1 files changed, 96 insertions, 6 deletions
diff --git a/kernel/main.c b/kernel/main.c
index ec40737..79039e6 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -1,12 +1,102 @@
 #include <stdint.h>
 
-int main(void)
+struct mb2_tag_header {
+	uint32_t type;
+	uint32_t size;
+} __attribute__((packed, aligned(8)));
+typedef struct mb2_tag_header mb2_tag_header;
+
+struct mb2_tag_fb {
+	uint32_t type;
+	uint32_t size;
+	uint64_t framebuffer_addr;
+	uint32_t framebuffer_pitch;
+	uint32_t framebuffer_width;
+	uint32_t framebuffer_height;
+	uint8_t framebuffer_bpp;
+	uint8_t framebuffer_type;
+} __attribute__((packed, aligned(8)));
+typedef struct mb2_tag_fb mb2_tag_fb;
+
+// multiboot2 magic check
+#define MB2_MAGIC		0x36D76289
+
+// multiboot2 tag
+#define MB2_TAG_END		0
+#define MB2_TAG_CMDLINE		1
+#define MB2_TAG_BOOTLOADER	2
+#define MB2_TAG_MODULES		3
+#define MB2_TAG_MEM		4
+#define MB2_TAG_BIOS		5
+#define MB2_TAG_MMAP		6
+#define MB2_TAG_VBE		7
+#define MB2_TAG_FB		8
+
+void breakpoint(void)
+{
+	__asm__ volatile ("xchgw %bx, %bx;");
+}
+
+void put_in_r8(uint64_t value)
+{
+	__asm__ volatile ("movq %0, %%r8;" : : "r"(value) : "%r8");
+}
+
+void put_in_r9(uint64_t value)
 {
-	uint16_t* ct_buffer = (uint16_t*)0xb8000;
-	ct_buffer[0] = 0x2f4c;
-	ct_buffer[1] = 0x2f4f;
-	ct_buffer[2] = 0x2f4e;
-	ct_buffer[3] = 0x2f47;
+	__asm__ volatile ("movq %0, %%r9;" : : "r"(value) : "%r9");
+}
+
+void put_in_r10(uint64_t value)
+{
+	__asm__ volatile ("movq %0, %%r10;" : : "r"(value) : "%r10");
+}
+
+int kernel_main(mb2_tag_header* multiboot_bootinfo, uint32_t multiboot_magic)
+{
+	if (multiboot_magic != MB2_MAGIC) {
+		// not loaded by multiboot2 bootloader
+		__asm__ volatile ("hlt;");
+	}
+
+	// we will store framebuffer information here
+	static mb2_tag_fb* tag_fb;
+
+	// skip first 8 bytes (total_size + reserved)
+	mb2_tag_header* tag_header = multiboot_bootinfo + 1;
+
+	while (tag_header->type != MB2_TAG_END) {
+		// process tag_type
+		switch(tag_header->type) {
+			case MB2_TAG_FB:
+				tag_fb = (mb2_tag_fb*)tag_header;
+				break;
+			default:
+				break;
+		}
+
+		// next mb2_tag
+		tag_header += tag_header->size / 8 + ((tag_header->size % 8) > 0);
+	}
+
+	uint64_t* framebuffer_addr = (uint64_t*)tag_fb->framebuffer_addr;
+	uint32_t framebuffer_width = tag_fb->framebuffer_width;
+	uint32_t framebuffer_height = tag_fb->framebuffer_height;
+	//uint8_t framebuffer_bpp = tag_fb->framebuffer_bpp;
+	uint32_t framebuffer_pitch = tag_fb->framebuffer_pitch;
+
+	put_in_r8(framebuffer_width);
+	put_in_r9(framebuffer_height);
+	put_in_r10(framebuffer_pitch);
+	breakpoint();
+
+	uint32_t value = 0x0000;
+	for (uint32_t x = 0 ; x < framebuffer_width; x++) {
+		for (uint32_t y = 0; y < framebuffer_height; y++) {
+			framebuffer_addr[y*framebuffer_width + x] = value;
+			value += 0x250;
+		}
+	}
 
 	return 0;
 }