/* $Id: SUPDrv-linux.c 162704 2024-04-09 12:24:51Z aeichner $ */
/** @file
 * VBoxDrv - The VirtualBox Support Driver - Linux specifics.
 */

/*
 * Copyright (C) 2006-2023 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>.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
 * in the VirtualBox distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 *
 * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
 */


/*********************************************************************************************************************************
*   Header Files                                                                                                                 *
*********************************************************************************************************************************/
#define LOG_GROUP LOG_GROUP_SUP_DRV
#include "../SUPDrvInternal.h"
#include "the-linux-kernel.h"
#include "version-generated.h"
#include "product-generated.h"
#include "revision-generated.h"

#include <iprt/assert.h>
#include <iprt/spinlock.h>
#include <iprt/semaphore.h>
#include <iprt/initterm.h>
#include <iprt/process.h>
#include <iprt/thread.h>
#include <VBox/err.h>
#include <iprt/mem.h>
#include <VBox/log.h>
#include <VBox/VBoxLnxModInline.h>
#include <iprt/mp.h>

/** @todo figure out the exact version number */
#if RTLNX_VER_MIN(2,6,16)
# include <iprt/power.h>
# define VBOX_WITH_SUSPEND_NOTIFICATION
#endif

#include <linux/sched.h>
#include <linux/miscdevice.h>
#ifdef VBOX_WITH_SUSPEND_NOTIFICATION
# include <linux/platform_device.h>
#endif
#if (RTLNX_VER_MIN(2,6,28)) && defined(SUPDRV_WITH_MSR_PROBER)
# define SUPDRV_LINUX_HAS_SAFE_MSR_API
# include <asm/msr.h>
#endif

#include <asm/desc.h>

#include <iprt/asm-amd64-x86.h>


/*********************************************************************************************************************************
*   Defined Constants And Macros                                                                                                 *
*********************************************************************************************************************************/
/* check kernel version */
# ifndef SUPDRV_AGNOSTIC
#  if RTLNX_VER_MAX(2,6,0)
#   error Unsupported kernel version!
#  endif
# endif

#ifdef CONFIG_X86_HIGH_ENTRY
# error "CONFIG_X86_HIGH_ENTRY is not supported by VBoxDrv at this time."
#endif

/* We cannot include x86.h, so we copy the defines we need here: */
#define X86_EFL_IF          RT_BIT(9)
#define X86_EFL_AC          RT_BIT(18)
#define X86_EFL_DF          RT_BIT(10)
#define X86_EFL_IOPL        (RT_BIT(12) | RT_BIT(13))

/* To include the version number of VirtualBox into kernel backtraces: */
#define VBoxDrvLinuxVersion RT_CONCAT3(RT_CONCAT(VBOX_VERSION_MAJOR, _), \
                                       RT_CONCAT(VBOX_VERSION_MINOR, _), \
                                       VBOX_VERSION_BUILD)
#define VBoxDrvLinuxIOCtl RT_CONCAT(VBoxDrvLinuxIOCtl_,VBoxDrvLinuxVersion)

/* Once externally provided, this string will be printed into kernel log on
 * module start together with the rest of versioning information. */
#ifndef VBOX_EXTRA_VERSION_STRING
# define VBOX_EXTRA_VERSION_STRING ""
#endif


/*********************************************************************************************************************************
*   Structures and Typedefs                                                                                                      *
*********************************************************************************************************************************/
#if RTLNX_VER_MIN(5,0,0)
/** Wrapper module list entry. */
typedef struct SUPDRVLNXMODULE
{
    RTLISTNODE      ListEntry;
    struct module  *pModule;
} SUPDRVLNXMODULE;
/** Pointer to a wrapper module list entry. */
typedef SUPDRVLNXMODULE *PSUPDRVLNXMODULE;
#endif


/*********************************************************************************************************************************
*   Internal Functions                                                                                                           *
*********************************************************************************************************************************/
static int  __init VBoxDrvLinuxInit(void);
static void __exit VBoxDrvLinuxUnload(void);
static int  VBoxDrvLinuxCreateSys(struct inode *pInode, struct file *pFilp);
static int  VBoxDrvLinuxCreateUsr(struct inode *pInode, struct file *pFilp);
static int  VBoxDrvLinuxClose(struct inode *pInode, struct file *pFilp);
#ifdef HAVE_UNLOCKED_IOCTL
static long VBoxDrvLinuxIOCtl(struct file *pFilp, unsigned int uCmd, unsigned long ulArg);
#else
static int  VBoxDrvLinuxIOCtl(struct inode *pInode, struct file *pFilp, unsigned int uCmd, unsigned long ulArg);
#endif
static int  VBoxDrvLinuxIOCtlSlow(struct file *pFilp, unsigned int uCmd, unsigned long ulArg, PSUPDRVSESSION pSession);
static int  VBoxDrvLinuxErr2LinuxErr(int);
#ifdef VBOX_WITH_SUSPEND_NOTIFICATION
static int  VBoxDrvProbe(struct platform_device *pDev);
# if RTLNX_VER_MIN(2,6,30)
static int  VBoxDrvSuspend(struct device *pDev);
static int  VBoxDrvResume(struct device *pDev);
# else
static int  VBoxDrvSuspend(struct platform_device *pDev, pm_message_t State);
static int  VBoxDrvResume(struct platform_device *pDev);
# endif
static void VBoxDevRelease(struct device *pDev);
#endif
#if RTLNX_VER_MIN(5,0,0)
static int  supdrvLinuxLdrModuleNotifyCallback(struct notifier_block *pBlock,
                                               unsigned long uModuleState, void *pvModule);
#endif


/*********************************************************************************************************************************
*   Global Variables                                                                                                             *
*********************************************************************************************************************************/
/**
 * Device extention & session data association structure.
 */
static SUPDRVDEVEXT         g_DevExt;

/** Module parameter.
 * Not prefixed because the name is used by macros and the end of this file. */
static int force_async_tsc = 0;

/** The system device name. */
#define DEVICE_NAME_SYS     "vboxdrv"
/** The user device name. */
#define DEVICE_NAME_USR     "vboxdrvu"

/** The file_operations structure. */
static struct file_operations gFileOpsVBoxDrvSys =
{
    owner:      THIS_MODULE,
    open:       VBoxDrvLinuxCreateSys,
    release:    VBoxDrvLinuxClose,
#ifdef HAVE_UNLOCKED_IOCTL
    unlocked_ioctl: VBoxDrvLinuxIOCtl,
#else
    ioctl:      VBoxDrvLinuxIOCtl,
#endif
};

/** The file_operations structure. */
static struct file_operations gFileOpsVBoxDrvUsr =
{
    owner:      THIS_MODULE,
    open:       VBoxDrvLinuxCreateUsr,
    release:    VBoxDrvLinuxClose,
#ifdef HAVE_UNLOCKED_IOCTL
    unlocked_ioctl: VBoxDrvLinuxIOCtl,
#else
    ioctl:      VBoxDrvLinuxIOCtl,
#endif
};

/** The miscdevice structure for vboxdrv. */
static struct miscdevice gMiscDeviceSys =
{
    minor:      MISC_DYNAMIC_MINOR,
    name:       DEVICE_NAME_SYS,
    fops:       &gFileOpsVBoxDrvSys,
# if RTLNX_VER_MAX(2,6,18)
    devfs_name: DEVICE_NAME_SYS,
# endif
};
/** The miscdevice structure for vboxdrvu. */
static struct miscdevice gMiscDeviceUsr =
{
    minor:      MISC_DYNAMIC_MINOR,
    name:       DEVICE_NAME_USR,
    fops:       &gFileOpsVBoxDrvUsr,
# if RTLNX_VER_MAX(2,6,18)
    devfs_name: DEVICE_NAME_USR,
# endif
};


#ifdef VBOX_WITH_SUSPEND_NOTIFICATION

# if RTLNX_VER_MIN(2,6,30)
static struct dev_pm_ops gPlatformPMOps =
{
    .suspend = VBoxDrvSuspend,  /* before entering deep sleep */
    .resume  = VBoxDrvResume,   /* after wakeup from deep sleep */
    .freeze  = VBoxDrvSuspend,  /* before creating hibernation image */
    .restore = VBoxDrvResume,   /* after waking up from hibernation */
};
# endif

static struct platform_driver gPlatformDriver =
{
    .probe = VBoxDrvProbe,
# if RTLNX_VER_MAX(2,6,30)
    .suspend = VBoxDrvSuspend,
    .resume  = VBoxDrvResume,
# endif
    /** @todo .shutdown? */
    .driver =
    {
        .name = "vboxdrv",
# if RTLNX_VER_MIN(2,6,30)
        .pm = &gPlatformPMOps,
# endif
    }
};

static struct platform_device gPlatformDevice =
{
    .name = "vboxdrv",
    .dev =
    {
        .release = VBoxDevRelease
    }
};

