drivers/gator/gator_fs.c

/**
 * @file gatorfs.c
 *
 * @remark Copyright 2002 OProfile authors
 * @remark Read the file COPYING
 *
 * @author John Levon
 *
 * A simple filesystem for configuration and
 * access of oprofile.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>


/* Kernel version 4.6.0 removes page_cache_{get,release} and related defines. Add them back here.
   (See https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=1fa64f198b9f8d6ec0f7aec7c18dc94684391140) */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 6, 0)
#   define PAGE_CACHE_SHIFT         PAGE_SHIFT
#   define PAGE_CACHE_SIZE          PAGE_SIZE
#   define PAGE_CACHE_MASK          PAGE_MASK
#   define PAGE_CACHE_ALIGN(addr)   (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
#   define page_cache_get(page)     get_page(page)
#   define page_cache_release(page) put_page(page)
#endif


#define gatorfs_MAGIC 0x24051020
#define TMPBUFSIZE 50
static DEFINE_SPINLOCK(gatorfs_lock);

static struct inode *gatorfs_get_inode(struct super_block *sb, int mode)
{
    struct inode *inode = new_inode(sb);

    if (inode) {
        inode->i_ino = get_next_ino();
        inode->i_mode = mode;
#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 12, 0)
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
#else
        inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
#endif
    }
    return inode;
}

static const struct super_operations s_ops = {
    .statfs = simple_statfs,
    .drop_inode = generic_delete_inode,
};

static ssize_t gatorfs_ulong_to_user(unsigned long val, char __user *buf, size_t count, loff_t *offset)
{
    char tmpbuf[TMPBUFSIZE];
    size_t maxlen = snprintf(tmpbuf, TMPBUFSIZE, "%lu\n", val);

    if (maxlen > TMPBUFSIZE)
        maxlen = TMPBUFSIZE;
    return simple_read_from_buffer(buf, count, offset, tmpbuf, maxlen);
}

static ssize_t gatorfs_u64_to_user(u64 val, char __user *buf, size_t count, loff_t *offset)
{
    char tmpbuf[TMPBUFSIZE];
    size_t maxlen = snprintf(tmpbuf, TMPBUFSIZE, "%llu\n", val);

    if (maxlen > TMPBUFSIZE)
        maxlen = TMPBUFSIZE;
    return simple_read_from_buffer(buf, count, offset, tmpbuf, maxlen);
}

static int gatorfs_ulong_from_user(unsigned long *val, char const __user *buf, size_t count)
{
    char tmpbuf[TMPBUFSIZE];
    unsigned long flags;

    if (!count)
        return 0;

    if (count > TMPBUFSIZE - 1)
        return -EINVAL;

    memset(tmpbuf, 0x0, TMPBUFSIZE);

    if (copy_from_user(tmpbuf, buf, count))
        return -EFAULT;

    spin_lock_irqsave(&gatorfs_lock, flags);
    *val = simple_strtoul(tmpbuf, NULL, 0);
    spin_unlock_irqrestore(&gatorfs_lock, flags);
    return 0;
}

static int gatorfs_u64_from_user(u64 *val, char const __user *buf, size_t count)
{
    char tmpbuf[TMPBUFSIZE];
    unsigned long flags;

    if (!count)
        return 0;

    if (count > TMPBUFSIZE - 1)
        return -EINVAL;

    memset(tmpbuf, 0x0, TMPBUFSIZE);

    if (copy_from_user(tmpbuf, buf, count))
        return -EFAULT;

    spin_lock_irqsave(&gatorfs_lock, flags);
    *val = simple_strtoull(tmpbuf, NULL, 0);
    spin_unlock_irqrestore(&gatorfs_lock, flags);
    return 0;
}

static ssize_t ulong_read_file(struct file *file, char __user *buf, size_t count, loff_t *offset)
{
    unsigned long *val = file->private_data;

    return gatorfs_ulong_to_user(*val, buf, count, offset);
}

static ssize_t u64_read_file(struct file *file, char __user *buf, size_t count, loff_t *offset)
{
    u64 *val = file->private_data;

    return gatorfs_u64_to_user(*val, buf, count, offset);
}

static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_t count, loff_t *offset)
{
    unsigned long *value = file->private_data;
    int retval;

    if (*offset)
        return -EINVAL;

    retval = gatorfs_ulong_from_user(value, buf, count);

    if (retval)
        return retval;
    return count;
}

static ssize_t u64_write_file(struct file *file, char const __user *buf, size_t count, loff_t *offset)
{
    u64 *value = file->private_data;
    int retval;

    if (*offset)
        return -EINVAL;

    retval = gatorfs_u64_from_user(value, buf, count);

    if (retval)
        return retval;
    return count;
}

static int default_open(struct inode *inode, struct file *filp)
{
    if (inode->i_private)
        filp->private_data = inode->i_private;
    return 0;
}

static const struct file_operations ulong_fops = {
    .read = ulong_read_file,
    .write = ulong_write_file,
    .open = default_open,
};

static const struct file_operations u64_fops = {
    .read = u64_read_file,
    .write = u64_write_file,
    .open = default_open,
};

static const struct file_operations ulong_ro_fops = {
    .read = ulong_read_file,
    .open = default_open,
};

