xref: /drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c

/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * Author: Nathan Rutman <nathan.rutman@sun.com>
 *
 * Kernel <-> userspace communication routines.
 * Using pipes for all arches.
 */

#define DEBUG_SUBSYSTEM S_CLASS
#define D_KUC D_OTHER

#include <linux/libcfs/libcfs.h>

#ifdef LUSTRE_UTILS
/* This is the userspace side. */

/** Start the userspace side of a KUC pipe.
 * @param link Private descriptor for pipe/socket.
 * @param groups KUC broadcast group to listen to
 *	  (can be null for unicast to this pid)
 */
int libcfs_ukuc_start(lustre_kernelcomm *link, int group)
{
	int pfd[2];

	if (pipe(pfd) < 0)
		return -errno;

	memset(link, 0, sizeof(*link));
	link->lk_rfd = pfd[0];
	link->lk_wfd = pfd[1];
	link->lk_group = group;
	link->lk_uid = getpid();
	return 0;
}

int libcfs_ukuc_stop(lustre_kernelcomm *link)
{
	if (link->lk_wfd > 0)
		close(link->lk_wfd);
	return close(link->lk_rfd);
}

#define lhsz sizeof(*kuch)

/** Read a message from the link.
 * Allocates memory, returns handle
 *
 * @param link Private descriptor for pipe/socket.
 * @param buf Buffer to read into, must include size for kuc_hdr
 * @param maxsize Maximum message size allowed
 * @param transport Only listen to messages on this transport
 *      (and the generic transport)
 */
int libcfs_ukuc_msg_get(lustre_kernelcomm *link, char *buf, int maxsize,
			int transport)
{
	struct kuc_hdr *kuch;
	int rc = 0;

	memset(buf, 0, maxsize);

	CDEBUG(D_KUC, "Waiting for message from kernel on fd %d\n",
	       link->lk_rfd);

	while (1) {
		/* Read header first to get message size */
		rc = read(link->lk_rfd, buf, lhsz);
		if (rc <= 0) {
			rc = -errno;
			break;
		}
		kuch = (struct kuc_hdr *)buf;

		CDEBUG(D_KUC, "Received message mg=%x t=%d m=%d l=%d\n",
		       kuch->kuc_magic, kuch->kuc_transport, kuch->kuc_msgtype,
		       kuch->kuc_msglen);

		if (kuch->kuc_magic != KUC_MAGIC) {
			CERROR("bad message magic %x != %x\n",
			       kuch->kuc_magic, KUC_MAGIC);
			rc = -EPROTO;
			break;
		}

		if (kuch->kuc_msglen > maxsize) {
			rc = -EMSGSIZE;
			break;
		}

		/* Read payload */
		rc = read(link->lk_rfd, buf + lhsz, kuch->kuc_msglen - lhsz);
		if (rc < 0) {
			rc = -errno;
			break;
		}
		if (rc < (kuch->kuc_msglen - lhsz)) {
			CERROR("short read: got %d of %d bytes\n",
			       rc, kuch->kuc_msglen);
			rc = -EPROTO;
			break;
		}

		if (kuch->kuc_transport == transport ||
		    kuch->kuc_transport == KUC_TRANSPORT_GENERIC) {
			return 0;
		}
		/* Drop messages for other transports */
	}
	return rc;
}

#else /* LUSTRE_UTILS */
/* This is the kernel side (liblustre as well). */

/**
 * libcfs_kkuc_msg_put - send an message from kernel to userspace
 * @param fp to send the message to
 * @param payload Payload data.  First field of payload is always
 *   struct kuc_hdr
 */
int libcfs_kkuc_msg_put(struct file *filp, void *payload)
{
	struct kuc_hdr *kuch = (struct kuc_hdr *)payload;
	ssize_t count = kuch->kuc_msglen;
	loff_t offset = 0;
	mm_segment_t fs;
	int rc = -ENOSYS;

	if (filp == NULL || IS_ERR(filp))
		return -EBADF;

	if (kuch->kuc_magic != KUC_MAGIC) {
		CERROR("KernelComm: bad magic %x\n", kuch->kuc_magic);
		return -ENOSYS;
	}

	fs = get_fs();
	set_fs(KERNEL_DS);
	while (count > 0) {
		rc = vfs_write(filp, (void __force __user *)payload,
			       count, &offset);
		if (rc < 0)
			break;
		count -= rc;
		payload += rc;
		rc = 0;
	}
	set_fs(fs);

	if (rc < 0)
		CWARN("message send failed (%d)\n", rc);
	else
		CDEBUG(D_KUC, "Sent message rc=%d, fp=%p\n", rc, filp);

	return rc;
}
EXPORT_SYMBOL(libcfs_kkuc_msg_put);

