file.c

/*
 * Copyright (c) 1998-2015 Erez Zadok
 * Copyright (c) 2009	   Shrikar Archak
 * Copyright (c) 2003-2015 Stony Brook University
 * Copyright (c) 2003-2015 The Research Foundation of SUNY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */


/*
 * CSE-506 : Operating Systems HW2
 * Author  : Meng-Chieh Yang
 * ID      : 110452591
 * Date    : 11/1/16
 *
 * file.c:
 * - add function trfs_record for output tracing data
 * - modify functions for tracing with trfs_record
 */



#include "trfs.h"

int trfs_record(struct super_block *sb, char* lower_pathname, unsigned char op_type, 
				int rval){

	int bytes;
	int path_len;
	int total_len;
	unsigned int bitmap;
	struct file *filp;
	struct record *r;
	void *op;
	mm_segment_t oldfs;

	bitmap = TRFS_SB(sb)->bitmap;

	if(CHECK_BIT(bitmap,op_type)){ // allow to record

		path_len = strlen(lower_pathname);
		total_len = path_len + sizeof(struct record); // record size 24

		r = kzalloc(total_len, GFP_KERNEL);
		if(!r){
			printk("MEM ERR: record r\n");
			return -ENOMEM;
		}

		r->r_id = TRFS_SB(sb)->cur_id++;
		r->r_size = (unsigned short) total_len-sizeof(int); //sizeof(int) is id size 
		r->r_type = op_type; 
		r->r_rval = rval;
		r->r_path_len = (unsigned short) path_len;
		r->r_path_name = lower_pathname;
		
		// printk("current id: %d \n", r->r_id);
		// printk("r rest size: %d \n", r->r_size);
		// printk("r type: %d \n",r->r_type);
		// printk("r rval: %d \n",r->r_rval);
		// printk("r path len: %d \n", r->r_path_len);
		// printk("path name: %s \n",r->r_path_name);
		
		op = kzalloc(total_len, GFP_KERNEL);
		memcpy(op, r, total_len);

		spin_lock(&sl);

		filp = filp_open(TRFS_SB(sb)->op_name, O_RDWR|O_APPEND|O_CREAT, 0644);
		if(IS_ERR(filp)){
			printk("trfs_record: cannot open record file.\n");
			bytes = PTR_ERR(filp);
			filp = NULL;
			spin_unlock(&sl);
			goto free;
		}
		spin_unlock(&sl);

		oldfs = get_fs();
		set_fs(KERNEL_DS);
		bytes = vfs_write(filp, op, total_len, &filp->f_pos);
		set_fs(oldfs);

		filp_close(filp, NULL);
			
	}
	else{
			printk("this operation is not allowed to trace.\n");
			bytes = 0;
			goto exit;
	}
			
free:
	
	kfree(op);
	kfree(r);

exit:
	return bytes;
}

static ssize_t trfs_read(struct file *file, char __user *buf,
			   size_t count, loff_t *ppos)
{
	
	int err;
	int bytes;
	char *path_buf;
	char *path_name;
	struct file *lower_file;
	struct dentry *dentry = file->f_path.dentry;

	lower_file = trfs_lower_file(file);
	err = vfs_read(lower_file, buf, count, ppos);
	/* update our inode atime upon a successful lower read */
	if (err >= 0)
		fsstack_copy_attr_atime(d_inode(dentry),
					file_inode(lower_file));

 	path_buf = kzalloc(4096, GFP_KERNEL);
	path_name = dentry_path_raw(lower_file->f_path.dentry, path_buf, 4096);
	
	bytes = trfs_record(file_inode(file)->i_sb, path_name, OP_READ, err);
	printk("record done at read, bytes: %d \n", bytes);

	kfree(path_buf);
	return err;
}

static ssize_t trfs_write(struct file *file, const char __user *buf,
			    size_t count, loff_t *ppos)
{
	int err;
	int bytes;
	char *path_buf;
	char *path_name;
	struct file *lower_file;
	struct dentry *dentry = file->f_path.dentry;

