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 #define NR_OPEN_MAX ~0U
26 
27 struct fdtable {
28 	unsigned int max_fds;
29 	struct file __rcu **fd;      /* current fd array */
30 	unsigned long *close_on_exec;
31 	unsigned long *open_fds;
32 	unsigned long *full_fds_bits;
33 	struct rcu_head rcu;
34 };
35 
close_on_exec(unsigned int fd,const struct fdtable * fdt)36 static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
37 {
38 	return test_bit(fd, fdt->close_on_exec);
39 }
40 
fd_is_open(unsigned int fd,const struct fdtable * fdt)41 static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
42 {
43 	return test_bit(fd, fdt->open_fds);
44 }
45 
46 /*
47  * Open file table structure
48  */
49 struct files_struct {
50   /*
51    * read mostly part
52    */
53 	atomic_t count;
54 	bool resize_in_progress;
55 	wait_queue_head_t resize_wait;
56 
57 	struct fdtable __rcu *fdt;
58 	struct fdtable fdtab;
59   /*
60    * written part on a separate cache line in SMP
61    */
62 	spinlock_t file_lock ____cacheline_aligned_in_smp;
63 	unsigned int next_fd;
64 	unsigned long close_on_exec_init[1];
65 	unsigned long open_fds_init[1];
66 	unsigned long full_fds_bits_init[1];
67 	struct file __rcu * fd_array[NR_OPEN_DEFAULT];
68 };
69 
70 struct file_operations;
71 struct vfsmount;
72 struct dentry;
73 
74 #define rcu_dereference_check_fdtable(files, fdtfd) \
75 	rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
76 
77 #define files_fdtable(files) \
78 	rcu_dereference_check_fdtable((files), (files)->fdt)
79 
80 /*
81  * The caller must ensure that fd table isn't shared or hold rcu or file lock
82  */
files_lookup_fd_raw(struct files_struct * files,unsigned int fd)83 static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd)
84 {
85 	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
86 
87 	if (fd < fdt->max_fds) {
88 		fd = array_index_nospec(fd, fdt->max_fds);
89 		return rcu_dereference_raw(fdt->fd[fd]);
90 	}
91 	return NULL;
92 }
93 
files_lookup_fd_locked(struct files_struct * files,unsigned int fd)94 static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd)
95 {
96 	RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock),
97 			   "suspicious rcu_dereference_check() usage");
98 	return files_lookup_fd_raw(files, fd);
99 }
100 
files_lookup_fd_rcu(struct files_struct * files,unsigned int fd)101 static inline struct file *files_lookup_fd_rcu(struct files_struct *files, unsigned int fd)
102 {
103 	RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
104 			   "suspicious rcu_dereference_check() usage");
105 	return files_lookup_fd_raw(files, fd);
106 }
107 
lookup_fd_rcu(unsigned int fd)108 static inline struct file *lookup_fd_rcu(unsigned int fd)
109 {
110 	return files_lookup_fd_rcu(current->files, fd);
111 }
112 
113 struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd);
114 struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *fd);
115 
116 struct task_struct;
117 
118 void put_files_struct(struct files_struct *fs);
119 int unshare_files(void);
120 struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy;
121 void do_close_on_exec(struct files_struct *);
122 int iterate_fd(struct files_struct *, unsigned,
123 		int (*)(const void *, struct file *, unsigned),
124 		const void *);
125 
126 extern int close_fd(unsigned int fd);
127 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
128 extern struct file *close_fd_get_file(unsigned int fd);
129 extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
130 		      struct files_struct **new_fdp);
131 
132 extern struct kmem_cache *files_cachep;
133 
134 #endif /* __LINUX_FDTABLE_H */
135