/*
 * VMware VMCI Driver
 *
 * Copyright (C) 2012 VMware, Inc. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation version 2 and no later version.
 *
 * 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
 * for more details.
 */

#include <linux/vmw_vmci_defs.h>
#include <linux/vmw_vmci_api.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/bug.h>

#include "vmci_datagram.h"
#include "vmci_resource.h"
#include "vmci_context.h"
#include "vmci_driver.h"
#include "vmci_event.h"
#include "vmci_route.h"

/*
 * struct datagram_entry describes the datagram entity. It is used for datagram
 * entities created only on the host.
 */
struct datagram_entry {
        struct vmci_resource resource;
        u32 flags;
        bool run_delayed;
        vmci_datagram_recv_cb recv_cb;
        void *client_data;
        u32 priv_flags;
};

struct delayed_datagram_info {
        struct datagram_entry *entry;
        struct work_struct work;
        bool in_dg_host_queue;
        /* msg and msg_payload must be together. */
        struct vmci_datagram msg;
        u8 msg_payload[];
};

/* Number of in-flight host->host datagrams */
static atomic_t delayed_dg_host_queue_size = ATOMIC_INIT(0);

/*
 * Create a datagram entry given a handle pointer.
 */
static int dg_create_handle(u32 resource_id,
                            u32 flags,
                            u32 priv_flags,
                            vmci_datagram_recv_cb recv_cb,
                            void *client_data, struct vmci_handle *out_handle)
{
        int result;
        u32 context_id;
        struct vmci_handle handle;
        struct datagram_entry *entry;

        if ((flags & VMCI_FLAG_WELLKNOWN_DG_HND) != 0)
                return VMCI_ERROR_INVALID_ARGS;

        if ((flags & VMCI_FLAG_ANYCID_DG_HND) != 0) {
                context_id = VMCI_INVALID_ID;
        } else {
                context_id = vmci_get_context_id();
                if (context_id == VMCI_INVALID_ID)
                        return VMCI_ERROR_NO_RESOURCES;
        }

        handle = vmci_make_handle(context_id, resource_id);

        entry = kmalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry) {
                pr_warn("Failed allocating memory for datagram entry\n");
                return VMCI_ERROR_NO_MEM;
        }

        entry->run_delayed = (flags & VMCI_FLAG_DG_DELAYED_CB) ? true : false;
        entry->flags = flags;
        entry->recv_cb = recv_cb;
        entry->client_data = client_data;
        entry->priv_flags = priv_flags;

        /* Make datagram resource live. */
        result = vmci_resource_add(&entry->resource,
                                   VMCI_RESOURCE_TYPE_DATAGRAM,
                                   handle);
        if (result != VMCI_SUCCESS) {
                pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d\n",
                        handle.context, handle.resource, result);
                kfree(entry);
                return result;
        }

        *out_handle = vmci_resource_handle(&entry->resource);
        return VMCI_SUCCESS;
}

/*
 * Internal utility function with the same purpose as
 * vmci_datagram_get_priv_flags that also takes a context_id.
 */
static int vmci_datagram_get_priv_flags(u32 context_id,
                                        struct vmci_handle handle,
                                        u32 *priv_flags)
{
        if (context_id == VMCI_INVALID_ID)
                return VMCI_ERROR_INVALID_ARGS;

        if (context_id == VMCI_HOST_CONTEXT_ID) {
                struct datagram_entry *src_entry;
                struct vmci_resource *resource;

                resource = vmci_resource_by_handle(handle,
                                                   VMCI_RESOURCE_TYPE_DATAGRAM);
                if (!resource)
                        return VMCI_ERROR_INVALID_ARGS;

                src_entry = container_of(resource, struct datagram_entry,
                                         resource);
                *priv_flags = src_entry->priv_flags;
                vmci_resource_put(resource);
        } else if (context_id == VMCI_HYPERVISOR_CONTEXT_ID)
                *priv_flags = VMCI_MAX_PRIVILEGE_FLAGS;
        else
                *priv_flags = vmci_context_get_priv_flags(context_id);

        return VMCI_SUCCESS;
}

/*
 * Calls the specified callback in a delayed context.
 */
static void dg_delayed_dispatch(struct work_struct *work)
{
        struct delayed_datagram_info *dg_info =
                        container_of(work, struct delayed_datagram_info, work);