static const struct file_operations u64_ro_fops = {
    .read = u64_read_file,
    .open = default_open,
};

static struct dentry *__gatorfs_create_file(struct super_block *sb,
                        struct dentry *root,
                        char const *name,
                        const struct file_operations *fops,
                        int perm)
{
    struct dentry *dentry;
    struct inode *inode;

    dentry = d_alloc_name(root, name);
    if (!dentry)
        return NULL;
    inode = gatorfs_get_inode(sb, S_IFREG | perm);
    if (!inode) {
        dput(dentry);
        return NULL;
    }
    inode->i_fop = fops;
    d_add(dentry, inode);
    return dentry;
}

int gatorfs_create_ulong(struct super_block *sb, struct dentry *root,
             char const *name, unsigned long *val)
{
    struct dentry *d = __gatorfs_create_file(sb, root, name,
                         &ulong_fops, 0644);
    if (!d)
        return -EFAULT;

    d->d_inode->i_private = val;
    return 0;
}

static int gatorfs_create_u64(struct super_block *sb, struct dentry *root,
                  char const *name, u64 *val)
{
    struct dentry *d = __gatorfs_create_file(sb, root, name,
                         &u64_fops, 0644);
    if (!d)
        return -EFAULT;

    d->d_inode->i_private = val;
    return 0;
}

int gatorfs_create_ro_ulong(struct super_block *sb, struct dentry *root,
                char const *name, unsigned long *val)
{
    struct dentry *d = __gatorfs_create_file(sb, root, name,
                         &ulong_ro_fops, 0444);
    if (!d)
        return -EFAULT;

    d->d_inode->i_private = val;
    return 0;
}

static int gatorfs_create_ro_u64(struct super_block *sb, struct dentry *root,
                 char const *name, u64 *val)
{
    struct dentry *d =
        __gatorfs_create_file(sb, root, name, &u64_ro_fops, 0444);
    if (!d)
        return -EFAULT;

    d->d_inode->i_private = val;
    return 0;
}

static ssize_t atomic_read_file(struct file *file, char __user *buf, size_t count, loff_t *offset)
{
    atomic_t *val = file->private_data;

    return gatorfs_ulong_to_user(atomic_read(val), buf, count, offset);
}

static const struct file_operations atomic_ro_fops = {
    .read = atomic_read_file,
    .open = default_open,
};

static int gatorfs_create_file_data(struct super_block *sb, struct dentry *root,
                                    char const *name, const struct file_operations *fops,
                                    void * private_data)
{
    struct dentry * dentry = __gatorfs_create_file(sb, root, name, fops, 0644);
    if (!dentry)
        return -EFAULT;

    dentry->d_inode->i_private = private_data;
    return 0;
}

static int gatorfs_create_file(struct super_block *sb, struct dentry *root,
                   char const *name, const struct file_operations *fops)
{
    return gatorfs_create_file_data(sb, root, name, fops, NULL);
}

static int gatorfs_create_file_perm(struct super_block *sb, struct dentry *root,
                    char const *name,
                    const struct file_operations *fops, int perm)
{
    if (!__gatorfs_create_file(sb, root, name, fops, perm))
        return -EFAULT;
    return 0;
}

struct dentry *gatorfs_mkdir(struct super_block *sb,
                 struct dentry *root, char const *name)
{
    struct dentry *dentry;
    struct inode *inode;

    dentry = d_alloc_name(root, name);
    if (!dentry)
        return NULL;
    inode = gatorfs_get_inode(sb, S_IFDIR | 0755);
    if (!inode) {
        dput(dentry);
        return NULL;
    }
    inode->i_op = &simple_dir_inode_operations;
    inode->i_fop = &simple_dir_operations;
    d_add(dentry, inode);
    return dentry;
}

static int gatorfs_fill_super(struct super_block *sb, void *data, int silent)
{
    struct inode *root_inode;
    struct dentry *root_dentry;

    sb->s_blocksize = PAGE_CACHE_SIZE;
    sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
    sb->s_magic = gatorfs_MAGIC;
    sb->s_op = &s_ops;
    sb->s_time_gran = 1;

    root_inode = gatorfs_get_inode(sb, S_IFDIR | 0755);
    if (!root_inode)
        return -ENOMEM;
    root_inode->i_op = &simple_dir_inode_operations;
    root_inode->i_fop = &simple_dir_operations;

    root_dentry = d_make_root(root_inode);

    if (!root_dentry) {
        return -ENOMEM;
    }

    sb->s_root = root_dentry;

    gator_op_create_files(sb, root_dentry);

    return 0;
}

static struct dentry *gatorfs_mount(struct file_system_type *fs_type,
                    int flags, const char *dev_name, void *data)
{
    return mount_nodev(fs_type, flags, data, gatorfs_fill_super);
}

static struct file_system_type gatorfs_type = {
    .owner = THIS_MODULE,
    .name = "gatorfs",
    .mount = gatorfs_mount,

    .kill_sb = kill_litter_super,
};

static int __init gatorfs_register(void)
{
    return register_filesystem(&gatorfs_type);
}

static void gatorfs_unregister(void)
{
    unregister_filesystem(&gatorfs_type);
}