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, 2886 insertions, 0 deletions

diff --git a/src/VBox/Additions/common/VBoxService/VBoxServiceControlSession.cpp b/src/VBox/Additions/common/VBoxService/VBoxServiceControlSession.cpp
new file mode 100644
index 00000000..001d468d
--- /dev/null
+++ b/src/VBox/Additions/common/VBoxService/VBoxServiceControlSession.cpp
@@ -0,0 +1,2886 @@
+/* $Id: VBoxServiceControlSession.cpp $ */
+/** @file
+ * VBoxServiceControlSession - Guest session handling. Also handles the spawned session processes.
+ */
+
+/*
+ * Copyright (C) 2013-2023 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
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+#include <iprt/dir.h>
+#include <iprt/env.h>
+#include <iprt/file.h>
+#include <iprt/getopt.h>
+#include <iprt/handle.h>
+#include <iprt/mem.h>
+#include <iprt/message.h>
+#include <iprt/path.h>
+#include <iprt/pipe.h>
+#include <iprt/poll.h>
+#include <iprt/process.h>
+#include <iprt/rand.h>
+#include <iprt/system.h> /* For RTShutdown. */
+
+#include "VBoxServiceInternal.h"
+#include "VBoxServiceUtils.h"
+#include "VBoxServiceControl.h"
+
+using namespace guestControl;
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+/** Generic option indices for session spawn arguments. */
+enum
+{
+    VBOXSERVICESESSIONOPT_FIRST = 1000, /* For initialization. */
+    VBOXSERVICESESSIONOPT_DOMAIN,
+#ifdef DEBUG
+    VBOXSERVICESESSIONOPT_DUMP_STDOUT,
+    VBOXSERVICESESSIONOPT_DUMP_STDERR,
+#endif
+    VBOXSERVICESESSIONOPT_LOG_FILE,
+    VBOXSERVICESESSIONOPT_USERNAME,
+    VBOXSERVICESESSIONOPT_SESSION_ID,
+    VBOXSERVICESESSIONOPT_SESSION_PROTO,
+    VBOXSERVICESESSIONOPT_THREAD_ID
+};
+
+
+static int vgsvcGstCtrlSessionCleanupProcesses(const PVBOXSERVICECTRLSESSION pSession);
+static int vgsvcGstCtrlSessionProcessRemoveInternal(PVBOXSERVICECTRLSESSION pSession, PVBOXSERVICECTRLPROCESS pProcess);
+
+
+/**
+ * Helper that grows the scratch buffer.
+ * @returns Success indicator.
+ */
+static bool vgsvcGstCtrlSessionGrowScratchBuf(void **ppvScratchBuf, uint32_t *pcbScratchBuf, uint32_t cbMinBuf)
+{
+    uint32_t cbNew = *pcbScratchBuf * 2;
+    if (   cbNew    <= VMMDEV_MAX_HGCM_DATA_SIZE
+        && cbMinBuf <= VMMDEV_MAX_HGCM_DATA_SIZE)
+    {
+        while (cbMinBuf > cbNew)
+            cbNew *= 2;
+        void *pvNew = RTMemRealloc(*ppvScratchBuf, cbNew);
+        if (pvNew)
+        {
+            *ppvScratchBuf = pvNew;
+            *pcbScratchBuf = cbNew;
+            return true;
+        }
+    }
+    return false;
+}
+
+
+
+static int vgsvcGstCtrlSessionFileFree(PVBOXSERVICECTRLFILE pFile)
+{
+    AssertPtrReturn(pFile, VERR_INVALID_POINTER);
+
+    int rc = RTFileClose(pFile->hFile);
+    if (RT_SUCCESS(rc))
+    {
+        RTStrFree(pFile->pszName);
+
+        /* Remove file entry in any case. */
+        RTListNodeRemove(&pFile->Node);
+        /* Destroy this object. */
+        RTMemFree(pFile);
+    }
+
+    return rc;
+}
+
+
+/** @todo No locking done yet! */
+static PVBOXSERVICECTRLFILE vgsvcGstCtrlSessionFileGetLocked(const PVBOXSERVICECTRLSESSION pSession, uint32_t uHandle)
+{
+    AssertPtrReturn(pSession, NULL);
+
+    /** @todo Use a map later! */
+    PVBOXSERVICECTRLFILE pFileCur;
+    RTListForEach(&pSession->lstFiles, pFileCur, VBOXSERVICECTRLFILE, Node)
+    {
+        if (pFileCur->uHandle == uHandle)
+            return pFileCur;
+    }
+
+    return NULL;
+}
+
+
+/**
+ * Recursion worker for vgsvcGstCtrlSessionHandleDirRemove.
+ * Only (recursively) removes directory structures which are not empty. Will fail if not empty.
+ *
+ * @returns IPRT status code.
+ * @param   pszDir              The directory buffer, RTPATH_MAX in length.
+ *                              Contains the abs path to the directory to
+ *                              recurse into. Trailing slash.
+ * @param   cchDir              The length of the directory we're recursing into,
+ *                              including the trailing slash.
+ * @param   pDirEntry           The dir entry buffer.  (Shared to save stack.)
+ */
+static int vgsvcGstCtrlSessionHandleDirRemoveSub(char *pszDir, size_t cchDir, PRTDIRENTRY pDirEntry)
+{
+    RTDIR hDir;
+    int rc = RTDirOpen(&hDir, pszDir);
+    if (RT_FAILURE(rc))
+    {
+        /* Ignore non-existing directories like RTDirRemoveRecursive does: */
+        if (rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND)
+            return VINF_SUCCESS;
+        return rc;
+    }
+
+    for (;;)
+    {
+        rc = RTDirRead(hDir, pDirEntry, NULL);
+        if (RT_FAILURE(rc))
+        {
+            if (rc == VERR_NO_MORE_FILES)
+                rc = VINF_SUCCESS;
+            break;
+        }
+
+        if (!RTDirEntryIsStdDotLink(pDirEntry))
+        {
+            /* Construct the full name of the entry. */
+            if (cchDir + pDirEntry->cbName + 1 /* dir slash */ < RTPATH_MAX)
+                memcpy(&pszDir[cchDir], pDirEntry->szName, pDirEntry->cbName + 1);
+            else
+            {
+                rc = VERR_FILENAME_TOO_LONG;
+                break;
+            }
+
+            /* Make sure we've got the entry type. */
+            if (pDirEntry->enmType == RTDIRENTRYTYPE_UNKNOWN)
+                RTDirQueryUnknownType(pszDir, false /*fFollowSymlinks*/, &pDirEntry->enmType);
+
+            /* Recurse into subdirs and remove them: */
+            if (pDirEntry->enmType == RTDIRENTRYTYPE_DIRECTORY)
+            {
+                size_t cchSubDir    = cchDir + pDirEntry->cbName;
+                pszDir[cchSubDir++] = RTPATH_SLASH;
+                pszDir[cchSubDir]   = '\0';
+                rc = vgsvcGstCtrlSessionHandleDirRemoveSub(pszDir, cchSubDir, pDirEntry);
+                if (RT_SUCCESS(rc))
+                {
+                    pszDir[cchSubDir] = '\0';
+                    rc = RTDirRemove(pszDir);
+                    if (RT_FAILURE(rc))
+                        break;
+                }
+                else
+                    break;
+            }
+            /* Not a subdirectory - fail: */
+            else
+            {
+                rc = VERR_DIR_NOT_EMPTY;
+                break;
+            }
+        }
+    }
+
+    RTDirClose(hDir);
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleDirRemove(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the message.
+     */
+    char        szDir[RTPATH_MAX];
+    uint32_t    fFlags; /* DIRREMOVE_FLAG_XXX */
+    int rc = VbglR3GuestCtrlDirGetRemove(pHostCtx, szDir, sizeof(szDir), &fFlags);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Do some validating before executing the job.
+         */
+        if (!(fFlags & ~DIRREMOVEREC_FLAG_VALID_MASK))
+        {
+            if (fFlags & DIRREMOVEREC_FLAG_RECURSIVE)
+            {
+                if (fFlags & (DIRREMOVEREC_FLAG_CONTENT_AND_DIR | DIRREMOVEREC_FLAG_CONTENT_ONLY))
+                {
+                    uint32_t fFlagsRemRec = fFlags & DIRREMOVEREC_FLAG_CONTENT_AND_DIR
+                                          ? RTDIRRMREC_F_CONTENT_AND_DIR : RTDIRRMREC_F_CONTENT_ONLY;
+                    rc = RTDirRemoveRecursive(szDir, fFlagsRemRec);
+                }
+                else /* Only remove empty directory structures. Will fail if non-empty. */
+                {
+                    RTDIRENTRY DirEntry;
+                    RTPathEnsureTrailingSeparator(szDir, sizeof(szDir));
+                    rc = vgsvcGstCtrlSessionHandleDirRemoveSub(szDir, strlen(szDir), &DirEntry);
+                }
+                VGSvcVerbose(4, "[Dir %s]: rmdir /s (%#x) -> rc=%Rrc\n", szDir, fFlags, rc);
+            }
+            else
+            {
+                /* Only delete directory if not empty. */
+                rc = RTDirRemove(szDir);
+                VGSvcVerbose(4, "[Dir %s]: rmdir (%#x), rc=%Rrc\n", szDir, fFlags, rc);
+            }
+        }
+        else
+        {
+            VGSvcError("[Dir %s]: Unsupported flags: %#x (all %#x)\n", szDir, (fFlags & ~DIRREMOVEREC_FLAG_VALID_MASK), fFlags);
+            rc = VERR_NOT_SUPPORTED;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlMsgReply(pHostCtx, rc);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("[Dir %s]: Failed to report removing status, rc=%Rrc\n", szDir, rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for rmdir operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+
+    VGSvcVerbose(6, "Removing directory '%s' returned rc=%Rrc\n", szDir, rc);
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileOpen(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the message.
+     */
+    char     szFile[RTPATH_MAX];
+    char     szAccess[64];
+    char     szDisposition[64];
+    char     szSharing[64];
+    uint32_t uCreationMode = 0;
+    uint64_t offOpen       = 0;
+    uint32_t uHandle       = 0;
+    int rc = VbglR3GuestCtrlFileGetOpen(pHostCtx,
+                                        /* File to open. */
+                                        szFile, sizeof(szFile),
+                                        /* Open mode. */
+                                        szAccess, sizeof(szAccess),
+                                        /* Disposition. */
+                                        szDisposition, sizeof(szDisposition),
+                                        /* Sharing. */
+                                        szSharing, sizeof(szSharing),
+                                        /* Creation mode. */
+                                        &uCreationMode,
+                                        /* Offset. */
+                                        &offOpen);
+    VGSvcVerbose(4, "[File %s]: szAccess=%s, szDisposition=%s, szSharing=%s, offOpen=%RU64, rc=%Rrc\n",
+                 szFile, szAccess, szDisposition, szSharing, offOpen, rc);
+    if (RT_SUCCESS(rc))
+    {
+        PVBOXSERVICECTRLFILE pFile = (PVBOXSERVICECTRLFILE)RTMemAllocZ(sizeof(VBOXSERVICECTRLFILE));
+        if (pFile)
+        {
+            pFile->hFile = NIL_RTFILE; /* Not zero or NULL! */
+            if (szFile[0])
+            {
+                pFile->pszName = RTStrDup(szFile);
+                if (!pFile->pszName)
+                    rc = VERR_NO_MEMORY;
+/** @todo
+ * Implement szSharing!
+ */
+                uint64_t fFlags;
+                if (RT_SUCCESS(rc))
+                {
+                    rc = RTFileModeToFlagsEx(szAccess, szDisposition, NULL /* pszSharing, not used yet */, &fFlags);
+                    VGSvcVerbose(4, "[File %s] Opening with fFlags=%#RX64 -> rc=%Rrc\n", pFile->pszName, fFlags, rc);
+                }
+
+                if (RT_SUCCESS(rc))
+                {
+                    fFlags |= (uCreationMode << RTFILE_O_CREATE_MODE_SHIFT) & RTFILE_O_CREATE_MODE_MASK;
+                    /* If we're opening a file in read-only mode, strip truncation mode.
+                     * rtFileRecalcAndValidateFlags() will validate it anyway, but avoid asserting in debug builds. */
+                    if (fFlags & RTFILE_O_READ)
+                        fFlags &= ~RTFILE_O_TRUNCATE;
+                    rc = RTFileOpen(&pFile->hFile, pFile->pszName, fFlags);
+                    if (RT_SUCCESS(rc))
+                    {
+                        RTFSOBJINFO objInfo;
+                        rc = RTFileQueryInfo(pFile->hFile, &objInfo, RTFSOBJATTRADD_NOTHING);
+                        if (RT_SUCCESS(rc))
+                        {
+                            /* Make sure that we only open stuff we really support.
+                             * Only POSIX / UNIX we could open stuff like directories and sockets as well. */
+                            if (   RT_LIKELY(RTFS_IS_FILE(objInfo.Attr.fMode))
+                                ||           RTFS_IS_SYMLINK(objInfo.Attr.fMode))
+                            {
+                                /* Seeking is optional. However, the whole operation
+                                 * will fail if we don't succeed seeking to the wanted position. */
+                                if (offOpen)
+                                    rc = RTFileSeek(pFile->hFile, (int64_t)offOpen, RTFILE_SEEK_BEGIN, NULL /* Current offset */);
+                                if (RT_SUCCESS(rc))
+                                {
+                                    /*
+                                     * Succeeded!