        dg_info->entry->recv_cb(dg_info->entry->client_data, &dg_info->msg);

        vmci_resource_put(&dg_info->entry->resource);

        if (dg_info->in_dg_host_queue)
                atomic_dec(&delayed_dg_host_queue_size);

        kfree(dg_info);
}

/*
 * Dispatch datagram as a host, to the host, or other vm context. This
 * function cannot dispatch to hypervisor context handlers. This should
 * have been handled before we get here by vmci_datagram_dispatch.
 * Returns number of bytes sent on success, error code otherwise.
 */
static int dg_dispatch_as_host(u32 context_id, struct vmci_datagram *dg)
{
        int retval;
        size_t dg_size;
        u32 src_priv_flags;

        dg_size = VMCI_DG_SIZE(dg);

        /* Host cannot send to the hypervisor. */
        if (dg->dst.context == VMCI_HYPERVISOR_CONTEXT_ID)
                return VMCI_ERROR_DST_UNREACHABLE;

        /* Check that source handle matches sending context. */
        if (dg->src.context != context_id) {
                pr_devel("Sender context (ID=0x%x) is not owner of src datagram entry (handle=0x%x:0x%x)\n",
                         context_id, dg->src.context, dg->src.resource);
                return VMCI_ERROR_NO_ACCESS;
        }

        /* Get hold of privileges of sending endpoint. */
        retval = vmci_datagram_get_priv_flags(context_id, dg->src,
                                              &src_priv_flags);
        if (retval != VMCI_SUCCESS) {
                pr_warn("Couldn't get privileges (handle=0x%x:0x%x)\n",
                        dg->src.context, dg->src.resource);
                return retval;
        }

        /* Determine if we should route to host or guest destination. */
        if (dg->dst.context == VMCI_HOST_CONTEXT_ID) {
                /* Route to host datagram entry. */
                struct datagram_entry *dst_entry;
                struct vmci_resource *resource;

                if (dg->src.context == VMCI_HYPERVISOR_CONTEXT_ID &&
                    dg->dst.resource == VMCI_EVENT_HANDLER) {
                        return vmci_event_dispatch(dg);
                }

                resource = vmci_resource_by_handle(dg->dst,
                                                   VMCI_RESOURCE_TYPE_DATAGRAM);
                if (!resource) {
                        pr_devel("Sending to invalid destination (handle=0x%x:0x%x)\n",
                                 dg->dst.context, dg->dst.resource);
                        return VMCI_ERROR_INVALID_RESOURCE;
                }
                dst_entry = container_of(resource, struct datagram_entry,
                                         resource);
                if (vmci_deny_interaction(src_priv_flags,
                                          dst_entry->priv_flags)) {
                        vmci_resource_put(resource);
                        return VMCI_ERROR_NO_ACCESS;
                }

                /*
                 * If a VMCI datagram destined for the host is also sent by the
                 * host, we always run it delayed. This ensures that no locks
                 * are held when the datagram callback runs.
                 */
                if (dst_entry->run_delayed ||
                    dg->src.context == VMCI_HOST_CONTEXT_ID) {
                        struct delayed_datagram_info *dg_info;

                        if (atomic_add_return(1, &delayed_dg_host_queue_size)
                            == VMCI_MAX_DELAYED_DG_HOST_QUEUE_SIZE) {
                                atomic_dec(&delayed_dg_host_queue_size);
                                vmci_resource_put(resource);
                                return VMCI_ERROR_NO_MEM;
                        }

                        dg_info = kmalloc(sizeof(*dg_info) +
                                    (size_t) dg->payload_size, GFP_ATOMIC);
                        if (!dg_info) {
                                atomic_dec(&delayed_dg_host_queue_size);
                                vmci_resource_put(resource);
                                return VMCI_ERROR_NO_MEM;
                        }

                        dg_info->in_dg_host_queue = true;
                        dg_info->entry = dst_entry;
                        memcpy(&dg_info->msg, dg, dg_size);

                        INIT_WORK(&dg_info->work, dg_delayed_dispatch);
                        schedule_work(&dg_info->work);
                        retval = VMCI_SUCCESS;

                } else {
                        retval = dst_entry->recv_cb(dst_entry->client_data, dg);
                        vmci_resource_put(resource);
                        if (retval < VMCI_SUCCESS)
                                return retval;
                }
        } else {
                /* Route to destination VM context. */
                struct vmci_datagram *new_dg;

                if (context_id != dg->dst.context) {
                        if (vmci_deny_interaction(src_priv_flags,
                                                  vmci_context_get_priv_flags
                                                  (dg->dst.context))) {
                                return VMCI_ERROR_NO_ACCESS;
                        } else if (VMCI_CONTEXT_IS_VM(context_id)) {
                                /*
                                 * If the sending context is a VM, it
                                 * cannot reach another VM.
                                 */

                                pr_devel("Datagram communication between VMs not supported (src=0x%x, dst=0x%x)\n",
                                         context_id, dg->dst.context);
                                return VMCI_ERROR_DST_UNREACHABLE;
                        }
                }

                /* We make a copy to enqueue. */
                new_dg = kmemdup(dg, dg_size, GFP_KERNEL);
                if (new_dg == NULL)
                        return VMCI_ERROR_NO_MEM;

                retval = vmci_ctx_enqueue_datagram(dg->dst.context, new_dg);
                if (retval < VMCI_SUCCESS) {
                        kfree(new_dg);
                        return retval;
                }
        }

        /*
         * We currently truncate the size to signed 32 bits. This doesn't
         * matter for this handler as it only support 4Kb messages.
         */
        return (int)dg_size;
}

/*
 * Dispatch datagram as a guest, down through the VMX and potentially to
 * the host.
 * Returns number of bytes sent on success, error code otherwise.
 */
static int dg_dispatch_as_guest(struct vmci_datagram *dg)
{
        int retval;
        struct vmci_resource *resource;

        resource = vmci_resource_by_handle(dg->src,
                                           VMCI_RESOURCE_TYPE_DATAGRAM);
        if (!resource)
                return VMCI_ERROR_NO_HANDLE;

        retval = vmci_send_datagram(dg);
        vmci_resource_put(resource);
        return retval;
}

/*
 * Dispatch datagram.  This will determine the routing for the datagram
 * and dispatch it accordingly.
 * Returns number of bytes sent on success, error code otherwise.
 */
int vmci_datagram_dispatch(u32 context_id,
                           struct vmci_datagram *dg, bool from_guest)
{
        int retval;
        enum vmci_route route;

        BUILD_BUG_ON(sizeof(struct vmci_datagram) != 24);

        if (dg->payload_size > VMCI_MAX_DG_SIZE ||
            VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
                pr_devel("Payload (size=%llu bytes) too big to send\n",
                         (unsigned long long)dg->payload_size);
                return VMCI_ERROR_INVALID_ARGS;
        }

        retval = vmci_route(&dg->src, &dg->dst, from_guest, &route);
        if (retval < VMCI_SUCCESS) {
                pr_devel("Failed to route datagram (src=0x%x, dst=0x%x, err=%d)\n",
                         dg->src.context, dg->dst.context, retval);
                return retval;
        }

        if (VMCI_ROUTE_AS_HOST == route) {
                if (VMCI_INVALID_ID == context_id)
                        context_id = VMCI_HOST_CONTEXT_ID;
                return dg_dispatch_as_host(context_id, dg);
        }

        if (VMCI_ROUTE_AS_GUEST == route)
                return dg_dispatch_as_guest(dg);

        pr_warn("Unknown route (%d) for datagram\n", route);
        return VMCI_ERROR_DST_UNREACHABLE;
}

/*
 * Invoke the handler for the given datagram.  This is intended to be
 * called only when acting as a guest and receiving a datagram from the
 * virtual device.
 */
int vmci_datagram_invoke_guest_handler(struct vmci_datagram *dg)
{
        struct vmci_resource *resource;
        struct datagram_entry *dst_entry;

        resource = vmci_resource_by_handle(dg->dst,
                                           VMCI_RESOURCE_TYPE_DATAGRAM);
        if (!resource) {
                pr_devel("destination (handle=0x%x:0x%x) doesn't exist\n",
                         dg->dst.context, dg->dst.resource);
                return VMCI_ERROR_NO_HANDLE;
        }

        dst_entry = container_of(resource, struct datagram_entry, resource);
        if (dst_entry->run_delayed) {
                struct delayed_datagram_info *dg_info;

                dg_info = kmalloc(sizeof(*dg_info) + (size_t)dg->payload_size,
                                  GFP_ATOMIC);
                if (!dg_info) {
                        vmci_resource_put(resource);
                        return VMCI_ERROR_NO_MEM;
                }

                dg_info->in_dg_host_queue = false;
                dg_info->entry = dst_entry;
                memcpy(&dg_info->msg, dg, VMCI_DG_SIZE(dg));

