Load ELF kernel instead of flat binary

[nameless-os.git] / kernel / entry.s

diff --git a/kernel/entry.s b/kernel/entry.s
index 236b81e967e459e4c6f684d137726dbf42743677..d6490a1159587a81cda63257b3ee3e9028fdaf68 100644 (file)
--- a/kernel/entry.s
+++ b/kernel/entry.s
@@ -1,5 +1,32 @@
-       bits 32
-       extern _start
+bits 32
+extern kmain
+extern __STACK_BOTTOM__
 
-       call _start
-       jmp $
+section .text
+global _start
+_start:
+       ; Here, the stack will look like:
+       ; return address, map pointer, map size.
+
+       ; Skip the return address.
+       add esp, 4
+       ; Save the kernel arguments.
+       ; Can this be done without the global variables?
+       pop dword [e820_map]
+       pop dword [e820_map_size]
+       sub esp, 12
+       ; Do the stack switch.
+       mov ebp, __STACK_BOTTOM__
+       mov esp, ebp
+       ; Restore the kernel arguments.
+       push dword [e820_map_size]
+       push dword [e820_map]
+       ; Call the actual kernel.
+       call kmain
+       hlt
+       jmp $-1
+
+; Temporarily save arguments here to survive the upcoming stack switch.
+section .bss
+e820_map: resd 1
+e820_map_size: resd 1