),
 97                            "suspicious rcu_dereference_check() usage");
 98         return __fcheck_files(files, fd);
 99 }
100 
101 /*
102  * Check whether the specified fd has an open file.
103  */
104 #define fcheck(fd)      fcheck_files(current->files, fd)
105 
106 struct task_struct;
107 
108 struct files_struct *get_files_struct(struct task_struct *);
109 void put_files_struct(struct files_struct *fs);
110 void reset_files_struct(struct files_struct *);
111 int unshare_files(struct files_struct **);
112 struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
113 void do_close_on_exec(struct files_struct *);
114 int iterate_fd(struct files_struct *, unsigned,
115                 int (*)(const void *, struct file *, unsigned),
116                 const void *);
117 
118 extern int __alloc_fd(struct files_struct *files,
119                       unsigned start, unsigned end, unsigned flags);
120 extern void __fd_install(struct files_struct *files,
121                       unsigned int fd, struct file *file);
122 extern int __close_fd(struct files_struct *files,
123                       unsigned int fd);
124 
125 extern struct kmem_cache *files_cachep;
126 
127 #endif /* __LINUX_FDTABLE_H */
128 

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