#endif /* VBOX_WITH_SUSPEND_NOTIFICATION */

#if RTLNX_VER_MIN(5,0,0)
/** Module load/unload notification registration record. */
static struct notifier_block    g_supdrvLinuxModuleNotifierBlock =
{
    .notifier_call = supdrvLinuxLdrModuleNotifyCallback,
    .priority      = 0
};
/** Spinlock protecting g_supdrvLinuxWrapperModuleList. */
static spinlock_t               g_supdrvLinuxWrapperModuleSpinlock;
/** List of potential wrapper modules (PSUPDRVLNXMODULE). */
static RTLISTANCHOR             g_supdrvLinuxWrapperModuleList;
#endif


/** Get the kernel UID for the current process. */
DECLINLINE(RTUID) vboxdrvLinuxKernUid(void)
{
#if RTLNX_VER_MIN(2,6,29)
# if RTLNX_VER_MIN(3,5,0)
    return __kuid_val(current->cred->uid);
# else
    return current->cred->uid;
# endif
#else
    return current->uid;
#endif
}


/** Get the kernel GID for the current process. */
DECLINLINE(RTGID) vboxdrvLinuxKernGid(void)
{
#if RTLNX_VER_MIN(2,6,29)
# if RTLNX_VER_MIN(3,5,0)
    return __kgid_val(current->cred->gid);
# else
    return current->cred->gid;
# endif
#else
    return current->gid;
#endif
}


#ifdef VBOX_WITH_HARDENING
/** Get the effective UID of the current process. */
DECLINLINE(RTUID) vboxdrvLinuxEuid(void)
{
# if RTLNX_VER_MIN(2,6,29)
#  if RTLNX_VER_MIN(3,5,0)
    return __kuid_val(current->cred->euid);
#  else
    return current->cred->euid;
#  endif
# else
    return current->euid;
# endif
}
#endif


/**
 * Initialize module.
 *
 * @returns appropriate status code.
 */
static int __init VBoxDrvLinuxInit(void)
{
    int       rc;

    /* Check if modue loading was disabled. */
    if (!vbox_mod_should_load())
        return -EINVAL;

#if RTLNX_VER_MIN(5,0,0)
    spin_lock_init(&g_supdrvLinuxWrapperModuleSpinlock);
    RTListInit(&g_supdrvLinuxWrapperModuleList);
#endif

    /*
     * Check for synchronous/asynchronous TSC mode.
     */
    printk(KERN_DEBUG "vboxdrv: Found %u processor cores/threads\n", (unsigned)RTMpGetOnlineCount());
    rc = misc_register(&gMiscDeviceSys);
    if (rc)
    {
        printk(KERN_ERR "vboxdrv: Can't register system misc device! rc=%d\n", rc);
        return rc;
    }
    rc = misc_register(&gMiscDeviceUsr);
    if (rc)
    {
        printk(KERN_ERR "vboxdrv: Can't register user misc device! rc=%d\n", rc);
        misc_deregister(&gMiscDeviceSys);
        return rc;
    }
    if (!rc)
    {
        /*
         * Initialize the runtime.
         * On AMD64 we'll have to donate the high rwx memory block to the exec allocator.
         */
        rc = RTR0Init(0);
        if (RT_SUCCESS(rc))
        {
            Log(("VBoxDrv::ModuleInit\n"));

            /*
             * Initialize the device extension.
             */
            rc = supdrvInitDevExt(&g_DevExt, sizeof(SUPDRVSESSION));
            if (RT_SUCCESS(rc))
            {
#ifdef VBOX_WITH_SUSPEND_NOTIFICATION
                rc = platform_driver_register(&gPlatformDriver);
                if (rc == 0)
                {
                    rc = platform_device_register(&gPlatformDevice);
                    if (rc == 0)
#endif
                    {
#if RTLNX_VER_MIN(5,0,0)
                        /*
                         * Register the module notifier.
                         */
                        int rc2 = register_module_notifier(&g_supdrvLinuxModuleNotifierBlock);
                        if (rc2)
                            printk(KERN_WARNING "vboxdrv: failed to register module notifier! rc2=%d\n", rc2);
#endif


                        printk(KERN_INFO "vboxdrv: TSC mode is %s, tentative frequency %llu Hz\n",
                               SUPGetGIPModeName(g_DevExt.pGip), g_DevExt.pGip->u64CpuHz);
                        LogFlow(("VBoxDrv::ModuleInit returning %#x\n", rc));
                        printk(KERN_DEBUG "vboxdrv: Successfully loaded version "
                                VBOX_VERSION_STRING " r" RT_XSTR(VBOX_SVN_REV)
                                VBOX_EXTRA_VERSION_STRING
                                " (interface " RT_XSTR(SUPDRV_IOC_VERSION) ")\n");
                        return rc;
                    }
#ifdef VBOX_WITH_SUSPEND_NOTIFICATION
                    else
                        platform_driver_unregister(&gPlatformDriver);
                }
#endif
            }

            rc = -EINVAL;
            RTR0TermForced();
        }
        else
            rc = -EINVAL;

        /*
         * Failed, cleanup and return the error code.
         */
    }
    misc_deregister(&gMiscDeviceSys);
    misc_deregister(&gMiscDeviceUsr);
    Log(("VBoxDrv::ModuleInit returning %#x (minor:%d & %d)\n", rc, gMiscDeviceSys.minor, gMiscDeviceUsr.minor));
    return rc;
}


/**
 * Unload the module.
 */
static void __exit VBoxDrvLinuxUnload(void)
{
    Log(("VBoxDrvLinuxUnload\n"));

#ifdef VBOX_WITH_SUSPEND_NOTIFICATION
    platform_device_unregister(&gPlatformDevice);
    platform_driver_unregister(&gPlatformDriver);
#endif

#if RTLNX_VER_MIN(5,0,0)
    /*
     * Kick the list of potential wrapper modules.
     */
    unregister_module_notifier(&g_supdrvLinuxModuleNotifierBlock);

    spin_lock(&g_supdrvLinuxWrapperModuleSpinlock);
    while (!RTListIsEmpty(&g_supdrvLinuxWrapperModuleList))
    {
        PSUPDRVLNXMODULE pCur = RTListRemoveFirst(&g_supdrvLinuxWrapperModuleList, SUPDRVLNXMODULE, ListEntry);
        spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);

        pCur->pModule = NULL;
        RTMemFree(pCur);

        spin_lock(&g_supdrvLinuxWrapperModuleSpinlock);
    }
    spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);
#endif

    /*
     * I Don't think it's possible to unload a driver which processes have
     * opened, at least we'll blindly assume that here.
     */
    misc_deregister(&gMiscDeviceUsr);
    misc_deregister(&gMiscDeviceSys);

    /*
     * Destroy GIP, delete the device extension and terminate IPRT.
     */
    supdrvDeleteDevExt(&g_DevExt);
    RTR0TermForced();
}


/**
 * Common open code.
 *
 * @param   pInode          Pointer to inode info structure.
 * @param   pFilp           Associated file pointer.
 * @param   fUnrestricted   Indicates which device node which was opened.
 */
static int vboxdrvLinuxCreateCommon(struct inode *pInode, struct file *pFilp, bool fUnrestricted)
{
    int                 rc;
    PSUPDRVSESSION      pSession;
    Log(("VBoxDrvLinuxCreate: pFilp=%p pid=%d/%d %s\n", pFilp, RTProcSelf(), current->pid, current->comm));

#ifdef VBOX_WITH_HARDENING
    /*
     * Only root is allowed to access the unrestricted device, enforce it!
     */
    if (   fUnrestricted
        && vboxdrvLinuxEuid() != 0 /* root */ )
    {
        Log(("VBoxDrvLinuxCreate: euid=%d, expected 0 (root)\n", vboxdrvLinuxEuid()));
        return -EPERM;
    }
#endif /* VBOX_WITH_HARDENING */

    /*
     * Call common code for the rest.
     */
    rc = supdrvCreateSession(&g_DevExt, true /* fUser */, fUnrestricted, &pSession);
    if (!rc)
    {
        pSession->Uid = vboxdrvLinuxKernUid();
        pSession->Gid = vboxdrvLinuxKernGid();
    }

    pFilp->private_data = pSession;

    Log(("VBoxDrvLinuxCreate: g_DevExt=%p pSession=%p rc=%d/%d (pid=%d/%d %s)\n",
         &g_DevExt, pSession, rc, VBoxDrvLinuxErr2LinuxErr(rc),
         RTProcSelf(), current->pid, current->comm));
    return VBoxDrvLinuxErr2LinuxErr(rc);
}


