Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1369 insertions, 0 deletions

diff --git a/src/VBox/Additions/x11/VBoxClient/display-drm.cpp b/src/VBox/Additions/x11/VBoxClient/display-drm.cpp
new file mode 100644
index 00000000..fa5d56d2
--- /dev/null
+++ b/src/VBox/Additions/x11/VBoxClient/display-drm.cpp
@@ -0,0 +1,1369 @@
+/* $Id: display-drm.cpp $ */
+/** @file
+ * Guest Additions - VMSVGA guest screen resize service.
+ *
+ * A user space daemon which communicates with VirtualBox host interface
+ * and performs VMSVGA-specific guest screen resize and communicates with
+ * Desktop Environment helper daemon over IPC.
+ */
+
+/*
+ * Copyright (C) 2016-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * 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, in version 3 of the
+ * License.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/** @page pg_vboxdrmcliet    VBoxDRMClient - The VMSVGA Guest Screen Resize Service
+ *
+ * The VMSVGA Guest Screen Resize Service is a service which communicates with a
+ * guest VMSVGA driver and triggers it to perform screen resize on a guest side.
+ *
+ * This service supposed to be started on early boot. On start it will try to find
+ * compatible VMSVGA graphics card and terminate immediately if not found.
+ * VMSVGA functionality implemented here is only supported starting from vmgfx
+ * driver version 2.10 which was introduced in Linux kernel 4.6. When compatible
+ * graphics card is found, service will start a worker loop in order to receive screen
+ * update data from host and apply it to local DRM stack.
+ *
+ * In addition, it will start a local IPC server in order to communicate with Desktop
+ * Environment specific service(s). Currently, it will propagate to IPC client information regarding to
+ * which display should be set as primary on Desktop Environment level. As well as
+ * receive screen layout change events obtained on Desktop Environment level and send it
+ * back to host, so host and guest will have the same screen layout representation.
+ *
+ * By default, access to IPC server socket is granted to all users. It can be restricted to
+ * only root and users from group 'vboxdrmipc' if '/VirtualBox/GuestAdd/DRMIpcRestricted' guest
+ * property is set and READ-ONLY for guest. User group 'vboxdrmipc' is created during Guest
+ * Additions installation. If this group is removed (or not found due to any reason) prior to
+ * service start, access to IPC server socket will be granted to root only regardless
+ * if '/VirtualBox/GuestAdd/DRMIpcRestricted' guest property is set or not. If guest property
+ * is set, but is not READ-ONLY for guest, property is ignored and IPC socket access is granted
+ * to all users.
+ *
+ * Logging is implemented in a way that errors are always printed out, VBClLogVerbose(1) and
+ * VBClLogVerbose(2) are used for debugging purposes. Verbosity level 1 is for messages related
+ * to service itself (excluding IPC), level 2 is for IPC communication debugging. In order to see
+ * logging on a host side it is enough to do:
+ *
+ *     echo 1 > /sys/module/vboxguest/parameters/r3_log_to_host.
+ *
+ *
+ * Service is running the following threads:
+ *
+ * DrmResizeThread - this thread listens for display layout update events from host.
+ *     Once event is received, it either injects new screen layout data into DRM stack,
+ *     and/or asks IPC client(s) to set primary display. This thread is accessing IPC
+ *     client connection list when it needs to sent new primary display data to all the
+ *     connected clients.
+ *
+ * DrmIpcSRV - this thread is a main loop for IPC server. It accepts new connection(s),
+ *     authenticates it and starts new client thread IpcCLT-XXX for processing client
+ *     requests. This thread is accessing IPC client connection list by adding a new
+ *     connection data into it.
+ *
+ * IpcCLT-%u - this thread processes all the client data. Suffix '-%u' in thread name is PID
+ *     of a remote client process. Typical name for client thread would be IpcCLT-1234. This
+ *     thread is accessing IPC client connection list when it removes connection data from it
+ *     when actual IPC connection is closed. Due to IPRT thread name limitation, actual thread
+ *     name will be cropped by 15 characters.
+ *
+ *
+ * The following locks are utilized:
+ *
+ * #g_ipcClientConnectionsListCritSect - protects access to list of IPC client connections.
+ *     It is used by each thread - DrmResizeThread, DrmIpcSRV and IpcCLT-XXX.
+ *
+ * #g_monitorPositionsCritSect - protects access to display layout data cache and vmwgfx driver
+ *      handle, serializes access to host interface and vmwgfx driver handle between
+ *      DrmResizeThread and IpcCLT-%u.
+ */
+
+#include "VBoxClient.h"
+#include "display-ipc.h"
+
+#include <VBox/VBoxGuestLib.h>
+#include <VBox/HostServices/GuestPropertySvc.h>
+
+#include <iprt/getopt.h>
+#include <iprt/assert.h>
+#include <iprt/file.h>
+#include <iprt/err.h>
+#include <iprt/string.h>
+#include <iprt/initterm.h>
+#include <iprt/message.h>
+#include <iprt/thread.h>
+#include <iprt/asm.h>
+#include <iprt/localipc.h>
+
+#include <unistd.h>
+#include <stdio.h>
+#include <limits.h>
+#include <signal.h>
+#include <grp.h>
+#include <errno.h>
+
+#ifdef RT_OS_LINUX
+# include <sys/ioctl.h>
+#else  /* Solaris and BSDs, in case they ever adopt the DRM driver. */
+# include <sys/ioccom.h>
+#endif
+
+/** Ioctl command to query vmwgfx version information. */
+#define DRM_IOCTL_VERSION               _IOWR('d', 0x00, struct DRMVERSION)
+/** Ioctl command to set new screen layout. */
+#define DRM_IOCTL_VMW_UPDATE_LAYOUT     _IOW('d', 0x40 + 20, struct DRMVMWUPDATELAYOUT)
+/** A driver name which identifies VMWare driver. */
+#define DRM_DRIVER_NAME "vmwgfx"
+/** VMWare driver compatible version number. On previous versions resizing does not seem work. */
+#define DRM_DRIVER_VERSION_MAJOR_MIN    (2)
+#define DRM_DRIVER_VERSION_MINOR_MIN    (10)
+
+/** VMWare char device driver minor numbers range. */
+#define VMW_CONTROL_DEVICE_MINOR_START  (64)
+#define VMW_RENDER_DEVICE_MINOR_START   (128)
+#define VMW_RENDER_DEVICE_MINOR_END     (192)
+
+/** Name of DRM resize thread. */
+#define DRM_RESIZE_THREAD_NAME          "DrmResizeThread"
+
+/** Name of DRM IPC server thread. */
+#define DRM_IPC_SERVER_THREAD_NAME      "DrmIpcSRV"
+/** Maximum length of thread name. */
+#define DRM_IPC_THREAD_NAME_MAX         (16)
+/** Name pattern of DRM IPC client thread. */
+#define DRM_IPC_CLIENT_THREAD_NAME_PTR  "IpcCLT-%u"
+/** Maximum number of simultaneous IPC client connections. */
+#define DRM_IPC_SERVER_CONNECTIONS_MAX  (16)
+
+/** IPC client connections counter. */
+static volatile uint32_t g_cDrmIpcConnections = 0;
+/* A flag which indicates whether access to IPC socket should be restricted.
