initial commit

1 files changed, 42 insertions, 0 deletions

diff --git a/kernel/entry.S b/kernel/entry.S
new file mode 100644
index 0000000..5b16b30
--- /dev/null
+++ b/kernel/entry.S
@@ -0,0 +1,42 @@
+# declare some constants
+.set ALIGN,    1<<0             # align loaded modules on page boundaries
+.set MEMINFO,  1<<1             # provide memory map
+.set FLAGS,    ALIGN | MEMINFO  # this is the Multiboot 'flag' field
+.set MAGIC,    0x1BADB002       # 'magic number' lets bootloader find the header
+.set CHECKSUM, -(MAGIC + FLAGS) # checksum of above, to prove we are multiboot
+
+# the bootloader will search for this magic sequence
+# and recognize us as a multiboot kernel
+.section .multiboot
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
+
+# allocatable, writable, contains no data
+.section .bootstrap_stack, "aw", @nobits
+stack_bottom:
+.skip 16384         # 16 KiB
+stack_top:
+
+# the linker script specifies _start as the entry point to the kernel and the
+# bootloader will jump to this position once the kernel has been loaded
+.section .text
+.global _start
+.type _start, @function
+_start:
+    movl $stack_top, %esp
+    push %eax
+    push %ebx
+
+    call kernel_main
+
+    cli
+
+hang:
+    hlt
+    jmp hang
+
+# Set the size of the _start symbol to the current location '.' minus its start.
+# This is useful when debugging or when you implement call tracing.
+.size _start, . - _start