/** /dev/vboxdrv.  */
static int VBoxDrvLinuxCreateSys(struct inode *pInode, struct file *pFilp)
{
    return vboxdrvLinuxCreateCommon(pInode, pFilp, true);
}


/** /dev/vboxdrvu.  */
static int VBoxDrvLinuxCreateUsr(struct inode *pInode, struct file *pFilp)
{
    return vboxdrvLinuxCreateCommon(pInode, pFilp, false);
}


/**
 * Close device.
 *
 * @param   pInode      Pointer to inode info structure.
 * @param   pFilp       Associated file pointer.
 */
static int VBoxDrvLinuxClose(struct inode *pInode, struct file *pFilp)
{
    Log(("VBoxDrvLinuxClose: pFilp=%p pSession=%p pid=%d/%d %s\n",
         pFilp, pFilp->private_data, RTProcSelf(), current->pid, current->comm));
    supdrvSessionRelease((PSUPDRVSESSION)pFilp->private_data);
    pFilp->private_data = NULL;
    return 0;
}


#ifdef VBOX_WITH_SUSPEND_NOTIFICATION
/**
 * Dummy device release function. We have to provide this function,
 * otherwise the kernel will complain.
 *
 * @param   pDev        Pointer to the platform device.
 */
static void VBoxDevRelease(struct device *pDev)
{
}

/**
 * Dummy probe function.
 *
 * @param   pDev        Pointer to the platform device.
 */
static int VBoxDrvProbe(struct platform_device *pDev)
{
    return 0;
}

/**
 * Suspend callback.
 * @param   pDev        Pointer to the platform device.
 * @param   State       Message type, see Documentation/power/devices.txt.
 *                      Ignored.
 */
# if RTLNX_VER_MIN(2,6,30) && !defined(DOXYGEN_RUNNING)
static int VBoxDrvSuspend(struct device *pDev)
# else
static int VBoxDrvSuspend(struct platform_device *pDev, pm_message_t State)
# endif
{
    RTPowerSignalEvent(RTPOWEREVENT_SUSPEND);
    return 0;
}

/**
 * Resume callback.
 *
 * @param   pDev        Pointer to the platform device.
 */
# if RTLNX_VER_MIN(2,6,30)
static int VBoxDrvResume(struct device *pDev)
# else
static int VBoxDrvResume(struct platform_device *pDev)
# endif
{
    RTPowerSignalEvent(RTPOWEREVENT_RESUME);
    return 0;
}
#endif /* VBOX_WITH_SUSPEND_NOTIFICATION */


/**
 * Device I/O Control entry point.
 *
 * @param   pFilp       Associated file pointer.
 * @param   uCmd        The function specified to ioctl().
 * @param   ulArg       The argument specified to ioctl().
 */
#if defined(HAVE_UNLOCKED_IOCTL) || defined(DOXYGEN_RUNNING)
static long VBoxDrvLinuxIOCtl(struct file *pFilp, unsigned int uCmd, unsigned long ulArg)
#else
static int VBoxDrvLinuxIOCtl(struct inode *pInode, struct file *pFilp, unsigned int uCmd, unsigned long ulArg)
#endif
{
    PSUPDRVSESSION pSession = (PSUPDRVSESSION)pFilp->private_data;
    int rc;
#ifndef VBOX_WITHOUT_EFLAGS_AC_SET_IN_VBOXDRV
# if defined(VBOX_STRICT) || defined(VBOX_WITH_EFLAGS_AC_SET_IN_VBOXDRV)
    RTCCUINTREG fSavedEfl;

    /*
     * Refuse all I/O control calls if we've ever detected EFLAGS.AC being cleared.
     *
     * This isn't a problem, as there is absolutely nothing in the kernel context that
     * depend on user context triggering cleanups.  That would be pretty wild, right?
     */
    if (RT_UNLIKELY(g_DevExt.cBadContextCalls > 0))
    {
        SUPR0Printf("VBoxDrvLinuxIOCtl: EFLAGS.AC=0 detected %u times, refusing all I/O controls!\n", g_DevExt.cBadContextCalls);
        return ESPIPE;
    }

    fSavedEfl = ASMAddFlags(X86_EFL_AC);
# else
    stac();
# endif
#endif

    /*
     * Deal with the two high-speed IOCtl that takes it's arguments from
     * the session and iCmd, and only returns a VBox status code.
     */
    AssertCompile(_IOC_NRSHIFT == 0 && _IOC_NRBITS == 8);
#ifdef HAVE_UNLOCKED_IOCTL
    if (RT_LIKELY(   (unsigned int)(uCmd - SUP_IOCTL_FAST_DO_FIRST) < (unsigned int)32
                  && pSession->fUnrestricted))
        rc = supdrvIOCtlFast(uCmd - SUP_IOCTL_FAST_DO_FIRST, ulArg, &g_DevExt, pSession);
    else
        rc = VBoxDrvLinuxIOCtlSlow(pFilp, uCmd, ulArg, pSession);
#else   /* !HAVE_UNLOCKED_IOCTL */
    unlock_kernel();
    if (RT_LIKELY(   (unsigned int)(uCmd - SUP_IOCTL_FAST_DO_FIRST) < (unsigned int)32
                  && pSession->fUnrestricted))
        rc = supdrvIOCtlFast(uCmd - SUP_IOCTL_FAST_DO_FIRST, ulArg, &g_DevExt, pSession);
    else
        rc = VBoxDrvLinuxIOCtlSlow(pFilp, uCmd, ulArg, pSession);
    lock_kernel();
#endif  /* !HAVE_UNLOCKED_IOCTL */

#ifndef VBOX_WITHOUT_EFLAGS_AC_SET_IN_VBOXDRV
# if defined(VBOX_STRICT) || defined(VBOX_WITH_EFLAGS_AC_SET_IN_VBOXDRV)
    /*
     * Before we restore AC and the rest of EFLAGS, check if the IOCtl handler code
     * accidentially modified it or some other important flag.
     */
    if (RT_UNLIKELY(   (ASMGetFlags() & (X86_EFL_AC | X86_EFL_IF | X86_EFL_DF))
                    != ((fSavedEfl    & (X86_EFL_AC | X86_EFL_IF | X86_EFL_DF)) | X86_EFL_AC) ))
    {
        char szTmp[48];
        RTStrPrintf(szTmp, sizeof(szTmp), "uCmd=%#x: %#x->%#x!", _IOC_NR(uCmd), (uint32_t)fSavedEfl, (uint32_t)ASMGetFlags());
        supdrvBadContext(&g_DevExt, "SUPDrv-linux.c",  __LINE__, szTmp);
    }
    ASMSetFlags(fSavedEfl);
# else
    clac();
# endif
#endif
    return rc;
}


/**
 * Device I/O Control entry point.
 *
 * @param   pFilp       Associated file pointer.
 * @param   uCmd        The function specified to ioctl().
 * @param   ulArg       The argument specified to ioctl().
 * @param   pSession    The session instance.
 */
static int VBoxDrvLinuxIOCtlSlow(struct file *pFilp, unsigned int uCmd, unsigned long ulArg, PSUPDRVSESSION pSession)
{
    int                 rc;
    SUPREQHDR           Hdr;
    PSUPREQHDR          pHdr;
    uint32_t            cbBuf;

    Log6(("VBoxDrvLinuxIOCtl: pFilp=%p uCmd=%#x ulArg=%p pid=%d/%d\n", pFilp, uCmd, (void *)ulArg, RTProcSelf(), current->pid));

    /*
     * Read the header.
     */
    if (RT_FAILURE(RTR0MemUserCopyFrom(&Hdr, ulArg, sizeof(Hdr))))
    {
        Log(("VBoxDrvLinuxIOCtl: copy_from_user(,%#lx,) failed; uCmd=%#x\n", ulArg, uCmd));
        return -EFAULT;
    }
    if (RT_UNLIKELY((Hdr.fFlags & SUPREQHDR_FLAGS_MAGIC_MASK) != SUPREQHDR_FLAGS_MAGIC))
    {
        Log(("VBoxDrvLinuxIOCtl: bad header magic %#x; uCmd=%#x\n", Hdr.fFlags & SUPREQHDR_FLAGS_MAGIC_MASK, uCmd));
        return -EINVAL;
    }