+                                     */
+                                    uHandle = VBOX_GUESTCTRL_CONTEXTID_GET_OBJECT(pHostCtx->uContextID);
+                                    pFile->uHandle = uHandle;
+                                    pFile->fOpen   = fFlags;
+                                    RTListAppend(&pSession->lstFiles, &pFile->Node);
+                                    VGSvcVerbose(2, "[File %s] Opened (ID=%RU32)\n", pFile->pszName, pFile->uHandle);
+                                }
+                                else
+                                    VGSvcError("[File %s] Seeking to offset %RU64 failed: rc=%Rrc\n", pFile->pszName, offOpen, rc);
+                            }
+                            else
+                            {
+                                VGSvcError("[File %s] Unsupported mode %#x\n", pFile->pszName, objInfo.Attr.fMode);
+                                rc = VERR_NOT_SUPPORTED;
+                            }
+                        }
+                        else
+                            VGSvcError("[File %s] Getting mode failed with rc=%Rrc\n", pFile->pszName, rc);
+                    }
+                    else
+                        VGSvcError("[File %s] Opening failed with rc=%Rrc\n", pFile->pszName, rc);
+                }
+            }
+            else
+            {
+                VGSvcError("[File %s] empty filename!\n", szFile);
+                rc = VERR_INVALID_NAME;
+            }
+
+            /* clean up if we failed. */
+            if (RT_FAILURE(rc))
+            {
+                RTStrFree(pFile->pszName);
+                if (pFile->hFile != NIL_RTFILE)
+                    RTFileClose(pFile->hFile);
+                RTMemFree(pFile);
+            }
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlFileCbOpen(pHostCtx, rc, uHandle);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("[File %s]: Failed to report file open status, rc=%Rrc\n", szFile, rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for open file operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+
+    VGSvcVerbose(4, "[File %s] Opening (open mode='%s', disposition='%s', creation mode=0x%x) returned rc=%Rrc\n",
+                 szFile, szAccess, szDisposition, uCreationMode, rc);
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileClose(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the message.
+     */
+    uint32_t uHandle = 0;
+    int rc = VbglR3GuestCtrlFileGetClose(pHostCtx, &uHandle /* File handle to close */);
+    if (RT_SUCCESS(rc))
+    {
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            VGSvcVerbose(2, "[File %s] Closing (handle=%RU32)\n", pFile ? pFile->pszName : "<Not found>", uHandle);
+            rc = vgsvcGstCtrlSessionFileFree(pFile);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlFileCbClose(pHostCtx, rc);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file close status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for close file operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileRead(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx,
+                                             void **ppvScratchBuf, uint32_t *pcbScratchBuf)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uHandle = 0;
+    uint32_t cbToRead;
+    int rc = VbglR3GuestCtrlFileGetRead(pHostCtx, &uHandle, &cbToRead);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the file and do the reading.
+         *
+         * If the request is larger than our scratch buffer, try grow it - just
+         * ignore failure as the host better respect our buffer limits.
+         */
+        uint32_t offNew = 0;
+        size_t   cbRead = 0;
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            if (*pcbScratchBuf < cbToRead)
+                 vgsvcGstCtrlSessionGrowScratchBuf(ppvScratchBuf, pcbScratchBuf, cbToRead);
+
+            rc = RTFileRead(pFile->hFile, *ppvScratchBuf, RT_MIN(cbToRead, *pcbScratchBuf), &cbRead);
+            offNew = (int64_t)RTFileTell(pFile->hFile);
+            VGSvcVerbose(5, "[File %s] Read %zu/%RU32 bytes, rc=%Rrc, offNew=%RI64\n", pFile->pszName, cbRead, cbToRead, rc, offNew);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result and data back to the host.
+         */
+        int rc2;
+        if (g_fControlHostFeatures0 & VBOX_GUESTCTRL_HF_0_NOTIFY_RDWR_OFFSET)
+            rc2 = VbglR3GuestCtrlFileCbReadOffset(pHostCtx, rc, *ppvScratchBuf, (uint32_t)cbRead, offNew);
+        else
+            rc2 = VbglR3GuestCtrlFileCbRead(pHostCtx, rc, *ppvScratchBuf, (uint32_t)cbRead);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file read status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file read operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileReadAt(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx,
+                                               void **ppvScratchBuf, uint32_t *pcbScratchBuf)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uHandle = 0;
+    uint32_t cbToRead;
+    uint64_t offReadAt;
+    int rc = VbglR3GuestCtrlFileGetReadAt(pHostCtx, &uHandle, &cbToRead, &offReadAt);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the file and do the reading.
+         *
+         * If the request is larger than our scratch buffer, try grow it - just
+         * ignore failure as the host better respect our buffer limits.
+         */
+        int64_t offNew = 0;
+        size_t  cbRead = 0;
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            if (*pcbScratchBuf < cbToRead)
+                 vgsvcGstCtrlSessionGrowScratchBuf(ppvScratchBuf, pcbScratchBuf, cbToRead);
+
+            rc = RTFileReadAt(pFile->hFile, (RTFOFF)offReadAt, *ppvScratchBuf, RT_MIN(cbToRead, *pcbScratchBuf), &cbRead);
+            if (RT_SUCCESS(rc))
+            {
+                offNew = offReadAt + cbRead;
+                RTFileSeek(pFile->hFile, offNew, RTFILE_SEEK_BEGIN, NULL); /* RTFileReadAt does not always change position. */
+            }
+            else
+                offNew = (int64_t)RTFileTell(pFile->hFile);
+            VGSvcVerbose(5, "[File %s] Read %zu bytes @ %RU64, rc=%Rrc, offNew=%RI64\n", pFile->pszName, cbRead, offReadAt, rc, offNew);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result and data back to the host.
+         */
+        int rc2;
+        if (g_fControlHostFeatures0 & VBOX_GUESTCTRL_HF_0_NOTIFY_RDWR_OFFSET)
+            rc2 = VbglR3GuestCtrlFileCbReadOffset(pHostCtx, rc, *ppvScratchBuf, (uint32_t)cbRead, offNew);
+        else
+            rc2 = VbglR3GuestCtrlFileCbRead(pHostCtx, rc, *ppvScratchBuf, (uint32_t)cbRead);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file read at status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file read at operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileWrite(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx,
+                                              void **ppvScratchBuf, uint32_t *pcbScratchBuf)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request and data to write.
+     */
+    uint32_t uHandle = 0;
+    uint32_t cbToWrite;
+    int rc = VbglR3GuestCtrlFileGetWrite(pHostCtx, &uHandle, *ppvScratchBuf, *pcbScratchBuf, &cbToWrite);
+    if (   rc == VERR_BUFFER_OVERFLOW
+        && vgsvcGstCtrlSessionGrowScratchBuf(ppvScratchBuf, pcbScratchBuf, cbToWrite))
+        rc = VbglR3GuestCtrlFileGetWrite(pHostCtx, &uHandle, *ppvScratchBuf, *pcbScratchBuf, &cbToWrite);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the file and do the writing.
+         */
+        int64_t offNew    = 0;
+        size_t  cbWritten = 0;
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            rc = RTFileWrite(pFile->hFile, *ppvScratchBuf, RT_MIN(cbToWrite, *pcbScratchBuf), &cbWritten);
+            offNew = (int64_t)RTFileTell(pFile->hFile);
+            VGSvcVerbose(5, "[File %s] Writing %p LB %RU32 =>  %Rrc, cbWritten=%zu, offNew=%RI64\n",
+                         pFile->pszName, *ppvScratchBuf, RT_MIN(cbToWrite, *pcbScratchBuf), rc, cbWritten, offNew);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2;
+        if (g_fControlHostFeatures0 & VBOX_GUESTCTRL_HF_0_NOTIFY_RDWR_OFFSET)
+            rc2 = VbglR3GuestCtrlFileCbWriteOffset(pHostCtx, rc, (uint32_t)cbWritten, offNew);
+        else
+            rc2 = VbglR3GuestCtrlFileCbWrite(pHostCtx, rc, (uint32_t)cbWritten);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file write status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file write operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileWriteAt(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx,
+                                                void **ppvScratchBuf, uint32_t *pcbScratchBuf)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request and data to write.
+     */
+    uint32_t uHandle = 0;
+    uint32_t cbToWrite;
+    uint64_t offWriteAt;
+    int rc = VbglR3GuestCtrlFileGetWriteAt(pHostCtx, &uHandle, *ppvScratchBuf, *pcbScratchBuf, &cbToWrite, &offWriteAt);
+    if (   rc == VERR_BUFFER_OVERFLOW
+        && vgsvcGstCtrlSessionGrowScratchBuf(ppvScratchBuf, pcbScratchBuf, cbToWrite))
+        rc = VbglR3GuestCtrlFileGetWriteAt(pHostCtx, &uHandle, *ppvScratchBuf, *pcbScratchBuf, &cbToWrite, &offWriteAt);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the file and do the writing.
+         */
+        int64_t offNew    = 0;
+        size_t  cbWritten = 0;
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            rc = RTFileWriteAt(pFile->hFile, (RTFOFF)offWriteAt, *ppvScratchBuf, RT_MIN(cbToWrite, *pcbScratchBuf), &cbWritten);
+            if (RT_SUCCESS(rc))
+            {
+                offNew = offWriteAt + cbWritten;
+
+                /* RTFileWriteAt does not always change position: */
+                if (!(pFile->fOpen & RTFILE_O_APPEND))
+                    RTFileSeek(pFile->hFile, offNew, RTFILE_SEEK_BEGIN, NULL);
+                else
+                    RTFileSeek(pFile->hFile, 0, RTFILE_SEEK_END, (uint64_t *)&offNew);
+            }
+            else
+                offNew = (int64_t)RTFileTell(pFile->hFile);
+            VGSvcVerbose(5, "[File %s] Writing %p LB %RU32 @ %RU64 =>  %Rrc, cbWritten=%zu, offNew=%RI64\n",
+                         pFile->pszName, *ppvScratchBuf, RT_MIN(cbToWrite, *pcbScratchBuf), offWriteAt, rc, cbWritten, offNew);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2;
+        if (g_fControlHostFeatures0 & VBOX_GUESTCTRL_HF_0_NOTIFY_RDWR_OFFSET)
+            rc2 = VbglR3GuestCtrlFileCbWriteOffset(pHostCtx, rc, (uint32_t)cbWritten, offNew);
+        else
+            rc2 = VbglR3GuestCtrlFileCbWrite(pHostCtx, rc, (uint32_t)cbWritten);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file write status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file write at operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileSeek(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uHandle = 0;
+    uint32_t uSeekMethod;
+    uint64_t offSeek; /* Will be converted to int64_t. */
+    int rc = VbglR3GuestCtrlFileGetSeek(pHostCtx, &uHandle, &uSeekMethod, &offSeek);
+    if (RT_SUCCESS(rc))
+    {
+        uint64_t offActual = 0;
+
+        /*
+         * Validate and convert the seek method to IPRT speak.
+         */
+        static const uint8_t s_abMethods[GUEST_FILE_SEEKTYPE_END + 1] =
+        {
+            UINT8_MAX, RTFILE_SEEK_BEGIN, UINT8_MAX, UINT8_MAX, RTFILE_SEEK_CURRENT,
+            UINT8_MAX, UINT8_MAX, UINT8_MAX, RTFILE_SEEK_END
+        };
+        if (   uSeekMethod < RT_ELEMENTS(s_abMethods)
+            && s_abMethods[uSeekMethod] != UINT8_MAX)
+        {
+            /*
+             * Locate the file and do the seek.
+             */
+            PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+            if (pFile)
+            {
+                rc = RTFileSeek(pFile->hFile, (int64_t)offSeek, s_abMethods[uSeekMethod], &offActual);
+                VGSvcVerbose(5, "[File %s]: Seeking to offSeek=%RI64, uSeekMethodIPRT=%u, rc=%Rrc\n",
+                             pFile->pszName, offSeek, s_abMethods[uSeekMethod], rc);
+            }
+            else
+            {
+                VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+                rc = VERR_NOT_FOUND;
+            }
+        }
+        else
+        {
+            VGSvcError("Invalid seek method: %#x\n", uSeekMethod);
+            rc = VERR_NOT_SUPPORTED;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlFileCbSeek(pHostCtx, rc, offActual);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file seek status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file seek operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileTell(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uHandle = 0;
+    int rc = VbglR3GuestCtrlFileGetTell(pHostCtx, &uHandle);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the file and ask for the current position.
+         */
+        uint64_t offCurrent = 0;
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            offCurrent = RTFileTell(pFile->hFile);
+            VGSvcVerbose(5, "[File %s]: Telling offCurrent=%RU64\n", pFile->pszName, offCurrent);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlFileCbTell(pHostCtx, rc, offCurrent);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file tell status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file tell operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleFileSetSize(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uHandle = 0;
+    uint64_t cbNew = 0;
+    int rc = VbglR3GuestCtrlFileGetSetSize(pHostCtx, &uHandle, &cbNew);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the file and ask for the current position.
