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 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 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 */ 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 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