    /*
     * Buffer the request.
     */
    cbBuf = RT_MAX(Hdr.cbIn, Hdr.cbOut);
    if (RT_UNLIKELY(cbBuf > _1M*16))
    {
        Log(("VBoxDrvLinuxIOCtl: too big cbBuf=%#x; uCmd=%#x\n", cbBuf, uCmd));
        return -E2BIG;
    }
    if (RT_UNLIKELY(_IOC_SIZE(uCmd) ? cbBuf != _IOC_SIZE(uCmd) : Hdr.cbIn < sizeof(Hdr)))
    {
        Log(("VBoxDrvLinuxIOCtl: bad ioctl cbBuf=%#x _IOC_SIZE=%#x; uCmd=%#x\n", cbBuf, _IOC_SIZE(uCmd), uCmd));
        return -EINVAL;
    }
    pHdr = RTMemAlloc(cbBuf);
    if (RT_UNLIKELY(!pHdr))
    {
        OSDBGPRINT(("VBoxDrvLinuxIOCtl: failed to allocate buffer of %d bytes for uCmd=%#x\n", cbBuf, uCmd));
        return -ENOMEM;
    }
    if (RT_FAILURE(RTR0MemUserCopyFrom(pHdr, ulArg, Hdr.cbIn)))
    {
        Log(("VBoxDrvLinuxIOCtl: copy_from_user(,%#lx, %#x) failed; uCmd=%#x\n", ulArg, Hdr.cbIn, uCmd));
        RTMemFree(pHdr);
        return -EFAULT;
    }
    if (Hdr.cbIn < cbBuf)
        RT_BZERO((uint8_t *)pHdr + Hdr.cbIn, cbBuf - Hdr.cbIn);

    /*
     * Process the IOCtl.
     */
    rc = supdrvIOCtl(uCmd, &g_DevExt, pSession, pHdr, cbBuf);

    /*
     * Copy ioctl data and output buffer back to user space.
     */
    if (RT_LIKELY(!rc))
    {
        uint32_t cbOut = pHdr->cbOut;
        if (RT_UNLIKELY(cbOut > cbBuf))
        {
            OSDBGPRINT(("VBoxDrvLinuxIOCtl: too much output! %#x > %#x; uCmd=%#x!\n", cbOut, cbBuf, uCmd));
            cbOut = cbBuf;
        }
        if (RT_FAILURE(RTR0MemUserCopyTo(ulArg, pHdr, cbOut)))
        {
            /* this is really bad! */
            OSDBGPRINT(("VBoxDrvLinuxIOCtl: copy_to_user(%#lx,,%#x); uCmd=%#x!\n", ulArg, cbOut, uCmd));
            rc = -EFAULT;
        }
    }
    else
    {
        Log(("VBoxDrvLinuxIOCtl: pFilp=%p uCmd=%#x ulArg=%p failed, rc=%d\n", pFilp, uCmd, (void *)ulArg, rc));
        rc = -EINVAL;
    }
    RTMemFree(pHdr);

    Log6(("VBoxDrvLinuxIOCtl: returns %d (pid=%d/%d)\n", rc, RTProcSelf(), current->pid));
    return rc;
}


/**
 * The SUPDRV IDC entry point.
 *
 * @returns VBox status code, see supdrvIDC.
 * @param   uReq        The request code.
 * @param   pReq        The request.
 */
int VBOXCALL SUPDrvLinuxIDC(uint32_t uReq, PSUPDRVIDCREQHDR pReq)
{
    PSUPDRVSESSION  pSession;

    /*
     * Some quick validations.
     */
    if (RT_UNLIKELY(!RT_VALID_PTR(pReq)))
        return VERR_INVALID_POINTER;

    pSession = pReq->pSession;
    if (pSession)
    {
        if (RT_UNLIKELY(!RT_VALID_PTR(pSession)))
            return VERR_INVALID_PARAMETER;
        if (RT_UNLIKELY(pSession->pDevExt != &g_DevExt))
            return VERR_INVALID_PARAMETER;
    }
    else if (RT_UNLIKELY(uReq != SUPDRV_IDC_REQ_CONNECT))
        return VERR_INVALID_PARAMETER;

    /*
     * Do the job.
     */
    return supdrvIDC(uReq, &g_DevExt, pSession, pReq);
}
EXPORT_SYMBOL(SUPDrvLinuxIDC);


#if RTLNX_VER_MIN(5,0,0)

/**
 * Checks if the given module is one of our potential wrapper modules or not.
 */
static bool supdrvLinuxLdrIsPotentialWrapperModule(struct module const *pModule)
{
    if (   pModule
        && strncmp(pModule->name, RT_STR_TUPLE("vbox_")) == 0)
        return true;
    return false;
}

/**
 * Called when a kernel module changes state.
 *
 * We use this to listen for wrapper modules being loaded, since some evil
 * bugger removed the find_module() export in 5.13.
 */
static int supdrvLinuxLdrModuleNotifyCallback(struct notifier_block *pBlock, unsigned long uModuleState, void *pvModule)
{
    struct module *pModule = (struct module *)pvModule;
    switch (uModuleState)
    {
        case MODULE_STATE_UNFORMED: /* Setting up the module... */
            break;

        /*
         * The module is about to have its ctors & init functions called.
         *
         * Add anything that looks like a wrapper module to our tracker list.
         */
        case MODULE_STATE_COMING:
            if (supdrvLinuxLdrIsPotentialWrapperModule(pModule))
            {
                PSUPDRVLNXMODULE pTracker = (PSUPDRVLNXMODULE)RTMemAlloc(sizeof(*pTracker));
                if (pTracker)
                {
                    pTracker->pModule = pModule;
                    spin_lock(&g_supdrvLinuxWrapperModuleSpinlock);
                    RTListPrepend(&g_supdrvLinuxWrapperModuleList, &pTracker->ListEntry);
                    spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);
                }
            }
            break;

        case MODULE_STATE_LIVE:
            break;

        /*
         * The module has been uninited and is going away.
         *
         * Remove the tracker entry for the module, if we have one.
         */
        case MODULE_STATE_GOING:
        {
            PSUPDRVLNXMODULE pCur;
            spin_lock(&g_supdrvLinuxWrapperModuleSpinlock);
            RTListForEach(&g_supdrvLinuxWrapperModuleList, pCur, SUPDRVLNXMODULE, ListEntry)
            {
                if (pCur->pModule == pModule)
                {
                    RTListNodeRemove(&pCur->ListEntry);
                    spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);

                    pCur->pModule = NULL;
                    RTMemFree(pCur);

                    spin_lock(&g_supdrvLinuxWrapperModuleSpinlock); /* silly */
                    break;
                }
            }
            spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);
            break;
        }
    }
    RT_NOREF(pBlock);
    return NOTIFY_OK;
}

/**
 * Replacement for find_module() that's no longer exported with 5.13.
 */
static struct module *supdrvLinuxLdrFindModule(const char *pszLnxModName)
{
    PSUPDRVLNXMODULE pCur;

    spin_lock(&g_supdrvLinuxWrapperModuleSpinlock);
    RTListForEach(&g_supdrvLinuxWrapperModuleList, pCur, SUPDRVLNXMODULE, ListEntry)
    {
        struct module * const pModule = pCur->pModule;
        if (   pModule
            && strcmp(pszLnxModName, pModule->name) == 0)
        {
            spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);
            return pModule;
        }
    }
    spin_unlock(&g_supdrvLinuxWrapperModuleSpinlock);
    return NULL;
}

#endif /* >= 5.0.0 */


/**
 * Used by native wrapper modules, forwarding to supdrvLdrRegisterWrappedModule
 * with device extension prepended to the argument list.
 */
SUPR0DECL(int)  SUPDrvLinuxLdrRegisterWrappedModule(PCSUPLDRWRAPPEDMODULE pWrappedModInfo,
                                                    const char *pszLnxModName, void **phMod)
{
    AssertPtrReturn(pszLnxModName, VERR_INVALID_POINTER);
    AssertReturn(*pszLnxModName, VERR_INVALID_NAME);

    /* Locate the module structure for the caller so can later reference
       and dereference it to prevent unloading while it is being used.

       Before Linux v5.9 this could be done by address (__module_address()
       or __module_text_address()), but someone (guess who) apparently on
       a mission to make life miserable for out-of-tree modules or something,
       decided it was only used by build-in code and unexported both of them.

       I could find no init callouts getting a struct module pointer either,
       nor any module name hint anywhere I could see.  So, we're left with
       hardcoding the module name via the compiler and pass it along to
       SUPDrv so we can call find_module() here.

       Sigh^2.

