/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2016-2018, Matthew Macy <mmacy@freebsd.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/queue.h>
#include <sys/blist.h>
#include <sys/conf.h>
#include <sys/exec.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/linker.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sbuf.h>
#include <sys/smp.h>
#include <sys/socket.h>
#include <sys/vnode.h>
#include <sys/bus.h>
#include <sys/pciio.h>

#include <dev/pci/pcivar.h>
#include <dev/pci/pcireg.h>

#include <net/if.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/swap_pager.h>

#include <machine/bus.h>

#include <compat/linux/linux_ioctl.h>
#include <compat/linux/linux_mib.h>
#include <compat/linux/linux_util.h>
#include <fs/pseudofs/pseudofs.h>

#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/compat.h>

MALLOC_DEFINE(M_DFSINT, "debugfsint", "Linux debugfs internal");

static struct pfs_node *debugfs_root;

#define DM_SYMLINK 0x1
#define DM_DIR 0x2
#define DM_FILE 0x3

struct dentry_meta {
	struct dentry dm_dnode;
	const struct file_operations *dm_fops;
	void *dm_data;
	umode_t dm_mode;
	int dm_type;
};

static int
debugfs_attr(PFS_ATTR_ARGS)
{
	struct dentry_meta *dm;

	dm = pn->pn_data;

	vap->va_mode = dm->dm_mode;
	return (0);
}

static int
debugfs_destroy(PFS_DESTROY_ARGS)
{
	struct dentry_meta *dm;

	dm = pn->pn_data;
	if (dm->dm_type == DM_SYMLINK)
		free(dm->dm_data, M_DFSINT);

	free(dm, M_DFSINT);
	return (0);
}

static int
debugfs_fill(PFS_FILL_ARGS)
{
	struct dentry_meta *d;
	struct linux_file lf = {};
	struct seq_file *sf;
	struct vnode vn;
	void *buf;
	int rc;
	size_t len;
	off_t off;

	d = pn->pn_data;

	if ((rc = linux_set_current_flags(curthread, M_NOWAIT)))
		return (rc);
	vn.v_data = d->dm_data;
	if (uio->uio_rw == UIO_READ) {
		buf = uio->uio_iov[0].iov_base;
		len = min(uio->uio_iov[0].iov_len, uio->uio_resid);
	} else {
		sbuf_finish(sb);
		buf = sbuf_data(sb);
		len = sbuf_len(sb);
	}
	off = 0;
	rc = d->dm_fops->open(&vn, &lf);
	if (rc < 0) {
#ifdef INVARIANTS
		printf("%s:%d open failed with %d\n", __FUNCTION__, __LINE__, rc);
#endif
		return (-rc);
	}
	sf = lf.private_data;
	sf->buf = sb;
	if (uio->uio_rw == UIO_READ) {
		if (d->dm_fops->read)
			rc = d->dm_fops->read(&lf, NULL, len, &off);
		else
			rc = -ENODEV;
	} else {
		if (d->dm_fops->write)
			rc = d->dm_fops->write(&lf, buf, len, &off);
		else
			rc = -ENODEV;
	}
	if (d->dm_fops->release)
		d->dm_fops->release(&vn, &lf);
	else
		single_release(&vn, &lf);

	if (rc < 0) {
#ifdef INVARIANTS
		printf("%s:%d read/write failed with %d\n", __FUNCTION__, __LINE__, rc);
#endif
		return (-rc);
	}
	return (0);
}

static int
debugfs_fill_data(PFS_FILL_ARGS)
{
	struct dentry_meta *dm;

	dm = pn->pn_data;
	sbuf_printf(sb, "%s", (char *)dm->dm_data);
	return (0);
}

struct dentry *
debugfs_create_file(const char *name, umode_t mode,
		    struct dentry *parent, void *data,
		    const struct file_operations *fops)
{
	struct dentry_meta *dm;
	struct dentry *dnode;
	struct pfs_node *pnode;
	int flags;

