Introduce legacy VGA text mode support

boot/xtldr/CMakeLists.txt

@@ -16,6 +16,7 @@ list(APPEND LIBXTLDR_SOURCE
 # Specify list of source code files
 list(APPEND XTLDR_SOURCE
     ${XTLDR_SOURCE_DIR}/arch/${ARCH}/memory.cc
+    ${XTLDR_SOURCE_DIR}/biosutil.cc
     ${XTLDR_SOURCE_DIR}/bootutil.cc
     ${XTLDR_SOURCE_DIR}/config.cc
     ${XTLDR_SOURCE_DIR}/console.cc

boot/xtldr/biosutil.cc

@@ -0,0 +1,190 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtldr/biosutil.cc
+ * DESCRIPTION:     Legacy BIOS support
+ * DEVELOPERS:      Aiken Harris <harraiken91@gmail.com>
+ */
+
+#include <xtldr.hh>
+
+
+/**
+ * Clears the entire screen and moves the cursor to the top-left corner.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+VOID
+BiosUtils::ClearScreen()
+{
+    VOLATILE PUSHORT VgaBuffer = (PUSHORT)0xB8000;
+    USHORT Blank;
+    UINT Index;
+
+    /* Set blank character */
+    Blank = (0x0F << 8) | L' ';
+
+    /* Fill the entire screen with blank characters */
+    for(Index = 0; Index < VgaWidth * VgaHeight; Index++)
+    {
+        VgaBuffer[Index] = Blank;
+    }
+
+    /* Reset cursor position to the top-left corner */
+    CursorX = 0;
+    CursorY = 0;
+
+    /* Update the hardware cursor position */
+    UpdateCursor();
+}
+
+/**
+ * Formats the input string and prints it out to the screen.
+ *
+ * @param Format
+ *        The formatted string that is to be written to the output.
+ *
+ * @param ...
+ *        Depending on the format string, this routine might expect a sequence of additional arguments.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+VOID
+BiosUtils::Print(IN PCWSTR Format,
+                 IN ...)
+{
+    RTL_PRINT_CONTEXT PrintContext;
+    VA_LIST Arguments;
+
+    /* Initialise the print contexts */
+    PrintContext.WriteWideCharacter = PutChar;
+
+    /* Initialise the va_list */
+    VA_START(Arguments, Format);
+
+    /* Format and print the string to the stdout */
+    RTL::WideString::FormatWideString(&PrintContext, (PWCHAR)Format, Arguments);
+
+    /* Clean up the va_list */
+    VA_END(Arguments);
+}
+
+/**
+ * Writes a single wide character to the screen using legacy BIOS VGA text mode.
+ *
+ * @param Character
+ *        The wide character to be printed.
+ *
+ * @return This routine returns a status code.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+XTSTATUS
+BiosUtils::PutChar(IN WCHAR Character)
+{
+    VOLATILE PUSHORT VgaBuffer = (PUSHORT)0xB8000;
+    USHORT VgaCharacter;
+
+    /* Handle special characters */
+    if(Character == L'\n')
+    {
+        /* Move to the next line */
+        CursorX = 0;
+        CursorY++;
+    }
+    else if(Character == L'\r')
+    {
+        /* Move to the beginning of the current line */
+        CursorX = 0;
+    }
+    else
+    {
+        /* Print character and move cursor to the right */
+        VgaCharacter = (0x0F << 8) | (Character & 0xFF);
+        VgaBuffer[CursorY * VgaWidth + CursorX] = VgaCharacter;
+        CursorX++;
+    }
+
+    /* Handle moving to the next line if cursor is at the end of the line */
+    if(CursorX >= VgaWidth)
+    {
+        CursorX = 0;
+        CursorY++;
+    }
+
+    /* Handle scrolling if cursor is at the end of the screen */
+    if(CursorY >= VgaHeight)
+    {
+        ScrollScreen();
+        CursorY = VgaHeight - 1;
+    }
+
+    /* Update the hardware cursor position */
+    UpdateCursor();
+
+    /* Return success */
+    return STATUS_EFI_SUCCESS;
+}
+
+/**
+ * Scrolls the entire screen content up by one line and clears the last line.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+VOID
+BiosUtils::ScrollScreen()
+{
+    VOLATILE PUSHORT VgaBuffer = (PUSHORT)0xB8000;
+    USHORT Blank;
+    UINT Index;
+
+    /* Set blank character */
+    Blank = (0x0F << 8) | L' ';
+
+    /* Move every line up by one */
+    for(Index = 0; Index < (VgaHeight - 1) * VgaWidth; Index++)
+    {
+        VgaBuffer[Index] = VgaBuffer[Index + VgaWidth];
+    }
+
+    /* Clear the last line */
+    for(Index = (VgaHeight - 1) * VgaWidth; Index < VgaHeight * VgaWidth; Index++)
+    {
+        VgaBuffer[Index] = Blank;
+    }
+}
+
+/**
+ * Updates the hardware cursor position on the screen.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+VOID
+BiosUtils::UpdateCursor()
+{
+    USHORT Position;
+
+    /* Calculate cursor position */
+    Position = CursorY * VgaWidth + CursorX;
+
+    /* Send command to set the high byte of the cursor position */
+    HL::IoPort::WritePort8(0x3D4, 0x0E);
+    HL::IoPort::WritePort8(0x3D5, (UCHAR)((Position >> 8) & 0xFF));
+
+    /* Send command to set the low byte of the cursor position */
+    HL::IoPort::WritePort8(0x3D4, 0x0F);
+    HL::IoPort::WritePort8(0x3D5, (UCHAR)(Position & 0xFF));
+}

boot/xtldr/data.cc

@@ -10,6 +10,18 @@
 #include <xtldr.hh>
 
 
+/* Legacy BIOS cursor X position */
+USHORT BiosUtils::CursorX = 0;
+
+/* Legacy BIOS cursor Y position */
+USHORT BiosUtils::CursorY = 0;
+
+/* Legacy BIOS screen height */
+CONST USHORT BiosUtils::VgaHeight = 25;
+
+/* Legacy BIOS screen width */
+CONST USHORT BiosUtils::VgaWidth = 80;
+
 /* XT Boot Loader menu list */
 PLIST_ENTRY Configuration::BootMenuList = NULLPTR;
 

boot/xtldr/includes/xtldr.hh

@@ -15,6 +15,25 @@
 #include <libxtos.hh>
 
 
+class BiosUtils
+{
+    private:
+        STATIC USHORT CursorX;
+        STATIC USHORT CursorY;
+        STATIC CONST USHORT VgaHeight;
+        STATIC CONST USHORT VgaWidth;
+
+    public:
+        STATIC XTCDECL VOID ClearScreen();
+        STATIC XTCDECL VOID Print(IN PCWSTR Format,
+                                  IN ...);
+        STATIC XTCDECL XTSTATUS PutChar(IN WCHAR Character);
+
+    private:
+        STATIC XTCDECL VOID ScrollScreen();
+        STATIC XTCDECL VOID UpdateCursor();
+};
+
 class BootUtils
 {
     public: