Update vesa.c

Try to fix the vesa assembly out of the clobber 

Seems like this works now.

kernel/vesa.c

@@ -0,0 +1,112 @@
+#include <stddef.h>
+#include "vesa.h"
+#include "io.h"
+#include "print.h"
+
+// VESA mode and controller information
+#define VESA_BIOS_INT 0x10
+#define VESA_BIOS_FUNC 0x4F
+
+// Function to call BIOS with specific VESA function
+static bool vesa_bios_call(uint16_t function, uint16_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx) {
+    // Set up registers for VESA function call
+    __asm__ __volatile__(
+        "movw %1, %%ax\n"           // Move function number into AX
+        "int $0x10\n"                // Call BIOS interrupt 0x10 (VESA)
+        "movw %%ax, %0\n"            // Move return value in AX to the return variable
+        : "=m"(*eax)                 // Output operand (eax)
+        : "m"(function)              // Input operand (function number)
+        : "%eax", "%ebx", "%ecx", "%edx", "memory"
+    );
+    // Check for success (return values vary depending on the function)
+    return *eax == 0x004F;
+}
+
+// Set the VESA video mode
+bool vesa_set_mode(uint16_t mode) {
+    uint16_t eax = VBE_FUNCTION_SET_MODE;
+    uint32_t ebx = mode;
+    uint32_t ecx = 0;
+    uint32_t edx = 0;
+    
+    if (vesa_bios_call(VBE_FUNCTION_SET_MODE, &eax, &ebx, &ecx, &edx)) {
+        return true;
+    }
+    return false;
+}
+
+// Get the VESA mode information
+bool vesa_get_mode_info(uint16_t mode, vbe_mode_info_t* info) {
+    uint16_t ax_ret;
+    
+    // Convert the 32-bit pointer to a Segment:Offset pair
+    // IMPORTANT: 'info' MUST be located in the first 1MB of RAM
+    uint32_t ptr = (uint32_t)info;
+    uint16_t segment = (uint16_t)((ptr >> 4) & 0xFFFF);
+    uint16_t offset  = (uint16_t)(ptr & 0x000F);
+
+    __asm__ __volatile__(
+        "push %%es\n\t"         // Save Protected Mode ES
+        "movw %1, %%es\n\t"     // Load the segment into ES
+        "int $0x10\n\t"         // BIOS Interrupt
+        "pop %%es\n\t"          // Restore Protected Mode ES
+        : "=a"(ax_ret)          // Result in AX
+        : "r"(segment),         // %1
+          "D"(offset),          // %2 (DI)
+          "a"((uint16_t)VBE_FUNCTION_GET_MODE_INFO), // AX (0x4F01)
+          "c"(mode)             // CX (The Mode Number)
+        : "memory", "cc"        // Removed %es from clobbers
+    );
+
+    return ax_ret == 0x004F;
+}
+
+bool vesa_get_controller_info(vbe_controller_info_t* info) {
+    uint16_t ax_ret;
+    
+    // We must use Segment:Offset for BIOS
+    uint32_t ptr = (uint32_t)info;
+    uint16_t segment = (uint16_t)((ptr >> 4) & 0xF000); // Base segment
+    uint16_t offset  = (uint16_t)(ptr & 0xFFFF);        // Offset
+
+    // Copy "VBE2" into signature to tell BIOS we want VBE 2.0+ info
+    info->Signature[0] = 'V';
+    info->Signature[1] = 'B';
+    info->Signature[2] = 'E';
+    info->Signature[3] = '2';
+
+    // To fix the error: Do not use %es in clobber. 
+    // Use a temporary register or a push/pop sequence if we MUST touch ES.
+    __asm__ __volatile__(
+        "push %%es\n\t"
+        "movw %1, %%es\n\t"
+        "int $0x10\n\t"
+        "pop %%es\n\t"
+        : "=a"(ax_ret)
+        : "r"(segment), "D"(offset), "a"(0x4F00)
+        : "memory", "cc" 
+    );
+
+    return ax_ret == 0x004F;
+}
+
+// Return pointer to the VESA framebuffer
+void* vesa_get_framebuffer(void) {
+    vbe_mode_info_t mode_info;
+    if (vesa_get_mode_info(0x101, &mode_info)) {
+        return (void*)mode_info.PhysBasePtr;
+    }
+    return NULL;
+}
+
+// Clear the screen with a color
+void vesa_clear_screen(uint32_t color) {
+    uint32_t* framebuffer = (uint32_t*)vesa_get_framebuffer();
+    if (framebuffer) {
+        for (int y = 0; y < 480; y++) { // For 640x480 mode
+            for (int x = 0; x < 640; x++) {
+                framebuffer[y * 640 + x] = color;
+            }
+        }
+    }
+}