+         */
+        PVBOXSERVICECTRLFILE pFile = vgsvcGstCtrlSessionFileGetLocked(pSession, uHandle);
+        if (pFile)
+        {
+            rc = RTFileSetSize(pFile->hFile, cbNew);
+            VGSvcVerbose(5, "[File %s]: Changing size to %RU64 (%#RX64), rc=%Rrc\n", pFile->pszName, cbNew, cbNew, rc);
+        }
+        else
+        {
+            VGSvcError("File %u (%#x) not found!\n", uHandle, uHandle);
+            cbNew = UINT64_MAX;
+            rc = VERR_NOT_FOUND;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlFileCbSetSize(pHostCtx, rc, cbNew);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report file tell status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for file tell operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandlePathRename(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    char     szSource[RTPATH_MAX];
+    char     szDest[RTPATH_MAX];
+    uint32_t fFlags = 0; /* PATHRENAME_FLAG_XXX */
+    int rc = VbglR3GuestCtrlPathGetRename(pHostCtx, szSource, sizeof(szSource), szDest, sizeof(szDest), &fFlags);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Validate the flags (kudos for using the same as IPRT), then do the renaming.
+         */
+        AssertCompile(PATHRENAME_FLAG_NO_REPLACE  == RTPATHRENAME_FLAGS_NO_REPLACE);
+        AssertCompile(PATHRENAME_FLAG_REPLACE     == RTPATHRENAME_FLAGS_REPLACE);
+        AssertCompile(PATHRENAME_FLAG_NO_SYMLINKS == RTPATHRENAME_FLAGS_NO_SYMLINKS);
+        AssertCompile(PATHRENAME_FLAG_VALID_MASK  == (RTPATHRENAME_FLAGS_NO_REPLACE | RTPATHRENAME_FLAGS_REPLACE | RTPATHRENAME_FLAGS_NO_SYMLINKS));
+        if (!(fFlags & ~PATHRENAME_FLAG_VALID_MASK))
+        {
+            VGSvcVerbose(4, "Renaming '%s' to '%s', fFlags=%#x, rc=%Rrc\n", szSource, szDest, fFlags, rc);
+            rc = RTPathRename(szSource, szDest, fFlags);
+        }
+        else
+        {
+            VGSvcError("Invalid rename flags: %#x\n", fFlags);
+            rc = VERR_NOT_SUPPORTED;
+        }
+
+        /*
+         * Report result back to host.
+         */
+        int rc2 = VbglR3GuestCtrlMsgReply(pHostCtx, rc);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report renaming status, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for rename operation: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    VGSvcVerbose(5, "Renaming '%s' to '%s' returned rc=%Rrc\n", szSource, szDest, rc);
+    return rc;
+}
+
+
+/**
+ * Handles getting the user's documents directory.
+ *
+ * @returns VBox status code.
+ * @param   pSession        Guest session.
+ * @param   pHostCtx        Host context.
+ */
+static int vgsvcGstCtrlSessionHandlePathUserDocuments(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    int rc = VbglR3GuestCtrlPathGetUserDocuments(pHostCtx);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Get the path and pass it back to the host..
+         */
+        char szPath[RTPATH_MAX];
+        rc = RTPathUserDocuments(szPath, sizeof(szPath));
+#ifdef DEBUG
+        VGSvcVerbose(2, "User documents is '%s', rc=%Rrc\n", szPath, rc);
+#endif
+
+        int rc2 = VbglR3GuestCtrlMsgReplyEx(pHostCtx, rc, 0 /* Type */, szPath,
+                                            RT_SUCCESS(rc) ? (uint32_t)strlen(szPath) + 1 /* Include terminating zero */ : 0);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report user documents, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for user documents path request: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+/**
+ * Handles shutting down / rebooting the guest OS.
+ *
+ * @returns VBox status code.
+ * @param   pSession        Guest session.
+ * @param   pHostCtx        Host context.
+ */
+static int vgsvcGstCtrlSessionHandleShutdown(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t fAction;
+    int rc = VbglR3GuestCtrlGetShutdown(pHostCtx, &fAction);
+    if (RT_SUCCESS(rc))
+    {
+        VGSvcVerbose(1, "Host requested to %s system ...\n", (fAction & RTSYSTEM_SHUTDOWN_REBOOT) ? "reboot" : "shutdown");
+
+        /* Reply first to the host, in order to avoid host hangs when issuing the guest shutdown. */
+        rc = VbglR3GuestCtrlMsgReply(pHostCtx, VINF_SUCCESS);
+        if (RT_FAILURE(rc))
+        {
+            VGSvcError("Failed to reply to shutdown / reboot request, rc=%Rrc\n", rc);
+        }
+        else
+        {
+            int fSystemShutdown = RTSYSTEM_SHUTDOWN_PLANNED;
+
+            /* Translate SHUTDOWN_FLAG_ into RTSYSTEM_SHUTDOWN_ flags. */
+            if (fAction & GUEST_SHUTDOWN_FLAG_REBOOT)
+                fSystemShutdown |= RTSYSTEM_SHUTDOWN_REBOOT;
+            else /* SHUTDOWN_FLAG_POWER_OFF */
+                fSystemShutdown |= RTSYSTEM_SHUTDOWN_POWER_OFF;
+
+            if (fAction & GUEST_SHUTDOWN_FLAG_FORCE)
+                fSystemShutdown |= RTSYSTEM_SHUTDOWN_FORCE;
+
+            rc = RTSystemShutdown(0 /*cMsDelay*/, fSystemShutdown, "VBoxService");
+            if (RT_FAILURE(rc))
+                VGSvcError("%s system failed with %Rrc\n",
+                           (fAction & RTSYSTEM_SHUTDOWN_REBOOT) ? "Rebooting" : "Shutting down", rc);
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for shutdown / reboot request: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+
+    return rc;
+}
+
+
+/**
+ * Handles getting the user's home directory.
+ *
+ * @returns VBox status code.
+ * @param   pSession        Guest session.
+ * @param   pHostCtx        Host context.
+ */
+static int vgsvcGstCtrlSessionHandlePathUserHome(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    int rc = VbglR3GuestCtrlPathGetUserHome(pHostCtx);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Get the path and pass it back to the host..
+         */
+        char szPath[RTPATH_MAX];
+        rc = RTPathUserHome(szPath, sizeof(szPath));
+
+#ifdef DEBUG
+        VGSvcVerbose(2, "User home is '%s', rc=%Rrc\n", szPath, rc);
+#endif
+        /* Report back in any case. */
+        int rc2 = VbglR3GuestCtrlMsgReplyEx(pHostCtx, rc, 0 /* Type */, szPath,
+                                            RT_SUCCESS(rc) ?(uint32_t)strlen(szPath) + 1 /* Include terminating zero */ : 0);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Failed to report user home, rc=%Rrc\n", rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for user home directory path request: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+/**
+ * Handles starting a guest processes.
+ *
+ * @returns VBox status code.
+ * @param   pSession        Guest session.
+ * @param   pHostCtx        Host context.
+ */
+static int vgsvcGstCtrlSessionHandleProcExec(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /* Initialize maximum environment block size -- needed as input
+     * parameter to retrieve the stuff from the host. On output this then
+     * will contain the actual block size. */
+    PVBGLR3GUESTCTRLPROCSTARTUPINFO pStartupInfo;
+    int rc = VbglR3GuestCtrlProcGetStart(pHostCtx, &pStartupInfo);
+    if (RT_SUCCESS(rc))
+    {
+        VGSvcVerbose(3, "Request to start process szCmd=%s, fFlags=0x%x, szArgs=%s, szEnv=%s, uTimeout=%RU32\n",
+                     pStartupInfo->pszCmd, pStartupInfo->fFlags,
+                     pStartupInfo->cArgs    ? pStartupInfo->pszArgs : "<None>",
+                     pStartupInfo->cEnvVars ? pStartupInfo->pszEnv  : "<None>",
+                     pStartupInfo->uTimeLimitMS);
+
+        bool fStartAllowed = false; /* Flag indicating whether starting a process is allowed or not. */
+        rc = VGSvcGstCtrlSessionProcessStartAllowed(pSession, &fStartAllowed);
+        if (RT_SUCCESS(rc))
+        {
+            vgsvcGstCtrlSessionCleanupProcesses(pSession);
+
+            if (fStartAllowed)
+                rc = VGSvcGstCtrlProcessStart(pSession, pStartupInfo, pHostCtx->uContextID);
+            else
+                rc = VERR_MAX_PROCS_REACHED; /* Maximum number of processes reached. */
+        }
+
+        /* We're responsible for signaling errors to the host (it will wait for ever otherwise). */
+        if (RT_FAILURE(rc))
+        {
+            VGSvcError("Starting process failed with rc=%Rrc, protocol=%RU32, parameters=%RU32\n",
+                       rc, pHostCtx->uProtocol, pHostCtx->uNumParms);
+            int rc2 = VbglR3GuestCtrlProcCbStatus(pHostCtx, 0 /*nil-PID*/, PROC_STS_ERROR, rc, NULL /*pvData*/, 0 /*cbData*/);
+            if (RT_FAILURE(rc2))
+                VGSvcError("Error sending start process status to host, rc=%Rrc\n", rc2);
+        }
+
+        VbglR3GuestCtrlProcStartupInfoFree(pStartupInfo);
+        pStartupInfo = NULL;
+    }
+    else
+    {
+        VGSvcError("Failed to retrieve parameters for process start: %Rrc (cParms=%u)\n", rc, pHostCtx->uNumParms);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+
+    return rc;
+}
+
+
+/**
+ * Sends stdin input to a specific guest process.
+ *
+ * @returns VBox status code.
+ * @param   pSession            The session which is in charge.
+ * @param   pHostCtx            The host context to use.
+ * @param   ppvScratchBuf       The scratch buffer, we may grow it.
+ * @param   pcbScratchBuf       The scratch buffer size for retrieving the input
+ *                              data.
+ */
+static int vgsvcGstCtrlSessionHandleProcInput(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx,
+                                              void **ppvScratchBuf, uint32_t *pcbScratchBuf)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the data from the host.
+     */
+    uint32_t uPID;
+    uint32_t fFlags;
+    uint32_t cbInput;
+    int rc = VbglR3GuestCtrlProcGetInput(pHostCtx, &uPID, &fFlags, *ppvScratchBuf, *pcbScratchBuf, &cbInput);
+    if (   rc == VERR_BUFFER_OVERFLOW
+        && vgsvcGstCtrlSessionGrowScratchBuf(ppvScratchBuf, pcbScratchBuf, cbInput))
+        rc = VbglR3GuestCtrlProcGetInput(pHostCtx, &uPID, &fFlags, *ppvScratchBuf, *pcbScratchBuf, &cbInput);
+    if (RT_SUCCESS(rc))
+    {
+        if (fFlags & GUEST_PROC_IN_FLAG_EOF)
+            VGSvcVerbose(4, "Got last process input block for PID=%RU32 (%RU32 bytes) ...\n", uPID, cbInput);
+
+        /*
+         * Locate the process and feed it.
+         */
+        PVBOXSERVICECTRLPROCESS pProcess = VGSvcGstCtrlSessionRetainProcess(pSession, uPID);
+        if (pProcess)
+        {
+            rc = VGSvcGstCtrlProcessHandleInput(pProcess, pHostCtx, RT_BOOL(fFlags & GUEST_PROC_IN_FLAG_EOF),
+                                                *ppvScratchBuf, RT_MIN(cbInput, *pcbScratchBuf));
+            if (RT_FAILURE(rc))
+                VGSvcError("Error handling input message for PID=%RU32, rc=%Rrc\n", uPID, rc);
+            VGSvcGstCtrlProcessRelease(pProcess);
+        }
+        else
+        {
+            VGSvcError("Could not find PID %u for feeding %u bytes to it.\n", uPID, cbInput);
+            rc = VERR_PROCESS_NOT_FOUND;
+            VbglR3GuestCtrlProcCbStatusInput(pHostCtx, uPID, INPUT_STS_ERROR, rc, 0);
+        }
+    }
+    else
+    {
+        VGSvcError("Failed to retrieve parameters for process input: %Rrc (scratch %u bytes)\n", rc, *pcbScratchBuf);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+
+    VGSvcVerbose(6, "Feeding input to PID=%RU32 resulted in rc=%Rrc\n", uPID, rc);
+    return rc;
+}
+
+
+/**
+ * Gets stdout/stderr output of a specific guest process.
+ *
+ * @returns VBox status code.
+ * @param   pSession            The session which is in charge.
+ * @param   pHostCtx            The host context to use.
+ */
+static int vgsvcGstCtrlSessionHandleProcOutput(PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uPID;
+    uint32_t uHandleID;
+    uint32_t fFlags;
+    int rc = VbglR3GuestCtrlProcGetOutput(pHostCtx, &uPID, &uHandleID, &fFlags);
+#ifdef DEBUG_andy
+    VGSvcVerbose(4, "Getting output for PID=%RU32, CID=%RU32, uHandleID=%RU32, fFlags=%RU32\n",
+                 uPID, pHostCtx->uContextID, uHandleID, fFlags);
+#endif
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the process and hand it the output request.
+         */
+        PVBOXSERVICECTRLPROCESS pProcess = VGSvcGstCtrlSessionRetainProcess(pSession, uPID);
+        if (pProcess)
+        {
+            rc = VGSvcGstCtrlProcessHandleOutput(pProcess, pHostCtx, uHandleID, _64K /* cbToRead */, fFlags);
+            if (RT_FAILURE(rc))
+                VGSvcError("Error getting output for PID=%RU32, rc=%Rrc\n", uPID, rc);
+            VGSvcGstCtrlProcessRelease(pProcess);
+        }
+        else
+        {
+            VGSvcError("Could not find PID %u for draining handle %u (%#x).\n", uPID, uHandleID, uHandleID);
+            rc = VERR_PROCESS_NOT_FOUND;
+/** @todo r=bird:
+ *
+ *  No way to report status status code for output requests?