       Update 5.13:
       The find_module() and module_mutex symbols are no longer exported,
       probably the doing of the same evil bugger mentioned above.  So, we now
       register a module notification callback and track the modules we're
       interested in that way. */

#if RTLNX_VER_MIN(5,0,0)
    struct module *pLnxModule = supdrvLinuxLdrFindModule(pszLnxModName);
    if (pLnxModule)
        return supdrvLdrRegisterWrappedModule(&g_DevExt, pWrappedModInfo, pLnxModule, phMod);
    printk("vboxdrv: supdrvLinuxLdrFindModule(%s) failed in SUPDrvLinuxLdrRegisterWrappedModule!\n", pszLnxModName);
    return VERR_MODULE_NOT_FOUND;

#elif RTLNX_VER_MIN(2,6,30)
    if (mutex_lock_interruptible(&module_mutex) == 0)
    {
        struct module *pLnxModule = find_module(pszLnxModName);
        mutex_unlock(&module_mutex);
        if (pLnxModule)
            return supdrvLdrRegisterWrappedModule(&g_DevExt, pWrappedModInfo, pLnxModule, phMod);
        printk("vboxdrv: find_module(%s) failed in SUPDrvLinuxLdrRegisterWrappedModule!\n", pszLnxModName);
        return VERR_MODULE_NOT_FOUND;
    }
    return VERR_INTERRUPTED;

#else
    printk("vboxdrv: wrapper modules are not supported on 2.6.29 and earlier. sorry.\n");
    return VERR_NOT_SUPPORTED;
#endif
}
EXPORT_SYMBOL(SUPDrvLinuxLdrRegisterWrappedModule);


/**
 * Used by native wrapper modules, forwarding to supdrvLdrDeregisterWrappedModule
 * with device extension prepended to the argument list.
 */
SUPR0DECL(int) SUPDrvLinuxLdrDeregisterWrappedModule(PCSUPLDRWRAPPEDMODULE pWrappedModInfo, void **phMod)
{
    return supdrvLdrDeregisterWrappedModule(&g_DevExt, pWrappedModInfo, phMod);
}
EXPORT_SYMBOL(SUPDrvLinuxLdrDeregisterWrappedModule);


RTCCUINTREG VBOXCALL supdrvOSChangeCR4(RTCCUINTREG fOrMask, RTCCUINTREG fAndMask)
{
#if RTLNX_VER_MIN(5,8,0)
    unsigned long fSavedFlags;
    local_irq_save(fSavedFlags);
    RTCCUINTREG const uOld = cr4_read_shadow();
    cr4_update_irqsoff(fOrMask, ~fAndMask); /* Same as this function, only it is not returning the old value. */
    AssertMsg(cr4_read_shadow() == ((uOld & fAndMask) | fOrMask),
              ("fOrMask=%#RTreg fAndMask=%#RTreg uOld=%#RTreg; new cr4=%#llx\n", fOrMask, fAndMask, uOld, cr4_read_shadow()));
    local_irq_restore(fSavedFlags);
#else
# if RTLNX_VER_MIN(3,20,0)
    RTCCUINTREG const uOld = this_cpu_read(cpu_tlbstate.cr4);
# else
    RTCCUINTREG const uOld = ASMGetCR4();
# endif
    RTCCUINTREG const uNew = (uOld & fAndMask) | fOrMask;
    if (uNew != uOld)
    {
# if RTLNX_VER_MIN(3,20,0)
        this_cpu_write(cpu_tlbstate.cr4, uNew);
        __write_cr4(uNew);
# else
        ASMSetCR4(uNew);
# endif
    }
#endif
    return uOld;
}


void VBOXCALL supdrvOSCleanupSession(PSUPDRVDEVEXT pDevExt, PSUPDRVSESSION pSession)
{
    NOREF(pDevExt);
    NOREF(pSession);
}


void VBOXCALL supdrvOSSessionHashTabInserted(PSUPDRVDEVEXT pDevExt, PSUPDRVSESSION pSession, void *pvUser)
{
    NOREF(pDevExt); NOREF(pSession); NOREF(pvUser);
}


void VBOXCALL supdrvOSSessionHashTabRemoved(PSUPDRVDEVEXT pDevExt, PSUPDRVSESSION pSession, void *pvUser)
{
    NOREF(pDevExt); NOREF(pSession); NOREF(pvUser);
}


/**
 * Initializes any OS specific object creator fields.
 */
void VBOXCALL supdrvOSObjInitCreator(PSUPDRVOBJ pObj, PSUPDRVSESSION pSession)
{
    NOREF(pObj);
    NOREF(pSession);
}


/**
 * Checks if the session can access the object.
 *
 * @returns true if a decision has been made.
 * @returns false if the default access policy should be applied.
 *
 * @param   pObj        The object in question.
 * @param   pSession    The session wanting to access the object.
 * @param   pszObjName  The object name, can be NULL.
 * @param   prc         Where to store the result when returning true.
 */
bool VBOXCALL supdrvOSObjCanAccess(PSUPDRVOBJ pObj, PSUPDRVSESSION pSession, const char *pszObjName, int *prc)
{
    NOREF(pObj);
    NOREF(pSession);
    NOREF(pszObjName);
    NOREF(prc);
    return false;
}


bool VBOXCALL supdrvOSGetForcedAsyncTscMode(PSUPDRVDEVEXT pDevExt)
{
    return force_async_tsc != 0;
}


bool VBOXCALL supdrvOSAreCpusOfflinedOnSuspend(void)
{
    return true;
}


bool VBOXCALL supdrvOSAreTscDeltasInSync(void)
{
    return false;
}


int  VBOXCALL   supdrvOSLdrOpen(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage, const char *pszFilename)
{
    NOREF(pDevExt); NOREF(pImage); NOREF(pszFilename);
    return VERR_NOT_SUPPORTED;
}


int  VBOXCALL   supdrvOSLdrValidatePointer(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage, void *pv,
                                           const uint8_t *pbImageBits, const char *pszSymbol)
{
    NOREF(pDevExt); NOREF(pImage); NOREF(pv); NOREF(pbImageBits); NOREF(pszSymbol);
    return VERR_NOT_SUPPORTED;
}


int  VBOXCALL   supdrvOSLdrLoad(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage, const uint8_t *pbImageBits, PSUPLDRLOAD pReq)
{
    NOREF(pDevExt); NOREF(pImage); NOREF(pbImageBits); NOREF(pReq);
    return VERR_NOT_SUPPORTED;
}


void VBOXCALL   supdrvOSLdrUnload(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage)
{
    NOREF(pDevExt); NOREF(pImage);
}


/** @def VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS
 * A very crude hack for debugging using perf and dtrace.
 *
 * DO ABSOLUTELY NOT ENABLE IN PRODUCTION BUILDS!  DEVELOPMENT ONLY!!
 * DO ABSOLUTELY NOT ENABLE IN PRODUCTION BUILDS!  DEVELOPMENT ONLY!!
 * DO ABSOLUTELY NOT ENABLE IN PRODUCTION BUILDS!  DEVELOPMENT ONLY!!
 *
 */
#if 0 || defined(DOXYGEN_RUNNING)
# define VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS
#endif

#if defined(VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS) && defined(CONFIG_MODULES_TREE_LOOKUP)
/** Whether g_pfnModTreeInsert and g_pfnModTreeRemove have been initialized.
 * @remarks can still be NULL after init. */
static volatile bool g_fLookedForModTreeFunctions = false;
static void (*g_pfnModTreeInsert)(struct mod_tree_node *) = NULL;   /**< __mod_tree_insert */
static void (*g_pfnModTreeRemove)(struct mod_tree_node *) = NULL;   /**< __mod_tree_remove */
#endif


void VBOXCALL   supdrvOSLdrNotifyOpened(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage, const char *pszFilename)
{
#ifdef VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS /* Not for production use!! Debugging only! */
    /*
     * This trick stops working with 4.2 when CONFIG_MODULES_TREE_LOOKUP is
     * defined.  The module lookups are done via a tree structure and we
     * cannot get at the root of it. :-(
     */
# ifdef CONFIG_KALLSYMS
    size_t const cchName = strlen(pImage->szName);
# endif
    struct module *pMyMod, *pSelfMod, *pTestMod, *pTestModByName;
    IPRT_LINUX_SAVE_EFL_AC();

    pImage->pLnxModHack    = NULL;

