/** @file

  Copyright (c) 2024, Mikhail Krichanov. All rights reserved.
  SPDX-License-Identifier: BSD-3-Clause

**/

#include <Library/ArmLib.h>
#include <Library/ArmMmuLib.h>
#include <Library/DefaultExceptionHandlerLib.h>

#include "DxeMain.h"

STATIC UINTN  mCoreSp;
UINTN         gUserPageTable;
UINTN         mRing3CallStackTop;
UINTN         mCoreSysCallStackTop;

EFI_STATUS
EFIAPI
ArmCallRing3 (
  IN RING3_CALL_DATA *Data,
  IN UINTN           StackPointer,
  IN VOID            *EntryPoint,
  IN UINTN           SysCallStack,
  IN VOID            *CoreStack,
  IN UINTN           UserPageTable
  );

VOID
EFIAPI
ArmReturnToCore (
  IN EFI_STATUS Status,
  IN UINTN      CoreSp
  );

VOID
EFIAPI
ReturnToCore (
  IN EFI_STATUS Status
  )
{
  ArmReturnToCore (Status, mCoreSp);
}

STATIC
EFI_STATUS
EFIAPI
SysCallBootService (
  IN  UINT8  Type,
  IN  VOID   *CoreRbp,
  IN  VOID   *UserRsp
  )
{
  EFI_STATUS              Status;
  EFI_PHYSICAL_ADDRESS    Physical;

  ArmEnableInterrupts ();

  Status = CoreAllocatePages (
             AllocateAnyPages,
             EfiRing3MemoryType,
             EFI_SIZE_TO_PAGES (9 * sizeof (UINTN)),
             &Physical
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  AllowSupervisorAccessToUserMemory ();
  //
  // First 3 arguments are passed through R1-R3 and copied to SysCall Stack.
  //
  CopyMem ((VOID *)((UINTN)Physical + 2 * sizeof (UINTN)), (VOID *)CoreRbp, 3 * sizeof (UINTN));
  //
  // All remaining arguments are on User Stack.
  //
  CopyMem ((VOID *)((UINTN)Physical + 5 * sizeof (UINTN)), (VOID *)UserRsp, 4 * sizeof (UINTN));
  ForbidSupervisorAccessToUserMemory ();

  Status = CallBootService (
             Type,
             (UINTN *)((UINTN)Physical + sizeof (UINTN))
             );
  //
  // TODO: Fix memory leak for ReturnToCore().
  //
  CoreFreePages (Physical, EFI_SIZE_TO_PAGES (9 * sizeof (UINTN)));

  ArmDisableInterrupts ();

  return Status;
}

VOID
EFIAPI
MakeUserPageTableTemplate (
  OUT UINTN  *UserPageTableTemplate,
  OUT UINTN  *UserPageTableTemplateSize
  )
{
  ARM_MEMORY_REGION_DESCRIPTOR  Descriptor;
  VOID                          *MemorySizeHob;

  MemorySizeHob = GetFirstGuidHob (&gArmVirtSystemMemorySizeGuid);
  ASSERT (MemorySizeHob != NULL);
  if (MemorySizeHob == NULL) {
    return;
  }

  Descriptor.PhysicalBase = PcdGet64 (PcdSystemMemoryBase);
  Descriptor.VirtualBase  = Descriptor.PhysicalBase;
  Descriptor.Length       = *(UINT64 *)GET_GUID_HOB_DATA (MemorySizeHob);
  Descriptor.Attributes   = ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK;

  ArmMakeUserPageTableTemplate (
    &Descriptor,
    UserPageTableTemplate,
    UserPageTableTemplateSize
    );
}

VOID
EFIAPI
InitializeMsr (
  IN OUT EFI_CONFIGURATION_TABLE *Table,
  IN     UINTN                   NumberOfEntries
  )
{
  if (ArmHasPan ()) {
    //
    // Enable Privileged Access Never feature.
    //
    ArmSetPan ();
  }

  InitializeSysCallHandler (SysCallBootService);
  SetExceptionAddresses (NULL, 0);
}

VOID
EFIAPI
AllowSupervisorAccessToUserMemory (
  VOID
  )
{
  if (ArmHasPan ()) {
    ArmClearPan ();
  }
}

VOID
EFIAPI
ForbidSupervisorAccessToUserMemory (
  VOID
  )
{
  if (ArmHasPan ()) {
    ArmSetPan ();
  }
}

EFI_STATUS
EFIAPI
CallRing3 (
  IN RING3_CALL_DATA *Data,
  IN UINTN            UserStackTop,
  IN UINTN            SysCallStackTop
  )
{
  mRing3CallStackTop   = UserStackTop;
  mCoreSysCallStackTop = SysCallStackTop;

  return ArmCallRing3 (Data, UserStackTop, gRing3EntryPoint, SysCallStackTop, &mCoreSp, gUserPageTable);
}