/*******************************************************************************
    Copyright (c) 2013-2018 NVIDIA Corporation

    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; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301, USA.
*******************************************************************************/

/*
 * This file contains code that is common to all variants of the (Linux) UVM
 * kernel module.
 */

#include "uvm_common.h"
#include "uvm_linux.h"

// TODO: Bug 1766109: Remove this when the GPU event stubs are no longer needed
#include "nv_uvm_interface.h"

#include "uvm8_init.h"
#include "uvm8_forward_decl.h"

// TODO: Bug 1710855: Tweak this number through benchmarks
#define UVM_SPIN_LOOP_SCHEDULE_TIMEOUT_NS   (10*1000ULL)
#define UVM_SPIN_LOOP_PRINT_TIMEOUT_SEC     30ULL

static dev_t g_uvmBaseDev;

static char* uvm_driver_mode = "8";

// There used to be other choices, but now there is only one driver mode: 8.
// If no more choices show up soon, we may just delete this module parameter
// entirely.
module_param(uvm_driver_mode, charp, S_IRUGO);
MODULE_PARM_DESC(uvm_driver_mode,
                "Set the uvm kernel driver mode. Choices include: 8");

// Default to debug prints being enabled for debug and develop builds and
// disabled for release builds.
static int uvm_debug_prints = UVM_IS_DEBUG() || UVM_IS_DEVELOP();

// Make the module param writable so that prints can be enabled or disabled at
// any time by modifying the module parameter.
module_param(uvm_debug_prints, int, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(uvm_debug_prints, "Enable uvm debug prints.");

bool uvm_debug_prints_enabled()
{
    return uvm_debug_prints != 0;
}

typedef enum
{
    UVM_DRIVER_MODE_8,
} UvmDriverMode;

static const char * uvm_driver_mode_to_string(UvmDriverMode uvmDriverMode)
{
    switch (uvmDriverMode)
    {
        case UVM_DRIVER_MODE_8:
            return "8";
    }
    return "invalid";
}

static UvmDriverMode uvm_get_mode(void)
{
    static NvBool bUvmDriverModeChecked = NV_FALSE;
    static UvmDriverMode uvmDriverMode;

    if (!bUvmDriverModeChecked)
    {
        uvmDriverMode = UVM_DRIVER_MODE_8;

        bUvmDriverModeChecked = NV_TRUE;
    }

    return uvmDriverMode;
}

NV_STATUS uvm_api_initialize(UVM_INITIALIZE_PARAMS *params, struct file *filp)
{
    params->rmStatus = uvm8_initialize(params, filp);
    return params->rmStatus;
}

// This function serves to 'stub' out functionality by being a No-Op and
// returning NV_OK early.
NV_STATUS uvm_api_stub(void *pParams, struct file *filp)
{
    return NV_OK;
}

// This function serves to identify functionality that isn't supported
// in this UVM driver, by returning NV_ERR_NOT_SUPPORTED early.
NV_STATUS uvm_api_unsupported(void *pParams, struct file *filp)
{
    return NV_ERR_NOT_SUPPORTED;
}

//
// TODO: Bug 1766109: uvm8: delete UVM-Lite files and remove -lite mode
//  ...just remove -lite mode, instead of the original to-do: which was:
//
static int __init uvm_init(void)
{
    NvBool allocated_dev = NV_FALSE;

    // The various helper init routines will create their own minor devices, so
    // we only need to create space for them here.
    int ret = alloc_chrdev_region(&g_uvmBaseDev,
                              0,
                              NVIDIA_UVM_NUM_MINOR_DEVICES,
                              NVIDIA_UVM_DEVICE_NAME);
    if (ret != 0) {
        UVM_ERR_PRINT("alloc_chrdev_region failed: %d\n", ret);
        goto error;
    }
    allocated_dev = NV_TRUE;

    ret = uvm8_init(g_uvmBaseDev);

    if (ret != 0) {
        UVM_ERR_PRINT("uvm init failed: %d\n", ret);
        goto error;
    }

    pr_info("Loaded the UVM driver in %s mode, major device number %d\n",
            uvm_driver_mode_to_string(uvm_get_mode()), MAJOR(g_uvmBaseDev));

    if (uvm_enable_builtin_tests)
        pr_info("Built-in UVM tests are enabled. This is a security risk.\n");

    return 0;

error:
    if (allocated_dev)
        unregister_chrdev_region(g_uvmBaseDev, NVIDIA_UVM_NUM_MINOR_DEVICES);

    return ret;
}

static void __exit uvm_exit(void)
{
    uvm8_exit();

    unregister_chrdev_region(g_uvmBaseDev, NVIDIA_UVM_NUM_MINOR_DEVICES);

    pr_info("Unloaded the UVM driver in %s mode\n", uvm_driver_mode_to_string(uvm_get_mode()));
}

//
// Convert kernel errno codes to corresponding NV_STATUS
//
NV_STATUS errno_to_nv_status(int errnoCode)
{
    if (errnoCode < 0)
        errnoCode = -errnoCode;

    switch (errnoCode)
    {
        case 0:
            return NV_OK;

        case E2BIG:
        case EINVAL:
            return NV_ERR_INVALID_ARGUMENT;

        case EACCES:
            return NV_ERR_INVALID_ACCESS_TYPE;

        case EADDRINUSE:
        case EADDRNOTAVAIL:
            return NV_ERR_UVM_ADDRESS_IN_USE;

        case EFAULT:
            return NV_ERR_INVALID_ADDRESS;

        case EINTR:
        case EBUSY:
        case EAGAIN:
            return NV_ERR_BUSY_RETRY;

        case ENXIO:
        case ENODEV:
            return NV_ERR_MODULE_LOAD_FAILED;