# ifdef CONFIG_MODULES_TREE_LOOKUP
    /*
     * This is pretty naive, but works for 4.2 on arch linux.  I don't think we
     * can count on finding __mod_tree_remove in all kernel builds as it's not
     * marked noinline like __mod_tree_insert.
     */
    if (!g_fLookedForModTreeFunctions)
    {
        unsigned long ulInsert = kallsyms_lookup_name("__mod_tree_insert");
        unsigned long ulRemove = kallsyms_lookup_name("__mod_tree_remove");
        if (!ulInsert || !ulRemove)
        {
            g_fLookedForModTreeFunctions = true;
            printk(KERN_ERR "vboxdrv: failed to locate __mod_tree_insert and __mod_tree_remove.\n");
            IPRT_LINUX_RESTORE_EFL_AC();
            return;
        }
        *(unsigned long *)&g_pfnModTreeInsert = ulInsert;
        *(unsigned long *)&g_pfnModTreeRemove = ulRemove;
        ASMCompilerBarrier();
        g_fLookedForModTreeFunctions = true;
    }
    else if (!g_pfnModTreeInsert || !g_pfnModTreeRemove)
        return;
#endif

    /*
     * Make sure we've found our own module, otherwise we cannot access the linked list.
     */
    mutex_lock(&module_mutex);
    pSelfMod = find_module("vboxdrv");
    mutex_unlock(&module_mutex);
    if (!pSelfMod)
    {
        IPRT_LINUX_RESTORE_EFL_AC();
        return;
    }

    /*
     * Cook up a module structure for the image.
     * We allocate symbol and string tables in the allocation and the module to keep things simple.
     */
# ifdef CONFIG_KALLSYMS
    pMyMod = (struct module *)RTMemAllocZ(sizeof(*pMyMod)
                                          + sizeof(Elf_Sym) * 3
                                          + 1 + cchName * 2 + sizeof("_start") + sizeof("_end") + 4 );
# else
    pMyMod = (struct module *)RTMemAllocZ(sizeof(*pMyMod));
# endif
    if (pMyMod)
    {
        int rc = VINF_SUCCESS;
# ifdef CONFIG_KALLSYMS
        Elf_Sym *paSymbols = (Elf_Sym *)(pMyMod + 1);
        char    *pchStrTab = (char *)(paSymbols + 3);
# endif

        pMyMod->state = MODULE_STATE_LIVE;
        INIT_LIST_HEAD(&pMyMod->list);  /* just in case */

        /* Perf only matches up files with a .ko extension (maybe .ko.gz),
           so in order for this crap to work smoothly, we append .ko to the
           module name and require the user to create symbolic links in
           /lib/modules/`uname -r`:
                for i in VMMR0.r0 VBoxDDR0.r0 VBoxDD2R0.r0; do
                    sudo ln -s /mnt/scratch/vbox/svn/trunk/out/linux.amd64/debug/bin/$i /lib/modules/`uname -r`/$i.ko;
                done  */
        RTStrPrintf(pMyMod->name, sizeof(pMyMod->name), "%s", pImage->szName);

        /* sysfs bits. */
        INIT_LIST_HEAD(&pMyMod->mkobj.kobj.entry); /* rest of kobj is already zeroed, hopefully never accessed... */
        pMyMod->mkobj.mod           = pMyMod;
        pMyMod->mkobj.drivers_dir   = NULL;
        pMyMod->mkobj.mp            = NULL;
        pMyMod->mkobj.kobj_completion = NULL;

        pMyMod->modinfo_attrs       = NULL; /* hopefully not accessed after setup. */
        pMyMod->holders_dir         = NULL; /* hopefully not accessed. */
        pMyMod->version             = "N/A";
        pMyMod->srcversion          = "N/A";

        /* We export no symbols. */
        pMyMod->num_syms            = 0;
        pMyMod->syms                = NULL;
        pMyMod->crcs                = NULL;

        pMyMod->num_gpl_syms        = 0;
        pMyMod->gpl_syms            = NULL;
        pMyMod->gpl_crcs            = NULL;

        pMyMod->num_gpl_future_syms = 0;
        pMyMod->gpl_future_syms     = NULL;
        pMyMod->gpl_future_crcs     = NULL;

# if CONFIG_UNUSED_SYMBOLS
        pMyMod->num_unused_syms     = 0;
        pMyMod->unused_syms         = NULL;
        pMyMod->unused_crcs         = NULL;

        pMyMod->num_unused_gpl_syms = 0;
        pMyMod->unused_gpl_syms     = NULL;
        pMyMod->unused_gpl_crcs     = NULL;
# endif
        /* No kernel parameters either. */
        pMyMod->kp                  = NULL;
        pMyMod->num_kp              = 0;

# ifdef CONFIG_MODULE_SIG
        /* Pretend ok signature. */
        pMyMod->sig_ok              = true;
# endif
        /* No exception table. */
        pMyMod->num_exentries       = 0;
        pMyMod->extable             = NULL;

        /* No init function */
        pMyMod->init                = NULL;
        pMyMod->module_init         = NULL;
        pMyMod->init_size           = 0;
        pMyMod->init_ro_size        = 0;
        pMyMod->init_text_size      = 0;

        /* The module address and size. It's all text. */
        pMyMod->module_core         = pImage->pvImage;
        pMyMod->core_size           = pImage->cbImageBits;
        pMyMod->core_text_size      = pImage->cbImageBits;
        pMyMod->core_ro_size        = pImage->cbImageBits;

#ifdef CONFIG_MODULES_TREE_LOOKUP
        /* Fill in the self pointers for the tree nodes. */
        pMyMod->mtn_core.mod        = pMyMod;
        pMyMod->mtn_init.mod        = pMyMod;
#endif
        /* They invented the tained bit for us, didn't they? */
        pMyMod->taints              = 1;

# ifdef CONFIG_GENERIC_BUGS
        /* No BUGs in our modules. */
        pMyMod->num_bugs            = 0;
        INIT_LIST_HEAD(&pMyMod->bug_list);
        pMyMod->bug_table           = NULL;
# endif

# ifdef CONFIG_KALLSYMS
        /* The core stuff is documented as only used when loading. So just zero them. */
        pMyMod->core_num_syms       = 0;
        pMyMod->core_symtab         = NULL;
        pMyMod->core_strtab         = NULL;

        /* Construct a symbol table with start and end symbols.
           Note! We don't have our own symbol table at this point, image bit
                 are not uploaded yet! */
        pMyMod->num_symtab          = 3;
        pMyMod->symtab              = paSymbols;
        pMyMod->strtab              = pchStrTab;
        RT_ZERO(paSymbols[0]);
        pchStrTab[0] = '\0';
        paSymbols[1].st_name        = 1;
        paSymbols[2].st_name        = 2 + RTStrPrintf(&pchStrTab[paSymbols[1].st_name], cchName + sizeof("_start"),
                                                      "%s_start", pImage->szName);
        RTStrPrintf(&pchStrTab[paSymbols[2].st_name], cchName + sizeof("_end"), "%s_end", pImage->szName);
        paSymbols[1].st_info = 't';
        paSymbols[2].st_info = 'b';
        paSymbols[1].st_other = 0;
        paSymbols[2].st_other = 0;
        paSymbols[1].st_shndx = 0;
        paSymbols[2].st_shndx = 0;
        paSymbols[1].st_value = (uintptr_t)pImage->pvImage;
        paSymbols[2].st_value = (uintptr_t)pImage->pvImage + pImage->cbImageBits - 1;
        paSymbols[1].st_size  = pImage->cbImageBits - 1;
        paSymbols[2].st_size  = 1;
# endif
        /* No arguments, but seems its always non-NULL so put empty string there. */
        pMyMod->args                = "";

# ifdef CONFIG_SMP
        /* No per CPU data. */
        pMyMod->percpu              = NULL;
        pMyMod->percpu_size         = 0;
# endif
# ifdef CONFIG_TRACEPOINTS
        /* No tracepoints we like to share. */
        pMyMod->num_tracepoints     = 0;
        pMyMod->tracepoints_ptrs    = NULL;
#endif
# ifdef HAVE_JUMP_LABEL
        /* No jump lable stuff either. */
        pMyMod->jump_entries        = NULL;
        pMyMod->num_jump_entries    = 0;
# endif
# ifdef CONFIG_TRACING
        pMyMod->num_trace_bprintk_fmt   = 0;
        pMyMod->trace_bprintk_fmt_start = NULL;
# endif
# ifdef CONFIG_EVENT_TRACING
        pMyMod->trace_events        = NULL;
        pMyMod->num_trace_events    = 0;
# endif
# ifdef CONFIG_FTRACE_MCOUNT_RECORD
        pMyMod->num_ftrace_callsites = 0;
        pMyMod->ftrace_callsites    = NULL;
# endif
# ifdef CONFIG_MODULE_UNLOAD
        /* Dependency lists, not worth sharing */
        INIT_LIST_HEAD(&pMyMod->source_list);
        INIT_LIST_HEAD(&pMyMod->target_list);

        /* Nobody waiting and no exit function. */
#  if RTLNX_VER_MAX(3,13,0)
        pMyMod->waiter              = NULL;
#  endif
        pMyMod->exit                = NULL;