	lower_file = trfs_lower_file(file);
	err = vfs_write(lower_file, buf, count, ppos);
	/* update our inode times+sizes upon a successful lower write */
	if (err >= 0) {
		fsstack_copy_inode_size(d_inode(dentry),
					file_inode(lower_file));
		fsstack_copy_attr_times(d_inode(dentry),
					file_inode(lower_file));
	}

	path_buf = kzalloc(4096, GFP_KERNEL);
	path_name = dentry_path_raw(lower_file->f_path.dentry, path_buf, 4096);
	
	bytes = trfs_record(file_inode(file)->i_sb, path_name, OP_WRITE, err);
	printk("record done at write, bytes: %d \n", bytes);

	kfree(path_buf);
	return err;
}

static int trfs_readdir(struct file *file, struct dir_context *ctx)
{
	int err;
	struct file *lower_file = NULL;
	struct dentry *dentry = file->f_path.dentry;

	lower_file = trfs_lower_file(file);
	err = iterate_dir(lower_file, ctx);
	file->f_pos = lower_file->f_pos;
	if (err >= 0)		/* copy the atime */
		fsstack_copy_attr_atime(d_inode(dentry),
					file_inode(lower_file));
	return err;
}

static long trfs_unlocked_ioctl(struct file *file, unsigned int cmd,
				  unsigned long arg)
{
	long err = -ENOTTY;
	struct file *lower_file;
	struct super_block *sb;

	sb = file_inode(file)->i_sb;
	lower_file = trfs_lower_file(file);

	/* XXX: use vfs_ioctl if/when VFS exports it */
	// if (!lower_file || !lower_file->f_op)
	// 	goto out;
	// if (lower_file->f_op->unlocked_ioctl)
	// 	err = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);

	/* some ioctls can change inode attributes (EXT2_IOC_SETFLAGS) */
	if (!err)
		fsstack_copy_attr_all(file_inode(file),
				      file_inode(lower_file));

	switch(cmd){
		case ALL:
			TRFS_SB(sb)->bitmap = 0xffffffff;
			printk("new bitmap: %x\n", TRFS_SB(sb)->bitmap);
			break;

		case NONE:
			TRFS_SB(sb)->bitmap = 0x00000000;
			printk("new bitmap: %x\n", TRFS_SB(sb)->bitmap);
			break;

		case RETRIEVE:
			err = copy_to_user((void *) arg, (void *)&TRFS_SB(sb)->bitmap, sizeof(unsigned int));
			if(err){
				printk("err: trfs_unlocked_ioctl: retrieve\n");
			 	err = -EFAULT;
			}
			break;

		case BITMAP:
			TRFS_SB(sb)->bitmap = (unsigned int) arg;
			printk("new bitmap: %x\n", TRFS_SB(sb)->bitmap);
			break;
	}

	return err;
}

#ifdef CONFIG_COMPAT
static long trfs_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg)
{
	long err = -ENOTTY;
	struct file *lower_file;

	lower_file = trfs_lower_file(file);

	/* XXX: use vfs_ioctl if/when VFS exports it */
	if (!lower_file || !lower_file->f_op)
		goto out;
	if (lower_file->f_op->compat_ioctl)
		err = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);

out:
	return err;
}
#endif

static int trfs_mmap(struct file *file, struct vm_area_struct *vma)
{
	int err = 0;
	bool willwrite;
	struct file *lower_file;
	const struct vm_operations_struct *saved_vm_ops = NULL;

	/* this might be deferred to mmap's writepage */
	willwrite = ((vma->vm_flags | VM_SHARED | VM_WRITE) == vma->vm_flags);

	/*
	 * File systems which do not implement ->writepage may use
	 * generic_file_readonly_mmap as their ->mmap op.  If you call
	 * generic_file_readonly_mmap with VM_WRITE, you'd get an -EINVAL.
	 * But we cannot call the lower ->mmap op, so we can't tell that
	 * writeable mappings won't work.  Therefore, our only choice is to
	 * check if the lower file system supports the ->writepage, and if
	 * not, return EINVAL (the same error that
	 * generic_file_readonly_mmap returns in that case).
	 */
	lower_file = trfs_lower_file(file);
	if (willwrite && !lower_file->f_mapping->a_ops->writepage) {
		err = -EINVAL;
		printk(KERN_ERR "trfs: lower file system does not "
		       "support writeable mmap\n");
		goto out;
	}