+ *
+ */
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for process output request: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+
+#ifdef DEBUG_andy
+    VGSvcVerbose(4, "Getting output for PID=%RU32 resulted in rc=%Rrc\n", uPID, rc);
+#endif
+    return rc;
+}
+
+
+/**
+ * Tells a guest process to terminate.
+ *
+ * @returns VBox status code.
+ * @param   pSession            The session which is in charge.
+ * @param   pHostCtx            The host context to use.
+ */
+static int vgsvcGstCtrlSessionHandleProcTerminate(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uPID;
+    int rc = VbglR3GuestCtrlProcGetTerminate(pHostCtx, &uPID);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the process and terminate it.
+         */
+        PVBOXSERVICECTRLPROCESS pProcess = VGSvcGstCtrlSessionRetainProcess(pSession, uPID);
+        if (pProcess)
+        {
+            rc = VGSvcGstCtrlProcessHandleTerm(pProcess);
+            if (RT_FAILURE(rc))
+                VGSvcError("Error terminating PID=%RU32, rc=%Rrc\n", uPID, rc);
+
+            VGSvcGstCtrlProcessRelease(pProcess);
+        }
+        else
+        {
+            VGSvcError("Could not find PID %u for termination.\n", uPID);
+            rc = VERR_PROCESS_NOT_FOUND;
+        }
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for process termination request: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+#ifdef DEBUG_andy
+    VGSvcVerbose(4, "Terminating PID=%RU32 resulted in rc=%Rrc\n", uPID, rc);
+#endif
+    return rc;
+}
+
+
+static int vgsvcGstCtrlSessionHandleProcWaitFor(const PVBOXSERVICECTRLSESSION pSession, PVBGLR3GUESTCTRLCMDCTX pHostCtx)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Retrieve the request.
+     */
+    uint32_t uPID;
+    uint32_t uWaitFlags;
+    uint32_t uTimeoutMS;
+    int rc = VbglR3GuestCtrlProcGetWaitFor(pHostCtx, &uPID, &uWaitFlags, &uTimeoutMS);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Locate the process and the realize that this call makes no sense
+         * since we'll notify the host when a process terminates anyway and
+         * hopefully don't need any additional encouragement.
+         */
+        PVBOXSERVICECTRLPROCESS pProcess = VGSvcGstCtrlSessionRetainProcess(pSession, uPID);
+        if (pProcess)
+        {
+            rc = VERR_NOT_IMPLEMENTED; /** @todo */
+            VGSvcGstCtrlProcessRelease(pProcess);
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else
+    {
+        VGSvcError("Error fetching parameters for process wait request: %Rrc\n", rc);
+        VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, rc, UINT32_MAX);
+    }
+    return rc;
+}
+
+
+int VGSvcGstCtrlSessionHandler(PVBOXSERVICECTRLSESSION pSession, uint32_t uMsg, PVBGLR3GUESTCTRLCMDCTX pHostCtx,
+                               void **ppvScratchBuf, uint32_t *pcbScratchBuf, volatile bool *pfShutdown)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHostCtx, VERR_INVALID_POINTER);
+    AssertPtrReturn(*ppvScratchBuf, VERR_INVALID_POINTER);
+    AssertPtrReturn(pfShutdown, VERR_INVALID_POINTER);
+
+
+    /*
+     * Only anonymous sessions (that is, sessions which run with local
+     * service privileges) or spawned session processes can do certain
+     * operations.
+     */
+    bool const fImpersonated = RT_BOOL(pSession->fFlags & (  VBOXSERVICECTRLSESSION_FLAG_SPAWN
+                                                           | VBOXSERVICECTRLSESSION_FLAG_ANONYMOUS));
+    int rc = VERR_NOT_SUPPORTED; /* Play safe by default. */
+
+    switch (uMsg)
+    {
+        case HOST_MSG_SESSION_CLOSE:
+            /* Shutdown (this spawn). */
+            rc = VGSvcGstCtrlSessionClose(pSession);
+            *pfShutdown = true; /* Shutdown in any case. */
+            break;
+
+        case HOST_MSG_DIR_REMOVE:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleDirRemove(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_EXEC_CMD:
+            rc = vgsvcGstCtrlSessionHandleProcExec(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_EXEC_SET_INPUT:
+            rc = vgsvcGstCtrlSessionHandleProcInput(pSession, pHostCtx, ppvScratchBuf, pcbScratchBuf);
+            break;
+
+        case HOST_MSG_EXEC_GET_OUTPUT:
+            rc = vgsvcGstCtrlSessionHandleProcOutput(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_EXEC_TERMINATE:
+            rc = vgsvcGstCtrlSessionHandleProcTerminate(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_EXEC_WAIT_FOR:
+            rc = vgsvcGstCtrlSessionHandleProcWaitFor(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_FILE_OPEN:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileOpen(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_FILE_CLOSE:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileClose(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_FILE_READ:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileRead(pSession, pHostCtx, ppvScratchBuf, pcbScratchBuf);
+            break;
+
+        case HOST_MSG_FILE_READ_AT:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileReadAt(pSession, pHostCtx, ppvScratchBuf, pcbScratchBuf);
+            break;
+
+        case HOST_MSG_FILE_WRITE:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileWrite(pSession, pHostCtx, ppvScratchBuf, pcbScratchBuf);
+            break;
+
+        case HOST_MSG_FILE_WRITE_AT:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileWriteAt(pSession, pHostCtx, ppvScratchBuf, pcbScratchBuf);
+            break;
+
+        case HOST_MSG_FILE_SEEK:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileSeek(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_FILE_TELL:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileTell(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_FILE_SET_SIZE:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandleFileSetSize(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_PATH_RENAME:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandlePathRename(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_PATH_USER_DOCUMENTS:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandlePathUserDocuments(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_PATH_USER_HOME:
+            if (fImpersonated)
+                rc = vgsvcGstCtrlSessionHandlePathUserHome(pSession, pHostCtx);
+            break;
+
+        case HOST_MSG_SHUTDOWN:
+            rc = vgsvcGstCtrlSessionHandleShutdown(pSession, pHostCtx);
+            break;
+
+        default: /* Not supported, see next code block. */
+            break;
+    }
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else if (rc != VERR_NOT_SUPPORTED) /* Note: Reply to host must must be sent by above handler. */
+        VGSvcError("Error while handling message (uMsg=%RU32, cParms=%RU32), rc=%Rrc\n", uMsg, pHostCtx->uNumParms, rc);
+    else
+    {
+        /* We must skip and notify host here as best we can... */
+        VGSvcVerbose(1, "Unsupported message (uMsg=%RU32, cParms=%RU32) from host, skipping\n", uMsg, pHostCtx->uNumParms);
+        if (VbglR3GuestCtrlSupportsOptimizations(pHostCtx->uClientID))
+            VbglR3GuestCtrlMsgSkip(pHostCtx->uClientID, VERR_NOT_SUPPORTED, uMsg);
+        else
+            VbglR3GuestCtrlMsgSkipOld(pHostCtx->uClientID);
+        rc = VINF_SUCCESS;
+    }
+
+    if (RT_FAILURE(rc))
+        VGSvcError("Error while handling message (uMsg=%RU32, cParms=%RU32), rc=%Rrc\n", uMsg, pHostCtx->uNumParms, rc);
+
+    return rc;
+}
+
+
+/**
+ * Thread main routine for a spawned guest session process.
+ *
+ * This thread runs in the main executable to control the spawned session process.
+ *
+ * @returns VBox status code.
+ * @param   hThreadSelf     Thread handle.
+ * @param   pvUser          Pointer to a VBOXSERVICECTRLSESSIONTHREAD structure.
+ *
+ */
+static DECLCALLBACK(int) vgsvcGstCtrlSessionThread(RTTHREAD hThreadSelf, void *pvUser)
+{
+    PVBOXSERVICECTRLSESSIONTHREAD pThread = (PVBOXSERVICECTRLSESSIONTHREAD)pvUser;
+    AssertPtrReturn(pThread, VERR_INVALID_POINTER);
+
+    uint32_t const idSession = pThread->pStartupInfo->uSessionID;
+    uint32_t const idClient  = g_idControlSvcClient;
+    VGSvcVerbose(3, "Session ID=%RU32 thread running\n", idSession);
+
+    /* Let caller know that we're done initializing, regardless of the result. */
+    int rc2 = RTThreadUserSignal(hThreadSelf);
+    AssertRC(rc2);
+
+    /*
+     * Wait for the child process to stop or the shutdown flag to be signalled.
+     */
+    RTPROCSTATUS    ProcessStatus       = { 0, RTPROCEXITREASON_NORMAL };
+    bool            fProcessAlive       = true;
+    bool            fSessionCancelled   = VbglR3GuestCtrlSupportsOptimizations(g_idControlSvcClient);
+    uint32_t        cMsShutdownTimeout  = 30 * 1000; /** @todo Make this configurable. Later. */
+    uint64_t        msShutdownStart     = 0;
+    uint64_t const  msStart             = RTTimeMilliTS();
+    size_t          offSecretKey        = 0;
+    int             rcWait;
+    for (;;)
+    {
+        /* Secret key feeding. */
+        if (offSecretKey < sizeof(pThread->abKey))
+        {
+            size_t cbWritten = 0;
+            rc2 = RTPipeWrite(pThread->hKeyPipe, &pThread->abKey[offSecretKey], sizeof(pThread->abKey) - offSecretKey, &cbWritten);
+            if (RT_SUCCESS(rc2))
+                offSecretKey += cbWritten;
+        }
+
+        /* Poll child process status. */
+        rcWait = RTProcWaitNoResume(pThread->hProcess, RTPROCWAIT_FLAGS_NOBLOCK, &ProcessStatus);
+        if (   rcWait == VINF_SUCCESS
+            || rcWait == VERR_PROCESS_NOT_FOUND)
+        {
+            fProcessAlive = false;
+            break;
+        }
+        AssertMsgBreak(rcWait == VERR_PROCESS_RUNNING || rcWait == VERR_INTERRUPTED,
+                       ("Got unexpected rc=%Rrc while waiting for session process termination\n", rcWait));
+
+        /* Shutting down? */
+        if (ASMAtomicReadBool(&pThread->fShutdown))
+        {
+            if (!msShutdownStart)
+            {
+                VGSvcVerbose(3, "Notifying guest session process (PID=%RU32, session ID=%RU32) ...\n",
+                             pThread->hProcess, idSession);
+
+                VBGLR3GUESTCTRLCMDCTX hostCtx =
+                {
+                    /* .idClient  = */  idClient,
+                    /* .idContext = */  VBOX_GUESTCTRL_CONTEXTID_MAKE_SESSION(idSession),
+                    /* .uProtocol = */  pThread->pStartupInfo->uProtocol,
+                    /* .cParams   = */  2
+                };
+                rc2 = VbglR3GuestCtrlSessionClose(&hostCtx, 0 /* fFlags */);
+                if (RT_FAILURE(rc2))
+                {
+                    VGSvcError("Unable to notify guest session process (PID=%RU32, session ID=%RU32), rc=%Rrc\n",
+                               pThread->hProcess, idSession, rc2);
+
+                    if (rc2 == VERR_NOT_SUPPORTED)
+                    {
+                        /* Terminate guest session process in case it's not supported by a too old host. */
+                        rc2 = RTProcTerminate(pThread->hProcess);
+                        VGSvcVerbose(3, "Terminating guest session process (PID=%RU32) ended with rc=%Rrc\n",
+                                     pThread->hProcess, rc2);
+                    }
+                    break;
+                }
+
+                VGSvcVerbose(3, "Guest session ID=%RU32 thread was asked to terminate, waiting for session process to exit (%RU32 ms timeout) ...\n",
+                             idSession, cMsShutdownTimeout);
+                msShutdownStart = RTTimeMilliTS();
+                continue; /* Don't waste time on waiting. */
+            }
+            if (RTTimeMilliTS() - msShutdownStart > cMsShutdownTimeout)
+            {
+                 VGSvcVerbose(3, "Guest session ID=%RU32 process did not shut down within time\n", idSession);
+                 break;
+            }
+        }
+
+        /* Cancel the prepared session stuff after 30 seconds. */
+        if (  !fSessionCancelled
+            && RTTimeMilliTS() - msStart >= 30000)
+        {
+            VbglR3GuestCtrlSessionCancelPrepared(g_idControlSvcClient, idSession);
+            fSessionCancelled = true;
+        }
+
+/** @todo r=bird: This 100ms sleep is _extremely_ sucky! */
+        RTThreadSleep(100); /* Wait a bit. */
+    }
+
+    if (!fSessionCancelled)
+        VbglR3GuestCtrlSessionCancelPrepared(g_idControlSvcClient, idSession);
+
+    if (!fProcessAlive)
+    {
+        VGSvcVerbose(2, "Guest session process (ID=%RU32) terminated with rc=%Rrc, reason=%d, status=%d\n",
+                     idSession, rcWait, ProcessStatus.enmReason, ProcessStatus.iStatus);
+        if (ProcessStatus.iStatus == RTEXITCODE_INIT)
+        {
+            VGSvcError("Guest session process (ID=%RU32) failed to initialize. Here some hints:\n", idSession);
+            VGSvcError("- Is logging enabled and the output directory is read-only by the guest session user?\n");
+            /** @todo Add more here. */
+        }
+    }
+
+    uint32_t uSessionStatus = GUEST_SESSION_NOTIFYTYPE_UNDEFINED;
+    int32_t  iSessionResult = VINF_SUCCESS;
+
+    if (fProcessAlive)
+    {
+        for (int i = 0; i < 3; i++)
+        {
+            if (i)
+                RTThreadSleep(3000);
+
+            VGSvcVerbose(2, "Guest session ID=%RU32 process still alive, killing attempt %d/3\n", idSession, i + 1);
+
+            rc2 = RTProcTerminate(pThread->hProcess);
+            if (RT_SUCCESS(rc2))
+                break;
+        }
+
+        VGSvcVerbose(2, "Guest session ID=%RU32 process termination resulted in rc=%Rrc\n", idSession, rc2);
+        uSessionStatus = RT_SUCCESS(rc2) ? GUEST_SESSION_NOTIFYTYPE_TOK : GUEST_SESSION_NOTIFYTYPE_TOA;
+    }
+    else if (RT_SUCCESS(rcWait))
+    {
+        switch (ProcessStatus.enmReason)
+        {
+            case RTPROCEXITREASON_NORMAL:
+                uSessionStatus = GUEST_SESSION_NOTIFYTYPE_TEN;
+                iSessionResult = ProcessStatus.iStatus; /* Report back the session's exit code. */
+                break;
+
+            case RTPROCEXITREASON_ABEND:
+                uSessionStatus = GUEST_SESSION_NOTIFYTYPE_TEA;
+                /* iSessionResult is undefined (0). */
+                break;
+
+            case RTPROCEXITREASON_SIGNAL:
+                uSessionStatus = GUEST_SESSION_NOTIFYTYPE_TES;
+                iSessionResult = ProcessStatus.iStatus; /* Report back the signal number. */
+                break;
+
+            default:
+                AssertMsgFailed(("Unhandled process termination reason (%d)\n", ProcessStatus.enmReason));
+                uSessionStatus = GUEST_SESSION_NOTIFYTYPE_TEA;
+                break;
+        }
+    }
+    else
+    {
+        /* If we didn't find the guest process anymore, just assume it terminated normally. */
+        uSessionStatus = GUEST_SESSION_NOTIFYTYPE_TEN;
+    }
+
+    /* Make sure to set stopped state before we let the host know. */
+    ASMAtomicWriteBool(&pThread->fStopped, true);
+
+    /* Report final status, regardless if we failed to wait above, so that the host knows what's going on. */
+    VGSvcVerbose(3, "Reporting final status %RU32 of session ID=%RU32\n", uSessionStatus, idSession);
+    Assert(uSessionStatus != GUEST_SESSION_NOTIFYTYPE_UNDEFINED);
+
+    VBGLR3GUESTCTRLCMDCTX ctx = { idClient, VBOX_GUESTCTRL_CONTEXTID_MAKE_SESSION(idSession),
+                                  0 /* uProtocol, unused */, 0 /* uNumParms, unused */ };
+    rc2 = VbglR3GuestCtrlSessionNotify(&ctx, uSessionStatus, iSessionResult);
+    if (RT_FAILURE(rc2))
+        VGSvcError("Reporting final status of session ID=%RU32 failed with rc=%Rrc\n", idSession, rc2);
+
+    VGSvcVerbose(3, "Thread for session ID=%RU32 ended with sessionStatus=%#x (%RU32), sessionRc=%#x (%Rrc)\n",
+                 idSession, uSessionStatus, uSessionStatus, iSessionResult, iSessionResult);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Reads the secret key the parent VBoxService instance passed us and pass it
+ * along as a authentication token to the host service.
