include/linux/fdtable.h

   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 *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
  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
 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
 108 /*
 109  * Check whether the specified fd has an open file.
 110  */
 111 #define fcheck(fd)      files_lookup_fd_rcu(current->files, fd)
 112
 113 struct task_struct;
 114
 115 struct files_struct *get_files_struct(struct task_struct *);
 116 void put_files_struct(struct files_struct *fs);
 117 int unshare_files(void);
 118 struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy;
 119 void do_close_on_exec(struct files_struct *);
 120 int iterate_fd(struct files_struct *, unsigned,
 121                 int (*)(const void *, struct file *, unsigned),
 122                 const void *);
 123
 124 extern int __alloc_fd(struct files_struct *files,
 125                       unsigned start, unsigned end, unsigned flags);
 126 extern void __fd_install(struct files_struct *files,
 127                       unsigned int fd, struct file *file);
 128 extern int __close_fd(struct files_struct *files,
 129                       unsigned int fd);
 130 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
 131 extern int __close_fd_get_file(unsigned int fd, struct file **res);
 132 extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
 133                       struct files_struct **new_fdp);
 134
 135 extern struct kmem_cache *files_cachep;
 136
 137 #endif /* __LINUX_FDTABLE_H */