system76-edk2/OvmfPkg/QemuVideoDxe/VbeShim.c

/** @file
  Install a fake VGABIOS service handler (real mode Int10h) for the buggy
  Windows 2008 R2 SP1 UEFI guest.

  The handler is never meant to be directly executed by a VCPU; it's there for
  the internal real mode emulator of Windows 2008 R2 SP1.

  The code is based on Ralf Brown's Interrupt List:
  <http://www.cs.cmu.edu/~ralf/files.html>
  <http://www.ctyme.com/rbrown.htm>

  Copyright (C) 2014, Red Hat, Inc.
  Copyright (c) 2013 - 2014, Intel Corporation. All rights reserved.<BR>

  This program and the accompanying materials are licensed and made available
  under the terms and conditions of the BSD License which accompanies this
  distribution. The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/

#include <IndustryStandard/LegacyVgaBios.h>
#include <Library/DebugLib.h>
#include <Library/PciLib.h>
#include <Library/PrintLib.h>

#include "Qemu.h"
#include "VbeShim.h"

#pragma pack (1)
typedef struct {
  UINT16 Offset;
  UINT16 Segment;
} IVT_ENTRY;
#pragma pack ()

//
// This string is displayed by Windows 2008 R2 SP1 in the Screen Resolution,
// Advanced Settings dialog. It should be short.
//
STATIC CONST CHAR8 mProductRevision[] = "OVMF Int10h (fake)";

/**
  Install the VBE Info and VBE Mode Info structures, and the VBE service
  handler routine in the C segment. Point the real-mode Int10h interrupt vector
  to the handler. The only advertised mode is 1024x768x32.

  @param[in] CardName         Name of the video card to be exposed in the
                              Product Name field of the VBE Info structure. The
                              parameter must originate from a
                              QEMU_VIDEO_CARD.Name field.
  @param[in] FrameBufferBase  Guest-physical base address of the video card's
                              frame buffer.
**/
VOID
InstallVbeShim (
  IN CONST CHAR16         *CardName,
  IN EFI_PHYSICAL_ADDRESS FrameBufferBase
  )
{
  EFI_PHYSICAL_ADDRESS Segment0, SegmentC, SegmentF;
  UINTN                Segment0Pages;
  IVT_ENTRY            *Int0x10;
  EFI_STATUS           Status;
  UINTN                Pam1Address;
  UINT8                Pam1;
  UINTN                SegmentCPages;
  VBE_INFO             *VbeInfoFull;
  VBE_INFO_BASE        *VbeInfo;
  UINT8                *Ptr;
  UINTN                Printed;
  VBE_MODE_INFO        *VbeModeInfo;

  Segment0 = 0x00000;
  SegmentC = 0xC0000;
  SegmentF = 0xF0000;

  //
  // Attempt to cover the real mode IVT with an allocation. This is a UEFI
  // driver, hence the arch protocols have been installed previously. Among
  // those, the CPU arch protocol has configured the IDT, so we can overwrite
  // the IVT used in real mode.
  //
  // The allocation request may fail, eg. if LegacyBiosDxe has already run.
  //
  Segment0Pages = 1;
  Int0x10       = (IVT_ENTRY *)(UINTN)Segment0 + 0x10;
  Status = gBS->AllocatePages (AllocateAddress, EfiBootServicesCode,
                  Segment0Pages, &Segment0);

  if (EFI_ERROR (Status)) {
    EFI_PHYSICAL_ADDRESS Handler;

    //
    // Check if a video BIOS handler has been installed previously -- we
    // shouldn't override a real video BIOS with our shim, nor our own shim if
    // it's already present.
    //
    Handler = (Int0x10->Segment << 4) + Int0x10->Offset;
    if (Handler >= SegmentC && Handler < SegmentF) {
      DEBUG ((EFI_D_INFO, "%a: Video BIOS handler found at %04x:%04x\n",
        __FUNCTION__, Int0x10->Segment, Int0x10->Offset));
      return;
    }

    //
    // Otherwise we'll overwrite the Int10h vector, even though we may not own
    // the page at zero.
    //
    DEBUG ((EFI_D_INFO, "%a: failed to allocate page at zero: %r\n",
      __FUNCTION__, Status));
  } else {
    //
    // We managed to allocate the page at zero. SVN r14218 guarantees that it
    // is NUL-filled.
    //
    ASSERT (Int0x10->Segment == 0x0000);
    ASSERT (Int0x10->Offset  == 0x0000);
  }

  //
  // Put the shim in place first.
  //
  Pam1Address = PCI_LIB_ADDRESS (0, 0, 0, 0x5A);
  //
  // low nibble covers 0xC0000 to 0xC3FFF
  // high nibble covers 0xC4000 to 0xC7FFF
  // bit1 in each nibble is Write Enable
  // bit0 in each nibble is Read Enable
  //
  Pam1 = PciRead8 (Pam1Address);
  PciWrite8 (Pam1Address, Pam1 | (BIT1 | BIT0));

  //
  // We never added memory space during PEI or DXE for the C segment, so we
  // don't need to (and can't) allocate from there. Also, guest operating
  // systems will see a hole in the UEFI memory map there.
  //
  SegmentCPages = 4;

  ASSERT (sizeof mVbeShim <= EFI_PAGES_TO_SIZE (SegmentCPages));
  CopyMem ((VOID *)(UINTN)SegmentC, mVbeShim, sizeof mVbeShim);

  //
  // Fill in the VBE INFO structure.
  //
  VbeInfoFull = (VBE_INFO *)(UINTN)SegmentC;
  VbeInfo     = &VbeInfoFull->Base;
  Ptr         = VbeInfoFull->Buffer;

