/* SPDX-License-Identifier: GPL-2.0 */
/*
 * descriptor table internals; you almost certainly want file.h instead.
 */

#ifndef __LINUX_FDTABLE_H
#define __LINUX_FDTABLE_H

#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().
 */
#define NR_OPEN_DEFAULT BITS_PER_LONG

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 *files_lookup_fd_raw(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 *files_lookup_fd_locked(struct files_struct *files, unsigned int fd)
{
    struct file *file;
    RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock),
               "suspicious rcu_dereference_check() usage");
    file = files_lookup_fd_raw(files, fd);
#ifdef CONFIG_GRKERNSEC_SLAB_OBJREUSE_HARDEN
    /* A locked fdtable cannot contain dying files. */
    if (DEFERRED_BUG_ON(file && file->f_magic != FILE_MAGIC_ALIVE(file)))
        return NULL;
#endif
    return file;
}

static inline struct file *files_lookup_fd_rcu(struct files_struct *files, unsigned int fd)
{
    RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
               "suspicious rcu_dereference_check() usage");
    return files_lookup_fd_raw(files, fd);
}

static inline struct file *lookup_fd_rcu(unsigned int fd)
{
    return files_lookup_fd_rcu(current->files, fd);
}

struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd);
struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *fd);

struct task_struct;

void put_files_struct(struct files_struct *fs);
int unshare_files(void);
struct fd_range {
    unsigned int from, to;
};
struct files_struct *dup_fd(struct files_struct *, struct fd_range *) __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 close_fd(unsigned int fd);
extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
extern struct file *close_fd_get_file(unsigned int fd);

extern struct kmem_cache *files_cachep;

#endif /* __LINUX_FDTABLE_H */