+ * This flag caches '/VirtualBox/GuestAdd/DRMIpcRestricted' guest property
+ * in order to prevent its retrieving from the host side each time a new IPC
+ * client connects to server. This flag is updated each time when property is
+ * changed on the host side. */
+static volatile bool g_fDrmIpcRestricted;
+
+/** Global handle to vmwgfx file descriptor (protected by #g_monitorPositionsCritSect). */
+static RTFILE g_hDevice = NIL_RTFILE;
+
+/** DRM version structure. */
+struct DRMVERSION
+{
+    int cMajor;
+    int cMinor;
+    int cPatchLevel;
+    size_t cbName;
+    char *pszName;
+    size_t cbDate;
+    char *pszDate;
+    size_t cbDescription;
+    char *pszDescription;
+};
+AssertCompileSize(struct DRMVERSION, 8 + 7 * sizeof(void *));
+
+/** Preferred screen layout information for DRM_VMW_UPDATE_LAYOUT IoCtl.  The
+ *  rects argument is a cast pointer to an array of drm_vmw_rect. */
+struct DRMVMWUPDATELAYOUT
+{
+    uint32_t cOutputs;
+    uint32_t u32Pad;
+    uint64_t ptrRects;
+};
+AssertCompileSize(struct DRMVMWUPDATELAYOUT, 16);
+
+/** A node of IPC client connections list. */
+typedef struct VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE
+{
+    /** The list node. */
+    RTLISTNODE      Node;
+    /** List node payload. */
+    PVBOX_DRMIPC_CLIENT   pClient;
+} VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE;
+
+/* Pointer to VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE. */
+typedef VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE *PVBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE;
+
+/** IPC client connections list.  */
+static VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE g_ipcClientConnectionsList;
+
+/** IPC client connections list critical section. */
+static RTCRITSECT g_ipcClientConnectionsListCritSect;
+
+/** Critical section used for reporting monitors position back to host. */
+static RTCRITSECT g_monitorPositionsCritSect;
+
+/** Counter of how often our daemon has been re-spawned. */
+unsigned g_cRespawn = 0;
+/** Logging verbosity level. */
+unsigned g_cVerbosity = 0;
+
+/** Path to the PID file. */
+static const char *g_pszPidFile = "/var/run/VBoxDRMClient";
+
+/** Global flag which is triggered when service requested to shutdown. */
+static bool volatile g_fShutdown;
+
+/**
+ * Go over all existing IPC client connection and put set-primary-screen request
+ * data into TX queue of each of them .
+ *
+ * @return  IPRT status code.
+ * @param   u32PrimaryDisplay   Primary display ID.
+ */
+static int vbDrmIpcBroadcastPrimaryDisplay(uint32_t u32PrimaryDisplay);
+
+/**
+ * Attempts to open DRM device by given path and check if it is
+ * capable for screen resize.
+ *
+ * @return  DRM device handle on success, NIL_RTFILE otherwise.
+ * @param   szPathPattern       Path name pattern to the DRM device.
+ * @param   uInstance           Driver / device instance.
+ */
+static RTFILE vbDrmTryDevice(const char *szPathPattern, uint8_t uInstance)
+{
+    int rc = VERR_NOT_FOUND;
+    char szPath[PATH_MAX];
+    struct DRMVERSION vmwgfxVersion;
+    RTFILE hDevice = NIL_RTFILE;
+
+    RT_ZERO(szPath);
+    RT_ZERO(vmwgfxVersion);
+
+    rc = RTStrPrintf(szPath, sizeof(szPath), szPathPattern, uInstance);
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTFileOpen(&hDevice, szPath, RTFILE_O_READWRITE | RTFILE_O_OPEN | RTFILE_O_DENY_NONE);
+        if (RT_SUCCESS(rc))
+        {
+            char szVmwgfxDriverName[sizeof(DRM_DRIVER_NAME)];
+            RT_ZERO(szVmwgfxDriverName);
+
+            vmwgfxVersion.cbName = sizeof(szVmwgfxDriverName);
+            vmwgfxVersion.pszName = szVmwgfxDriverName;
+
+            /* Query driver version information and check if it can be used for screen resizing. */
+            rc = RTFileIoCtl(hDevice, DRM_IOCTL_VERSION, &vmwgfxVersion, sizeof(vmwgfxVersion), NULL);
+            if (   RT_SUCCESS(rc)
+                && strncmp(szVmwgfxDriverName, DRM_DRIVER_NAME, sizeof(DRM_DRIVER_NAME) - 1) == 0
+                && (   vmwgfxVersion.cMajor > DRM_DRIVER_VERSION_MAJOR_MIN
+                    || (   vmwgfxVersion.cMajor == DRM_DRIVER_VERSION_MAJOR_MIN
+                        && vmwgfxVersion.cMinor >= DRM_DRIVER_VERSION_MINOR_MIN)))
+            {
+                VBClLogInfo("found compatible device: %s\n", szPath);
+            }
+            else
+            {
+                RTFileClose(hDevice);
+                hDevice = NIL_RTFILE;
+                rc = VERR_NOT_FOUND;
+            }
+        }
+    }
+    else
+    {
+        VBClLogError("unable to construct path to DRM device: %Rrc\n", rc);
+    }
+
+    return RT_SUCCESS(rc) ? hDevice : NIL_RTFILE;
+}
+
+/**
+ * Attempts to find and open DRM device to be used for screen resize.
+ *
+ * @return  DRM device handle on success, NIL_RTFILE otherwise.
+ */
+static RTFILE vbDrmOpenVmwgfx(void)
+{
+    /* Control devices for drm graphics driver control devices go from
+     * controlD64 to controlD127.  Render node devices go from renderD128
+     * to renderD192. The driver takes resize hints via the control device
+     * on pre-4.10 (???) kernels and on the render device on newer ones.
+     * At first, try to find control device and render one if not found.
+     */
+    uint8_t i;
+    RTFILE hDevice = NIL_RTFILE;
+
+    /* Lookup control device. */
+    for (i = VMW_CONTROL_DEVICE_MINOR_START; i < VMW_RENDER_DEVICE_MINOR_START; i++)
+    {
+        hDevice = vbDrmTryDevice("/dev/dri/controlD%u", i);
+        if (hDevice != NIL_RTFILE)
+            return hDevice;
+    }
+
+    /* Lookup render device. */
+    for (i = VMW_RENDER_DEVICE_MINOR_START; i <= VMW_RENDER_DEVICE_MINOR_END; i++)
+    {
+        hDevice = vbDrmTryDevice("/dev/dri/renderD%u", i);
+        if (hDevice != NIL_RTFILE)
+            return hDevice;
+    }
+
+    VBClLogError("unable to find DRM device\n");
+
+    return hDevice;
+}
+
+/**
+ * This function converts input monitors layout array passed from DevVMM
+ * into monitors layout array to be passed to DRM stack. Last validation
+ * request is cached.
+ *
+ * @return  VINF_SUCCESS on success, VERR_DUPLICATE if monitors layout was not changed, IPRT error code otherwise.
+ * @param   aDisplaysIn         Input displays array.
+ * @param   cDisplaysIn         Number of elements in input displays array.
+ * @param   aDisplaysOut        Output displays array.
+ * @param   cDisplaysOutMax     Number of elements in output displays array.
+ * @param   pu32PrimaryDisplay  ID of a display which marked as primary.
+ * @param   pcActualDisplays    Number of displays to report to DRM stack (number of enabled displays).
+ * @param   fPartialLayout      Whether aDisplaysIn array contains complete display layout information or not.
+ *                              When layout is reported by Desktop Environment helper, aDisplaysIn does not have
+ *                              idDisplay, fDisplayFlags and cBitsPerPixel data (guest has no info about them).
+ */
+static int vbDrmValidateLayout(VMMDevDisplayDef *aDisplaysIn, uint32_t cDisplaysIn,
+                               struct VBOX_DRMIPC_VMWRECT *aDisplaysOut, uint32_t *pu32PrimaryDisplay,
+                               uint32_t cDisplaysOutMax, uint32_t *pcActualDisplays, bool fPartialLayout)
+{
+    /* This array is a cache of what was received from DevVMM so far.
