linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 *  linux/fs/file.c

 *

 *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes

 *

 *  Manage the dynamic fd arrays in the process files_struct.

 */

​

#include <linux/syscalls.h>

#include <linux/export.h>

#include <linux/fs.h>

#include <linux/mm.h>

#include <linux/sched/signal.h>

#include <linux/slab.h>

#include <linux/file.h>

#include <linux/fdtable.h>

#include <linux/bitops.h>

#include <linux/spinlock.h>

#include <linux/rcupdate.h>

​

unsigned int sysctl_nr_open __read_mostly = 1024*1024;

unsigned int sysctl_nr_open_min = BITS_PER_LONG;

/* our min() is unusable in constant expressions ;-/ */

#define __const_min(x, y) ((x) < (y) ? (x) : (y))

unsigned int sysctl_nr_open_max =

    __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;

​

static void __free_fdtable(struct fdtable *fdt)

{

    kvfree(fdt->fd);

    kvfree(fdt->open_fds);

    kfree(fdt);

}

​

static void free_fdtable_rcu(struct rcu_head *rcu)

{

    __free_fdtable(container_of(rcu, struct fdtable, rcu));

}

​

#define BITBIT_NR(nr)   BITS_TO_LONGS(BITS_TO_LONGS(nr))

#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))

​

/*

 * Copy 'count' fd bits from the old table to the new table and clear the extra

 * space if any.  This does not copy the file pointers.  Called with the files

 * spinlock held for write.

 */

static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,

                unsigned int count)

{

    unsigned int cpy, set;

​

    cpy = count / BITS_PER_BYTE;

    set = (nfdt->max_fds - count) / BITS_PER_BYTE;

    memcpy(nfdt->open_fds, ofdt->open_fds, cpy);

    memset((char *)nfdt->open_fds + cpy, 0, set);

    memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);

    memset((char *)nfdt->close_on_exec + cpy, 0, set);

​

    cpy = BITBIT_SIZE(count);

    set = BITBIT_SIZE(nfdt->max_fds) - cpy;

    memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);

    memset((char *)nfdt->full_fds_bits + cpy, 0, set);

}

​

/*

 * Copy all file descriptors from the old table to the new, expanded table and

 * clear the extra space.  Called with the files spinlock held for write.

 */

static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)

{

    unsigned int cpy, set;

​

    BUG_ON(nfdt->max_fds < ofdt->max_fds);

​

    cpy = ofdt->max_fds * sizeof(struct file *);

    set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);

    memcpy(nfdt->fd, ofdt->fd, cpy);

    memset((char *)nfdt->fd + cpy, 0, set);

​

    copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);

}

​

static struct fdtable * alloc_fdtable(unsigned int nr)

{

    struct fdtable *fdt;

    void *data;

​

    /*

     * Figure out how many fds we actually want to support in this fdtable.

     * Allocation steps are keyed to the size of the fdarray, since it