/** @file
  Call into 16-bit BIOS code, Use AsmThunk16 function of BaseLib.

Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>

SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "LegacyBiosInterface.h"

THUNK_CONTEXT  mThunkContext;

/**
  Sets the counter value for Timer #0 in a legacy 8254 timer.

  @param  Count - The 16-bit counter value to program into Timer #0 of the legacy 8254 timer.

**/
VOID
SetPitCount (
  IN UINT16  Count
  )
{
  IoWrite8 (TIMER_CONTROL_PORT, TIMER0_CONTROL_WORD);
  IoWrite8 (TIMER0_COUNT_PORT, (UINT8)(Count & 0xFF));
  IoWrite8 (TIMER0_COUNT_PORT, (UINT8)((Count>>8) & 0xFF));
}

/**
  Thunk to 16-bit real mode and execute a software interrupt with a vector
  of BiosInt. Regs will contain the 16-bit register context on entry and
  exit.

  @param  This    Protocol instance pointer.
  @param  BiosInt Processor interrupt vector to invoke
  @param  Regs    Register contexted passed into (and returned) from thunk to
                  16-bit mode

  @retval FALSE   Thunk completed, and there were no BIOS errors in the target code.
                  See Regs for status.
  @retval TRUE    There was a BIOS erro in the target code.

**/
BOOLEAN
EFIAPI
LegacyBiosInt86 (
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN  UINT8                     BiosInt,
  IN  EFI_IA32_REGISTER_SET     *Regs
  )
{
  UINT16  Segment;
  UINT16  Offset;

  Regs->X.Flags.Reserved1 = 1;
  Regs->X.Flags.Reserved2 = 0;
  Regs->X.Flags.Reserved3 = 0;
  Regs->X.Flags.Reserved4 = 0;
  Regs->X.Flags.IOPL      = 3;
  Regs->X.Flags.NT        = 0;
  Regs->X.Flags.IF        = 0;
  Regs->X.Flags.TF        = 0;
  Regs->X.Flags.CF        = 0;
  //
  // The base address of legacy interrupt vector table is 0.
  // We use this base address to get the legacy interrupt handler.
  //
  ACCESS_PAGE0_CODE (
    Segment = (UINT16)(((UINT32 *)0)[BiosInt] >> 16);
    Offset  = (UINT16)((UINT32 *)0)[BiosInt];
    );

  return InternalLegacyBiosFarCall (
           This,
           Segment,
           Offset,
           Regs,
           &Regs->X.Flags,
           sizeof (Regs->X.Flags)
           );
}

/**
  Thunk to 16-bit real mode and call Segment:Offset. Regs will contain the
  16-bit register context on entry and exit. Arguments can be passed on
  the Stack argument

  @param  This                   Protocol instance pointer.
  @param  Segment                Segemnt of 16-bit mode call
  @param  Offset                 Offset of 16-bit mdoe call
  @param  Regs                   Register contexted passed into (and returned) from
                                 thunk to  16-bit mode
  @param  Stack                  Caller allocated stack used to pass arguments
  @param  StackSize              Size of Stack in bytes

  @retval FALSE                  Thunk completed, and there were no BIOS errors in
                                 the target code. See Regs for status.
  @retval TRUE                   There was a BIOS erro in the target code.

**/
BOOLEAN
EFIAPI
LegacyBiosFarCall86 (
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN  UINT16                    Segment,
  IN  UINT16                    Offset,
  IN  EFI_IA32_REGISTER_SET     *Regs,
  IN  VOID                      *Stack,
  IN  UINTN                     StackSize
  )
{
  Regs->X.Flags.Reserved1 = 1;
  Regs->X.Flags.Reserved2 = 0;
  Regs->X.Flags.Reserved3 = 0;
  Regs->X.Flags.Reserved4 = 0;
  Regs->X.Flags.IOPL      = 3;
  Regs->X.Flags.NT        = 0;
  Regs->X.Flags.IF        = 1;
  Regs->X.Flags.TF        = 0;
  Regs->X.Flags.CF        = 0;

  return InternalLegacyBiosFarCall (This, Segment, Offset, Regs, Stack, StackSize);
}

/**
  Provide NULL interrupt handler which is used to check
  if there is more than one HW interrupt registers with the CPU AP.