+     * DevVMM may send to us partial information bout scree layout. This
+     * cache remembers entire picture. */
+    static struct VMMDevDisplayDef aVmMonitorsCache[VBOX_DRMIPC_MONITORS_MAX];
+    /* Number of valid (enabled) displays in output array. */
+    uint32_t cDisplaysOut = 0;
+    /* Flag indicates that current layout cache is consistent and can be passed to DRM stack. */
+    bool fValid = true;
+
+    /* Make sure input array fits cache size. */
+    if (cDisplaysIn > VBOX_DRMIPC_MONITORS_MAX)
+    {
+        VBClLogError("unable to validate screen layout: input (%u) array does not fit to cache size (%u)\n",
+                         cDisplaysIn, VBOX_DRMIPC_MONITORS_MAX);
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Make sure there is enough space in output array. */
+    if (cDisplaysIn > cDisplaysOutMax)
+    {
+        VBClLogError("unable to validate screen layout: input array (%u) is bigger than output one (%u)\n",
+                         cDisplaysIn, cDisplaysOut);
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Make sure input and output arrays are of non-zero size. */
+    if (!(cDisplaysIn > 0 && cDisplaysOutMax > 0))
+    {
+        VBClLogError("unable to validate screen layout: invalid size of either input (%u) or output display array\n",
+                         cDisplaysIn, cDisplaysOutMax);
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Update cache. */
+    for (uint32_t i = 0; i < cDisplaysIn; i++)
+    {
+        uint32_t idDisplay = !fPartialLayout ? aDisplaysIn[i].idDisplay : i;
+        if (idDisplay < VBOX_DRMIPC_MONITORS_MAX)
+        {
+            if (!fPartialLayout)
+            {
+                aVmMonitorsCache[idDisplay].idDisplay = idDisplay;
+                aVmMonitorsCache[idDisplay].fDisplayFlags = aDisplaysIn[i].fDisplayFlags;
+                aVmMonitorsCache[idDisplay].cBitsPerPixel = aDisplaysIn[i].cBitsPerPixel;
+            }
+
+            aVmMonitorsCache[idDisplay].cx = aDisplaysIn[i].cx;
+            aVmMonitorsCache[idDisplay].cy = aDisplaysIn[i].cy;
+            aVmMonitorsCache[idDisplay].xOrigin = aDisplaysIn[i].xOrigin;
+            aVmMonitorsCache[idDisplay].yOrigin = aDisplaysIn[i].yOrigin;
+        }
+        else
+        {
+            VBClLogError("received display ID (0x%x, position %u) is invalid\n", idDisplay, i);
+            /* If monitor configuration cannot be placed into cache, consider entire cache is invalid. */
+            fValid = false;
+        }
+    }
+
+    /* Now, go though complete cache and check if it is valid. */
+    for (uint32_t i = 0; i < VBOX_DRMIPC_MONITORS_MAX; i++)
+    {
+        if (i == 0)
+        {
+            if (aVmMonitorsCache[i].fDisplayFlags & VMMDEV_DISPLAY_DISABLED)
+            {
+                VBClLogError("unable to validate screen layout: first monitor is not allowed to be disabled\n");
+                fValid = false;
+            }
+            else
+                cDisplaysOut++;
+        }
+        else
+        {
+            /* Check if there is no hole in between monitors (i.e., if current monitor is enabled, but previous one does not). */
+            if (   !(aVmMonitorsCache[i].fDisplayFlags & VMMDEV_DISPLAY_DISABLED)
+                && aVmMonitorsCache[i - 1].fDisplayFlags & VMMDEV_DISPLAY_DISABLED)
+            {
+                VBClLogError("unable to validate screen layout: there is a hole in displays layout config, "
+                                 "monitor (%u) is ENABLED while (%u) does not\n", i, i - 1);
+                fValid = false;
+            }
+            else
+            {
+                /* Always align screens since unaligned layout will result in disaster. */
+                aVmMonitorsCache[i].xOrigin = aVmMonitorsCache[i - 1].xOrigin + aVmMonitorsCache[i - 1].cx;
+                aVmMonitorsCache[i].yOrigin = aVmMonitorsCache[i - 1].yOrigin;
+
+                /* Only count enabled monitors. */
+                if (!(aVmMonitorsCache[i].fDisplayFlags & VMMDEV_DISPLAY_DISABLED))
+                    cDisplaysOut++;
+            }
+        }
+    }
+
+    /* Copy out layout data. */
+    if (fValid)
+    {
+        /* Start with invalid display ID. */
+        uint32_t u32PrimaryDisplay = VBOX_DRMIPC_MONITORS_MAX;
+
+        for (uint32_t i = 0; i < cDisplaysOut; i++)
+        {
+            aDisplaysOut[i].x = aVmMonitorsCache[i].xOrigin;
+            aDisplaysOut[i].y = aVmMonitorsCache[i].yOrigin;
+            aDisplaysOut[i].w = aVmMonitorsCache[i].cx;
+            aDisplaysOut[i].h = aVmMonitorsCache[i].cy;
+
+            if (aVmMonitorsCache[i].fDisplayFlags & VMMDEV_DISPLAY_PRIMARY)
+            {
+                /* Make sure display layout has only one primary display
+                 * set (for display 0, host side sets primary flag, so exclude it). */
+                Assert(u32PrimaryDisplay == 0 || u32PrimaryDisplay == VBOX_DRMIPC_MONITORS_MAX);
+                u32PrimaryDisplay = i;
+            }
+
+            VBClLogVerbose(1, "update monitor %u parameters: %dx%d, (%d, %d)\n",
+                           i, aDisplaysOut[i].w, aDisplaysOut[i].h, aDisplaysOut[i].x, aDisplaysOut[i].y);
+        }
+
+        *pu32PrimaryDisplay = u32PrimaryDisplay;
+        *pcActualDisplays = cDisplaysOut;
+    }
+
+    return (fValid && cDisplaysOut > 0) ? VINF_SUCCESS : VERR_INVALID_PARAMETER;
+}
+
+/**
+ * This function sends screen layout data to DRM stack.
+ *
+ * Helper function for vbDrmPushScreenLayout(). Should be called
+ * under g_monitorPositionsCritSect lock.
+ *
+ * @return  VINF_SUCCESS on success, IPRT error code otherwise.
+ * @param   hDevice     Handle to opened DRM device.
+ * @param   paRects     Array of screen configuration data.
+ * @param   cRects      Number of elements in screen configuration array.
+ */
+static int vbDrmSendHints(RTFILE hDevice, struct VBOX_DRMIPC_VMWRECT *paRects, uint32_t cRects)
+{
+    int rc = 0;
+    uid_t curuid;
+
+    /* Store real user id. */
+    curuid = getuid();
+
+    /* Change effective user id. */
+    if (setreuid(0, 0) == 0)
+    {
+        struct DRMVMWUPDATELAYOUT ioctlLayout;
+
+        RT_ZERO(ioctlLayout);
+        ioctlLayout.cOutputs = cRects;
+        ioctlLayout.ptrRects = (uint64_t)paRects;
+
+        rc = RTFileIoCtl(hDevice, DRM_IOCTL_VMW_UPDATE_LAYOUT,
+                         &ioctlLayout, sizeof(ioctlLayout), NULL);
+
+        if (setreuid(curuid, 0) != 0)
+        {
+            VBClLogError("reset of setreuid failed after drm ioctl");
+            rc = VERR_ACCESS_DENIED;
+        }
+    }
+    else
+    {
+        VBClLogError("setreuid failed during drm ioctl\n");
+        rc = VERR_ACCESS_DENIED;
+    }
+
+    return rc;
+}
+
+/**
+ * This function converts vmwgfx monitors layout data into an array of monitor offsets
+ * and sends it back to the host in order to ensure that host and guest have the same
+ * monitors layout representation.