	dm = malloc(sizeof(*dm), M_DFSINT, M_NOWAIT | M_ZERO);
	if (dm == NULL)
		return (NULL);
	dnode = &dm->dm_dnode;
	dm->dm_fops = fops;
	dm->dm_data = data;
	dm->dm_mode = mode;
	dm->dm_type = DM_FILE;
	if (parent != NULL)
		pnode = parent->d_pfs_node;
	else
		pnode = debugfs_root;

	flags = fops->write ? PFS_RDWR : PFS_RD;
	dnode->d_pfs_node = pfs_create_file(pnode, name, debugfs_fill,
	    debugfs_attr, NULL, debugfs_destroy, flags | PFS_NOWAIT);
	if (dnode->d_pfs_node == NULL) {
		free(dm, M_DFSINT);
		return (NULL);
	}
	dnode->d_pfs_node->pn_data = dm;

	return (dnode);
}

struct dentry *
debugfs_create_dir(const char *name, struct dentry *parent)
{
	struct dentry_meta *dm;
	struct dentry *dnode;
	struct pfs_node *pnode;

	dm = malloc(sizeof(*dm), M_DFSINT, M_NOWAIT | M_ZERO);
	if (dm == NULL)
		return (NULL);
	dnode = &dm->dm_dnode;
	dm->dm_mode = 0700;
	dm->dm_type = DM_DIR;
	if (parent != NULL)
		pnode = parent->d_pfs_node;
	else
		pnode = debugfs_root;

	dnode->d_pfs_node = pfs_create_dir(pnode, name, debugfs_attr, NULL, debugfs_destroy, PFS_RD | PFS_NOWAIT);
	if (dnode->d_pfs_node == NULL) {
		free(dm, M_DFSINT);
		return (NULL);
	}
	dnode->d_pfs_node->pn_data = dm;
	return (dnode);
}

struct dentry *
debugfs_create_symlink(const char *name, struct dentry *parent,
	const char *dest)
{
	struct dentry_meta *dm;
	struct dentry *dnode;
	struct pfs_node *pnode;
	void *data;

	data = strdup_flags(dest, M_DFSINT, M_NOWAIT);
	if (data == NULL)
		return (NULL);
	dm = malloc(sizeof(*dm), M_DFSINT, M_NOWAIT | M_ZERO);
	if (dm == NULL)
		goto fail1;
	dnode = &dm->dm_dnode;
	dm->dm_mode = 0700;
	dm->dm_type = DM_SYMLINK;
	dm->dm_data = data;
	if (parent != NULL)
		pnode = parent->d_pfs_node;
	else
		pnode = debugfs_root;

	dnode->d_pfs_node = pfs_create_link(pnode, name, &debugfs_fill_data, NULL, NULL, NULL, PFS_NOWAIT);
	if (dnode->d_pfs_node == NULL)
		goto fail;
	dnode->d_pfs_node->pn_data = dm;
	return (dnode);
 fail:
	free(dm, M_DFSINT);
 fail1:
	free(data, M_DFSINT);
	return (NULL);
}

void
debugfs_remove(struct dentry *dnode)
{
	if (dnode == NULL)
		return;

	pfs_destroy(dnode->d_pfs_node);
}

void
debugfs_remove_recursive(struct dentry *dnode)
{
	if (dnode == NULL)
		return;

	pfs_destroy(dnode->d_pfs_node);
}

static int
debugfs_init(PFS_INIT_ARGS)
{

	debugfs_root = pi->pi_root;

	(void)debugfs_create_symlink("kcov", NULL, "/dev/kcov");

	return (0);
}

static int
debugfs_uninit(PFS_INIT_ARGS)
{
	return (0);
}

#ifdef PR_ALLOW_MOUNT_LINSYSFS
PSEUDOFS(debugfs, 1, PR_ALLOW_MOUNT_LINSYSFS);
#else
PSEUDOFS(debugfs, 1, VFCF_JAIL);
#endif
MODULE_DEPEND(lindebugfs, linuxkpi, 1, 1, 1);