        /* References, very important as we must not allow the module
           to be unloaded using rmmod. */
#  if RTLNX_VER_MIN(3,19,0)
        atomic_set(&pMyMod->refcnt, 42);
#  else
        pMyMod->refptr              = alloc_percpu(struct module_ref);
        if (pMyMod->refptr)
        {
            int iCpu;
            for_each_possible_cpu(iCpu)
            {
                per_cpu_ptr(pMyMod->refptr, iCpu)->decs = 0;
                per_cpu_ptr(pMyMod->refptr, iCpu)->incs = 1;
            }
        }
        else
            rc = VERR_NO_MEMORY;
#  endif
# endif
# ifdef CONFIG_CONSTRUCTORS
        /* No constructors. */
        pMyMod->ctors               = NULL;
        pMyMod->num_ctors           = 0;
# endif
        if (RT_SUCCESS(rc))
        {
            bool fIsModText;

            /*
             * Add the module to the list.
             */
            mutex_lock(&module_mutex);
            list_add_rcu(&pMyMod->list, &pSelfMod->list);
            pImage->pLnxModHack = pMyMod;
# ifdef CONFIG_MODULES_TREE_LOOKUP
            g_pfnModTreeInsert(&pMyMod->mtn_core); /* __mod_tree_insert */
# endif
            mutex_unlock(&module_mutex);

            /*
             * Test it.
             */
            mutex_lock(&module_mutex);
            pTestModByName = find_module(pMyMod->name);
            pTestMod = __module_address((uintptr_t)pImage->pvImage + pImage->cbImageBits / 4);
            fIsModText = __module_text_address((uintptr_t)pImage->pvImage + pImage->cbImageBits / 2);
            mutex_unlock(&module_mutex);
            if (   pTestMod == pMyMod
                && pTestModByName == pMyMod
                && fIsModText)
                printk(KERN_ERR "vboxdrv: fake module works for '%s' (%#lx to %#lx)\n",
                       pMyMod->name, (unsigned long)paSymbols[1].st_value, (unsigned long)paSymbols[2].st_value);
            else
                printk(KERN_ERR "vboxdrv: failed to find fake module (pTestMod=%p, pTestModByName=%p, pMyMod=%p, fIsModText=%d)\n",
                       pTestMod, pTestModByName, pMyMod, fIsModText);
        }
        else
            RTMemFree(pMyMod);
    }

    IPRT_LINUX_RESTORE_EFL_AC();
#else
    pImage->pLnxModHack    = NULL;
#endif
    NOREF(pDevExt); NOREF(pImage);
}


void VBOXCALL   supdrvOSLdrNotifyUnloaded(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage)
{
#ifdef VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS /* Not for production use!! Debugging only! */
    struct module *pMyMod = pImage->pLnxModHack;
    pImage->pLnxModHack = NULL;
    if (pMyMod)
    {
        /*
         * Remove the fake module list entry and free it.
         */
        IPRT_LINUX_SAVE_EFL_AC();
        mutex_lock(&module_mutex);
        list_del_rcu(&pMyMod->list);
# ifdef CONFIG_MODULES_TREE_LOOKUP
        g_pfnModTreeRemove(&pMyMod->mtn_core);
# endif
        synchronize_sched();
        mutex_unlock(&module_mutex);

# if RTLNX_VER_MAX(3,19,0)
        free_percpu(pMyMod->refptr);
# endif
        RTMemFree(pMyMod);
        IPRT_LINUX_RESTORE_EFL_AC();
    }

#else
    Assert(pImage->pLnxModHack == NULL);
#endif
    NOREF(pDevExt); NOREF(pImage);
}


int  VBOXCALL   supdrvOSLdrQuerySymbol(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage,
                                       const char *pszSymbol, size_t cchSymbol, void **ppvSymbol)
{
#ifdef VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS
# error "implement me!"
#endif
    RT_NOREF(pDevExt, pImage, pszSymbol, cchSymbol, ppvSymbol);
    return VERR_WRONG_ORDER;
}


void VBOXCALL   supdrvOSLdrRetainWrapperModule(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage)
{
    struct module *pLnxMod = (struct module *)pImage->pvWrappedNative;
    Assert(!pImage->fLnxWrapperRef);
    AssertReturnVoid(pLnxMod);
    pImage->fLnxWrapperRef = try_module_get(pLnxMod);
    RT_NOREF(pDevExt);
}


void VBOXCALL   supdrvOSLdrReleaseWrapperModule(PSUPDRVDEVEXT pDevExt, PSUPDRVLDRIMAGE pImage)
{
    if (pImage->fLnxWrapperRef)
    {
        struct module *pLnxMod = (struct module *)pImage->pvWrappedNative;
        pImage->fLnxWrapperRef = false;
        module_put(pLnxMod);
    }
    RT_NOREF(pDevExt);
}


#ifdef SUPDRV_WITH_MSR_PROBER

int VBOXCALL    supdrvOSMsrProberRead(uint32_t uMsr, RTCPUID idCpu, uint64_t *puValue)
{
# ifdef SUPDRV_LINUX_HAS_SAFE_MSR_API
    uint32_t u32Low, u32High;
    int rc;

    IPRT_LINUX_SAVE_EFL_AC();
    if (idCpu == NIL_RTCPUID)
        rc = rdmsr_safe(uMsr, &u32Low, &u32High);
    else if (RTMpIsCpuOnline(idCpu))
        rc = rdmsr_safe_on_cpu(idCpu, uMsr, &u32Low, &u32High);
    else
        return VERR_CPU_OFFLINE;
    IPRT_LINUX_RESTORE_EFL_AC();
    if (rc == 0)
    {
        *puValue = RT_MAKE_U64(u32Low, u32High);
        return VINF_SUCCESS;
    }
    return VERR_ACCESS_DENIED;
# else
    return VERR_NOT_SUPPORTED;
# endif
}


int VBOXCALL    supdrvOSMsrProberWrite(uint32_t uMsr, RTCPUID idCpu, uint64_t uValue)
{
# ifdef SUPDRV_LINUX_HAS_SAFE_MSR_API
    int rc;

    IPRT_LINUX_SAVE_EFL_AC();
    if (idCpu == NIL_RTCPUID)
        rc = wrmsr_safe(uMsr, RT_LODWORD(uValue), RT_HIDWORD(uValue));
    else if (RTMpIsCpuOnline(idCpu))
        rc = wrmsr_safe_on_cpu(idCpu, uMsr, RT_LODWORD(uValue), RT_HIDWORD(uValue));
    else
        return VERR_CPU_OFFLINE;
    IPRT_LINUX_RESTORE_EFL_AC();

    if (rc == 0)
        return VINF_SUCCESS;
    return VERR_ACCESS_DENIED;
# else
    return VERR_NOT_SUPPORTED;
# endif
}

# ifdef SUPDRV_LINUX_HAS_SAFE_MSR_API
/**
 * Worker for supdrvOSMsrProberModify.
 */
static DECLCALLBACK(void) supdrvLnxMsrProberModifyOnCpu(RTCPUID idCpu, void *pvUser1, void *pvUser2)
{
    PSUPMSRPROBER               pReq    = (PSUPMSRPROBER)pvUser1;
    register uint32_t           uMsr    = pReq->u.In.uMsr;
    bool const                  fFaster = pReq->u.In.enmOp == SUPMSRPROBEROP_MODIFY_FASTER;
    uint64_t                    uBefore;
    uint64_t                    uWritten;
    uint64_t                    uAfter;
    int                         rcBefore, rcWrite, rcAfter, rcRestore;
    RTCCUINTREG                 fOldFlags;

    /* Initialize result variables. */
    uBefore = uWritten = uAfter    = 0;
    rcWrite = rcAfter  = rcRestore = -EIO;

    /*
     * Do the job.
     */
    fOldFlags = ASMIntDisableFlags();
    ASMCompilerBarrier(); /* paranoia */
    if (!fFaster)
        ASMWriteBackAndInvalidateCaches();

    rcBefore = rdmsrl_safe(uMsr, &uBefore);
    if (rcBefore >= 0)
    {
        register uint64_t uRestore = uBefore;
        uWritten  = uRestore;
        uWritten &= pReq->u.In.uArgs.Modify.fAndMask;
        uWritten |= pReq->u.In.uArgs.Modify.fOrMask;

        rcWrite   = wrmsr_safe(uMsr, RT_LODWORD(uWritten), RT_HIDWORD(uWritten));
        rcAfter   = rdmsrl_safe(uMsr, &uAfter);
        rcRestore = wrmsr_safe(uMsr, RT_LODWORD(uRestore), RT_HIDWORD(uRestore));

        if (!fFaster)
        {
            ASMWriteBackAndInvalidateCaches();
            ASMReloadCR3();
            ASMNopPause();
        }
    }