  @param  InterruptType - The type of interrupt that occurred
  @param  SystemContext - A pointer to the system context when the interrupt occurred

**/
VOID
EFIAPI
LegacyBiosNullInterruptHandler (
  IN EFI_EXCEPTION_TYPE  InterruptType,
  IN EFI_SYSTEM_CONTEXT  SystemContext
  )
{
}

/**
  Thunk to 16-bit real mode and call Segment:Offset. Regs will contain the
  16-bit register context on entry and exit. Arguments can be passed on
  the Stack argument

  @param  This       Protocol instance pointer.
  @param  Segment    Segemnt of 16-bit mode call
  @param  Offset     Offset of 16-bit mdoe call
  @param  Regs       Register contexted passed into (and returned) from thunk to
                     16-bit mode
  @param  Stack      Caller allocated stack used to pass arguments
  @param  StackSize  Size of Stack in bytes

  @retval FALSE      Thunk completed, and there were no BIOS errors in the target code.
                     See Regs for status.
  @retval TRUE       There was a BIOS erro in the target code.

**/
BOOLEAN
EFIAPI
InternalLegacyBiosFarCall (
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN  UINT16                    Segment,
  IN  UINT16                    Offset,
  IN  EFI_IA32_REGISTER_SET     *Regs,
  IN  VOID                      *Stack,
  IN  UINTN                     StackSize
  )
{
  UINTN                 Status;
  LEGACY_BIOS_INSTANCE  *Private;
  UINT16                *Stack16;
  EFI_TPL               OriginalTpl;
  IA32_REGISTER_SET     ThunkRegSet;
  BOOLEAN               InterruptState;
  UINT64                TimerPeriod;

  Private = LEGACY_BIOS_INSTANCE_FROM_THIS (This);

  ZeroMem (&ThunkRegSet, sizeof (ThunkRegSet));
  ThunkRegSet.X.DI = Regs->X.DI;
  ThunkRegSet.X.SI = Regs->X.SI;
  ThunkRegSet.X.BP = Regs->X.BP;
  ThunkRegSet.X.BX = Regs->X.BX;
  ThunkRegSet.X.DX = Regs->X.DX;
  //
  // Sometimes, ECX is used to pass in 32 bit data. For example, INT 1Ah, AX = B10Dh is
  // "PCI BIOS v2.0c + Write Configuration DWORD" and ECX has the dword to write.
  //
  ThunkRegSet.E.ECX = Regs->E.ECX;
  ThunkRegSet.X.AX  = Regs->X.AX;
  ThunkRegSet.E.DS  = Regs->X.DS;
  ThunkRegSet.E.ES  = Regs->X.ES;

  CopyMem (&(ThunkRegSet.E.EFLAGS.UintN), &(Regs->X.Flags), sizeof (Regs->X.Flags));

  //
  // Clear the error flag; thunk code may set it. Stack16 should be the high address
  // Make Statk16 address the low 16 bit must be not zero.
  //
  Stack16 = (UINT16 *)((UINT8 *)mThunkContext.RealModeBuffer + mThunkContext.RealModeBufferSize - sizeof (UINT16));

  //
  // Save current rate of DXE Timer
  //
  Private->Timer->GetTimerPeriod (Private->Timer, &TimerPeriod);

  //
  // Disable DXE Timer while executing in real mode
  //
  Private->Timer->SetTimerPeriod (Private->Timer, 0);

  //
  // Save and disable interrupt of debug timer
  //
  InterruptState = SaveAndSetDebugTimerInterrupt (FALSE);