  CopyMem (VbeInfo->Signature, "VESA", 4);
  VbeInfo->VesaVersion = 0x0300;

  VbeInfo->OemNameAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
  CopyMem (Ptr, "QEMU", 5);
  Ptr += 5;

  VbeInfo->Capabilities = BIT0; // DAC can be switched into 8-bit mode

  VbeInfo->ModeListAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
  *(UINT16*)Ptr = 0x00f1; // mode number
  Ptr += 2;
  *(UINT16*)Ptr = 0xFFFF; // mode list terminator
  Ptr += 2;

  VbeInfo->VideoMem64K = (UINT16)((1024 * 768 * 4 + 65535) / 65536);
  VbeInfo->OemSoftwareVersion = 0x0000;

  VbeInfo->VendorNameAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
  CopyMem (Ptr, "OVMF", 5);
  Ptr += 5;

  VbeInfo->ProductNameAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
  Printed = AsciiSPrint ((CHAR8 *)Ptr,
              sizeof VbeInfoFull->Buffer - (Ptr - VbeInfoFull->Buffer), "%s",
              CardName);
  Ptr += Printed + 1;

  VbeInfo->ProductRevAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
  CopyMem (Ptr, mProductRevision, sizeof mProductRevision);
  Ptr += sizeof mProductRevision;

  ASSERT (sizeof VbeInfoFull->Buffer >= Ptr - VbeInfoFull->Buffer);
  ZeroMem (Ptr, sizeof VbeInfoFull->Buffer - (Ptr - VbeInfoFull->Buffer));

  //
  // Fil in the VBE MODE INFO structure.
  //
  VbeModeInfo = (VBE_MODE_INFO *)(VbeInfoFull + 1);

  //
  // bit0: mode supported by present hardware configuration
  // bit1: optional information available (must be =1 for VBE v1.2+)
  // bit3: set if color, clear if monochrome
  // bit4: set if graphics mode, clear if text mode
  // bit5: mode is not VGA-compatible
  // bit7: linear framebuffer mode supported
  //
  VbeModeInfo->ModeAttr = BIT7 | BIT5 | BIT4 | BIT3 | BIT1 | BIT0;

  //
  // bit0: exists
  // bit1: bit1: readable
  // bit2: writeable
  //
  VbeModeInfo->WindowAAttr              = BIT2 | BIT1 | BIT0;

  VbeModeInfo->WindowBAttr              = 0x00;
  VbeModeInfo->WindowGranularityKB      = 0x0040;
  VbeModeInfo->WindowSizeKB             = 0x0040;
  VbeModeInfo->WindowAStartSegment      = 0xA000;
  VbeModeInfo->WindowBStartSegment      = 0x0000;
  VbeModeInfo->WindowPositioningAddress = 0x0000;
  VbeModeInfo->BytesPerScanLine         = 1024 * 4;

  VbeModeInfo->Width                = 1024;
  VbeModeInfo->Height               = 768;
  VbeModeInfo->CharCellWidth        = 8;
  VbeModeInfo->CharCellHeight       = 16;
  VbeModeInfo->NumPlanes            = 1;
  VbeModeInfo->BitsPerPixel         = 32;
  VbeModeInfo->NumBanks             = 1;
  VbeModeInfo->MemoryModel          = 6; // direct color
  VbeModeInfo->BankSizeKB           = 0;
  VbeModeInfo->NumImagePagesLessOne = 0;
  VbeModeInfo->Vbe3                 = 0x01;

  VbeModeInfo->RedMaskSize      = 8;
  VbeModeInfo->RedMaskPos       = 16;
  VbeModeInfo->GreenMaskSize    = 8;
  VbeModeInfo->GreenMaskPos     = 8;
  VbeModeInfo->BlueMaskSize     = 8;
  VbeModeInfo->BlueMaskPos      = 0;
  VbeModeInfo->ReservedMaskSize = 8;
  VbeModeInfo->ReservedMaskPos  = 24;

  //
  // bit1: Bytes in reserved field may be used by application
  //
  VbeModeInfo->DirectColorModeInfo = BIT1;

  VbeModeInfo->LfbAddress       = (UINT32)FrameBufferBase;
  VbeModeInfo->OffScreenAddress = 0;
  VbeModeInfo->OffScreenSizeKB  = 0;

  VbeModeInfo->BytesPerScanLineLinear = 1024 * 4;
  VbeModeInfo->NumImagesLessOneBanked = 0;
  VbeModeInfo->NumImagesLessOneLinear = 0;
  VbeModeInfo->RedMaskSizeLinear      = 8;
  VbeModeInfo->RedMaskPosLinear       = 16;
  VbeModeInfo->GreenMaskSizeLinear    = 8;
  VbeModeInfo->GreenMaskPosLinear     = 8;
  VbeModeInfo->BlueMaskSizeLinear     = 8;
  VbeModeInfo->BlueMaskPosLinear      = 0;
  VbeModeInfo->ReservedMaskSizeLinear = 8;
  VbeModeInfo->ReservedMaskPosLinear  = 24;
  VbeModeInfo->MaxPixelClockHz        = 0;

  ZeroMem (VbeModeInfo->Reserved, sizeof VbeModeInfo->Reserved);

  //
  // Clear Write Enable (bit1), keep Read Enable (bit0) set
  //
  PciWrite8 (Pam1Address, (Pam1 & ~BIT1) | BIT0);

  //
  // Second, point the Int10h vector at the shim.
  //
  Int0x10->Segment = (UINT16) ((UINT32)SegmentC >> 4);
  Int0x10->Offset  = (UINT16) ((UINTN) (VbeModeInfo + 1) - SegmentC);

  DEBUG ((EFI_D_INFO, "%a: VBE shim installed\n", __FUNCTION__));
}