+ *
+ * @return  IPRT status code.
+ * @param   cDisplays   Number of displays (elements in pDisplays).
+ * @param   pDisplays   Displays parameters as it was sent to vmwgfx driver.
+ */
+static int drmSendMonitorPositions(uint32_t cDisplays, struct VBOX_DRMIPC_VMWRECT *pDisplays)
+{
+    static RTPOINT aPositions[VBOX_DRMIPC_MONITORS_MAX];
+
+    if (!pDisplays || !cDisplays || cDisplays > VBOX_DRMIPC_MONITORS_MAX)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Prepare monitor offsets list to be sent to the host. */
+    for (uint32_t i = 0; i < cDisplays; i++)
+    {
+        aPositions[i].x = pDisplays[i].x;
+        aPositions[i].y = pDisplays[i].y;
+    }
+
+    return VbglR3SeamlessSendMonitorPositions(cDisplays, aPositions);
+}
+
+/**
+ * Validate and apply screen layout data.
+ *
+ * @return  IPRT status code.
+ * @param   aDisplaysIn     An array with screen layout data.
+ * @param   cDisplaysIn     Number of elements in aDisplaysIn.
+ * @param   fPartialLayout  Whether aDisplaysIn array contains complete display layout information or not.
+ *                          When layout is reported by Desktop Environment helper, aDisplaysIn does not have
+ *                          idDisplay, fDisplayFlags and cBitsPerPixel data (guest has no info about them).
+ * @param   fApply          Whether to apply provided display layout data to the DRM stack or send display offsets only.
+ */
+static int vbDrmPushScreenLayout(VMMDevDisplayDef *aDisplaysIn, uint32_t cDisplaysIn, bool fPartialLayout, bool fApply)
+{
+    int rc;
+
+    struct VBOX_DRMIPC_VMWRECT aDisplaysOut[VBOX_DRMIPC_MONITORS_MAX];
+    uint32_t cDisplaysOut = 0;
+
+    uint32_t u32PrimaryDisplay = VBOX_DRMIPC_MONITORS_MAX;
+
+    rc = RTCritSectEnter(&g_monitorPositionsCritSect);
+    if (RT_FAILURE(rc))
+    {
+        VBClLogError("unable to lock monitor data cache, rc=%Rrc\n", rc);
+        return rc;
+    }
+
+    static uint32_t u32PrimaryDisplayLast = VBOX_DRMIPC_MONITORS_MAX;
+
+    RT_ZERO(aDisplaysOut);
+
+    /* Validate displays layout and push it to DRM stack if valid. */
+    rc = vbDrmValidateLayout(aDisplaysIn, cDisplaysIn, aDisplaysOut, &u32PrimaryDisplay,
+                             sizeof(aDisplaysOut), &cDisplaysOut, fPartialLayout);
+    if (RT_SUCCESS(rc))
+    {
+        if (fApply)
+        {
+            rc = vbDrmSendHints(g_hDevice, aDisplaysOut, cDisplaysOut);
+            VBClLogInfo("push screen layout data of %u display(s) to DRM stack, fPartialLayout=%RTbool, rc=%Rrc\n",
+                        cDisplaysOut, fPartialLayout, rc);
+        }
+
+        /* In addition, notify host that configuration was successfully applied to the guest vmwgfx driver. */
+        if (RT_SUCCESS(rc))
+        {
+            rc = drmSendMonitorPositions(cDisplaysOut, aDisplaysOut);
+            if (RT_FAILURE(rc))
+                VBClLogError("cannot send host notification: %Rrc\n", rc);
+
+            /* If information about primary display is present in display layout, send it to DE over IPC. */
+            if (u32PrimaryDisplay != VBOX_DRMIPC_MONITORS_MAX
+                && u32PrimaryDisplayLast != u32PrimaryDisplay)
+            {
+                rc = vbDrmIpcBroadcastPrimaryDisplay(u32PrimaryDisplay);
+
+                /* Cache last value in order to avoid sending duplicate data over IPC. */
+                u32PrimaryDisplayLast = u32PrimaryDisplay;
+
+                VBClLogVerbose(2, "DE was notified that display %u is now primary, rc=%Rrc\n", u32PrimaryDisplay, rc);
+            }
+            else
+                VBClLogVerbose(2, "do not notify DE second time that display %u is now primary, rc=%Rrc\n", u32PrimaryDisplay, rc);
+        }
+    }
+    else if (rc == VERR_DUPLICATE)
+        VBClLogVerbose(2, "do not notify DRM stack about monitors layout change twice, rc=%Rrc\n", rc);
+    else
+        VBClLogError("displays layout is invalid, will not notify guest driver, rc=%Rrc\n", rc);
+
+    int rc2 = RTCritSectLeave(&g_monitorPositionsCritSect);
+    if (RT_FAILURE(rc2))
+        VBClLogError("unable to unlock monitor data cache, rc=%Rrc\n", rc);
+
+    return rc;
+}
+
+/** Worker thread for resize task. */
+static DECLCALLBACK(int) vbDrmResizeWorker(RTTHREAD ThreadSelf, void *pvUser)
+{
+    int rc = VERR_GENERAL_FAILURE;
+
+    RT_NOREF(ThreadSelf);
+    RT_NOREF(pvUser);
+
+    for (;;)
+    {
+        /* Do not acknowledge the first event we query for to pick up old events,
+         * e.g. from before a guest reboot. */
+        bool fAck = false;
+
+        uint32_t events;
+
+        VMMDevDisplayDef aDisplaysIn[VBOX_DRMIPC_MONITORS_MAX];
+        uint32_t cDisplaysIn = 0;
+
+        RT_ZERO(aDisplaysIn);
+
+        /* Query the first size without waiting.  This lets us e.g. pick up
+         * the last event before a guest reboot when we start again after. */
+        rc = VbglR3GetDisplayChangeRequestMulti(VBOX_DRMIPC_MONITORS_MAX, &cDisplaysIn, aDisplaysIn, fAck);
+        fAck = true;
+        if (RT_SUCCESS(rc))
+        {
+            rc = vbDrmPushScreenLayout(aDisplaysIn, cDisplaysIn, false, true);
+            if (RT_FAILURE(rc))
+                VBClLogError("Failed to push display change as requested by host, rc=%Rrc\n", rc);
+        }
+        else
+            VBClLogError("Failed to get display change request, rc=%Rrc\n", rc);
+
+        do
+        {
+            rc = VbglR3WaitEvent(VMMDEV_EVENT_DISPLAY_CHANGE_REQUEST, VBOX_DRMIPC_RX_TIMEOUT_MS, &events);
+        } while ((rc == VERR_TIMEOUT || rc == VERR_INTERRUPTED) && !ASMAtomicReadBool(&g_fShutdown));
+
+        if (ASMAtomicReadBool(&g_fShutdown))
+        {
+            VBClLogInfo("exiting resize thread: shutdown requested\n");
+            /* This is a case when we should return positive status. */
+            rc = (rc == VERR_TIMEOUT) ? VINF_SUCCESS : rc;
+            break;
+        }
+        else if (RT_FAILURE(rc))
+            VBClLogFatalError("VBoxDRMClient: resize thread: failure waiting for event, rc=%Rrc\n", rc);
+    }
+
+    return rc;
+}
+
+/**
+ * Go over all existing IPC client connection and put set-primary-screen request
+ * data into TX queue of each of them .