    ASMCompilerBarrier(); /* paranoia */
    ASMSetFlags(fOldFlags);

    /*
     * Write out the results.
     */
    pReq->u.Out.uResults.Modify.uBefore    = uBefore;
    pReq->u.Out.uResults.Modify.uWritten   = uWritten;
    pReq->u.Out.uResults.Modify.uAfter     = uAfter;
    pReq->u.Out.uResults.Modify.fBeforeGp  = rcBefore  != 0;
    pReq->u.Out.uResults.Modify.fModifyGp  = rcWrite   != 0;
    pReq->u.Out.uResults.Modify.fAfterGp   = rcAfter   != 0;
    pReq->u.Out.uResults.Modify.fRestoreGp = rcRestore != 0;
    RT_ZERO(pReq->u.Out.uResults.Modify.afReserved);
}
# endif


int VBOXCALL    supdrvOSMsrProberModify(RTCPUID idCpu, PSUPMSRPROBER pReq)
{
# ifdef SUPDRV_LINUX_HAS_SAFE_MSR_API
    if (idCpu == NIL_RTCPUID)
    {
        supdrvLnxMsrProberModifyOnCpu(idCpu, pReq, NULL);
        return VINF_SUCCESS;
    }
    return RTMpOnSpecific(idCpu, supdrvLnxMsrProberModifyOnCpu, pReq, NULL);
# else
    return VERR_NOT_SUPPORTED;
# endif
}

#endif /* SUPDRV_WITH_MSR_PROBER */


/**
 * Converts a supdrv error code to an linux error code.
 *
 * @returns corresponding linux error code.
 * @param   rc          IPRT status code.
 */
static int VBoxDrvLinuxErr2LinuxErr(int rc)
{
    switch (rc)
    {
        case VINF_SUCCESS:              return 0;
        case VERR_GENERAL_FAILURE:      return -EACCES;
        case VERR_INVALID_PARAMETER:    return -EINVAL;
        case VERR_INVALID_MAGIC:        return -EILSEQ;
        case VERR_INVALID_HANDLE:       return -ENXIO;
        case VERR_INVALID_POINTER:      return -EFAULT;
        case VERR_LOCK_FAILED:          return -ENOLCK;
        case VERR_ALREADY_LOADED:       return -EEXIST;
        case VERR_PERMISSION_DENIED:    return -EPERM;
        case VERR_VERSION_MISMATCH:     return -ENOSYS;
        case VERR_IDT_FAILED:           return -1000;
    }

    return -EPERM;
}


SUPR0DECL(int) SUPR0HCPhysToVirt(RTHCPHYS HCPhys, void **ppv)
{
    AssertReturn(!(HCPhys & PAGE_OFFSET_MASK), VERR_INVALID_POINTER);
    AssertReturn(HCPhys != NIL_RTHCPHYS, VERR_INVALID_POINTER);
    /* Would've like to use valid_phys_addr_range for this test, but it isn't exported. */
    AssertReturn((HCPhys | PAGE_OFFSET_MASK) < __pa(high_memory), VERR_INVALID_POINTER);
    *ppv = phys_to_virt(HCPhys);
    return VINF_SUCCESS;
}
SUPR0_EXPORT_SYMBOL(SUPR0HCPhysToVirt);


RTDECL(int) SUPR0PrintfV(const char *pszFormat, va_list va)
{
    char    szMsg[512];
    IPRT_LINUX_SAVE_EFL_AC();

    RTStrPrintfV(szMsg, sizeof(szMsg) - 1, pszFormat, va);
    szMsg[sizeof(szMsg) - 1] = '\0';

    printk("%s", szMsg);

    IPRT_LINUX_RESTORE_EFL_AC();
    return 0;
}
SUPR0_EXPORT_SYMBOL(SUPR0PrintfV);


SUPR0DECL(uint32_t) SUPR0GetKernelFeatures(void)
{
    uint32_t fFlags = 0;
    /* Note! bird 2023-10-20: Apparently, with CONFIG_PAX_KERNEXEC these days,
             not only is the regular GDT read-only, but the one returned by
             get_current_gdt_rw() is also read-only despite the name.

             We don't know exactly when this started, or if it was always like
             this, but getting hold of the relevant patches isn't all that
             straight forward any longer it seems (which is weird for linux
             patches), so, we've just enabled slow-mode for all PAX_KERNEXEC
             kernels regardless of kernel version.

             Looking at grsecurity patch for 4.9.9, it looks like the writable
             GDT stuff never worked with PaX/grsec.
             */
#ifdef CONFIG_PAX_KERNEXEC
    fFlags |= SUPKERNELFEATURES_GDT_READ_ONLY;
#elif RTLNX_VER_MIN(4,12,0)
    fFlags |= SUPKERNELFEATURES_GDT_NEED_WRITABLE;
#endif

#if defined(VBOX_STRICT) || defined(VBOX_WITH_EFLAGS_AC_SET_IN_VBOXDRV)
    fFlags |= SUPKERNELFEATURES_SMAP;
#elif defined(CONFIG_X86_SMAP)
    if (ASMGetCR4() & X86_CR4_SMAP)
        fFlags |= SUPKERNELFEATURES_SMAP;
#endif
    return fFlags;
}
SUPR0_EXPORT_SYMBOL(SUPR0GetKernelFeatures);


SUPR0DECL(bool) SUPR0FpuBegin(bool fCtxHook)
{
    RT_NOREF(fCtxHook);
#if RTLNX_VER_MIN(4,19,0) /* Going back to 4.19.0 for better coverage, we
                             probably only need 5.17.7+ in the end. */
    /*
     * HACK ALERT!
     *
     * We'd like to use the old __kernel_fpu_begin() API which was removed in
     * early 2019, because we typically run with preemption enabled and have an
     * preemption hook installed which will call kernel_fpu_end() in case we're
     * scheduled out after getting in here.  The preemption hook is almost
     * useless if we run with preemption disabled.
     *
     * For the case where the kernel does not have preemption hooks, we get here
     * with preemption already disabled and one more count doesn't make any
     * difference.
     *
     * So, after the kernel_fpu_begin() call we undo the implicit preempt_disable()
     * call it does, so the preemption hook can do its work and the VBox user has
     * a more responsive system.
     *
     * See @bugref{10209#c12} and onwards for more details.
     */
    Assert(fCtxHook || !RTThreadPreemptIsEnabled(NIL_RTTHREAD));
    kernel_fpu_begin();
# if 0 /* Always do it for now for better test coverage. */
    if (fCtxHook)
# endif
        preempt_enable();
    return false; /** @todo Not sure if we have license to use any extended state, or
                   *        if we're limited to the SSE & x87 FPU. If it's the former,
                   *        we should return @a true and the caller can skip
                   *        saving+restoring the host state and save some time. */
#else
    return false;
#endif
}
SUPR0_EXPORT_SYMBOL(SUPR0FpuBegin);


SUPR0DECL(void) SUPR0FpuEnd(bool fCtxHook)
{
    RT_NOREF(fCtxHook);
#if RTLNX_VER_MIN(4,19,0)
    /* HACK ALERT! See SUPR0FpuBegin for an explanation of this. */
    Assert(!RTThreadPreemptIsEnabled(NIL_RTTHREAD));
# if 0 /* Always do it for now for better test coverage. */
    if (fCtxHook)
# endif
        preempt_disable();
    kernel_fpu_end();
#endif
}
SUPR0_EXPORT_SYMBOL(SUPR0FpuEnd);


int VBOXCALL    supdrvOSGetCurrentGdtRw(RTHCUINTPTR *pGdtRw)
{
#if RTLNX_VER_MIN(4,12,0) && !defined(CONFIG_PAX_KERNEXEC)
    *pGdtRw = (RTHCUINTPTR)get_current_gdt_rw();
    return VINF_SUCCESS;
#else
    return VERR_NOT_IMPLEMENTED;
#endif
}


module_init(VBoxDrvLinuxInit);
module_exit(VBoxDrvLinuxUnload);

MODULE_AUTHOR(VBOX_VENDOR);
MODULE_DESCRIPTION(VBOX_PRODUCT " Support Driver");
MODULE_LICENSE("GPL");
#ifdef MODULE_VERSION
MODULE_VERSION(VBOX_VERSION_STRING " r" RT_XSTR(VBOX_SVN_REV) " (" RT_XSTR(SUPDRV_IOC_VERSION) ")");
#endif

module_param(force_async_tsc, int, 0444);
MODULE_PARM_DESC(force_async_tsc, "force the asynchronous TSC mode");