kernel/vesa.h

@@ -0,0 +1,75 @@
+#ifndef VESA_H
+#define VESA_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+// VESA BIOS Extension 2.0 Function Calls
+#define VBE_FUNCTION_SET_MODE        0x4F02
+#define VBE_FUNCTION_GET_MODE_INFO   0x4F01
+#define VBE_FUNCTION_GET_CONTROLLER_INFO 0x4F00
+#define VBE_FUNCTION_SET_DISPLAY_START 0x4F05
+
+// VESA Mode Information Structure (VBE 2.0)
+typedef struct {
+    uint16_t ModeAttributes;      // Mode attributes
+    uint8_t WinAAttributes;       // Window A attributes
+    uint8_t WinBAttributes;       // Window B attributes
+    uint16_t WinGranularity;      // Window granularity
+    uint16_t WinSize;             // Window size
+    uint16_t WinASegment;         // Window A segment address
+    uint16_t WinBSegment;         // Window B segment address
+    uint32_t WinFuncPtr;          // Function pointer for window
+    uint16_t BytesPerScanLine;    // Bytes per scanline
+    uint16_t XResolution;         // Horizontal resolution in pixels
+    uint16_t YResolution;         // Vertical resolution in pixels
+    uint8_t XCharSize;            // Character cell width
+    uint8_t YCharSize;            // Character cell height
+    uint8_t NumberOfPlanes;       // Number of memory planes
+    uint8_t BitsPerPixel;         // Bits per pixel
+    uint8_t NumberOfBanks;        // Number of banks
+    uint8_t MemoryModel;          // Memory model type
+    uint8_t BankSize;             // Bank size in kB
+    uint8_t NumberOfImagePages;   // Number of image pages
+    uint8_t Reserved0;            // Reserved
+    uint8_t RedMaskSize;          // Red mask size
+    uint8_t RedFieldPosition;     // Red field position
+    uint8_t GreenMaskSize;        // Green mask size
+    uint8_t GreenFieldPosition;   // Green field position
+    uint8_t BlueMaskSize;         // Blue mask size
+    uint8_t BlueFieldPosition;    // Blue field position
+    uint8_t RsvdMaskSize;         // Reserved mask size
+    uint8_t RsvdFieldPosition;    // Reserved field position
+    uint8_t DirectColorModeInfo;  // Direct color mode info
+    uint32_t PhysBasePtr;         // Physical base address of the linear framebuffer
+    uint32_t OffScreenMemOff;     // Offset to off-screen memory
+    uint16_t OffScreenMemSize;    // Size of off-screen memory
+    uint8_t Reserved1[206];       // Reserved
+} __attribute__((packed)) vbe_mode_info_t;
+
+// VESA Controller Information
+
+typedef struct {
+    char Signature[4];             // Should be "VESA" (or "VBE2" for request)
+    uint16_t Version;              // VBE version; high byte is major, low is minor
+    uint32_t OEMStringPtr;         // Segment:Offset pointer to OEM string
+    uint32_t Capabilities;         // Capabilities of graphics controller
+    uint32_t VideoModePtr;         // Segment:Offset pointer to supported modes list
+    uint16_t TotalMemory;          // Number of 64KB memory blocks
+    uint16_t OEMSoftwareRev;       // VBE implementation Software revision
+    uint32_t OEMVendorNamePtr;     // Segment:Offset pointer to Vendor Name string
+    uint32_t OEMProductNamePtr;    // Segment:Offset pointer to Product Name string
+    uint32_t OEMProductRevPtr;     // Segment:Offset pointer to Product Revision string
+    uint8_t Reserved[222];         // Reserved for VBE implementation scratch area
+    uint8_t OEMData[256];          // Data area for OEM strings
+} __attribute__((packed)) vbe_controller_info_t;
+
+// Function Prototypes
+bool vesa_set_mode(uint16_t mode);
+bool vesa_get_mode_info(uint16_t mode, vbe_mode_info_t* info);
+bool vesa_get_controller_info(vbe_controller_info_t* info);
+void* vesa_get_framebuffer(void);
+void vesa_clear_screen(uint32_t color);
+
+#endif // VESA_H