  //
  // The call to Legacy16 is a critical section to EFI
  //
  OriginalTpl = gBS->RaiseTPL (TPL_HIGH_LEVEL);

  //
  // Check to see if there is more than one HW interrupt registers with the CPU AP.
  // If there is, then ASSERT() since that is not compatible with the CSM because
  // interupts other than the Timer interrupt that was disabled above can not be
  // handled properly from real mode.
  //
  DEBUG_CODE_BEGIN ();
  UINTN  Vector;
  UINTN  Count;

  for (Vector = 0x20, Count = 0; Vector < 0x100; Vector++) {
    Status = Private->Cpu->RegisterInterruptHandler (Private->Cpu, Vector, LegacyBiosNullInterruptHandler);
    if (Status == EFI_ALREADY_STARTED) {
      Count++;
    }

    if (Status == EFI_SUCCESS) {
      Private->Cpu->RegisterInterruptHandler (Private->Cpu, Vector, NULL);
    }
  }

  if (Count >= 2) {
    DEBUG ((DEBUG_ERROR, "ERROR: More than one HW interrupt active with CSM enabled\n"));
  }

  ASSERT (Count < 2);
  DEBUG_CODE_END ();

  //
  // If the Timer AP has enabled the 8254 timer IRQ and the current 8254 timer
  // period is less than the CSM required rate of 54.9254, then force the 8254
  // PIT counter to 0, which is the CSM required rate of 54.9254 ms
  //
  if (Private->TimerUses8254 && (TimerPeriod < 549254)) {
    SetPitCount (0);
  }

  if ((Stack != NULL) && (StackSize != 0)) {
    //
    // Copy Stack to low memory stack
    //
    Stack16 -= StackSize / sizeof (UINT16);
    CopyMem (Stack16, Stack, StackSize);
  }

  ThunkRegSet.E.SS  = (UINT16)(((UINTN)Stack16 >> 16) << 12);
  ThunkRegSet.E.ESP = (UINT16)(UINTN)Stack16;
  ThunkRegSet.E.CS  = Segment;
  ThunkRegSet.E.Eip = Offset;

  mThunkContext.RealModeState = &ThunkRegSet;

  //
  // Set Legacy16 state. 0x08, 0x70 is legacy 8259 vector bases.
  //
  Status = Private->Legacy8259->SetMode (Private->Legacy8259, Efi8259LegacyMode, NULL, NULL);
  ASSERT_EFI_ERROR (Status);

  AsmThunk16 (&mThunkContext);

  if ((Stack != NULL) && (StackSize != 0)) {
    //
    // Copy low memory stack to Stack
    //
    CopyMem (Stack, Stack16, StackSize);
  }

  //
  // Restore protected mode interrupt state
  //
  Status = Private->Legacy8259->SetMode (Private->Legacy8259, Efi8259ProtectedMode, NULL, NULL);
  ASSERT_EFI_ERROR (Status);

  mThunkContext.RealModeState = NULL;

  //
  // Enable and restore rate of DXE Timer
  //
  Private->Timer->SetTimerPeriod (Private->Timer, TimerPeriod);

  //
  // End critical section
  //
  gBS->RestoreTPL (OriginalTpl);

  //
  // OPROM may allocate EBDA range by itself and change EBDA base and EBDA size.
  // Get the current EBDA base address, and compared with pre-allocate minimum
  // EBDA base address, if the current EBDA base address is smaller, it indicates
  // PcdEbdaReservedMemorySize should be adjusted to larger for more OPROMs.
  //
  DEBUG_CODE_BEGIN ();
  {
    UINTN  EbdaBaseAddress;
    UINTN  ReservedEbdaBaseAddress;

