Added framebuffer initialization using GOP.

targets/x86_64/include/boot.hpp

@@ -63,4 +63,19 @@ struct EfiMemoryMap
     }
 };
 
+struct EfiDisplayInfo
+{
+    void* frameBufferBase;
+    uint64_t frameBufferSize;
+    uint32_t frameBufferWidth;
+    uint32_t frameBufferHeight;
+    uint32_t frameBufferPitch;
+};
+
+struct EfiBootInfo
+{
+    EfiMemoryMap memoryMap;
+    EfiDisplayInfo displayInfo;
+};
+
 #endif // BOOT_HPP_INCLUDED

targets/x86_64/src/kernel/boot.s

@@ -12,7 +12,7 @@ stack_top:
 .type _start, @function
 _start:
     // store the memory map
-    mov %rbx, (gMemoryMap)
+    mov %rbx, (gBootInfo)
 
 	// setup stack
 	mov $stack_top, %rsp

targets/x86_64/src/kernel/startup.cpp

@@ -61,7 +61,7 @@ void initGlobals()
 
 extern "C"
 {
-EfiMemoryMap* gMemoryMap;
+EfiBootInfo* gBootInfo;
 
 void _init();
 void _fini();
@@ -76,10 +76,30 @@ void kernel_main()
 
     std::printf("Kernel End: %p\n", &gKernelEnd);
 
+    struct Pixel
+    {
+        uint8_t blue = 0;
+        uint8_t green = 0;
+        uint8_t red = 0;
+        uint8_t reserved = 0;
+    };
+    auto setPixel = [](unsigned x, unsigned y, Pixel color)
+    {
+        Pixel* framebuffer = static_cast<Pixel*>(gBootInfo->displayInfo.frameBufferBase);
+        framebuffer[y * gBootInfo->displayInfo.frameBufferPitch / 4 + x] = color;
+    };
+    for (int x = 0; x < 100; ++x)
+    {
+        for (int y = 0; y < 100; ++y)
+        {
+            setPixel(x, y, {.red = 255});
+        }
+    }
+
     /* Initialize the heap */
     // assert(gMultibootHeader->flags & MULTIBOOT_INFO_MEM_MAP);
     // initHeapFromMultibootHeader(gMultibootHeader->mmap_addr, gMultibootHeader->mmap_length);
-    initHeapFromEfiMemoryMap(*gMemoryMap);
+    initHeapFromEfiMemoryMap(gBootInfo->memoryMap);
 
     main();
 

targets/x86_64/src/loader/main.cpp

@@ -9,6 +9,7 @@ extern "C"
 #include "miniprintf.hpp"
 
 // debug stuff
+// #define DUMP_DISPLAY_MODES
 // #define DUMP_MEMORY_MAP
 // #define DUMP_ELF
 
@@ -16,6 +17,7 @@ namespace
 {
 EFI_SYSTEM_TABLE* gSystemTable;
 EFI_BOOT_SERVICES* gBootServices;
+EFI_GRAPHICS_OUTPUT_PROTOCOL* gGraphicsOutputProtocol;
 
 EFI_STATUS openImageVolume(EFI_HANDLE image, EFI_FILE_HANDLE& outHandle)
 {
@@ -132,6 +134,59 @@ EFI_STATUS getEfiMemoryMap(EfiMemoryMap& outMemoryMap)
     return EFI_SUCCESS;
 }
 