                INIT_WORK(&dg_info->work, dg_delayed_dispatch);
                schedule_work(&dg_info->work);
        } else {
                dst_entry->recv_cb(dst_entry->client_data, dg);
                vmci_resource_put(resource);
        }

        return VMCI_SUCCESS;
}

/*
 * vmci_datagram_create_handle_priv() - Create host context datagram endpoint
 * @resource_id:        The resource ID.
 * @flags:      Datagram Flags.
 * @priv_flags: Privilege Flags.
 * @recv_cb:    Callback when receiving datagrams.
 * @client_data:        Pointer for a datagram_entry struct
 * @out_handle: vmci_handle that is populated as a result of this function.
 *
 * Creates a host context datagram endpoint and returns a handle to it.
 */
int vmci_datagram_create_handle_priv(u32 resource_id,
                                     u32 flags,
                                     u32 priv_flags,
                                     vmci_datagram_recv_cb recv_cb,
                                     void *client_data,
                                     struct vmci_handle *out_handle)
{
        if (out_handle == NULL)
                return VMCI_ERROR_INVALID_ARGS;

        if (recv_cb == NULL) {
                pr_devel("Client callback needed when creating datagram\n");
                return VMCI_ERROR_INVALID_ARGS;
        }

        if (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS)
                return VMCI_ERROR_INVALID_ARGS;

        return dg_create_handle(resource_id, flags, priv_flags, recv_cb,
                                client_data, out_handle);
}
EXPORT_SYMBOL_GPL(vmci_datagram_create_handle_priv);

/*
 * vmci_datagram_create_handle() - Create host context datagram endpoint
 * @resource_id:        Resource ID.
 * @flags:      Datagram Flags.
 * @recv_cb:    Callback when receiving datagrams.
 * @client_ata: Pointer for a datagram_entry struct
 * @out_handle: vmci_handle that is populated as a result of this function.
 *
 * Creates a host context datagram endpoint and returns a handle to
 * it.  Same as vmci_datagram_create_handle_priv without the priviledge
 * flags argument.
 */
int vmci_datagram_create_handle(u32 resource_id,
                                u32 flags,
                                vmci_datagram_recv_cb recv_cb,
                                void *client_data,
                                struct vmci_handle *out_handle)
{
        return vmci_datagram_create_handle_priv(
                resource_id, flags,
                VMCI_DEFAULT_PROC_PRIVILEGE_FLAGS,
                recv_cb, client_data,
                out_handle);
}
EXPORT_SYMBOL_GPL(vmci_datagram_create_handle);

/*
 * vmci_datagram_destroy_handle() - Destroys datagram handle
 * @handle:     vmci_handle to be destroyed and reaped.
 *
 * Use this function to destroy any datagram handles created by
 * vmci_datagram_create_handle{,Priv} functions.
 */
int vmci_datagram_destroy_handle(struct vmci_handle handle)
{
        struct datagram_entry *entry;
        struct vmci_resource *resource;

        resource = vmci_resource_by_handle(handle, VMCI_RESOURCE_TYPE_DATAGRAM);
        if (!resource) {
                pr_devel("Failed to destroy datagram (handle=0x%x:0x%x)\n",
                         handle.context, handle.resource);
                return VMCI_ERROR_NOT_FOUND;
        }

        entry = container_of(resource, struct datagram_entry, resource);

        vmci_resource_put(&entry->resource);
        vmci_resource_remove(&entry->resource);
        kfree(entry);

        return VMCI_SUCCESS;
}
EXPORT_SYMBOL_GPL(vmci_datagram_destroy_handle);

/*
 * vmci_datagram_send() - Send a datagram
 * @msg:        The datagram to send.
 *
 * Sends the provided datagram on its merry way.
 */
int vmci_datagram_send(struct vmci_datagram *msg)
{
        if (msg == NULL)
                return VMCI_ERROR_INVALID_ARGS;

        return vmci_datagram_dispatch(VMCI_INVALID_ID, msg, false);
}
EXPORT_SYMBOL_GPL(vmci_datagram_send);