    ACCESS_PAGE0_CODE (
      EbdaBaseAddress         = (*(UINT16 *)(UINTN)0x40E) << 4;
      ReservedEbdaBaseAddress = CONVENTIONAL_MEMORY_TOP
                                - PcdGet32 (PcdEbdaReservedMemorySize);
      ASSERT (ReservedEbdaBaseAddress <= EbdaBaseAddress);
      );
  }
  DEBUG_CODE_END ();

  //
  // Restore interrupt of debug timer
  //
  SaveAndSetDebugTimerInterrupt (InterruptState);

  Regs->E.EDI = ThunkRegSet.E.EDI;
  Regs->E.ESI = ThunkRegSet.E.ESI;
  Regs->E.EBP = ThunkRegSet.E.EBP;
  Regs->E.EBX = ThunkRegSet.E.EBX;
  Regs->E.EDX = ThunkRegSet.E.EDX;
  Regs->E.ECX = ThunkRegSet.E.ECX;
  Regs->E.EAX = ThunkRegSet.E.EAX;
  Regs->X.SS  = ThunkRegSet.E.SS;
  Regs->X.CS  = ThunkRegSet.E.CS;
  Regs->X.DS  = ThunkRegSet.E.DS;
  Regs->X.ES  = ThunkRegSet.E.ES;

  CopyMem (&(Regs->X.Flags), &(ThunkRegSet.E.EFLAGS.UintN), sizeof (Regs->X.Flags));

  return (BOOLEAN)(Regs->X.Flags.CF == 1);
}

/**
  Allocate memory < 1 MB and copy the thunker code into low memory. Se up
  all the descriptors.

  @param  Private                Private context for Legacy BIOS

  @retval EFI_SUCCESS            Should only pass.

**/
EFI_STATUS
LegacyBiosInitializeThunk (
  IN  LEGACY_BIOS_INSTANCE  *Private
  )
{
  EFI_STATUS            Status;
  EFI_PHYSICAL_ADDRESS  MemoryAddress;
  UINT8                 TimerVector;

  MemoryAddress = (EFI_PHYSICAL_ADDRESS)(UINTN)Private->IntThunk;

  mThunkContext.RealModeBuffer     = (VOID *)(UINTN)(MemoryAddress + ((sizeof (LOW_MEMORY_THUNK) / EFI_PAGE_SIZE) + 1) * EFI_PAGE_SIZE);
  mThunkContext.RealModeBufferSize = EFI_PAGE_SIZE;
  mThunkContext.ThunkAttributes    = THUNK_ATTRIBUTE_BIG_REAL_MODE | THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15;

  AsmPrepareThunk16 (&mThunkContext);

  //
  // Get the interrupt vector number corresponding to IRQ0 from the 8259 driver
  //
  TimerVector = 0;
  Status      = Private->Legacy8259->GetVector (Private->Legacy8259, Efi8259Irq0, &TimerVector);
  ASSERT_EFI_ERROR (Status);

  //
  // Check to see if the Timer AP has hooked the IRQ0 from the 8254 PIT
  //
  Status = Private->Cpu->RegisterInterruptHandler (
                           Private->Cpu,
                           TimerVector,
                           LegacyBiosNullInterruptHandler
                           );
  if (Status == EFI_SUCCESS) {
    //
    // If the Timer AP has not enabled the 8254 timer IRQ, then force the 8254 PIT
    // counter to 0, which is the CSM required rate of 54.9254 ms
    //
    Private->Cpu->RegisterInterruptHandler (
                    Private->Cpu,
                    TimerVector,
                    NULL
                    );
    SetPitCount (0);

    //
    // Save status that the Timer AP is not using the 8254 PIT
    //
    Private->TimerUses8254 = FALSE;
  } else if (Status == EFI_ALREADY_STARTED) {
    //
    // Save status that the Timer AP is using the 8254 PIT
    //
    Private->TimerUses8254 = TRUE;
  } else {
    //
    // Unexpected status from CPU AP RegisterInterruptHandler()
    //
    ASSERT (FALSE);
  }

  return EFI_SUCCESS;
}