+ *
+ * For older hosts, this sets up the message filtering.
+ *
+ * @returns VBox status code.
+ * @param   idClient        The HGCM client ID.
+ * @param   idSession       The session ID.
+ */
+static int vgsvcGstCtrlSessionReadKeyAndAccept(uint32_t idClient, uint32_t idSession)
+{
+    /*
+     * Read it.
+     */
+    RTHANDLE Handle;
+    int rc = RTHandleGetStandard(RTHANDLESTD_INPUT, true /*fLeaveOpen*/, &Handle);
+    if (RT_SUCCESS(rc))
+    {
+        if (Handle.enmType == RTHANDLETYPE_PIPE)
+        {
+            uint8_t abSecretKey[RT_SIZEOFMEMB(VBOXSERVICECTRLSESSIONTHREAD, abKey)];
+            rc = RTPipeReadBlocking(Handle.u.hPipe, abSecretKey, sizeof(abSecretKey), NULL);
+            if (RT_SUCCESS(rc))
+            {
+                VGSvcVerbose(3, "Got secret key from standard input.\n");
+
+                /*
+                 * Do the accepting, if appropriate.
+                 */
+                if (g_fControlSupportsOptimizations)
+                {
+                    rc = VbglR3GuestCtrlSessionAccept(idClient, idSession, abSecretKey, sizeof(abSecretKey));
+                    if (RT_SUCCESS(rc))
+                        VGSvcVerbose(3, "Session %u accepted (client ID %u)\n", idClient, idSession);
+                    else
+                        VGSvcError("Failed to accept session %u (client ID %u): %Rrc\n", idClient, idSession, rc);
+                }
+                else
+                {
+                    /* For legacy hosts, we do the filtering thingy. */
+                    rc = VbglR3GuestCtrlMsgFilterSet(idClient, VBOX_GUESTCTRL_CONTEXTID_MAKE_SESSION(idSession),
+                                                     VBOX_GUESTCTRL_FILTER_BY_SESSION(idSession), 0);
+                    if (RT_SUCCESS(rc))
+                        VGSvcVerbose(3, "Session %u filtering successfully enabled\n", idSession);
+                    else
+                        VGSvcError("Failed to set session filter: %Rrc\n", rc);
+                }
+            }
+            else
+                VGSvcError("Error reading secret key from standard input: %Rrc\n", rc);
+        }
+        else
+        {
+            VGSvcError("Standard input is not a pipe!\n");
+            rc = VERR_INVALID_HANDLE;
+        }
+        RTHandleClose(&Handle);
+    }
+    else
+        VGSvcError("RTHandleGetStandard failed on standard input: %Rrc\n", rc);
+    return rc;
+}
+
+/**
+ * Invalidates a guest session by updating all it's internal parameters like host features and stuff.
+ *
+ * @param   pSession            Session to invalidate.
+ * @param   idClient            Client ID to use.
+ */
+static void vgsvcGstCtrlSessionInvalidate(PVBOXSERVICECTRLSESSION pSession, uint32_t idClient)
+{
+    RT_NOREF(pSession);
+
+    VGSvcVerbose(1, "Invalidating session %RU32 (client ID=%RU32)\n", idClient, pSession->StartupInfo.uSessionID);
+
+    int rc2 = VbglR3GuestCtrlQueryFeatures(idClient, &g_fControlHostFeatures0);
+    if (RT_SUCCESS(rc2)) /* Querying host features is not fatal -- do not use rc here. */
+    {
+        VGSvcVerbose(1, "g_fControlHostFeatures0=%#x\n", g_fControlHostFeatures0);
+    }
+    else
+        VGSvcVerbose(1, "Querying host features failed with %Rrc\n", rc2);
+}
+
+/**
+ * Main message handler for the guest control session process.
+ *
+ * @returns exit code.
+ * @param   pSession    Pointer to g_Session.
+ * @thread  main.
+ */
+static RTEXITCODE vgsvcGstCtrlSessionSpawnWorker(PVBOXSERVICECTRLSESSION pSession)
+{
+    AssertPtrReturn(pSession, RTEXITCODE_FAILURE);
+    VGSvcVerbose(0, "Hi, this is guest session ID=%RU32\n", pSession->StartupInfo.uSessionID);
+
+    /*
+     * Connect to the host service.
+     */
+    uint32_t idClient;
+    int rc = VbglR3GuestCtrlConnect(&idClient);
+    if (RT_FAILURE(rc))
+        return VGSvcError("Error connecting to guest control service, rc=%Rrc\n", rc);
+    g_fControlSupportsOptimizations = VbglR3GuestCtrlSupportsOptimizations(idClient);
+    g_idControlSvcClient            = idClient;
+
+    VGSvcVerbose(1, "Using client ID=%RU32\n", idClient);
+
+    vgsvcGstCtrlSessionInvalidate(pSession, idClient);
+
+    rc = vgsvcGstCtrlSessionReadKeyAndAccept(idClient, pSession->StartupInfo.uSessionID);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Report started status.
+         * If session status cannot be posted to the host for some reason, bail out.
+         */
+        VBGLR3GUESTCTRLCMDCTX ctx = { idClient, VBOX_GUESTCTRL_CONTEXTID_MAKE_SESSION(pSession->StartupInfo.uSessionID),
+                                      0 /* uProtocol, unused */, 0 /* uNumParms, unused */ };
+        rc = VbglR3GuestCtrlSessionNotify(&ctx, GUEST_SESSION_NOTIFYTYPE_STARTED, VINF_SUCCESS);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Allocate a scratch buffer for messages which also send payload data with them.
+             * This buffer may grow if the host sends us larger chunks of data.
+             */
+            uint32_t cbScratchBuf = _64K;
+            void    *pvScratchBuf = RTMemAlloc(cbScratchBuf);
+            if (pvScratchBuf)
+            {
+                int cFailedMsgPeeks = 0;
+
+                /*
+                 * Message processing loop.
+                 */
+                VBGLR3GUESTCTRLCMDCTX CtxHost = { idClient, 0 /* Context ID */, pSession->StartupInfo.uProtocol, 0 };
+                for (;;)
+                {
+                    VGSvcVerbose(3, "Waiting for host msg ...\n");
+                    uint32_t uMsg = 0;
+                    rc = VbglR3GuestCtrlMsgPeekWait(idClient, &uMsg, &CtxHost.uNumParms, NULL);
+                    if (RT_SUCCESS(rc))
+                    {
+                        VGSvcVerbose(4, "Msg=%RU32 (%RU32 parms) retrieved (%Rrc)\n", uMsg, CtxHost.uNumParms, rc);
+
+                        /*
+                         * Pass it on to the session handler.
+                         * Note! Only when handling HOST_SESSION_CLOSE is the rc used.
+                         */
+                        bool fShutdown = false;
+                        rc = VGSvcGstCtrlSessionHandler(pSession, uMsg, &CtxHost, &pvScratchBuf, &cbScratchBuf, &fShutdown);
+                        if (fShutdown)
+                            break;
+
+                        cFailedMsgPeeks = 0;
+
+                        /* Let others run (guests are often single CPU) ... */
+                        RTThreadYield();
+                    }
+                    /*
+                     * Handle restore notification from host.  All the context IDs (sessions,
+                     * files, proceses, etc) are invalidated by a VM restore and must be closed.
+                     */
+                    else if (rc == VERR_VM_RESTORED)
+                    {
+                        VGSvcVerbose(1, "The VM session ID changed (i.e. restored), closing stale session %RU32\n",
+                                     pSession->StartupInfo.uSessionID);
+
+                        /* We currently don't serialize guest sessions, guest processes and other guest control objects
+                         * within saved states. So just close this session and report success to the parent process.
+                         *
+                         * Note: Not notifying the host here is intentional, as it wouldn't have any information
+                         *       about what to do with it.
+                         */
+                        rc = VINF_SUCCESS; /* Report success as exit code. */
+                        break;
+                    }
+                    else
+                    {
+                        VGSvcVerbose(1, "Getting host message failed with %Rrc\n", rc);
+
+                        if (cFailedMsgPeeks++ == 3)
+                            break;
+
+                        RTThreadSleep(3 * RT_MS_1SEC);
+
+                        /** @todo Shouldn't we have a plan for handling connection loss and such? */
+                    }
+                }
+
+                /*
+                 * Shutdown.
+                 */
+                RTMemFree(pvScratchBuf);
+            }
+            else
+                rc = VERR_NO_MEMORY;
+
+            VGSvcVerbose(0, "Session %RU32 ended\n", pSession->StartupInfo.uSessionID);
+        }
+        else
+            VGSvcError("Reporting session ID=%RU32 started status failed with rc=%Rrc\n", pSession->StartupInfo.uSessionID, rc);
+    }
+    else
+        VGSvcError("Setting message filterAdd=0x%x failed with rc=%Rrc\n", pSession->StartupInfo.uSessionID, rc);
+
+    VGSvcVerbose(3, "Disconnecting client ID=%RU32 ...\n", idClient);
+    VbglR3GuestCtrlDisconnect(idClient);
+    g_idControlSvcClient = 0;
+
+    VGSvcVerbose(3, "Session worker returned with rc=%Rrc\n", rc);
+    return RT_SUCCESS(rc) ? RTEXITCODE_SUCCESS : RTEXITCODE_FAILURE;
+}
+
+
+/**
+ * Finds a (formerly) started guest process given by its PID and increases its
+ * reference count.
+ *
+ * Must be decreased by the caller with VGSvcGstCtrlProcessRelease().
