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 */
119