fdtable.h

  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
 26struct 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/*
 36 * Open file table structure
 37 */
 38struct files_struct {
 39  /*
 40   * read mostly part
 41   */
 42	atomic_t count;
 43	bool resize_in_progress;
 44	wait_queue_head_t resize_wait;
 45
 46	struct fdtable __rcu *fdt;
 47	struct fdtable fdtab;
 48  /*
 49   * written part on a separate cache line in SMP
 50   */
 51	spinlock_t file_lock ____cacheline_aligned_in_smp;
 52	unsigned int next_fd;
 53	unsigned long close_on_exec_init[1];
 54	unsigned long open_fds_init[1];
 55	unsigned long full_fds_bits_init[1];
 56	struct file __rcu * fd_array[NR_OPEN_DEFAULT];
 57};
 58
 59struct file_operations;
 60struct vfsmount;
 61struct dentry;
 62
 63#define rcu_dereference_check_fdtable(files, fdtfd) \
 64	rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
 65
 66#define files_fdtable(files) \
 67	rcu_dereference_check_fdtable((files), (files)->fdt)
 68
 69/*
 70 * The caller must ensure that fd table isn't shared or hold rcu or file lock
 71 */
 72static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd)
 73{
 74	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
 75	unsigned long mask = array_index_mask_nospec(fd, fdt->max_fds);
 76	struct file *needs_masking;
 77
 78	/*
 79	 * 'mask' is zero for an out-of-bounds fd, all ones for ok.
 80	 * 'fd&mask' is 'fd' for ok, or 0 for out of bounds.
 81	 *
 82	 * Accessing fdt->fd[0] is ok, but needs masking of the result.
 83	 */
 84	needs_masking = rcu_dereference_raw(fdt->fd[fd&mask]);
 85	return (struct file *)(mask & (unsigned long)needs_masking);
 86}
 87
 88static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd)
 89{
 90	RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock),
 91			   "suspicious rcu_dereference_check() usage");
 92	return files_lookup_fd_raw(files, fd);
 93}
 94
 95static inline bool close_on_exec(unsigned int fd, const struct files_struct *files)
 96{
 97	return test_bit(fd, files_fdtable(files)->close_on_exec);
 98}
 99
100struct task_struct;
101
102void put_files_struct(struct files_struct *fs);
103int unshare_files(void);
104struct fd_range {
105	unsigned int from, to;
106};
107struct files_struct *dup_fd(struct files_struct *, struct fd_range *) __latent_entropy;
108void do_close_on_exec(struct files_struct *);
109int iterate_fd(struct files_struct *, unsigned,
110		int (*)(const void *, struct file *, unsigned),
111		const void *);
112
113extern int close_fd(unsigned int fd);
114extern struct file *file_close_fd(unsigned int fd);
115
116extern struct kmem_cache *files_cachep;
117
118#endif /* __LINUX_FDTABLE_H */