+ *
+ * @returns Guest process if found, otherwise NULL.
+ * @param   pSession    Pointer to guest session where to search process in.
+ * @param   uPID        PID to search for.
+ *
+ * @note    This does *not lock the process!
+ */
+PVBOXSERVICECTRLPROCESS VGSvcGstCtrlSessionRetainProcess(PVBOXSERVICECTRLSESSION pSession, uint32_t uPID)
+{
+    AssertPtrReturn(pSession, NULL);
+
+    PVBOXSERVICECTRLPROCESS pProcess = NULL;
+    int rc = RTCritSectEnter(&pSession->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        PVBOXSERVICECTRLPROCESS pCurProcess;
+        RTListForEach(&pSession->lstProcesses, pCurProcess, VBOXSERVICECTRLPROCESS, Node)
+        {
+            if (pCurProcess->uPID == uPID)
+            {
+                rc = RTCritSectEnter(&pCurProcess->CritSect);
+                if (RT_SUCCESS(rc))
+                {
+                    pCurProcess->cRefs++;
+                    rc = RTCritSectLeave(&pCurProcess->CritSect);
+                    AssertRC(rc);
+                }
+
+                if (RT_SUCCESS(rc))
+                    pProcess = pCurProcess;
+                break;
+            }
+        }
+
+        rc = RTCritSectLeave(&pSession->CritSect);
+        AssertRC(rc);
+    }
+
+    return pProcess;
+}
+
+
+int VGSvcGstCtrlSessionClose(PVBOXSERVICECTRLSESSION pSession)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+
+    VGSvcVerbose(0, "Session %RU32 is about to close ...\n", pSession->StartupInfo.uSessionID);
+
+    int rc = RTCritSectEnter(&pSession->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Close all guest processes.
+         */
+        VGSvcVerbose(0, "Stopping all guest processes ...\n");
+
+        /* Signal all guest processes in the active list that we want to shutdown. */
+        PVBOXSERVICECTRLPROCESS pProcess;
+        RTListForEach(&pSession->lstProcesses, pProcess, VBOXSERVICECTRLPROCESS, Node)
+            VGSvcGstCtrlProcessStop(pProcess);
+
+        VGSvcVerbose(1, "%RU32 guest processes were signalled to stop\n", pSession->cProcesses);
+
+        /* Wait for all active threads to shutdown and destroy the active thread list. */
+        PVBOXSERVICECTRLPROCESS pProcessNext;
+        RTListForEachSafe(&pSession->lstProcesses, pProcess, pProcessNext, VBOXSERVICECTRLPROCESS, Node)
+        {
+            int rc3 = RTCritSectLeave(&pSession->CritSect);
+            AssertRC(rc3);
+
+            int rc2 = VGSvcGstCtrlProcessWait(pProcess, 30 * 1000 /* Wait 30 seconds max. */, NULL /* rc */);
+
+            rc3 = RTCritSectEnter(&pSession->CritSect);
+            AssertRC(rc3);
+
+            if (RT_SUCCESS(rc2))
+            {
+                rc2 = vgsvcGstCtrlSessionProcessRemoveInternal(pSession, pProcess);
+                if (RT_SUCCESS(rc2))
+                {
+                    VGSvcGstCtrlProcessFree(pProcess);
+                    pProcess = NULL;
+                }
+            }
+        }
+
+        AssertMsg(pSession->cProcesses == 0,
+                  ("Session process list still contains %RU32 when it should not\n", pSession->cProcesses));
+        AssertMsg(RTListIsEmpty(&pSession->lstProcesses),
+                  ("Session process list is not empty when it should\n"));
+
+        /*
+         * Close all left guest files.
+         */
+        VGSvcVerbose(0, "Closing all guest files ...\n");
+
+        PVBOXSERVICECTRLFILE pFile, pFileNext;
+        RTListForEachSafe(&pSession->lstFiles, pFile, pFileNext, VBOXSERVICECTRLFILE, Node)
+        {
+            int rc2 = vgsvcGstCtrlSessionFileFree(pFile);
+            if (RT_FAILURE(rc2))
+            {
+                VGSvcError("Unable to close file '%s'; rc=%Rrc\n", pFile->pszName, rc2);
+                if (RT_SUCCESS(rc))
+                    rc = rc2;
+                /* Keep going. */
+            }
+
+            pFile = NULL; /* To make it obvious. */
+        }
+
+        AssertMsg(pSession->cFiles == 0,
+                  ("Session file list still contains %RU32 when it should not\n", pSession->cFiles));
+        AssertMsg(RTListIsEmpty(&pSession->lstFiles),
+                  ("Session file list is not empty when it should\n"));
+
+        int rc2 = RTCritSectLeave(&pSession->CritSect);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    return rc;
+}
+
+
+int VGSvcGstCtrlSessionDestroy(PVBOXSERVICECTRLSESSION pSession)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+
+    int rc = VGSvcGstCtrlSessionClose(pSession);
+
+    /* Destroy critical section. */
+    RTCritSectDelete(&pSession->CritSect);
+
+    return rc;
+}
+
+
+int VGSvcGstCtrlSessionInit(PVBOXSERVICECTRLSESSION pSession, uint32_t fFlags)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+
+    RTListInit(&pSession->lstProcesses);
+    RTListInit(&pSession->lstFiles);
+
+    pSession->cProcesses = 0;
+    pSession->cFiles     = 0;
+
+    pSession->fFlags = fFlags;
+
+    /* Init critical section for protecting the thread lists. */
+    int rc = RTCritSectInit(&pSession->CritSect);
+    AssertRC(rc);
+
+    return rc;
+}
+
+
+/**
+ * Adds a guest process to a session's process list.
+ *
+ * @return  VBox status code.
+ * @param   pSession                Guest session to add process to.
+ * @param   pProcess                Guest process to add.
+ */
+int VGSvcGstCtrlSessionProcessAdd(PVBOXSERVICECTRLSESSION pSession, PVBOXSERVICECTRLPROCESS pProcess)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pProcess, VERR_INVALID_POINTER);
+
+    int rc = RTCritSectEnter(&pSession->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        VGSvcVerbose(3, "Adding process (PID %RU32) to session ID=%RU32\n", pProcess->uPID, pSession->StartupInfo.uSessionID);
+
+        /* Add process to session list. */
+        RTListAppend(&pSession->lstProcesses, &pProcess->Node);
+
+        pSession->cProcesses++;
+        VGSvcVerbose(3, "Now session ID=%RU32 has %RU32 processes total\n",
+                     pSession->StartupInfo.uSessionID, pSession->cProcesses);
+
+        int rc2 = RTCritSectLeave(&pSession->CritSect);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Removes a guest process from a session's process list.
+ * Internal version, does not do locking.
+ *
+ * @return  VBox status code.
+ * @param   pSession                Guest session to remove process from.
+ * @param   pProcess                Guest process to remove.
+ */
+static int vgsvcGstCtrlSessionProcessRemoveInternal(PVBOXSERVICECTRLSESSION pSession, PVBOXSERVICECTRLPROCESS pProcess)
+{
+    VGSvcVerbose(3, "Removing process (PID %RU32) from session ID=%RU32\n", pProcess->uPID, pSession->StartupInfo.uSessionID);
+    AssertReturn(pProcess->cRefs == 0, VERR_WRONG_ORDER);
+
+    RTListNodeRemove(&pProcess->Node);
+
+    AssertReturn(pSession->cProcesses, VERR_WRONG_ORDER);
+    pSession->cProcesses--;
+    VGSvcVerbose(3, "Now session ID=%RU32 has %RU32 processes total\n",
+                 pSession->StartupInfo.uSessionID, pSession->cProcesses);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Removes a guest process from a session's process list.
+ *
+ * @return  VBox status code.
+ * @param   pSession                Guest session to remove process from.
+ * @param   pProcess                Guest process to remove.
+ */
+int VGSvcGstCtrlSessionProcessRemove(PVBOXSERVICECTRLSESSION pSession, PVBOXSERVICECTRLPROCESS pProcess)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pProcess, VERR_INVALID_POINTER);
+
+    int rc = RTCritSectEnter(&pSession->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        rc = vgsvcGstCtrlSessionProcessRemoveInternal(pSession, pProcess);
+
+        int rc2 = RTCritSectLeave(&pSession->CritSect);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    return rc;
+}
+
+
+/**
+ * Determines whether starting a new guest process according to the
+ * maximum number of concurrent guest processes defined is allowed or not.
+ *
+ * @return  VBox status code.
+ * @param   pSession            The guest session.
+ * @param   pfAllowed           \c True if starting (another) guest process
+ *                              is allowed, \c false if not.
+ */
+int VGSvcGstCtrlSessionProcessStartAllowed(const PVBOXSERVICECTRLSESSION pSession, bool *pfAllowed)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+    AssertPtrReturn(pfAllowed, VERR_INVALID_POINTER);
+
+    int rc = RTCritSectEnter(&pSession->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Check if we're respecting our memory policy by checking
+         * how many guest processes are started and served already.
+         */
+        bool fLimitReached = false;
+        if (pSession->uProcsMaxKept) /* If we allow unlimited processes (=0), take a shortcut. */
+        {
+            VGSvcVerbose(3, "Maximum kept guest processes set to %RU32, acurrent=%RU32\n",
+                         pSession->uProcsMaxKept, pSession->cProcesses);
+
+            int32_t iProcsLeft = (pSession->uProcsMaxKept - pSession->cProcesses - 1);
+            if (iProcsLeft < 0)
+            {
+                VGSvcVerbose(3, "Maximum running guest processes reached (%RU32)\n", pSession->uProcsMaxKept);
+                fLimitReached = true;
+            }
+        }
+
+        *pfAllowed = !fLimitReached;
+
+        int rc2 = RTCritSectLeave(&pSession->CritSect);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    return rc;
+}
+
+
+/**
+ * Cleans up stopped and no longer used processes.
+ *
+ * This will free and remove processes from the session's process list.
+ *
+ * @returns VBox status code.
+ * @param   pSession            Session to clean up processes for.
+ */
+static int vgsvcGstCtrlSessionCleanupProcesses(const PVBOXSERVICECTRLSESSION pSession)
+{
+    AssertPtrReturn(pSession, VERR_INVALID_POINTER);
+
+    VGSvcVerbose(3, "Cleaning up stopped processes for session %RU32 ...\n", pSession->StartupInfo.uSessionID);
+
+    int rc2 = RTCritSectEnter(&pSession->CritSect);
+    AssertRC(rc2);
+
+    int rc = VINF_SUCCESS;
+
+    PVBOXSERVICECTRLPROCESS pCurProcess, pNextProcess;
+    RTListForEachSafe(&pSession->lstProcesses, pCurProcess, pNextProcess, VBOXSERVICECTRLPROCESS, Node)
+    {
+        if (ASMAtomicReadBool(&pCurProcess->fStopped))
+        {
+            rc2 = RTCritSectLeave(&pSession->CritSect);
+            AssertRC(rc2);
+
+            rc = VGSvcGstCtrlProcessWait(pCurProcess, 30 * 1000 /* Wait 30 seconds max. */, NULL /* rc */);
+            if (RT_SUCCESS(rc))
+            {
+                VGSvcGstCtrlSessionProcessRemove(pSession, pCurProcess);
+                VGSvcGstCtrlProcessFree(pCurProcess);
+            }
+
+            rc2 = RTCritSectEnter(&pSession->CritSect);
+            AssertRC(rc2);
+
+            /* If failed, try next time we're being called. */
+        }
+    }
+
+    rc2 = RTCritSectLeave(&pSession->CritSect);
+    AssertRC(rc2);
+
+    if (RT_FAILURE(rc))
+        VGSvcError("Cleaning up stopped processes for session %RU32 failed with %Rrc\n", pSession->StartupInfo.uSessionID, rc);
+
+    return rc;
+}
+
+
+/**
+ * Creates the process for a guest session.
+ *
+ * @return  VBox status code.
+ * @param   pSessionStartupInfo     Session startup info.
+ * @param   pSessionThread          The session thread under construction.
+ * @param   uCtrlSessionThread      The session thread debug ordinal.
+ */
+static int vgsvcVGSvcGstCtrlSessionThreadCreateProcess(const PVBGLR3GUESTCTRLSESSIONSTARTUPINFO pSessionStartupInfo,
+                                                       PVBOXSERVICECTRLSESSIONTHREAD pSessionThread, uint32_t uCtrlSessionThread)
+{
+    RT_NOREF(uCtrlSessionThread);
+
+    /*
+     * Is this an anonymous session?  Anonymous sessions run with the same
+     * privileges as the main VBoxService executable.
+     */
+    bool const fAnonymous =    pSessionThread->pStartupInfo->pszUser
+                            && pSessionThread->pStartupInfo->pszUser[0] == '\0';
+    if (fAnonymous)
+    {
+        Assert(!strlen(pSessionThread->pStartupInfo->pszPassword));
+        Assert(!strlen(pSessionThread->pStartupInfo->pszDomain));
+
+        VGSvcVerbose(3, "New anonymous guest session ID=%RU32 created, fFlags=%x, using protocol %RU32\n",
+                     pSessionStartupInfo->uSessionID,
+                     pSessionStartupInfo->fFlags,
+                     pSessionStartupInfo->uProtocol);
+    }
+    else
+    {
+        VGSvcVerbose(3, "Spawning new guest session ID=%RU32, szUser=%s, szPassword=%s, szDomain=%s, fFlags=%x, using protocol %RU32\n",
+                     pSessionStartupInfo->uSessionID,
+                     pSessionStartupInfo->pszUser,
+#ifdef DEBUG
+                     pSessionStartupInfo->pszPassword,
+#else
+                     "XXX", /* Never show passwords in release mode. */
+#endif
+                     pSessionStartupInfo->pszDomain,
+                     pSessionStartupInfo->fFlags,
+                     pSessionStartupInfo->uProtocol);
+    }
+
+    /*
+     * Spawn a child process for doing the actual session handling.
