/**
 * @file oprofilefs.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/oprofile.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <asm/uaccess.h>

#include "oprof.h"

#define OPROFILEFS_MAGIC 0x6f70726f

DEFINE_SPINLOCK(oprofilefs_lock);

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

        if (inode) {
                inode->i_mode = mode;
                inode->i_uid = 0;
                inode->i_gid = 0;
                inode->i_blocks = 0;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        }
        return inode;
}


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


ssize_t oprofilefs_str_to_user(char const * str, char __user * buf, size_t count, loff_t * offset)
{
        return simple_read_from_buffer(buf, count, offset, str, strlen(str));
}


#define TMPBUFSIZE 50

ssize_t oprofilefs_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);
}


int oprofilefs_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(&oprofilefs_lock, flags);
        *val = simple_strtoul(tmpbuf, NULL, 0);
        spin_unlock_irqrestore(&oprofilefs_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 oprofilefs_ulong_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 = oprofilefs_ulong_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 ulong_ro_fops = {
        .read           = ulong_read_file,
        .open           = default_open,
};


static struct dentry * __oprofilefs_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 = oprofilefs_get_inode(sb, S_IFREG | perm);
        if (!inode) {
                dput(dentry);
                return NULL;
        }
        inode->i_fop = fops;
        d_add(dentry, inode);
        return dentry;
}


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

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


int oprofilefs_create_ro_ulong(struct super_block * sb, struct dentry * root,
        char const * name, unsigned long * val)
{
        struct dentry * d = __oprofilefs_create_file(sb, root, name,
                                                     &ulong_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 oprofilefs_ulong_to_user(atomic_read(val), buf, count, offset);
}
 

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

int oprofilefs_create_ro_atomic(struct super_block * sb, struct dentry * root,
        char const * name, atomic_t * val)
{
        struct dentry * d = __oprofilefs_create_file(sb, root, name,
                                                     &atomic_ro_fops, 0444);
        if (!d)
                return -EFAULT;

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

 
int oprofilefs_create_file(struct super_block * sb, struct dentry * root,
        char const * name, const struct file_operations * fops)
{
        if (!__oprofilefs_create_file(sb, root, name, fops, 0644))
                return -EFAULT;
        return 0;
}


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


struct dentry * oprofilefs_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 = oprofilefs_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 oprofilefs_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 = OPROFILEFS_MAGIC;
        sb->s_op = &s_ops;
        sb->s_time_gran = 1;

        root_inode = oprofilefs_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_alloc_root(root_inode);
        if (!root_dentry) {
                iput(root_inode);
                return -ENOMEM;
        }

        sb->s_root = root_dentry;

        oprofile_create_files(sb, root_dentry);

        // FIXME: verify kill_litter_super removes our dentries
        return 0;
}


static int oprofilefs_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
        return get_sb_single(fs_type, flags, data, oprofilefs_fill_super, mnt);
}


static struct file_system_type oprofilefs_type = {
        .owner          = THIS_MODULE,
        .name           = "oprofilefs",
        .get_sb         = oprofilefs_get_sb,
        .kill_sb        = kill_litter_super,
};


int __init oprofilefs_register(void)
{
        return register_filesystem(&oprofilefs_type);
}


void __exit oprofilefs_unregister(void)
{
        unregister_filesystem(&oprofilefs_type);
}