/* Broadcast groups are global across all mounted filesystems;
 * i.e. registering for a group on 1 fs will get messages for that
 * group from any fs */
/** A single group reigstration has a uid and a file pointer */
struct kkuc_reg {
	struct list_head	kr_chain;
	int		kr_uid;
	struct file	*kr_fp;
	__u32		kr_data;
};
static struct list_head kkuc_groups[KUC_GRP_MAX+1] = {};
/* Protect message sending against remove and adds */
static DECLARE_RWSEM(kg_sem);

/** Add a receiver to a broadcast group
 * @param filp pipe to write into
 * @param uid identidier for this receiver
 * @param group group number
 */
int libcfs_kkuc_group_add(struct file *filp, int uid, int group, __u32 data)
{
	struct kkuc_reg *reg;

	if (group > KUC_GRP_MAX) {
		CDEBUG(D_WARNING, "Kernelcomm: bad group %d\n", group);
		return -EINVAL;
	}

	/* fput in group_rem */
	if (filp == NULL)
		return -EBADF;

	/* freed in group_rem */
	reg = kmalloc(sizeof(*reg), 0);
	if (reg == NULL)
		return -ENOMEM;

	reg->kr_fp = filp;
	reg->kr_uid = uid;
	reg->kr_data = data;

	down_write(&kg_sem);
	if (kkuc_groups[group].next == NULL)
		INIT_LIST_HEAD(&kkuc_groups[group]);
	list_add(&reg->kr_chain, &kkuc_groups[group]);
	up_write(&kg_sem);

	CDEBUG(D_KUC, "Added uid=%d fp=%p to group %d\n", uid, filp, group);

	return 0;
}
EXPORT_SYMBOL(libcfs_kkuc_group_add);

int libcfs_kkuc_group_rem(int uid, int group)
{
	struct kkuc_reg *reg, *next;

	if (kkuc_groups[group].next == NULL)
		RETURN(0);

	if (uid == 0) {
		/* Broadcast a shutdown message */
		struct kuc_hdr lh;

		lh.kuc_magic = KUC_MAGIC;
		lh.kuc_transport = KUC_TRANSPORT_GENERIC;
		lh.kuc_msgtype = KUC_MSG_SHUTDOWN;
		lh.kuc_msglen = sizeof(lh);
		libcfs_kkuc_group_put(group, &lh);
	}

	down_write(&kg_sem);
	list_for_each_entry_safe(reg, next, &kkuc_groups[group], kr_chain) {
		if ((uid == 0) || (uid == reg->kr_uid)) {
			list_del(&reg->kr_chain);
			CDEBUG(D_KUC, "Removed uid=%d fp=%p from group %d\n",
			       reg->kr_uid, reg->kr_fp, group);
			if (reg->kr_fp != NULL)
				fput(reg->kr_fp);
			kfree(reg);
		}
	}
	up_write(&kg_sem);

	RETURN(0);
}
EXPORT_SYMBOL(libcfs_kkuc_group_rem);

int libcfs_kkuc_group_put(int group, void *payload)
{
	struct kkuc_reg	*reg;
	int		 rc = 0;
	int one_success = 0;

	down_read(&kg_sem);
	list_for_each_entry(reg, &kkuc_groups[group], kr_chain) {
		if (reg->kr_fp != NULL) {
			rc = libcfs_kkuc_msg_put(reg->kr_fp, payload);
			if (rc == 0)
				one_success = 1;
			else if (rc == -EPIPE) {
				fput(reg->kr_fp);
				reg->kr_fp = NULL;
			}
		}
	}
	up_read(&kg_sem);

	/* don't return an error if the message has been delivered
	 * at least to one agent */
	if (one_success)
		rc = 0;

	RETURN(rc);
}
EXPORT_SYMBOL(libcfs_kkuc_group_put);

/**
 * Calls a callback function for each link of the given kuc group.
 * @param group the group to call the function on.
 * @param cb_func the function to be called.
 * @param cb_arg iextra argument to be passed to the callback function.
 */
int libcfs_kkuc_group_foreach(int group, libcfs_kkuc_cb_t cb_func,
			      void *cb_arg)
{
	struct kkuc_reg *reg;
	int rc = 0;

	if (group > KUC_GRP_MAX) {
		CDEBUG(D_WARNING, "Kernelcomm: bad group %d\n", group);
		RETURN(-EINVAL);
	}

	/* no link for this group */
	if (kkuc_groups[group].next == NULL)
		RETURN(0);

	down_read(&kg_sem);
	list_for_each_entry(reg, &kkuc_groups[group], kr_chain) {
		if (reg->kr_fp != NULL) {
			rc = cb_func(reg->kr_data, cb_arg);
		}
	}
	up_read(&kg_sem);

	RETURN(rc);
}
EXPORT_SYMBOL(libcfs_kkuc_group_foreach);

#endif /* LUSTRE_UTILS */