+     * Start by assembling the argument list.
+     */
+    char szExeName[RTPATH_MAX];
+    char *pszExeName = RTProcGetExecutablePath(szExeName, sizeof(szExeName));
+    AssertPtrReturn(pszExeName, VERR_FILENAME_TOO_LONG);
+
+    char szParmSessionID[32];
+    RTStrPrintf(szParmSessionID, sizeof(szParmSessionID), "--session-id=%RU32", pSessionThread->pStartupInfo->uSessionID);
+
+    char szParmSessionProto[32];
+    RTStrPrintf(szParmSessionProto, sizeof(szParmSessionProto), "--session-proto=%RU32",
+                pSessionThread->pStartupInfo->uProtocol);
+#ifdef DEBUG
+    char szParmThreadId[32];
+    RTStrPrintf(szParmThreadId, sizeof(szParmThreadId), "--thread-id=%RU32", uCtrlSessionThread);
+#endif
+    unsigned    idxArg = 0; /* Next index in argument vector. */
+    char const *apszArgs[24];
+
+    apszArgs[idxArg++] = pszExeName;
+#ifdef VBOXSERVICE_ARG1_UTF8_ARGV
+    apszArgs[idxArg++] = VBOXSERVICE_ARG1_UTF8_ARGV; Assert(idxArg == 2);
+#endif
+    apszArgs[idxArg++] = "guestsession";
+    apszArgs[idxArg++] = szParmSessionID;
+    apszArgs[idxArg++] = szParmSessionProto;
+#ifdef DEBUG
+    apszArgs[idxArg++] = szParmThreadId;
+#endif
+    if (!fAnonymous) /* Do we need to pass a user name? */
+    {
+        apszArgs[idxArg++] = "--user";
+        apszArgs[idxArg++] = pSessionThread->pStartupInfo->pszUser;
+
+        if (strlen(pSessionThread->pStartupInfo->pszDomain))
+        {
+            apszArgs[idxArg++] = "--domain";
+            apszArgs[idxArg++] = pSessionThread->pStartupInfo->pszDomain;
+        }
+    }
+
+    /* Add same verbose flags as parent process. */
+    char szParmVerbose[32];
+    if (g_cVerbosity > 0)
+    {
+        unsigned cVs = RT_MIN(g_cVerbosity, RT_ELEMENTS(szParmVerbose) - 2);
+        szParmVerbose[0] = '-';
+        memset(&szParmVerbose[1], 'v', cVs);
+        szParmVerbose[1 + cVs] = '\0';
+        apszArgs[idxArg++] = szParmVerbose;
+    }
+
+    /* Add log file handling. Each session will have an own
+     * log file, naming based on the parent log file. */
+    char szParmLogFile[sizeof(g_szLogFile) + 128];
+    if (g_szLogFile[0])
+    {
+        const char *pszSuffix = RTPathSuffix(g_szLogFile);
+        if (!pszSuffix)
+            pszSuffix = strchr(g_szLogFile, '\0');
+        size_t cchBase = pszSuffix - g_szLogFile;
+
+        RTTIMESPEC Now;
+        RTTimeNow(&Now);
+        char szTime[64];
+        RTTimeSpecToString(&Now, szTime, sizeof(szTime));
+
+        /* Replace out characters not allowed on Windows platforms, put in by RTTimeSpecToString(). */
+        static const RTUNICP s_uszValidRangePairs[] =
+        {
+            ' ', ' ',
+            '(', ')',
+            '-', '.',
+            '0', '9',
+            'A', 'Z',
+            'a', 'z',
+            '_', '_',
+            0xa0, 0xd7af,
+            '\0'
+        };
+        ssize_t cReplaced = RTStrPurgeComplementSet(szTime, s_uszValidRangePairs, '_' /* chReplacement */);
+        AssertReturn(cReplaced, VERR_INVALID_UTF8_ENCODING);
+
+#ifndef DEBUG
+        RTStrPrintf(szParmLogFile, sizeof(szParmLogFile), "%.*s-%RU32-%s-%s%s",
+                    cchBase, g_szLogFile, pSessionStartupInfo->uSessionID, pSessionStartupInfo->pszUser, szTime, pszSuffix);
+#else
+        RTStrPrintf(szParmLogFile, sizeof(szParmLogFile), "%.*s-%RU32-%RU32-%s-%s%s",
+                    cchBase, g_szLogFile, pSessionStartupInfo->uSessionID, uCtrlSessionThread,
+                    pSessionStartupInfo->pszUser, szTime, pszSuffix);
+#endif
+        apszArgs[idxArg++] = "--logfile";
+        apszArgs[idxArg++] = szParmLogFile;
+    }
+
+#ifdef DEBUG
+    if (g_Session.fFlags & VBOXSERVICECTRLSESSION_FLAG_DUMPSTDOUT)
+        apszArgs[idxArg++] = "--dump-stdout";
+    if (g_Session.fFlags & VBOXSERVICECTRLSESSION_FLAG_DUMPSTDERR)
+        apszArgs[idxArg++] = "--dump-stderr";
+#endif
+    apszArgs[idxArg] = NULL;
+    Assert(idxArg < RT_ELEMENTS(apszArgs));
+
+    if (g_cVerbosity > 3)
+    {
+        VGSvcVerbose(4, "Spawning parameters:\n");
+        for (idxArg = 0; apszArgs[idxArg]; idxArg++)
+            VGSvcVerbose(4, "    %s\n", apszArgs[idxArg]);
+    }
+
+    /*
+     * Flags.
+     */
+    uint32_t const fProcCreate = RTPROC_FLAGS_PROFILE
+#ifdef RT_OS_WINDOWS
+                               | RTPROC_FLAGS_SERVICE
+                               | RTPROC_FLAGS_HIDDEN
+#endif
+                               | VBOXSERVICE_PROC_F_UTF8_ARGV;
+
+    /*
+     * Configure standard handles.
+     */
+    RTHANDLE hStdIn;
+    int rc = RTPipeCreate(&hStdIn.u.hPipe, &pSessionThread->hKeyPipe, RTPIPE_C_INHERIT_READ);
+    if (RT_SUCCESS(rc))
+    {
+        hStdIn.enmType = RTHANDLETYPE_PIPE;
+
+        RTHANDLE hStdOutAndErr;
+        rc = RTFileOpenBitBucket(&hStdOutAndErr.u.hFile, RTFILE_O_WRITE);
+        if (RT_SUCCESS(rc))
+        {
+            hStdOutAndErr.enmType = RTHANDLETYPE_FILE;
+
+            /*
+             * Windows: If a domain name is given, construct an UPN (User Principle Name)
+             *          with the domain name built-in, e.g. "joedoe@example.com".
+             */
+            const char *pszUser    = pSessionThread->pStartupInfo->pszUser;
+#ifdef RT_OS_WINDOWS
+            char       *pszUserUPN = NULL;
+            if (pSessionThread->pStartupInfo->pszDomain[0])
+            {
+                int cchbUserUPN = RTStrAPrintf(&pszUserUPN, "%s@%s",
+                                               pSessionThread->pStartupInfo->pszUser,
+                                               pSessionThread->pStartupInfo->pszDomain);
+                if (cchbUserUPN > 0)
+                {
+                    pszUser = pszUserUPN;
+                    VGSvcVerbose(3, "Using UPN: %s\n", pszUserUPN);
+                }
+                else
+                    rc = VERR_NO_STR_MEMORY;
+            }
+            if (RT_SUCCESS(rc))
+#endif
+            {
+                /*
+                 * Finally, create the process.
+                 */
+                rc = RTProcCreateEx(pszExeName, apszArgs, RTENV_DEFAULT, fProcCreate,
+                                    &hStdIn, &hStdOutAndErr, &hStdOutAndErr,
+                                    !fAnonymous ? pszUser : NULL,
+                                    !fAnonymous ? pSessionThread->pStartupInfo->pszPassword : NULL,
+                                    NULL /*pvExtraData*/,
+                                    &pSessionThread->hProcess);
+            }
+#ifdef RT_OS_WINDOWS
+            RTStrFree(pszUserUPN);
+#endif
+            RTFileClose(hStdOutAndErr.u.hFile);
+        }
+
+        RTPipeClose(hStdIn.u.hPipe);
+    }
+    return rc;
+}
+
+
+/**
+ * Creates a guest session.
+ *
+ * This will spawn a new VBoxService.exe instance under behalf of the given user
+ * which then will act as a session host. On successful open, the session will
+ * be added to the given session thread list.
+ *
+ * @return  VBox status code.
+ * @param   pList                   Which list to use to store the session thread in.
+ * @param   pSessionStartupInfo     Session startup info.
+ * @param   ppSessionThread         Returns newly created session thread on success.
+ *                                  Optional.
+ */
+int VGSvcGstCtrlSessionThreadCreate(PRTLISTANCHOR pList, const PVBGLR3GUESTCTRLSESSIONSTARTUPINFO pSessionStartupInfo,
+                                    PVBOXSERVICECTRLSESSIONTHREAD *ppSessionThread)
+{
+    AssertPtrReturn(pList, VERR_INVALID_POINTER);
+    AssertPtrReturn(pSessionStartupInfo, VERR_INVALID_POINTER);
+    /* ppSessionThread is optional. */
+
+#ifdef VBOX_STRICT
+    /* Check for existing session in debug mode. Should never happen because of
+     * Main consistency. */
+    PVBOXSERVICECTRLSESSIONTHREAD pSessionCur;
+    RTListForEach(pList, pSessionCur, VBOXSERVICECTRLSESSIONTHREAD, Node)
+    {
+        AssertMsgReturn(   pSessionCur->fStopped == true
+                        || pSessionCur->pStartupInfo->uSessionID != pSessionStartupInfo->uSessionID,
+                        ("Guest session thread ID=%RU32 already exists (fStopped=%RTbool)\n",
+                         pSessionCur->pStartupInfo->uSessionID, pSessionCur->fStopped), VERR_ALREADY_EXISTS);
+    }
+#endif
+
+    /* Static counter to help tracking session thread <-> process relations. */
+    static uint32_t s_uCtrlSessionThread = 0;
+
+    /*
+     * Allocate and initialize the session thread structure.
+     */
+    int rc;
+    PVBOXSERVICECTRLSESSIONTHREAD pSessionThread = (PVBOXSERVICECTRLSESSIONTHREAD)RTMemAllocZ(sizeof(*pSessionThread));
+    if (pSessionThread)
+    {
+        //pSessionThread->fShutdown = false;
+        //pSessionThread->fStarted  = false;
+        //pSessionThread->fStopped  = false;
+        pSessionThread->hKeyPipe  = NIL_RTPIPE;
+        pSessionThread->Thread    = NIL_RTTHREAD;
+        pSessionThread->hProcess  = NIL_RTPROCESS;
+
+        /* Duplicate startup info. */
+        pSessionThread->pStartupInfo = VbglR3GuestCtrlSessionStartupInfoDup(pSessionStartupInfo);
+        AssertPtrReturn(pSessionThread->pStartupInfo, VERR_NO_MEMORY);
+
+        /* Generate the secret key. */
+        RTRandBytes(pSessionThread->abKey, sizeof(pSessionThread->abKey));
+
+        rc = RTCritSectInit(&pSessionThread->CritSect);
+        AssertRC(rc);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Give the session key to the host so it can validate the client.
+             */
+            if (VbglR3GuestCtrlSupportsOptimizations(g_idControlSvcClient))
+            {
+                for (uint32_t i = 0; i < 10; i++)
+                {
+                    rc = VbglR3GuestCtrlSessionPrepare(g_idControlSvcClient, pSessionStartupInfo->uSessionID,
+                                                       pSessionThread->abKey, sizeof(pSessionThread->abKey));
+                    if (rc != VERR_OUT_OF_RESOURCES)
+                        break;
+                    RTThreadSleep(100);
+                }
+            }
+            if (RT_SUCCESS(rc))
+            {
+                s_uCtrlSessionThread++;
+
+                /*
+                 * Start the session child process.
+                 */
+                rc = vgsvcVGSvcGstCtrlSessionThreadCreateProcess(pSessionStartupInfo, pSessionThread, s_uCtrlSessionThread);
+                if (RT_SUCCESS(rc))
+                {
+                    /*
+                     * Start the session thread.
+                     */
+                    rc = RTThreadCreateF(&pSessionThread->Thread, vgsvcGstCtrlSessionThread, pSessionThread /*pvUser*/, 0 /*cbStack*/,
+                                         RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "gctls%RU32", s_uCtrlSessionThread);
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Wait for the thread to initialize. */
+                        rc = RTThreadUserWait(pSessionThread->Thread, RT_MS_1MIN);
+                        if (   RT_SUCCESS(rc)
+                            && !ASMAtomicReadBool(&pSessionThread->fShutdown))
+                        {
+                            VGSvcVerbose(2, "Thread for session ID=%RU32 started\n", pSessionThread->pStartupInfo->uSessionID);
+
+                            ASMAtomicXchgBool(&pSessionThread->fStarted, true);
+
+                            /* Add session to list. */
+                            RTListAppend(pList, &pSessionThread->Node);
+                            if (ppSessionThread) /* Return session if wanted. */
+                                *ppSessionThread = pSessionThread;
+                            return VINF_SUCCESS;
+                        }
+
+                        /*
+                         * Bail out.
