towards multi-arch

arch/bochs/lib.c

@@ -0,0 +1,4 @@
+#pragma once
+
+#define ARCH_ASM_CLOBBER_ALL "eax", "ebx", "ecx", "edx", "esi", "edi", "ebp"
+

arch/bochs/startup.s

@@ -0,0 +1,59 @@
+## Bare bone boot.s from wiki.osdev.org
+
+# multiboot header
+.section .rodata.multiboot
+.align 4
+
+# magic number
+.long 0x1BADB002
+
+# flags: align, meminfo
+.long 0x3
+
+# checksum: -(magic+flags)
+.long -(0x1BADB002 + 0x3)
+
+
+
+# the initial kernel stack
+.section .kernel_stack
+.global os_stack
+.size os_stack, 4096
+#.Lstack_bottom:
+os_stack:
+.byte 0
+#.skip 16384 # 16 KiB
+.skip 4094 # 4 KiB
+.byte 0
+.Lstack_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. It
+# doesn't make sense to return from this function as the bootloader is gone.
+.section .text.startup
+.global _start
+.type _start, @function
+_start:
+	# Welcome to kernel mode! 
+	# To set up a stack, we simply set the esp register to point to the top of
+	# our stack (as it grows downwards).
+	movl $.Lstack_top, %esp
+	# We are now ready to actually execute C code. (see ./startup.cc)
+	call os_main
+
+	# In case the function returns, we'll want to put the computer into an
+	# infinite loop. To do that, we use the clear interrupt ('cli') instruction
+	# to disable interrupts, the halt instruction ('hlt') to stop the CPU until
+	# the next interrupt arrives, and jumping to the halt instruction if it ever
+	# continues execution, just to be safe. We will create a local label rather
+	# than real symbol and jump to there endlessly.
+	cli
+	hlt
+.Lhang:
+	jmp .Lhang
+
+# 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