oprofilefs.c

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#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_RAW_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_ino = get_next_ino();
        inode->i_mode = mode;
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
    }
    return inode;
}


static const 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);
}


/*
 * Note: If oprofilefs_ulong_from_user() returns 0, then *val remains
 * unchanged and might be uninitialized. This follows write syscall
 * implementation when count is zero: "If count is zero ... [and if]
 * no errors are detected, 0 will be returned without causing any
 * other effect." (man 2 write)
 */
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;

    raw_spin_lock_irqsave(&oprofilefs_lock, flags);
    *val = simple_strtoul(tmpbuf, NULL, 0);
    raw_spin_unlock_irqrestore(&oprofilefs_lock, flags);
    return count;
}


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;
    int retval;

    if (*offset)
        return -EINVAL;

    retval = oprofilefs_ulong_from_user(&value, buf, count);
    if (retval <= 0)
        return retval;

    retval = oprofile_set_ulong(file->private_data, value);
    if (retval)
        return retval;

    return count;
}


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


static const struct file_operations ulong_ro_fops = {
    .read       = ulong_read_file,
    .open       = simple_open,
    .llseek     = default_llseek,
};


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

    dentry = d_alloc_name(root, name);
    if (!dentry)
        return -ENOMEM;
    inode = oprofilefs_get_inode(sb, S_IFREG | perm);
    if (!inode) {
        dput(dentry);
        return -ENOMEM;
    }
    inode->i_fop = fops;
    d_add(dentry, inode);
    dentry->d_inode->i_private = priv;
    return 0;
}


int oprofilefs_create_ulong(struct super_block *sb, struct dentry *root,
    char const *name, unsigned long *val)
{
    return __oprofilefs_create_file(sb, root, name,
                    &ulong_fops, 0644, val);
}


int oprofilefs_create_ro_ulong(struct super_block *sb, struct dentry *root,
    char const *name, unsigned long *val)
{
    return __oprofilefs_create_file(sb, root, name,
                    &ulong_ro_fops, 0444, val);
}


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       = simple_open,
    .llseek     = default_llseek,
};


int oprofilefs_create_ro_atomic(struct super_block *sb, struct dentry *root,
    char const *name, atomic_t *val)
{
    return __oprofilefs_create_file(sb, root, name,
                    &atomic_ro_fops, 0444, val);
}


int oprofilefs_create_file(struct super_block *sb, struct dentry *root,
    char const *name, const struct file_operations *fops)
{
    return __oprofilefs_create_file(sb, root, name, fops, 0644, NULL);
}


int oprofilefs_create_file_perm(struct super_block *sb, struct dentry *root,
    char const *name, const struct file_operations *fops, int perm)
{
    return __oprofilefs_create_file(sb, root, name, fops, perm, NULL);
}


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;

    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;
    sb->s_root = d_make_root(root_inode);
    if (!sb->s_root)
        return -ENOMEM;

    oprofile_create_files(sb, sb->s_root);

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


static struct dentry *oprofilefs_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
{
    return mount_single(fs_type, flags, data, oprofilefs_fill_super);
}


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


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


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