LXR linux/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
  27struct 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
  36static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
  37{
  38        return test_bit(fd, fdt->close_on_exec);
  39}
  40
  41static 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 */
  49struct 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
  70struct file_operations;
  71struct vfsmount;
  72struct 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 */
  83static 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
  94static 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
 107struct task_struct;
 108
 109struct files_struct *get_files_struct(struct task_struct *);
 110void put_files_struct(struct files_struct *fs);
 111void reset_files_struct(struct files_struct *);
 112int unshare_files(struct files_struct **);
 113struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy;
 114void do_close_on_exec(struct files_struct *);
 115int iterate_fd(struct files_struct *, unsigned,
 116                int (*)(const void *, struct file *, unsigned),
 117                const void *);
 118
 119extern int __alloc_fd(struct files_struct *files,
 120                      unsigned start, unsigned end, unsigned flags);
 121extern void __fd_install(struct files_struct *files,
 122                      unsigned int fd, struct file *file);
 123extern int __close_fd(struct files_struct *files,
 124                      unsigned int fd);
 125extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
 126extern int __close_fd_get_file(unsigned int fd, struct file **res);
 127extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
 128                      struct files_struct **new_fdp);
 129
 130extern struct kmem_cache *files_cachep;
 131
 132#endif /* __LINUX_FDTABLE_H */
 133