	/*
	 * find and save lower vm_ops.
	 *
	 * XXX: the VFS should have a cleaner way of finding the lower vm_ops
	 */
	if (!TRFS_F(file)->lower_vm_ops) {
		err = lower_file->f_op->mmap(lower_file, vma);
		if (err) {
			printk(KERN_ERR "trfs: lower mmap failed %d\n", err);
			goto out;
		}
		saved_vm_ops = vma->vm_ops; /* save: came from lower ->mmap */
	}

	/*
	 * Next 3 lines are all I need from generic_file_mmap.  I definitely
	 * don't want its test for ->readpage which returns -ENOEXEC.
	 */
	file_accessed(file);
	vma->vm_ops = &trfs_vm_ops;

	file->f_mapping->a_ops = &trfs_aops; /* set our aops */
	if (!TRFS_F(file)->lower_vm_ops) /* save for our ->fault */
		TRFS_F(file)->lower_vm_ops = saved_vm_ops;

out:
	return err;
}

static int trfs_open(struct inode *inode, struct file *file)
{
	int err = 0;
	int bytes;
	char *path_buf;
	char *path_name;
	struct file *lower_file = NULL;
	struct path lower_path;

	/* don't open unhashed/deleted files */
	if (d_unhashed(file->f_path.dentry)) {
		err = -ENOENT;
		goto out_err;
	}

	// here is pre-call
	file->private_data =
		kzalloc(sizeof(struct trfs_file_info), GFP_KERNEL);
	if (!TRFS_F(file)) {
		err = -ENOMEM;
		goto out_err;
	}

	/* open lower object and link trfs's file struct to lower's */
	trfs_get_lower_path(file->f_path.dentry, &lower_path);
	lower_file = dentry_open(&lower_path, file->f_flags, current_cred());
	path_put(&lower_path);
	if (IS_ERR(lower_file)) {
		err = PTR_ERR(lower_file);
		lower_file = trfs_lower_file(file);
		if (lower_file) {
			trfs_set_lower_file(file, NULL);
			fput(lower_file); /* fput calls dput for lower_dentry */
		}
	} else {
		trfs_set_lower_file(file, lower_file);
	}

	if (err)
		kfree(TRFS_F(file));
	else
		fsstack_copy_attr_all(inode, trfs_lower_inode(inode)); // update trfs level inode

	path_buf = kzalloc(4096, GFP_KERNEL);
	path_name = dentry_path_raw(lower_file->f_path.dentry, path_buf, 4096);
	
	bytes = trfs_record(file_inode(file)->i_sb, path_name, OP_OPEN, err);
	printk("record done at open, bytes: %d \n", bytes);

	kfree(path_buf);

out_err:
	return err;
}

static int trfs_flush(struct file *file, fl_owner_t id)
{
	int err = 0;
	struct file *lower_file = NULL;

	lower_file = trfs_lower_file(file);
	if (lower_file && lower_file->f_op && lower_file->f_op->flush) {
		filemap_write_and_wait(file->f_mapping);
		err = lower_file->f_op->flush(lower_file, id);
	}

	return err;
}

/* release all lower object references & free the file info structure */
static int trfs_file_release(struct inode *inode, struct file *file)
{
	
	
	int bytes;
	char *path_buf;
	char *path_name;
	struct file *lower_file;

	lower_file = trfs_lower_file(file);

	path_buf = kzalloc(4096, GFP_KERNEL);
	path_name = dentry_path_raw(lower_file->f_path.dentry, path_buf, 4096);

	if (lower_file) {
		trfs_set_lower_file(file, NULL);
		fput(lower_file);
	}	

	bytes = trfs_record(file_inode(file)->i_sb, path_name, OP_CLOSE, 0);
	printk("record done at close, bytes: %d \n", bytes);

	kfree(TRFS_F(file));
	return 0;
}

static int trfs_fsync(struct file *file, loff_t start, loff_t end,
			int datasync)
{
	int err;
	struct file *lower_file;
	struct path lower_path;
	struct dentry *dentry = file->f_path.dentry;