+ *
+ * @return  IPRT status code.
+ * @param   u32PrimaryDisplay   Primary display ID.
+ */
+static int vbDrmIpcBroadcastPrimaryDisplay(uint32_t u32PrimaryDisplay)
+{
+    int rc;
+
+    rc = RTCritSectEnter(&g_ipcClientConnectionsListCritSect);
+    if (RT_SUCCESS(rc))
+    {
+        if (!RTListIsEmpty(&g_ipcClientConnectionsList.Node))
+        {
+            PVBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE pEntry;
+            RTListForEach(&g_ipcClientConnectionsList.Node, pEntry, VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE, Node)
+            {
+                AssertReturn(pEntry, VERR_INVALID_PARAMETER);
+                AssertReturn(pEntry->pClient, VERR_INVALID_PARAMETER);
+                AssertReturn(pEntry->pClient->hThread, VERR_INVALID_PARAMETER);
+
+                rc = vbDrmIpcSetPrimaryDisplay(pEntry->pClient, u32PrimaryDisplay);
+
+                VBClLogInfo("thread %s notified IPC Client that display %u is now primary, rc=%Rrc\n",
+                                RTThreadGetName(pEntry->pClient->hThread), u32PrimaryDisplay, rc);
+            }
+        }
+
+        int rc2 = RTCritSectLeave(&g_ipcClientConnectionsListCritSect);
+        if (RT_FAILURE(rc2))
+            VBClLogError("notify DE: unable to leave critical section, rc=%Rrc\n", rc2);
+    }
+    else
+        VBClLogError("notify DE: unable to enter critical section, rc=%Rrc\n", rc);
+
+    return rc;
+}
+
+/**
+ * Main loop for IPC client connection handling.
+ *
+ * @return  IPRT status code.
+ * @param   pClient     Pointer to IPC client data.
+ */
+static int vbDrmIpcConnectionProc(PVBOX_DRMIPC_CLIENT pClient)
+{
+    int rc = VERR_GENERAL_FAILURE;
+
+    AssertReturn(pClient, VERR_INVALID_PARAMETER);
+
+    /* This loop handles incoming messages. */
+    for (;;)
+    {
+        rc = vbDrmIpcConnectionHandler(pClient);
+
+        /* Try to detect if we should shutdown as early as we can. */
+        if (ASMAtomicReadBool(&g_fShutdown))
+            break;
+
+        /* Normal case. No data received within short interval. */
+        if (rc == VERR_TIMEOUT)
+        {
+            continue;
+        }
+        else if (RT_FAILURE(rc))
+        {
+            /* Terminate connection handling in case of error. */
+            VBClLogError("unable to handle IPC session, rc=%Rrc\n", rc);
+            break;
+        }
+    }
+
+    return rc;
+}
+
+/**
+ * Add IPC client connection data into list of connections.
+ *
+ * List size is limited indirectly by DRM_IPC_SERVER_CONNECTIONS_MAX value.
+ * This function should only be invoked from client thread context
+ * (from vbDrmIpcClientWorker() in particular).
+ *
+ * @return  IPRT status code.
+ * @param   pClientNode     Client connection information to add to the list.
+ */
+static int vbDrmIpcClientsListAdd(PVBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE pClientNode)
+{
+    int rc;
+
+    AssertReturn(pClientNode, VERR_INVALID_PARAMETER);
+
+    rc = RTCritSectEnter(&g_ipcClientConnectionsListCritSect);
+    if (RT_SUCCESS(rc))
+    {
+        RTListAppend(&g_ipcClientConnectionsList.Node, &pClientNode->Node);
+
+        int rc2 = RTCritSectLeave(&g_ipcClientConnectionsListCritSect);
+        if (RT_FAILURE(rc2))
+            VBClLogError("add client connection: unable to leave critical section, rc=%Rrc\n", rc2);
+    }
+    else
+        VBClLogError("add client connection: unable to enter critical section, rc=%Rrc\n", rc);
+
+    return rc;
+}
+
+/**
+ * Remove IPC client connection data from list of connections.
+ *
+ * This function should only be invoked from client thread context
+ * (from vbDrmIpcClientWorker() in particular).
+ *
+ * @return  IPRT status code.
+ * @param   pClientNode     Client connection information to remove from the list.
+ */
+static int vbDrmIpcClientsListRemove(PVBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE pClientNode)
+{
+    int rc;
+    PVBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE pEntry, pNextEntry, pFound = NULL;
+
+    AssertReturn(pClientNode, VERR_INVALID_PARAMETER);
+
+    rc = RTCritSectEnter(&g_ipcClientConnectionsListCritSect);
+    if (RT_SUCCESS(rc))
+    {
+
+        if (!RTListIsEmpty(&g_ipcClientConnectionsList.Node))
+        {
+            RTListForEachSafe(&g_ipcClientConnectionsList.Node, pEntry, pNextEntry, VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE, Node)
+            {
+                if (pEntry == pClientNode)
+                    pFound = (PVBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE)RTListNodeRemoveRet(&pEntry->Node);
+            }
+        }
+        else
+            VBClLogError("remove client connection: connections list empty, node %p not there\n", pClientNode);
+
+        int rc2 = RTCritSectLeave(&g_ipcClientConnectionsListCritSect);
+        if (RT_FAILURE(rc2))
+            VBClLogError("remove client connection: unable to leave critical section, rc=%Rrc\n", rc2);
+    }
+    else
+        VBClLogError("remove client connection: unable to enter critical section, rc=%Rrc\n", rc);
+
+    if (!pFound)
+        VBClLogError("remove client connection: node not found\n");
+
+    return !rc && pFound ? VINF_SUCCESS : VERR_INVALID_PARAMETER;
+}
+
+/**
+ * Convert VBOX_DRMIPC_VMWRECT into VMMDevDisplayDef and check layout correctness.
+ *
+ * VBOX_DRMIPC_VMWRECT does not represent enough information needed for
+ * VMMDevDisplayDef. Missing fields (fDisplayFlags, idDisplay, cBitsPerPixel)
+ * are initialized with default (invalid) values due to this.
+ *
+ * @return  True if given screen layout is correct (i.e., has no displays which overlap), False
+ *          if it needs to be adjusted before injecting into DRM stack.
+ * @param   cDisplays Number of displays in configuration data.
+ * @param   pIn       A pointer to display configuration data array in form of VBOX_DRMIPC_VMWRECT (input).
+ * @param   pOut      A pointer to display configuration data array in form of VMMDevDisplayDef (output).
