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/types.h> 14 #include <linux/init.h> 15 #include <linux/fs.h> 16 17 #include <linux/atomic.h> 18 19 /* 20 * The default fd array needs to be at least BITS_PER_LONG, 21 * as this is the granularity returned by copy_fdset(). 22 */ 23 #define NR_OPEN_DEFAULT BITS_PER_LONG 24 25 struct fdtable { 26 unsigned int max_fds; 27 struct file __rcu **fd; /* current fd array */ 28 unsigned long *close_on_exec; 29 unsigned long *open_fds; 30 unsigned long *full_fds_bits; 31 struct rcu_head rcu; 32 }; 33 34 static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt) 35 { 36 return test_bit(fd, fdt->close_on_exec); 37 } 38 39 static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt) 40 { 41 return test_bit(fd, fdt->open_fds); 42 } 43 44 /* 45 * Open file table structure 46 */ 47 struct files_struct { 48 /* 49 * read mostly part 50 */ 51 atomic_t count; 52 bool resize_in_progress; 53 wait_queue_head_t resize_wait; 54 55 struct fdtable __rcu *fdt; 56 struct fdtable fdtab; 57 /* 58 * written part on a separate cache line in SMP 59 */ 60 spinlock_t file_lock ____cacheline_aligned_in_smp; 61 unsigned int next_fd; 62 unsigned long close_on_exec_init[1]; 63 unsigned long open_fds_init[1]; 64 unsigned long full_fds_bits_init[1]; 65 struct file __rcu * fd_array[NR_OPEN_DEFAULT]; 66 }; 67 68 struct file_operations; 69 struct vfsmount; 70 struct dentry; 71 72 #define rcu_dereference_check_fdtable(files, fdtfd) \ 73 rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock)) 74 75 #define files_fdtable(files) \ 76 rcu_dereference_check_fdtable((files), (files)->fdt) 77 78 /* 79 * The caller must ensure that fd table isn't shared or hold rcu or file lock 80 */ 81 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd) 82 { 83 struct fdtable *fdt = rcu_dereference_raw(files->fdt); 84 85 if (fd < fdt->max_fds) 86 return rcu_dereference_raw(fdt->fd[fd]); 87 return NULL; 88 } 89 90 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd) 91 { 92 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && 93 !lockdep_is_held(&files->file_lock), 94 "suspicious rcu_dereference_check() usage"); 95 return __fcheck_files(files, fd); 96 } 97 98 /* 99 * Check whether the specified fd has an open file. 100 */ 101 #define fcheck(fd) fcheck_files(current->files, fd) 102 103 struct task_struct; 104 105 struct files_struct *get_files_struct(struct task_struct *); 106 void put_files_struct(struct files_struct *fs); 107 void reset_files_struct(struct files_struct *); 108 int unshare_files(struct files_struct **); 109 struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy; 110 void do_close_on_exec(struct files_struct *); 111 int iterate_fd(struct files_struct *, unsigned, 112 int (*)(const void *, struct file *, unsigned), 113 const void *); 114 115 extern int __alloc_fd(struct files_struct *files, 116 unsigned start, unsigned end, unsigned flags); 117 extern void __fd_install(struct files_struct *files, 118 unsigned int fd, struct file *file); 119 extern int __close_fd(struct files_struct *files, 120 unsigned int fd); 121 122 extern struct kmem_cache *files_cachep; 123 124 #endif /* __LINUX_FDTABLE_H */ 125