+EFI_STATUS getEfiGraphicsOutputProtocol(EFI_GRAPHICS_OUTPUT_PROTOCOL*& outGOP)
+{
+    static const EFI_GUID GOP_GUID = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
+
+    EFI_GRAPHICS_OUTPUT_PROTOCOL* gop;
+    EFI_STATUS status = gBootServices->LocateProtocol(const_cast<EFI_GUID*>(&GOP_GUID), nullptr, reinterpret_cast<void**>(&gop));
+    if (EFI_ERROR(status)) {
+        return status;
+    }
+    outGOP = gop;
+    return EFI_SUCCESS;
+}
+
+EFI_STATUS queryEfiDisplayModes(EFI_GRAPHICS_OUTPUT_MODE_INFORMATION*& outModes)
+{
+    UINTN sizeOfInfo = gGraphicsOutputProtocol->Mode->SizeOfInfo;
+    outModes = new EFI_GRAPHICS_OUTPUT_MODE_INFORMATION[gGraphicsOutputProtocol->Mode->MaxMode];
+    EFI_GRAPHICS_OUTPUT_MODE_INFORMATION* buffer = static_cast<EFI_GRAPHICS_OUTPUT_MODE_INFORMATION*>(malloc(sizeOfInfo));
+
+    for (UINT32 modeIdx = 0; modeIdx < gGraphicsOutputProtocol->Mode->MaxMode; ++modeIdx)
+    {
+        EFI_STATUS status = gGraphicsOutputProtocol->QueryMode(gGraphicsOutputProtocol, modeIdx, &sizeOfInfo, &buffer);
+        if (EFI_ERROR(status))
+        {
+            delete[] outModes;
+            free(buffer);
+            return status;
+        }
+        outModes[modeIdx] = *buffer;
+    }
+    free(buffer);
+    return EFI_SUCCESS;
+}
+
+UINT32 findBestDisplayMode(EFI_GRAPHICS_OUTPUT_MODE_INFORMATION* displayModes)
+{
+    UINT32 bestMode = 0;
+    uint32_t bestModePixels = 0;
+    for (UINT32 modeIdx = 0; modeIdx < gGraphicsOutputProtocol->Mode->MaxMode; ++modeIdx)
+    {
+        if (displayModes[modeIdx].PixelFormat != PixelBlueGreenRedReserved8BitPerColor) {
+            continue; // we don't care about anything but RGB
+        }
+        const uint32_t pixels = displayModes[modeIdx].VerticalResolution * displayModes[modeIdx].HorizontalResolution;
+        if (pixels > bestModePixels)
+        {
+            bestMode = modeIdx;
+            bestModePixels = pixels;
+        }
+    }
+    return bestMode;
+}
+
 bool isEfiMemoryTypeUsable(EFI_MEMORY_TYPE type)
 {
     switch (type)
@@ -167,17 +222,56 @@ if (EFI_ERROR(status))             \
 
 extern "C" EFI_STATUS efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE* systemTable)
 {
-    /* Store the system table for future use in other functions */
+    // store the system table for future use in other functions
     gSystemTable = systemTable;
     gBootServices = systemTable->BootServices;
 
     initMiniMalloc();
     initMiniPrintf(&putchar);
 
+    // this will be passed to the OS
+    EfiBootInfo* bootInfo = new EfiBootInfo;
+
     gSystemTable->ConOut->ClearScreen(gSystemTable->ConOut);
 