+ */
+static bool vbDrmVmwRectToDisplayDef(uint32_t cDisplays, struct VBOX_DRMIPC_VMWRECT *pIn, VMMDevDisplayDef *pOut)
+{
+    bool fCorrect = true;
+
+    for (uint32_t i = 0; i < cDisplays; i++)
+    {
+        /* VBOX_DRMIPC_VMWRECT has no information about this fields. */
+        pOut[i].fDisplayFlags = 0;
+        pOut[i].idDisplay = VBOX_DRMIPC_MONITORS_MAX;
+        pOut[i].cBitsPerPixel = 0;
+
+        pOut[i].xOrigin = pIn[i].x;
+        pOut[i].yOrigin = pIn[i].y;
+        pOut[i].cx = pIn[i].w;
+        pOut[i].cy = pIn[i].h;
+
+        /* Make sure that displays do not overlap within reported screen layout. Ask IPC server to fix layout otherwise. */
+        fCorrect =    i > 0
+                  && pIn[i].x != (int32_t)pIn[i - 1].w + pIn[i - 1].x
+                  ?  false
+                  :  fCorrect;
+    }
+
+    return fCorrect;
+}
+
+/**
+ * @interface_method_impl{VBOX_DRMIPC_CLIENT,pfnRxCb}
+ */
+static DECLCALLBACK(int) vbDrmIpcClientRxCallBack(uint8_t idCmd, void *pvData, uint32_t cbData)
+{
+    int rc = VERR_INVALID_PARAMETER;
+
+    AssertReturn(pvData, VERR_INVALID_PARAMETER);
+    AssertReturn(cbData, VERR_INVALID_PARAMETER);
+
+    switch (idCmd)
+    {
+        case VBOXDRMIPCSRVCMD_REPORT_DISPLAY_OFFSETS:
+        {
+            VMMDevDisplayDef aDisplays[VBOX_DRMIPC_MONITORS_MAX];
+            bool fCorrect;
+
+            PVBOX_DRMIPC_COMMAND_REPORT_DISPLAY_OFFSETS pCmd = (PVBOX_DRMIPC_COMMAND_REPORT_DISPLAY_OFFSETS)pvData;
+            AssertReturn(cbData == sizeof(VBOX_DRMIPC_COMMAND_REPORT_DISPLAY_OFFSETS), VERR_INVALID_PARAMETER);
+            AssertReturn(pCmd->cDisplays < VBOX_DRMIPC_MONITORS_MAX, VERR_INVALID_PARAMETER);
+
+            /* Convert input display config into VMMDevDisplayDef representation. */
+            RT_ZERO(aDisplays);
+            fCorrect = vbDrmVmwRectToDisplayDef(pCmd->cDisplays, pCmd->aDisplays, aDisplays);
+
+            rc = vbDrmPushScreenLayout(aDisplays, pCmd->cDisplays, true, !fCorrect);
+            if (RT_FAILURE(rc))
+                VBClLogError("Failed to push display change as requested by Desktop Environment helper, rc=%Rrc\n", rc);
+
+            break;
+        }
+
+        default:
+        {
+            VBClLogError("received unknown IPC command 0x%x\n", idCmd);
+            break;
+        }
+    }
+
+    return rc;
+}
+
+/** Worker thread for IPC client task. */
+static DECLCALLBACK(int) vbDrmIpcClientWorker(RTTHREAD ThreadSelf, void *pvUser)
+{
+    VBOX_DRMIPC_CLIENT  hClient  = VBOX_DRMIPC_CLIENT_INITIALIZER;
+    RTLOCALIPCSESSION   hSession = (RTLOCALIPCSESSION)pvUser;
+    int                 rc;
+
+    AssertReturn(RT_VALID_PTR(hSession), VERR_INVALID_PARAMETER);
+
+    /* Initialize client session resources. */
+    rc = vbDrmIpcClientInit(&hClient, ThreadSelf, hSession, VBOX_DRMIPC_TX_QUEUE_SIZE, vbDrmIpcClientRxCallBack);
+    if (RT_SUCCESS(rc))
+    {
+        /* Add IPC client connection data into clients list. */
+        VBOX_DRMIPC_CLIENT_CONNECTION_LIST_NODE hClientNode = { { 0, 0 } , &hClient };
+
+        rc = vbDrmIpcClientsListAdd(&hClientNode);
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTThreadUserSignal(ThreadSelf);
+            if (RT_SUCCESS(rc))
+            {
+                /* Start spinning the connection. */
+                VBClLogInfo("IPC client connection started\n", rc);
+                rc = vbDrmIpcConnectionProc(&hClient);
+                VBClLogInfo("IPC client connection ended, rc=%Rrc\n", rc);
+            }
+            else
+                VBClLogError("unable to report IPC client connection handler start, rc=%Rrc\n", rc);
+
+            /* Remove IPC client connection data from clients list. */
+            rc = vbDrmIpcClientsListRemove(&hClientNode);
+            if (RT_FAILURE(rc))
+                VBClLogError("unable to remove IPC client session from list of connections, rc=%Rrc\n", rc);
+        }
+        else
+            VBClLogError("unable to add IPC client connection to the list, rc=%Rrc\n");
+
+        /* Disconnect remote peer if still connected. */
+        if (RT_VALID_PTR(hSession))
+        {
+            rc = RTLocalIpcSessionClose(hSession);
+            VBClLogInfo("IPC session closed, rc=%Rrc\n", rc);
+        }
+
+        /* Connection handler loop has ended, release session resources. */
+        rc = vbDrmIpcClientReleaseResources(&hClient);
+        if (RT_FAILURE(rc))
+            VBClLogError("unable to release IPC client session, rc=%Rrc\n", rc);
+
+        ASMAtomicDecU32(&g_cDrmIpcConnections);
+    }
+    else
+        VBClLogError("unable to initialize IPC client session, rc=%Rrc\n", rc);
+
+    VBClLogInfo("closing IPC client session, rc=%Rrc\n", rc);
+
+    return rc;
+}
+
+/**
+ * Start processing thread for IPC client requests handling.
+ *
+ * @returns IPRT status code.
+ * @param   hSession    IPC client connection handle.
+ */
+static int vbDrmIpcClientStart(RTLOCALIPCSESSION hSession)
+{
+    int         rc;
+    RTTHREAD    hThread = 0;
+    RTPROCESS   hProcess = 0;
+
+    rc = RTLocalIpcSessionQueryProcess(hSession, &hProcess);
+    if (RT_SUCCESS(rc))
+    {
+        char pszThreadName[DRM_IPC_THREAD_NAME_MAX];
+        RT_ZERO(pszThreadName);
+
+        RTStrPrintf2(pszThreadName, DRM_IPC_THREAD_NAME_MAX, DRM_IPC_CLIENT_THREAD_NAME_PTR, hProcess);
+
+        /* Attempt to start IPC client connection handler task. */
+        rc = RTThreadCreate(&hThread, vbDrmIpcClientWorker, (void *)hSession, 0,
+                            RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, pszThreadName);
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTThreadUserWait(hThread, RT_MS_5SEC);
+        }
+    }
+
+    return rc;
+}
+
+/** Worker thread for IPC server task. */
+static DECLCALLBACK(int) vbDrmIpcServerWorker(RTTHREAD ThreadSelf, void *pvUser)
+{
+    int rc = VERR_GENERAL_FAILURE;
+    RTLOCALIPCSERVER hIpcServer = (RTLOCALIPCSERVER)pvUser;
+
+    RT_NOREF1(ThreadSelf);
+
+    AssertReturn(hIpcServer, VERR_INVALID_PARAMETER);
+
+    /* This loop accepts incoming connections. */
+    for (;;)
+    {
+        RTLOCALIPCSESSION hClientSession;
+
+        /* Wait for incoming connection. */
+        rc = RTLocalIpcServerListen(hIpcServer, &hClientSession);
+        if (RT_SUCCESS(rc))
+        {
+            VBClLogVerbose(2, "new IPC session\n");
+
+            if (ASMAtomicIncU32(&g_cDrmIpcConnections) <= DRM_IPC_SERVER_CONNECTIONS_MAX)
+            {
+                /* Authenticate remote peer. */
+                if (ASMAtomicReadBool(&g_fDrmIpcRestricted))
+                    rc = vbDrmIpcAuth(hClientSession);
+
+                if (RT_SUCCESS(rc))
+                {
+                    /* Start incoming connection handler thread. */
+                    rc = vbDrmIpcClientStart(hClientSession);
+                    VBClLogVerbose(2, "connection processing ended, rc=%Rrc\n", rc);
+                }
+                else
+                    VBClLogError("IPC authentication failed, rc=%Rrc\n", rc);
+            }
+            else
+                rc = VERR_RESOURCE_BUSY;
+
+            /* Release resources in case of error. */
+            if (RT_FAILURE(rc))
+            {
+                VBClLogError("maximum amount of IPC client connections reached, dropping connection\n");
+
+                int rc2 = RTLocalIpcSessionClose(hClientSession);
+                if (RT_FAILURE(rc2))
+                    VBClLogError("unable to close IPC session, rc=%Rrc\n", rc2);
+
+                ASMAtomicDecU32(&g_cDrmIpcConnections);
+            }
+        }
+        else
+            VBClLogError("IPC authentication failed, rc=%Rrc\n", rc);
+
+        /* Check shutdown was requested. */
+        if (ASMAtomicReadBool(&g_fShutdown))
+        {
+            VBClLogInfo("exiting IPC thread: shutdown requested\n");
+            break;
+        }
+
+        /* Wait a bit before spinning a loop if something went wrong. */
+        if (RT_FAILURE(rc))
+            RTThreadSleep(VBOX_DRMIPC_RX_RELAX_MS);
+    }
+
+    return rc;
+}
+
+/** A signal handler. */
+static void vbDrmRequestShutdown(int sig)
+{
+    RT_NOREF(sig);
+    ASMAtomicWriteBool(&g_fShutdown, true);
+}
+
+/**
+ * Grant access to DRM IPC server socket depending on VM configuration.
