Print some multiboot2 information

1 files changed, 18 insertions, 10 deletions

diff --git a/boot.asm b/boot.asm
index e4897e4..d787d64 100644
--- a/boot.asm
+++ b/boot.asm
@@ -1,9 +1,6 @@
 ; Declare constants for the multiboot header.
-MBALIGN  equ  1 << 0            ; align loaded modules on page boundaries
-MEMINFO  equ  1 << 1            ; provide memory map
-FLAGS    equ  MBALIGN | MEMINFO ; this is the Multiboot 'flag' field
-MAGIC    equ  0x1BADB002        ; 'magic number' lets bootloader find the header
-CHECKSUM equ -(MAGIC + FLAGS)   ; checksum of above, to prove we are multiboot
+MAGIC    equ 0xE85250D6         ; multiboot2 magic
+ARCH     equ 0                  ; protected mode i386
  
 ; Declare a multiboot header that marks the program as a kernel. These are magic
 ; values that are documented in the multiboot standard. The bootloader will
@@ -11,10 +8,19 @@ CHECKSUM equ -(MAGIC + FLAGS)   ; checksum of above, to prove we are multiboot
 ; 32-bit boundary. The signature is in its own section so the header can be
 ; forced to be within the first 8 KiB of the kernel file.
 section .multiboot
-align 4
-	dd MAGIC
-	dd FLAGS
-	dd CHECKSUM
+header_start:
+    dd MAGIC
+    dd ARCH
+    dd header_end - header_start ; header length
+    dd 0x100000000 - (MAGIC + ARCH + (header_end - header_start))
+
+    ; optional multiboot tags here
+
+    ; required end tag (u16, u16, u32) = (0, 0, 8)
+    dw 0 ; type
+    dw 0 ; flags
+    dd 8 ; size
+header_end:
  
 ; The multiboot standard does not define the value of the stack pointer register
 ; (esp) and it is up to the kernel to provide a stack. This allocates room for a
@@ -29,7 +35,7 @@ align 4
 section .bss
 align 16
 stack_bottom:
-resb 16384 ; 16 KiB
+    resb 16384 ; 16 KiB
 stack_top:
  
 ; The linker script specifies _start as the entry point to the kernel and the
@@ -54,6 +60,8 @@ _start:
 	; stack (as it grows downwards on x86 systems). This is necessarily done
 	; in assembly as languages such as C cannot function without a stack.
 	mov esp, stack_top
+        push ebx
+        push eax
  
 	; This is a good place to initialize crucial processor state before the
 	; high-level kernel is entered. It's best to minimize the early