readme, also paging is enabled

kernel-rs/Makefile

@@ -7,7 +7,6 @@ grub.cfg			:= src/arch/$(arch)/grub.cfg
 asm_source_files	:= $(wildcard src/arch/$(arch)/*.asm)
 asm_object_files	:= $(patsubst src/arch/$(arch)/%.asm, \
 	build/arch/$(arch)/%.o, $(asm_source_files)) 
-
 .PHONY: all clean run iso
 
 all: $(kernel)
@@ -22,10 +21,10 @@ iso: $(iso)
 
 $(iso): $(kernel) $(grub.cfg)
 	@mkdir -p build/isofiles/boot/grub
-	@cp $(kernel) build/isofiles/boot/kernel.bin
+	cp $(kernel) build/isofiles/boot/kernel.bin
-	@cp $(grub.cfg) build/isofiles/boot/grub
+	cp $(grub.cfg) build/isofiles/boot/grub
-	@grub-mkrescue -o $(iso) build/isofiles 2>/dev/null
+	grub-mkrescue -o $(iso) build/isofiles 2>/dev/null
-	@rm -r build/isofiles
+	rm -r build/isofiles
 
 $(kernel): $(asm_object_files) $(linker_script)
 	@ld -n -T $(linker_script) -o $(kernel) $(asm_object_files)

kernel-rs/README.md

@@ -0,0 +1,13 @@
+# compiling
+
+a standard development environment can be invoked:
+
+```
+docker run jzck/arch-kernel -it /usr/bin/zsh
+```
+
+clone the repo and `make iso`
+
+# running
+
+`make run` in your host operating system to launch qemu gtk window

kernel-rs/src/arch/x86_64/boot.asm

@@ -3,6 +3,138 @@ global start
 section .text
 bits 32
 start:
-	; print OK to screen
+	mov		esp, stack_top
-	mov dword [0xb8000], 0x2f4b2f4f
+
+	call	check_multiboot
+	call	check_cpuid
+	call	check_long_mode
+
+	call	set_up_page_tables
+	call	enable_paging
+
+	; print 'OK' to screen
+	mov		dword [0xb8000], 0x2f4b2f4f
 	hlt	
+error:
+	; print 'ERR: ' and the given error code to screen and hangs
+	mov		dword [0xb8000], 0x4f524f45
+	mov		dword [0xb8004], 0x4f3a4f52
+	mov		dword [0xb8008], 0x4f204f20
+	mov		byte [0xb800a], al
+	hlt
+
+check_multiboot:
+	cmp		eax, 0x36d76289
+	jne		.no_multiboot
+	ret
+.no_multiboot:
+	mov		al, "0"
+	jmp		error
+
+check_cpuid:
+	; Check if CPUID is supported by attempting to flip the ID bit (bit 21)
+	; in the FLAGS register. If we can flip it, CPUID is available.
+
+	; Copy FLAGS in to EAX via stack
+	pushfd
+	pop		eax
+	; Copy to ECX as well for comparing later on
+	mov		ecx, eax
+	; Flip the ID bit
+	xor		eax, 1 << 21
+	; Copy EAX to FLAGS via the stack
+	push	eax
+	popfd
+	; Copy FLAGS back to EAX (with the flipped bit if CPUID is supported)
+	pushfd
+	pop		eax
+	; Restore FLAGS from the old version stored in ECX (i.e. flipping the
+			; ID bit back if it was ever flipped).
+	push	ecx
+	popfd
+
+	; Compare EAX and ECX. If they are equal then that means the bit
+	; wasn't flipped, and CPUID isn't supported.
+	cmp		eax, ecx
+	je		.no_cpuid
+	ret
+.no_cpuid:
+	mov		al, "1"
+	jmp		error
+
+check_long_mode:
+	; test if extended processor info in available
+	mov		eax, 0x80000000		; implicit argument for cpuid
+	cpuid						; get highest supported argument
+	cmp		eax, 0x80000001		; it needs to be at least 0x80000001
+	jb		.no_long_mode		; if it's less, the CPU is too old for long mode
+
+	; use extended info to test if long mode is available
+	mov		eax, 0x80000001		; argument for extended processor info
+	cpuid						; returns various feature bits in ecx and edx
+	test	edx, 1 << 29		; test if the LM-bit is set in the D-register
+	jz		.no_long_mode		; If it's not set, there is no long mode
+	ret
+.no_long_mode:
+	mov		al, "2"
+	jmp		error
+
+set_up_page_tables:
+	; map first P4 entry to P3 table
+	mov		eax, p3_table
+	or		eax, 0b11				; present + writeable
+	mov		[p4_table], eax
+	
+	; map first P3 entry to P2 table
+	mov		eax, p2_table
+	or		eax, 0b11				; present + writeable
+	mov		[p3_table], eax
+
+	mov		ecx, 0					;counter variable
+.map_p2_table:
+	; map ecx-th P2 entry to a huge page that start at address 2MiB*ecx
+	mov		eax, 0x200000				; 2MiB
+	mul		ecx							; start address of ecx-th page
+	or		eax, 0b10000011				; present + writeable + huge
+	mov		[p2_table + ecx * 8], eax	; map ecx-th entry
+	
+	inc		ecx							; increase counter
+	cmp		ecx, 512					; if counter == 512, the whole P2 table is mapped
+	jne		.map_p2_table				; else map the next entry
+
+	ret
+
+enable_paging:
+	; load P4 to cr3 register (cpu uses this to acces the P4 table)
+	mov		eax, p4_table
+	mov		cr3, eax
+
+	; enable PAE-flag in cr4 (Physical Address Extension)
+    mov		eax, cr4
+    or		eax, 1 << 5
+    mov		cr4, eax
+
+    ; set the long mode bit in the EFER MSR (model specific register)
+    mov		ecx, 0xC0000080
+    rdmsr
+    or		eax, 1 << 8
+    wrmsr
+
+    ; enable paging in the cr0 register
+    mov		eax, cr0
+    or		eax, 1 << 31
+    mov		cr0, eax
+
+    ret
+
+section .bss
+	align 4096
+p4_table:
+	resb 4096
+p3_table:
+	resb 4096
+p2_table:
+	resb 4096
+stack_bottom:
+	resb	64
+stack_top:

kernel-rs/src/arch/x86_64/grub.cfg

@@ -0,0 +1,7 @@
+set timeout=0
+set default=0
+
+menuentry "my os" {
+	multiboot2 /boot/kernel.bin
+	boot
+}