	err = __generic_file_fsync(file, start, end, datasync);
	if (err)
		goto out;
	lower_file = trfs_lower_file(file);
	trfs_get_lower_path(dentry, &lower_path);
	err = vfs_fsync_range(lower_file, start, end, datasync);
	trfs_put_lower_path(dentry, &lower_path);
out:
	return err;
}

static int trfs_fasync(int fd, struct file *file, int flag)
{
	int err = 0;
	struct file *lower_file = NULL;

	lower_file = trfs_lower_file(file);
	if (lower_file->f_op && lower_file->f_op->fasync)
		err = lower_file->f_op->fasync(fd, lower_file, flag);

	return err;
}

/*
 * Wrapfs cannot use generic_file_llseek as ->llseek, because it would
 * only set the offset of the upper file.  So we have to implement our
 * own method to set both the upper and lower file offsets
 * consistently.
 */
static loff_t trfs_file_llseek(struct file *file, loff_t offset, int whence)
{
	int err;
	struct file *lower_file;

	err = generic_file_llseek(file, offset, whence);
	if (err < 0)
		goto out;

	lower_file = trfs_lower_file(file);
	err = generic_file_llseek(lower_file, offset, whence);

out:
	return err;
}

/*
 * Wrapfs read_iter, redirect modified iocb to lower read_iter
 */
ssize_t
trfs_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
	int err;
	struct file *file = iocb->ki_filp, *lower_file;

	lower_file = trfs_lower_file(file);
	if (!lower_file->f_op->read_iter) {
		err = -EINVAL;
		goto out;
	}

	get_file(lower_file); /* prevent lower_file from being released */
	iocb->ki_filp = lower_file;
	err = lower_file->f_op->read_iter(iocb, iter);
	iocb->ki_filp = file;
	fput(lower_file);
	/* update upper inode atime as needed */
	if (err >= 0 || err == -EIOCBQUEUED)
		fsstack_copy_attr_atime(d_inode(file->f_path.dentry),
					file_inode(lower_file));
out:
	return err;
}

/*
 * Wrapfs write_iter, redirect modified iocb to lower write_iter
 */
ssize_t
trfs_write_iter(struct kiocb *iocb, struct iov_iter *iter)
{
	int err;
	struct file *file = iocb->ki_filp, *lower_file;

	lower_file = trfs_lower_file(file);
	if (!lower_file->f_op->write_iter) {
		err = -EINVAL;
		goto out;
	}

	get_file(lower_file); /* prevent lower_file from being released */
	iocb->ki_filp = lower_file;
	err = lower_file->f_op->write_iter(iocb, iter);
	iocb->ki_filp = file;
	fput(lower_file);
	/* update upper inode times/sizes as needed */
	if (err >= 0 || err == -EIOCBQUEUED) {
		fsstack_copy_inode_size(d_inode(file->f_path.dentry),
					file_inode(lower_file));
		fsstack_copy_attr_times(d_inode(file->f_path.dentry),
					file_inode(lower_file));
	}
out:
	return err;
}

const struct file_operations trfs_main_fops = {
	.llseek		= generic_file_llseek,
	.read		= trfs_read,
	.write		= trfs_write,
	.unlocked_ioctl	= trfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl	= trfs_compat_ioctl,
#endif
	.mmap		= trfs_mmap,
	.open		= trfs_open,
	.flush		= trfs_flush,
	.release	= trfs_file_release,
	.fsync		= trfs_fsync,
	.fasync		= trfs_fasync,
	.read_iter	= trfs_read_iter,
	.write_iter	= trfs_write_iter,
};

/* trimmed directory options */
const struct file_operations trfs_dir_fops = {
	.llseek		= trfs_file_llseek,
	.read		= generic_read_dir,
	.iterate	= trfs_readdir,
	.unlocked_ioctl	= trfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl	= trfs_compat_ioctl,
#endif
	.open		= trfs_open,
	.release	= trfs_file_release,
	.flush		= trfs_flush,
	.fsync		= trfs_fsync,
	.fasync		= trfs_fasync,
};