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
close_on_exec(unsigned int fd,const struct fdtable * fdt)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
fd_is_open(unsigned int fd,const struct fdtable * fdt)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 */
__fcheck_files(struct files_struct * files,unsigned int fd)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
fcheck_files(struct files_struct * files,unsigned int fd)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 extern int __close_fd_get_file(unsigned int fd, struct file **res);
125
126 extern struct kmem_cache *files_cachep;
127
128 #endif /* __LINUX_FDTABLE_H */
129