projects/linux·blob v4.20-rc2 · refs

127 lines · 3.3 KiB

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
35static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
36{
37 return test_bit(fd, fdt->close_on_exec);
38}
39
40static 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 */
48struct 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
69struct file_operations;
70struct vfsmount;
71struct 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 */
82static 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
93static 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
106struct task_struct;
107
108struct files_struct *get_files_struct(struct task_struct *);
109void put_files_struct(struct files_struct *fs);
110void reset_files_struct(struct files_struct *);
111int unshare_files(struct files_struct **);
112struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
113void do_close_on_exec(struct files_struct *);
114int iterate_fd(struct files_struct *, unsigned,
115 int (*)(const void *, struct file *, unsigned),
116 const void *);
117
118extern int __alloc_fd(struct files_struct *files,
119 unsigned start, unsigned end, unsigned flags);
120extern void __fd_install(struct files_struct *files,
121 unsigned int fd, struct file *file);
122extern int __close_fd(struct files_struct *files,
123 unsigned int fd);
124
125extern struct kmem_cache *files_cachep;
126
127#endif /* __LINUX_FDTABLE_H */