+                         */
+                        VGSvcError("Thread for session ID=%RU32 failed to start, rc=%Rrc\n",
+                                   pSessionThread->pStartupInfo->uSessionID, rc);
+                        if (RT_SUCCESS_NP(rc))
+                            rc = VERR_CANT_CREATE; /** @todo Find a better rc. */
+                    }
+                    else
+                        VGSvcError("Creating session thread failed, rc=%Rrc\n", rc);
+
+                    RTProcTerminate(pSessionThread->hProcess);
+                    uint32_t cMsWait = 1;
+                    while (   RTProcWait(pSessionThread->hProcess, RTPROCWAIT_FLAGS_NOBLOCK, NULL) == VERR_PROCESS_RUNNING
+                           && cMsWait <= 9) /* 1023 ms */
+                    {
+                        RTThreadSleep(cMsWait);
+                        cMsWait <<= 1;
+                    }
+                }
+
+                if (VbglR3GuestCtrlSupportsOptimizations(g_idControlSvcClient))
+                    VbglR3GuestCtrlSessionCancelPrepared(g_idControlSvcClient, pSessionStartupInfo->uSessionID);
+            }
+            else
+                VGSvcVerbose(3, "VbglR3GuestCtrlSessionPrepare failed: %Rrc\n", rc);
+            RTPipeClose(pSessionThread->hKeyPipe);
+            pSessionThread->hKeyPipe = NIL_RTPIPE;
+            RTCritSectDelete(&pSessionThread->CritSect);
+        }
+        RTMemFree(pSessionThread);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    VGSvcVerbose(3, "Spawning session thread returned returned rc=%Rrc\n", rc);
+    return rc;
+}
+
+
+/**
+ * Waits for a formerly opened guest session process to close.
+ *
+ * @return  VBox status code.
+ * @param   pThread                 Guest session thread to wait for.
+ * @param   uTimeoutMS              Waiting timeout (in ms).
+ * @param   fFlags                  Closing flags.
+ */
+int VGSvcGstCtrlSessionThreadWait(PVBOXSERVICECTRLSESSIONTHREAD pThread, uint32_t uTimeoutMS, uint32_t fFlags)
+{
+    RT_NOREF(fFlags);
+    AssertPtrReturn(pThread, VERR_INVALID_POINTER);
+    /** @todo Validate closing flags. */
+
+    AssertMsgReturn(pThread->Thread != NIL_RTTHREAD,
+                    ("Guest session thread of session %p does not exist when it should\n", pThread),
+                    VERR_NOT_FOUND);
+
+    int rc = VINF_SUCCESS;
+
+    /*
+     * The spawned session process should have received the same closing request,
+     * so just wait for the process to close.
+     */
+    if (ASMAtomicReadBool(&pThread->fStarted))
+    {
+        /* Ask the thread to shutdown. */
+        ASMAtomicXchgBool(&pThread->fShutdown, true);
+
+        VGSvcVerbose(3, "Waiting for session thread ID=%RU32 to close (%RU32ms) ...\n",
+                     pThread->pStartupInfo->uSessionID, uTimeoutMS);
+
+        int rcThread;
+        rc = RTThreadWait(pThread->Thread, uTimeoutMS, &rcThread);
+        if (RT_SUCCESS(rc))
+        {
+            AssertMsg(pThread->fStopped, ("Thread of session ID=%RU32 not in stopped state when it should\n",
+                      pThread->pStartupInfo->uSessionID));
+
+            VGSvcVerbose(3, "Session thread ID=%RU32 ended with rc=%Rrc\n", pThread->pStartupInfo->uSessionID, rcThread);
+        }
+        else
+            VGSvcError("Waiting for session thread ID=%RU32 to close failed with rc=%Rrc\n", pThread->pStartupInfo->uSessionID, rc);
+    }
+    else
+        VGSvcVerbose(3, "Thread for session ID=%RU32 not in started state, skipping wait\n", pThread->pStartupInfo->uSessionID);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Waits for the specified session thread to end and remove
+ * it from the session thread list.
+ *
+ * @return  VBox status code.
+ * @param   pThread                 Session thread to destroy.
+ * @param   fFlags                  Closing flags.
+ */
+int VGSvcGstCtrlSessionThreadDestroy(PVBOXSERVICECTRLSESSIONTHREAD pThread, uint32_t fFlags)
+{
+    AssertPtrReturn(pThread, VERR_INVALID_POINTER);
+    AssertPtrReturn(pThread->pStartupInfo, VERR_WRONG_ORDER);
+
+    const uint32_t uSessionID = pThread->pStartupInfo->uSessionID;
+
+    VGSvcVerbose(3, "Destroying session ID=%RU32 ...\n", uSessionID);
+
+    int rc = VGSvcGstCtrlSessionThreadWait(pThread, 5 * 60 * 1000 /* 5 minutes timeout */, fFlags);
+    if (RT_SUCCESS(rc))
+    {
+        VbglR3GuestCtrlSessionStartupInfoFree(pThread->pStartupInfo);
+        pThread->pStartupInfo = NULL;
+
+        RTPipeClose(pThread->hKeyPipe);
+        pThread->hKeyPipe = NIL_RTPIPE;
+
+        RTCritSectDelete(&pThread->CritSect);
+
+        /* Remove session from list and destroy object. */
+        RTListNodeRemove(&pThread->Node);
+
+        RTMemFree(pThread);
+        pThread = NULL;
+    }
+
+    VGSvcVerbose(3, "Destroyed session ID=%RU32 with %Rrc\n", uSessionID, rc);
+    return rc;
+}
+
+/**
+ * Close all open guest session threads.
+ *
+ * @note    Caller is responsible for locking!
+ *
+ * @return  VBox status code.
+ * @param   pList                   Which list to close the session threads for.
+ * @param   fFlags                  Closing flags.
+ */
+int VGSvcGstCtrlSessionThreadDestroyAll(PRTLISTANCHOR pList, uint32_t fFlags)
+{
+    AssertPtrReturn(pList, VERR_INVALID_POINTER);
+
+    int rc = VINF_SUCCESS;
+
+    /*int rc = VbglR3GuestCtrlClose
+        if (RT_FAILURE(rc))
+            VGSvcError("Cancelling pending waits failed; rc=%Rrc\n", rc);*/
+
+    PVBOXSERVICECTRLSESSIONTHREAD pSessIt;
+    PVBOXSERVICECTRLSESSIONTHREAD pSessItNext;
+    RTListForEachSafe(pList, pSessIt, pSessItNext, VBOXSERVICECTRLSESSIONTHREAD, Node)
+    {
+        int rc2 = VGSvcGstCtrlSessionThreadDestroy(pSessIt, fFlags);
+        if (RT_FAILURE(rc2))
+        {
+            VGSvcError("Closing session thread '%s' failed with rc=%Rrc\n", RTThreadGetName(pSessIt->Thread), rc2);
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+            /* Keep going. */
+        }
+    }
+
+    VGSvcVerbose(4, "Destroying guest session threads ended with %Rrc\n", rc);
+    return rc;
+}
+
+
+/**
+ * Main function for the session process.
+ *
+ * @returns exit code.
+ * @param   argc        Argument count.
+ * @param   argv        Argument vector (UTF-8).
+ */
+RTEXITCODE VGSvcGstCtrlSessionSpawnInit(int argc, char **argv)
+{
+    static const RTGETOPTDEF s_aOptions[] =
+    {
+        { "--domain",          VBOXSERVICESESSIONOPT_DOMAIN,          RTGETOPT_REQ_STRING },
+#ifdef DEBUG
+        { "--dump-stdout",     VBOXSERVICESESSIONOPT_DUMP_STDOUT,     RTGETOPT_REQ_NOTHING },
+        { "--dump-stderr",     VBOXSERVICESESSIONOPT_DUMP_STDERR,     RTGETOPT_REQ_NOTHING },
+#endif
+        { "--logfile",         VBOXSERVICESESSIONOPT_LOG_FILE,        RTGETOPT_REQ_STRING },
+        { "--user",            VBOXSERVICESESSIONOPT_USERNAME,        RTGETOPT_REQ_STRING },
+        { "--session-id",      VBOXSERVICESESSIONOPT_SESSION_ID,      RTGETOPT_REQ_UINT32 },
+        { "--session-proto",   VBOXSERVICESESSIONOPT_SESSION_PROTO,   RTGETOPT_REQ_UINT32 },
+#ifdef DEBUG
+        { "--thread-id",       VBOXSERVICESESSIONOPT_THREAD_ID,       RTGETOPT_REQ_UINT32 },
+#endif /* DEBUG */
+        { "--verbose",         'v',                                   RTGETOPT_REQ_NOTHING }
+    };
+
+    RTGETOPTSTATE GetState;
+    RTGetOptInit(&GetState, argc, argv,
+                 s_aOptions, RT_ELEMENTS(s_aOptions),
+                 1 /*iFirst*/, RTGETOPTINIT_FLAGS_OPTS_FIRST);
+
+    uint32_t fSession = VBOXSERVICECTRLSESSION_FLAG_SPAWN;
+
+    /* Protocol and session ID must be specified explicitly. */
+    g_Session.StartupInfo.uProtocol  = UINT32_MAX;
+    g_Session.StartupInfo.uSessionID = UINT32_MAX;
+
+    int ch;
+    RTGETOPTUNION ValueUnion;
+    while ((ch = RTGetOpt(&GetState, &ValueUnion)) != 0)
+    {
+        /* For options that require an argument, ValueUnion has received the value. */
+        switch (ch)
+        {
+            case VBOXSERVICESESSIONOPT_DOMAIN:
+                /* Information not needed right now, skip. */
+                break;
+#ifdef DEBUG
+            case VBOXSERVICESESSIONOPT_DUMP_STDOUT:
+                fSession |= VBOXSERVICECTRLSESSION_FLAG_DUMPSTDOUT;
+                break;
+
+            case VBOXSERVICESESSIONOPT_DUMP_STDERR:
+                fSession |= VBOXSERVICECTRLSESSION_FLAG_DUMPSTDERR;
+                break;
+#endif
+            case VBOXSERVICESESSIONOPT_SESSION_ID:
+                g_Session.StartupInfo.uSessionID = ValueUnion.u32;
+                break;
+
+            case VBOXSERVICESESSIONOPT_SESSION_PROTO:
+                g_Session.StartupInfo.uProtocol = ValueUnion.u32;
+                break;
+#ifdef DEBUG
+            case VBOXSERVICESESSIONOPT_THREAD_ID:
+                /* Not handled. Mainly for processs listing. */
+                break;
+#endif
+            case VBOXSERVICESESSIONOPT_LOG_FILE:
+            {
+                int rc = RTStrCopy(g_szLogFile, sizeof(g_szLogFile), ValueUnion.psz);
+                if (RT_FAILURE(rc))
+                    return RTMsgErrorExit(RTEXITCODE_FAILURE, "Error copying log file name: %Rrc", rc);
+                break;
+            }
+
+            case VBOXSERVICESESSIONOPT_USERNAME:
+                /* Information not needed right now, skip. */
+                break;
+
+            /** @todo Implement help? */
+
+            case 'v':
+                g_cVerbosity++;
+                break;
+
+            case VINF_GETOPT_NOT_OPTION:
+            {
+                if (!RTStrICmp(ValueUnion.psz, VBOXSERVICECTRLSESSION_GETOPT_PREFIX))
+                    break;
+                /* else fall through and bail out. */
+                RT_FALL_THROUGH();
+            }
+            default:
+                return RTMsgErrorExit(RTEXITCODE_SYNTAX, "Unknown argument '%s'", ValueUnion.psz);
+        }
+    }
+
+    /* Check that we've got all the required options. */
+    if (g_Session.StartupInfo.uProtocol == UINT32_MAX)
+        return RTMsgErrorExit(RTEXITCODE_SYNTAX, "No protocol version specified");
+
+    if (g_Session.StartupInfo.uSessionID == UINT32_MAX)
+        return RTMsgErrorExit(RTEXITCODE_SYNTAX, "No session ID specified");
+
+    /* Init the session object. */
+    int rc = VGSvcGstCtrlSessionInit(&g_Session, fSession);
+    if (RT_FAILURE(rc))
+        return RTMsgErrorExit(RTEXITCODE_INIT, "Failed to initialize session object, rc=%Rrc\n", rc);
+
+    rc = VGSvcLogCreate(g_szLogFile[0] ? g_szLogFile : NULL);
+    if (RT_FAILURE(rc))
+        return RTMsgErrorExit(RTEXITCODE_INIT, "Failed to create log file '%s', rc=%Rrc\n",
+                              g_szLogFile[0] ? g_szLogFile : "<None>", rc);
+
+    RTEXITCODE rcExit = vgsvcGstCtrlSessionSpawnWorker(&g_Session);
+
+    VGSvcLogDestroy();
+    return rcExit;
+}
+