M include/linker.h → include/linker.h

@@ -6,36 +6,20 @@ #define LINKER_H
 
 #include <stdint.h>
 
-extern uint8_t __SS_VMA;
-extern uint8_t __SS_LMA;
-extern uint8_t __SS_SIZE;
-
 extern uint8_t __KERNEL_VMA;
 extern uint8_t __KERNEL_LMA;
 extern uint8_t __KERNEL_SIZE;
 
-extern uint8_t __APP_VMA;
-extern uint8_t __APP_LMA;
-extern uint8_t __APP_SIZE;
-
-extern uint8_t __ELF_VMA;
-extern uint8_t __ELF_LMA;
-extern uint8_t __ELF_SIZE;
-
-#define SS_VMA (&__SS_VMA)
-#define SS_LMA (&__SS_LMA)
-#define SS_SIZE (uint32_t)(&__SS_SIZE)
-
 #define KERNEL_VMA (&__KERNEL_VMA)
 #define KERNEL_LMA (&__KERNEL_LMA)
 #define KERNEL_SIZE (uint32_t)(&__KERNEL_SIZE)
 
-#define APP_VMA (&__APP_VMA)
-#define APP_LMA (&__APP_LMA)
-#define APP_SIZE (uint32_t)(&__APP_SIZE)
+extern uint8_t __REALMD_VMA;
+extern uint8_t __REALMD_LMA;
+extern uint8_t __REALMD_SIZE;
 
-#define ELF_VMA (&__ELF_VMA)
-#define ELF_LMA (&__ELF_LMA)
-#define ELF_SIZE (uint32_t)(&__ELF_SIZE)
+#define REALMD_VMA (&__REALMD_VMA)
+#define REALMD_LMA (&__REALMD_LMA)
+#define REALMD_SIZE (uint32_t)(&__REALMD_SIZE)
 
 #endif

A src/kernel/graphics.s

@@ -0,0 +1,74 @@
+.section .text_realmode
+realmode_int10h:
+    push %ebp
+    mov %esp, %ebp
+    
+    pusha
+
+    push %ds
+    push %es
+    push %fs
+    push %ss
+
+    mov %esp, %eax
+    mov %eax, %esi
+
+    mov %ebp, %eax
+    mov %eax, %edi
+
+    # setup real mode stack
+    mov $0xF000, %eax
+    mov %eax, %esp
+    mov %eax, %ebp
+
+    push %esi
+    push %edi
+
+    # switch to realmode temporarily
+    mov %cr0, %eax
+    and $0xFFFFFFFE, %eax
+    mov %eax, %cr0
+
+    # perform long jump to set code segment
+    ljmp $0, $realmode
+return_pmode:
+    # set data segments
+    movw $0x10, %ax
+    movw %ax, %ss
+    movw %ax, %ds
+    movw %ax, %es
+    movw %ax, %fs
+
+    # restore stack
+    pop %ebp
+    pop %eax
+    mov %eax, %esp
+
+    # restore original segments and registers
+    pop %ss
+    pop %fs
+    pop %es
+    pop %ds
+
+    popa
+    
+    # return
+    pop %ebp
+
+
+.code16
+realmode:
+    # setup real mode segments
+    movw $0x0000, %ax
+    movw %ax, %ss
+    movw %ax, %ds
+    movw %ax, %es
+    movw %ax, %fs
+
+    # perform the actual interrupt
+
+    mov %cr0, %eax
+    and $0x00000001, %eax
+    mov %eax, %cr0
+
+    ljmp $0x8, $return_pmode

M src/kernel/link.txt → src/kernel/link.txt

@@ -5,22 +5,33 @@ PAGE_SIZE = 1 << 12;
 
 MEMORY
 {
+  REALMD_VMA :        ORIGIN = 0x00009000, LENGTH = 0x30000000
   KERNEL_VMA :        ORIGIN = 0xC0000000, LENGTH = 0x30000000
 }
 
 SECTIONS
 {
-  KERNEL : AT(0x4E00)
+  KERNEL : 
   {
     */*(.text)
     */*(.data)
     */*(.rodata*)
     
   } >KERNEL_VMA
+
+  REALMD : 
+  {
+    */*(.text_realmode)
+    
+  } >REALMD_VMA
 }
 
 __KERNEL_LMA = LOADADDR(KERNEL);
 __KERNEL_VMA = ADDR(KERNEL);
 __KERNEL_SIZE = SIZEOF(KERNEL);
+
+__REALMD_LMA = LOADADDR(REALMD);
+__REALMD_VMA = ADDR(REALMD);
+__REALMD_SIZE = SIZEOF(REALMD);
 
 __KERNEL_STACK_ADDR = 0xC0400000;