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 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 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 */ 83 static inline struct file *__fcheck_files(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 94 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd) 95 { 96 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && 97 !lockdep_is_held(&files->file_lock), 98 "suspicious rcu_dereference_check() usage"); 99 return __fcheck_files(files, fd); 100 } 101 102 /* 103 * Check whether the specified fd has an open file. 104 */ 105 #define fcheck(fd) fcheck_files(current->files, fd) 106 107 struct task_struct; 108 109 struct files_struct *get_files_struct(struct task_struct *); 110 void put_files_struct(struct files_struct *fs); 111 void reset_files_struct(struct files_struct *); 112 int unshare_files(struct files_struct **); 113 struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy; 114 void do_close_on_exec(struct files_struct *); 115 int iterate_fd(struct files_struct *, unsigned, 116 int (*)(const void *, struct file *, unsigned), 117 const void *); 118 119 extern int __alloc_fd(struct files_struct *files, 120 unsigned start, unsigned end, unsigned flags); 121 extern void __fd_install(struct files_struct *files, 122 unsigned int fd, struct file *file); 123 extern int __close_fd(struct files_struct *files, 124 unsigned int fd); 125 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags); 126 extern int __close_fd_get_file(unsigned int fd, struct file **res); 127 extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, 128 struct files_struct **new_fdp); 129 130 extern struct kmem_cache *files_cachep; 131 132 #endif /* __LINUX_FDTABLE_H */ 133