add boot stub

1 files changed, 31 insertions, 0 deletions

diff --git a/boot.S b/boot.S
new file mode 100644
index 0000000..90cf9d1
--- /dev/null
+++ b/boot.S
@@ -0,0 +1,31 @@
+        .set ALIGN,      1<<0
+        .set MEMINFO,    1<<1
+        .set FLAGS,      ALIGN | MEMINFO
+        .set MAGIC,      0x1BADB002 # "1 Bad Boot"
+        .set CHECKSUM,   -(MAGIC + FLAGS)
+
+.section .multiboot
+        .align 4
+multiboot_header:
+        .long MAGIC
+        .long FLAGS
+        .long CHECKSUM
+
+.section .stack
+stack_bottom:                   # Stack grows up in addresses, so bottom is
+                                # lower than the top
+        .skip 32768             # 32KB stack
+stack_top:
+
+.section .text
+        .global _start
+        .type _start, @function
+_start:                         # This is where execution begins
+        movl $stack_bottom, %esp        # Initialize the stack
+        push %ebp               # Add register ebp to the arguments of kernel_main
+        call kernel_main        # Start the kernel, shouldn't return
+        cli
+        hlt
+.kernel_hang:                   # Idle
+        jmp .kernel_hang
+        .size _start, . - _start