        case ENOMEM:
            return NV_ERR_NO_MEMORY;

        case EPERM:
            return NV_ERR_INSUFFICIENT_PERMISSIONS;

        case ESRCH:
            return NV_ERR_PID_NOT_FOUND;

        case ETIMEDOUT:
            return NV_ERR_TIMEOUT;

        case EEXIST:
            return NV_ERR_IN_USE;

        case ENOSYS:
            return NV_ERR_NOT_SUPPORTED;

        case ENOENT:
            return NV_ERR_NO_VALID_PATH;

        case EIO:
            return NV_ERR_RC_ERROR;

        default:
            return NV_ERR_GENERIC;
    };
}

// Returns POSITIVE errno
int nv_status_to_errno(NV_STATUS status)
{
    switch (status) {
        case NV_OK:
            return 0;

        case NV_ERR_BUSY_RETRY:
            return EAGAIN;

        case NV_ERR_INSUFFICIENT_PERMISSIONS:
            return EPERM;

        case NV_ERR_GPU_UUID_NOT_FOUND:
            return ENODEV;

        case NV_ERR_INSUFFICIENT_RESOURCES:
        case NV_ERR_NO_MEMORY:
            return ENOMEM;

        case NV_ERR_INVALID_ACCESS_TYPE:
            return EACCES;

        case NV_ERR_INVALID_ADDRESS:
            return EFAULT;

        case NV_ERR_INVALID_ARGUMENT:
        case NV_ERR_INVALID_DEVICE:
        case NV_ERR_INVALID_PARAMETER:
        case NV_ERR_INVALID_REQUEST:
        case NV_ERR_INVALID_STATE:
            return EINVAL;

        case NV_ERR_NOT_SUPPORTED:
            return ENOSYS;

        case NV_ERR_MODULE_LOAD_FAILED:
            return ENXIO;

        case NV_ERR_OVERLAPPING_UVM_COMMIT:
        case NV_ERR_UVM_ADDRESS_IN_USE:
            return EADDRINUSE;

        case NV_ERR_PID_NOT_FOUND:
            return ESRCH;

        case NV_ERR_TIMEOUT:
        case NV_ERR_TIMEOUT_RETRY:
            return ETIMEDOUT;

        case NV_ERR_IN_USE:
            return EEXIST;

        case NV_ERR_NO_VALID_PATH:
            return ENOENT;

        case NV_ERR_RC_ERROR:
        case NV_ERR_ECC_ERROR:
            return EIO;

        default:
            UVM_ASSERT_MSG(0, "No errno conversion set up for NV_STATUS %s\n", nvstatusToString(status));
            return EINVAL;
    }
}

//
// This routine retrieves the process ID of current, but makes no attempt to
// refcount or lock the pid in place, because that capability is only available
// to GPL-licenses device drivers.
//
// TODO: Bug 1483843: Use the GPL-protected routines if and when we are able to
// change over to a dual MIT/GPL license.
//
unsigned uvm_get_stale_process_id(void)
{
    return (unsigned) current->tgid;
}

unsigned uvm_get_stale_thread_id(void)
{
    return (unsigned) current->pid;
}

//
// A simple security rule for allowing access to UVM user space memory: if you
// are the same user as the owner of the memory, or if you are root, then you
// are granted access. The idea is to allow debuggers and profilers to work, but
// without opening up any security holes.
//
NvBool uvm_user_id_security_check(uid_t euidTarget)
{
    return (NV_CURRENT_EUID() == euidTarget) ||
           (UVM_ROOT_UID == euidTarget);
}

void on_uvm_assert(void)
{
    (void)NULL;
}

NV_STATUS uvm_spin_loop(uvm_spin_loop_t *spin)
{
    NvU64 curr = NV_GETTIME();

    // This schedule() is required for functionality, not just system
    // performance. It allows RM to run and unblock the UVM driver:
    //
    // - UVM must service faults in order for RM to idle/preempt a context
    // - RM must service interrupts which stall UVM (SW methods, stalling CE
    //   interrupts, etc) in order for UVM to service faults
    //
    // Even though UVM's bottom half is preemptable, we have encountered cases
    // in which a user thread running in RM won't preempt the UVM driver's
    // thread unless the UVM driver thread gives up its timeslice. This is also
    // theoretically possible if the RM thread has a low nice priority.
    //
    // TODO: Bug 1710855: Look into proper prioritization of these threads as a longer-term
    //       solution.
    if (curr - spin->start_time_ns >= UVM_SPIN_LOOP_SCHEDULE_TIMEOUT_NS && NV_MAY_SLEEP()) {
        schedule();
        curr = NV_GETTIME();
    }

    cpu_relax();

    // TODO: Bug 1710855: Also check fatal_signal_pending() here if the caller can handle it.

    if (curr - spin->print_time_ns >= 1000*1000*1000*UVM_SPIN_LOOP_PRINT_TIMEOUT_SEC) {
        spin->print_time_ns = curr;
        return NV_ERR_TIMEOUT_RETRY;
    }

    return NV_OK;
}

module_init(uvm_init);
module_exit(uvm_exit);

// This parameter allows a program in user mode to call the kernel tests
// defined in this module. This parameter should only be used for testing and
// must not be set to true otherwise since it breaks security when it is
// enabled. By default and for safety reasons this parameter is set to false.
int uvm_enable_builtin_tests = 0;
module_param(uvm_enable_builtin_tests, int, S_IRUGO);
MODULE_PARM_DESC(uvm_enable_builtin_tests,
                 "Enable the UVM built-in tests. (This is a security risk)");

MODULE_LICENSE("Dual MIT/GPL");
MODULE_INFO(supported, "external");
