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
  26struct 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
  35static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
  36{
  37        return test_bit(fd, fdt->close_on_exec);
  38}
  39
  40static 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 */
  48struct 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
  69struct file_operations;
  70struct vfsmount;
  71struct 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 */
  82static 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
  93static 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
 106struct task_struct;
 107
 108struct files_struct *get_files_struct(struct task_struct *);
 109void put_files_struct(struct files_struct *fs);
 110void reset_files_struct(struct files_struct *);
 111int unshare_files(struct files_struct **);
 112struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
 113void do_close_on_exec(struct files_struct *);
 114int iterate_fd(struct files_struct *, unsigned,
 115                int (*)(const void *, struct file *, unsigned),
 116                const void *);
 117
 118extern int __alloc_fd(struct files_struct *files,
 119                      unsigned start, unsigned end, unsigned flags);
 120extern void __fd_install(struct files_struct *files,
 121                      unsigned int fd, struct file *file);
 122extern int __close_fd(struct files_struct *files,
 123                      unsigned int fd);
 124extern int __close_fd_get_file(unsigned int fd, struct file **res);
 125
 126extern struct kmem_cache *files_cachep;
 127
 128#endif /* __LINUX_FDTABLE_H */
 129