+    // load GOP and detect modes
+    EFI_STATUS status = getEfiGraphicsOutputProtocol(gGraphicsOutputProtocol);
+    DIE_ON_ERROR(L"Error getting EFI GOP.");
+
+    EFI_GRAPHICS_OUTPUT_MODE_INFORMATION* displayModes = nullptr;
+    status = queryEfiDisplayModes(displayModes);
+    DIE_ON_ERROR(L"Error querying EFI display modes.");
+
+    const UINT32 bestModeIdx = findBestDisplayMode(displayModes);
+    status = gGraphicsOutputProtocol->SetMode(gGraphicsOutputProtocol, bestModeIdx);
+    DIE_ON_ERROR(L"Error setting display mode.");
+
+    bootInfo->displayInfo = {
+        .frameBufferBase = reinterpret_cast<void*>(gGraphicsOutputProtocol->Mode->FrameBufferBase),
+        .frameBufferSize = gGraphicsOutputProtocol->Mode->FrameBufferSize,
+        .frameBufferWidth = gGraphicsOutputProtocol->Mode->Info->HorizontalResolution,
+        .frameBufferHeight = gGraphicsOutputProtocol->Mode->Info->VerticalResolution,
+        .frameBufferPitch = 4 * gGraphicsOutputProtocol->Mode->Info->PixelsPerScanLine
+    };
+
+#if defined(DUMP_DISPLAY_MODES)
+    printf("Display modes:\n");
+    for (UINT32 modeIdx = 0; modeIdx < gGraphicsOutputProtocol->Mode->MaxMode; ++modeIdx)
+    {
+        const EFI_GRAPHICS_OUTPUT_MODE_INFORMATION& mode = displayModes[modeIdx];
+        printf(
+            "Mode %d: width=%d, height=%d, format=%d%s\n",
+            modeIdx,
+            mode.HorizontalResolution,
+            mode.VerticalResolution,
+            mode.PixelFormat,
+            modeIdx == gGraphicsOutputProtocol->Mode->Mode ? " (current)" : ""
+        );
+    }
+#endif // defined(DUMP_DISPLAY_MODES)
+
     EFI_FILE_HANDLE volume;
-    EFI_STATUS status = openImageVolume(imageHandle, volume);
+    status = openImageVolume(imageHandle, volume);
     DIE_ON_ERROR(L"Error opening image volume.");
 
     const CHAR16* fileName = L"kernel.bin";
@@ -204,7 +298,7 @@ extern "C" EFI_STATUS efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE* systemT
     for (uint16_t phtEntry = 0; phtEntry < header.phtEntryCount; ++phtEntry)
     {
         status = fileHandle->SetPosition(fileHandle, header.phtOffset + phtEntry * header.phtEntrySize);
-        DIE_ON_ERROR("Error seeking in EFI64 file.");
+        DIE_ON_ERROR(L"Error seeking in EFI64 file.");
         Efi64ProgramHeader programHeader = {};
         bufferSize = sizeof(Efi64ProgramHeader);
         status = fileHandle->Read(fileHandle, &bufferSize, &programHeader);
@@ -230,8 +324,7 @@ extern "C" EFI_STATUS efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE* systemT
         DIE_ON_ERROR("Error reading ELF64 section.");
     }
 
-    EfiMemoryMap* memoryMap = new EfiMemoryMap;
+    status = getEfiMemoryMap(bootInfo->memoryMap);
-    status = getEfiMemoryMap(*memoryMap);
     DIE_ON_ERROR("Error getting EFI memory map.");
 
 #if defined(DUMP_MEMORY_MAP)
@@ -245,7 +338,7 @@ extern "C" EFI_STATUS efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE* systemT
             continue;
         }
         printf(
-            "Entry %d: type: %d, physicalStart: 0x%lX, numberOfPages: %ld\n",
+            "Entry %d: type=%d, physicalStart=0x%lX, numberOfPages=%ld\n",
            entry,
            static_cast<int>(descriptor.Type),
            static_cast<unsigned long>(descriptor.PhysicalStart),
@@ -259,7 +352,7 @@ extern "C" EFI_STATUS efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE* systemT
 #undef DUMP_MEMORY_MAP
 #endif // defined(DUMP_MEMORY_MAP)
 
-    status = gBootServices->ExitBootServices(imageHandle, memoryMap->mapKey);
+    status = gBootServices->ExitBootServices(imageHandle, bootInfo->memoryMap.mapKey);
     DIE_ON_ERROR("Error exiting EFI boot services.");
 
     // up up and away!
@@ -267,7 +360,7 @@ extern "C" EFI_STATUS efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE* systemT
     (
         "jmp %0"
         :
-        : "a"(header.entry), "b"(memoryMap)
+        : "a"(header.entry), "b"(bootInfo)
     );
 
     // we should never get here