+ *
+ * If VM has '/VirtualBox/GuestAdd/DRMIpcRestricted' guest property set
+ * and this property is READ-ONLY for the guest side, access will be
+ * granted to root and users from 'vboxdrmipc' group only. If group does
+ * not exists, only root will have access to the socket.  When property is
+ * not set or not READ-ONLY, all users will have access to the socket.
+ *
+ * @param   hIpcServer  IPC server handle.
+ * @param   fRestrict   Whether to restrict access to socket or not.
+ */
+static void vbDrmSetIpcServerAccessPermissions(RTLOCALIPCSERVER hIpcServer, bool fRestrict)
+{
+    int rc;
+
+    if (fRestrict)
+    {
+        struct group *pGrp;
+        pGrp = getgrnam(VBOX_DRMIPC_USER_GROUP);
+        if (pGrp)
+        {
+            rc = RTLocalIpcServerGrantGroupAccess(hIpcServer, pGrp->gr_gid);
+            if (RT_SUCCESS(rc))
+                VBClLogInfo("IPC server socket access granted to '" VBOX_DRMIPC_USER_GROUP "' users\n");
+            else
+                VBClLogError("unable to grant IPC server socket access to '" VBOX_DRMIPC_USER_GROUP "' users, rc=%Rrc\n", rc);
+
+        }
+        else
+            VBClLogError("unable to grant IPC server socket access to '" VBOX_DRMIPC_USER_GROUP "', group does not exist\n");
+    }
+    else
+    {
+        rc = RTLocalIpcServerSetAccessMode(hIpcServer,
+                                           RTFS_UNIX_IRUSR | RTFS_UNIX_IWUSR |
+                                           RTFS_UNIX_IRGRP | RTFS_UNIX_IWGRP |
+                                           RTFS_UNIX_IROTH | RTFS_UNIX_IWOTH);
+        if (RT_SUCCESS(rc))
+            VBClLogInfo("IPC server socket access granted to all users\n");
+        else
+            VBClLogError("unable to grant IPC server socket access to all users, rc=%Rrc\n", rc);
+    }
+
+    /* Set flag for the thread which serves incomming IPC connections. */
+    ASMAtomicWriteBool(&g_fDrmIpcRestricted, fRestrict);
+}
+
+/**
+ * Wait and handle '/VirtualBox/GuestAdd/DRMIpcRestricted' guest property change.
+ *
+ * This function is executed in context of main().
+ *
+ * @param   hIpcServer  IPC server handle.
+ */
+static void vbDrmPollIpcServerAccessMode(RTLOCALIPCSERVER hIpcServer)
+{
+    HGCMCLIENTID idClient;
+    int rc;
+
+    rc = VbglR3GuestPropConnect(&idClient);
+    if (RT_SUCCESS(rc))
+    {
+        do
+        {
+            /* Buffer should be big enough to fit guest property data layout: Name\0Value\0Flags\0fWasDeleted\0. */
+            static char achBuf[GUEST_PROP_MAX_NAME_LEN];
+            char *pszName = NULL;
+            char *pszValue = NULL;
+            char *pszFlags = NULL;
+            bool fWasDeleted = false;
+            uint64_t u64Timestamp = 0;
+
+            rc = VbglR3GuestPropWait(idClient, VBGLR3DRMPROPPTR, achBuf, sizeof(achBuf), u64Timestamp,
+                                     VBOX_DRMIPC_RX_TIMEOUT_MS, &pszName, &pszValue, &u64Timestamp,
+                                     &pszFlags, NULL, &fWasDeleted);
+            if (RT_SUCCESS(rc))
+            {
+                uint32_t fFlags = 0;
+
+                VBClLogVerbose(1, "guest property change: name: %s, val: %s, flags: %s, fWasDeleted: %RTbool\n",
+                               pszName, pszValue, pszFlags, fWasDeleted);
+
+                if (RT_SUCCESS(GuestPropValidateFlags(pszFlags, &fFlags)))
+                {
+                    if (RTStrNCmp(pszName, VBGLR3DRMIPCPROPRESTRICT, GUEST_PROP_MAX_NAME_LEN) == 0)
+                    {
+                        /* Enforce restricted socket access until guest property exist and READ-ONLY for the guest. */
+                        vbDrmSetIpcServerAccessPermissions(hIpcServer, !fWasDeleted && fFlags & GUEST_PROP_F_RDONLYGUEST);
+                    }
+
+                } else
+                    VBClLogError("guest property change: name: %s, val: %s, flags: %s, fWasDeleted: %RTbool: bad flags\n",
+                                 pszName, pszValue, pszFlags, fWasDeleted);
+
+            } else if (   rc != VERR_TIMEOUT
+                     && rc != VERR_INTERRUPTED)
+            {
+                VBClLogError("error on waiting guest property notification, rc=%Rrc\n", rc);
+                RTThreadSleep(VBOX_DRMIPC_RX_RELAX_MS);
+            }
+
+        } while (!ASMAtomicReadBool(&g_fShutdown));
+
+        VbglR3GuestPropDisconnect(idClient);
+    }
+    else
+        VBClLogError("cannot connect to VM guest properties service, rc=%Rrc\n", rc);
+}
+
+int main(int argc, char *argv[])
+{
+    /** Custom log prefix to be used for logger instance of this process. */
+    static const char *pszLogPrefix = "VBoxDRMClient:";
+
+    static const RTGETOPTDEF s_aOptions[] = { { "--verbose", 'v', RTGETOPT_REQ_NOTHING }, };
+    RTGETOPTUNION ValueUnion;
+    RTGETOPTSTATE GetState;
+    int ch;
+
+    RTFILE hPidFile;
+
+    RTLOCALIPCSERVER hIpcServer;
+    RTTHREAD vbDrmIpcThread;
+    int rcDrmIpcThread = 0;
+
+    RTTHREAD drmResizeThread;
+    int rcDrmResizeThread = 0;
+    int rc, rc2 = 0;
+
+    rc = RTR3InitExe(argc, &argv, 0);
+    if (RT_FAILURE(rc))
+        return RTMsgInitFailure(rc);
+
+    rc = VbglR3InitUser();
+    if (RT_FAILURE(rc))
+        VBClLogFatalError("VBoxDRMClient: VbglR3InitUser failed: %Rrc", rc);
+
+    /* Process command line options. */
+    rc = RTGetOptInit(&GetState, argc, argv, s_aOptions, RT_ELEMENTS(s_aOptions), 0, 0 /* fFlags */);
+    if (RT_FAILURE(rc))
+        VBClLogFatalError("VBoxDRMClient: unable to process command line options, rc=%Rrc\n", rc);
+    while ((ch = RTGetOpt(&GetState, &ValueUnion)) != 0)
+    {
+        switch (ch)
+        {
+            case 'v':
+            {
+                g_cVerbosity++;
+                break;
+            }
+
+            case VERR_GETOPT_UNKNOWN_OPTION:
+            {
+                VBClLogFatalError("unknown command line option '%s'\n", ValueUnion.psz);
+                return RTEXITCODE_SYNTAX;
+
+            }
+
+            default:
+                break;
+        }
+    }
+
+    rc = VBClLogCreate("");
+    if (RT_FAILURE(rc))
+        VBClLogFatalError("VBoxDRMClient: failed to setup logging, rc=%Rrc\n", rc);
+    VBClLogSetLogPrefix(pszLogPrefix);
+
+    /* Check PID file before attempting to initialize anything. */
+    rc = VbglR3PidFile(g_pszPidFile, &hPidFile);
+    if (rc == VERR_FILE_LOCK_VIOLATION)
+    {
+        VBClLogInfo("already running, exiting\n");
+        return RTEXITCODE_SUCCESS;
+    }
+    if (RT_FAILURE(rc))
+    {
+        VBClLogError("unable to lock PID file (%Rrc), exiting\n", rc);
+        return RTEXITCODE_FAILURE;
+    }
+
+    g_hDevice = vbDrmOpenVmwgfx();
+    if (g_hDevice == NIL_RTFILE)
+        return RTEXITCODE_FAILURE;
+
+    rc = VbglR3CtlFilterMask(VMMDEV_EVENT_DISPLAY_CHANGE_REQUEST, 0);
+    if (RT_FAILURE(rc))
+    {
+        VBClLogFatalError("Failed to request display change events, rc=%Rrc\n", rc);
+        return RTEXITCODE_FAILURE;
+    }
+    rc = VbglR3AcquireGuestCaps(VMMDEV_GUEST_SUPPORTS_GRAPHICS, 0, false);
+    if (RT_FAILURE(rc))
+    {
+        VBClLogFatalError("Failed to register resizing support, rc=%Rrc\n", rc);
+        return RTEXITCODE_FAILURE;
+    }
+
+    /* Setup signals: gracefully terminate on SIGINT, SIGTERM. */
+    if (   signal(SIGINT, vbDrmRequestShutdown) == SIG_ERR
+        || signal(SIGTERM, vbDrmRequestShutdown) == SIG_ERR)
+    {
+        VBClLogError("unable to setup signals\n");
+        return RTEXITCODE_FAILURE;
+    }
+
+    /* Init IPC client connection list. */
+    RTListInit(&g_ipcClientConnectionsList.Node);
+    rc = RTCritSectInit(&g_ipcClientConnectionsListCritSect);
+    if (RT_FAILURE(rc))
+    {
+        VBClLogError("unable to initialize IPC client connection list critical section\n");
+        return RTEXITCODE_FAILURE;
+    }
+
+    /* Init critical section which is used for reporting monitors offset back to host. */
+    rc = RTCritSectInit(&g_monitorPositionsCritSect);
+    if (RT_FAILURE(rc))
+    {
+        VBClLogError("unable to initialize monitors position critical section\n");
+        return RTEXITCODE_FAILURE;
+    }
+
+    /* Instantiate IPC server for VBoxClient service communication. */
+    rc = RTLocalIpcServerCreate(&hIpcServer, VBOX_DRMIPC_SERVER_NAME, 0);
+    if (RT_FAILURE(rc))
+    {
+        VBClLogError("unable to setup IPC server, rc=%Rrc\n", rc);
+        return RTEXITCODE_FAILURE;
+    }
+
+    /* Set IPC server socket access permissions according to VM configuration. */
+    vbDrmSetIpcServerAccessPermissions(hIpcServer, VbglR3DrmRestrictedIpcAccessIsNeeded());
+
+    /* Attempt to start DRM resize task. */
+    rc = RTThreadCreate(&drmResizeThread, vbDrmResizeWorker, NULL, 0,
+                        RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, DRM_RESIZE_THREAD_NAME);
+    if (RT_SUCCESS(rc))
+    {
+        /* Attempt to start IPC task. */
+        rc = RTThreadCreate(&vbDrmIpcThread, vbDrmIpcServerWorker, (void *)hIpcServer, 0,
+                            RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, DRM_IPC_SERVER_THREAD_NAME);
+        if (RT_SUCCESS(rc))
+        {
+            /* Poll for host notification about IPC server socket access mode change. */
+            vbDrmPollIpcServerAccessMode(hIpcServer);
+
+            /* HACK ALERT!
+             * The sequence of RTThreadWait(drmResizeThread) -> RTLocalIpcServerDestroy() -> RTThreadWait(vbDrmIpcThread)
+             * is intentional! Once process received a signal, it will pull g_fShutdown flag, which in turn will cause
+             * drmResizeThread to quit. The vbDrmIpcThread might hang on accept() call, so we terminate IPC server to
+             * release it and then wait for its termination. */
+
+            rc = RTThreadWait(drmResizeThread, RT_INDEFINITE_WAIT, &rcDrmResizeThread);
+            VBClLogInfo("%s thread exited with status, rc=%Rrc\n", DRM_RESIZE_THREAD_NAME, rcDrmResizeThread);
+
+            rc = RTLocalIpcServerCancel(hIpcServer);
+            if (RT_FAILURE(rc))
+                VBClLogError("unable to notify IPC server about shutdown, rc=%Rrc\n", rc);
+
+            /* Wait for threads to terminate gracefully. */
+            rc = RTThreadWait(vbDrmIpcThread, RT_INDEFINITE_WAIT, &rcDrmIpcThread);
+            VBClLogInfo("%s thread exited with status, rc=%Rrc\n", DRM_IPC_SERVER_THREAD_NAME, rcDrmResizeThread);
+
+        }
+        else
+            VBClLogError("unable to start IPC thread, rc=%Rrc\n", rc);
+    }
+    else
+        VBClLogError("unable to start resize thread, rc=%Rrc\n", rc);
+
+    rc = RTLocalIpcServerDestroy(hIpcServer);
+    if (RT_FAILURE(rc))
+        VBClLogError("unable to stop IPC server,  rc=%Rrc\n", rc);
+
+    rc2 = RTCritSectDelete(&g_monitorPositionsCritSect);
+    if (RT_FAILURE(rc2))
+        VBClLogError("unable to destroy g_monitorPositionsCritSect critsect, rc=%Rrc\n", rc2);
+
+    rc2 = RTCritSectDelete(&g_ipcClientConnectionsListCritSect);
+    if (RT_FAILURE(rc2))
+        VBClLogError("unable to destroy g_ipcClientConnectionsListCritSect critsect, rc=%Rrc\n", rc2);
+
+    RTFileClose(g_hDevice);
+
+    VBClLogInfo("releasing PID file lock\n");
+    VbglR3ClosePidFile(g_pszPidFile, hPidFile);
+
+    VBClLogDestroy();
+
+    return rc == 0 ? RTEXITCODE_SUCCESS : RTEXITCODE_FAILURE;
+}