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/* SPDX-License-Identifier: GPL-2.0 */
* descriptor table internals; you almost certainly want file.h instead.
#include <linux/posix_types.h>
#include <linux/compiler.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/nospec.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/atomic.h>
* The default fd array needs to be at least BITS_PER_LONG,
* as this is the granularity returned by copy_fdset().
struct fdtable {
unsigned int max_fds;
struct file __rcu **fd; /* current fd array */
unsigned long *close_on_exec;
unsigned long *open_fds;
unsigned long *full_fds_bits;
struct rcu_head rcu;
static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
return test_bit(fd, fdt->close_on_exec);
static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
return test_bit(fd, fdt->open_fds);
* Open file table structure
struct files_struct {
* read mostly part
atomic_t count;
bool resize_in_progress;
wait_queue_head_t resize_wait;
struct fdtable __rcu *fdt;
struct fdtable fdtab;
* written part on a separate cache line in SMP
spinlock_t file_lock ____cacheline_aligned_in_smp;
unsigned int next_fd;
unsigned long close_on_exec_init[1];
unsigned long open_fds_init[1];
unsigned long full_fds_bits_init[1];
struct file __rcu * fd_array[NR_OPEN_DEFAULT];
struct file_operations;
struct vfsmount;
struct dentry;
#define rcu_dereference_check_fdtable(files, fdtfd) \
rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
#define files_fdtable(files) \
rcu_dereference_check_fdtable((files), (files)->fdt)
* The caller must ensure that fd table isn't shared or hold rcu or file lock
static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
struct fdtable *fdt = rcu_dereference_raw(files->fdt);
if (fd < fdt->max_fds) {
fd = array_index_nospec(fd, fdt->max_fds);
return rcu_dereference_raw(fdt->fd[fd]);
return NULL;
static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
"suspicious rcu_dereference_check() usage");
return __fcheck_files(files, fd);
* Check whether the specified fd has an open file.
#define fcheck(fd) fcheck_files(current->files, fd)
struct task_struct;
struct files_struct *get_files_struct(struct task_struct *);
void put_files_struct(struct files_struct *fs);
void reset_files_struct(struct files_struct *);
int unshare_files(struct files_struct **);
struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
void do_close_on_exec(struct files_struct *);
int iterate_fd(struct files_struct *, unsigned,
int (*)(const void *, struct file *, unsigned),
const void *);
extern int __alloc_fd(struct files_struct *files,
unsigned start, unsigned end, unsigned flags);
extern void __fd_install(struct files_struct *files,
unsigned int fd, struct file *file);
extern int __close_fd(struct files_struct *files,
unsigned int fd);
extern struct kmem_cache *files_cachep;
#endif /* __LINUX_FDTABLE_H */