feat: print available memory

Makefile

@@ -18,7 +18,9 @@ TOOLS_DIR	= tools
 
 include $(TOOLS_DIR)/build.mk
 
-ASFLAGS	= -DSTUPID_VERSION=\"$(shell $(GIT-VERSION))\" -Ilib
+ASFLAGS	= -DSTUPID_VERSION="\"$(shell $(GIT-VERSION))\"" -Ilib \
+	-DBUILD_DATE="\"$(shell date --iso)\"" \
+	-DNASM_VERSION="\"$(shell nasm -v)\""
 QEMUFLAGS = -serial stdio
 
 GARBADGE	= stupid.iso

kernel/build.mk

@@ -1,11 +1,11 @@
 include kernel/drivers/build.mk
 
-KERNEL_SRCS	= head.s gdt.s pic.s isr.s idt.s paging.s lib/log.s
+KERNEL_SRCS	= head.s gdt.s pic.s isr.s idt.s pmm.s paging.s lib/log.s
 KERNEL_OBJS	= $(addprefix kernel/, $(KERNEL_SRCS:.s=.o) $(DRIVERS_OBJS))
 KERNEL_BIN	= vmstupid
 KERNEL_DUMP = $(KERNEL_BIN).dump
 
-KERNEL_ASFLAGS	= $(ASFLAGS) -D__KERNEL__
+KERNEL_ASFLAGS	= $(ASFLAGS) -D__KERNEL__ -Ikernel
 
 GARBADGE += $(KERNEL_OBJS) $(KERNEL_BIN) $(KERNEL_DUMP)
 

kernel/head.s

@@ -1,6 +1,7 @@
 [BITS 32]
 
 %include "base.inc"
+%include "multiboot.inc"
 
 MULTIBOOT_MAGIC equ 0x1BADB002
 MULTIBOOT_ALIGN equ 1 << 0
@@ -23,14 +24,29 @@ section .text
 global entry
 entry:
 	mov esp, stack_top
-
 	cli
 
+	mov edi, eax
+	mov esi, ebx
+
+	;; initialize serial (mostly used for debug)
 	extern serial_init
 	call serial_init
 
-	LOG msg_hello_world
+	;; eax <- magic
+	;; ebx <- multiboot struct
+	cmp edi, 0x2BADB002
+	je .multiboot_valid
 
+	LOG err_invalid_boot_magic, edi
+	jmp hang
+	
+.multiboot_valid:
+	
+	LOG msg_hello_world
+	mov eax, [esi + mb_info.bootloader_name]
+	LOG msg_boot_info, eax
+	
 	extern setup_gdt
 	call setup_gdt
 
@@ -40,20 +56,32 @@ entry:
 	extern setup_idt
 	call setup_idt
 
-	;extern setup_paging
+	push esi
-	;call setup_paging
+	extern setup_pmm
+	call setup_pmm
+	add esp, 4
+	test eax, 0
+	jz .mem_ok
 
-	int3
+	LOG err_cannot_map_memory
 
-	LOG file
-
-	cli
-hang:
-	hlt
 	jmp hang
 
+.mem_ok:
 
+	extern setup_paging
+	call setup_paging
+
+hang:
+	cli
+	hlt
+	jmp hang
+	
 section .rodata
 
-msg_hello_world db "StupidOS ", STUPID_VERSION, 0
+msg_hello_world db "StupidOS v", STUPID_VERSION, " (built with ", NASM_VERSION, " on ", BUILD_DATE, ")", 0
+msg_boot_info db "Bootloader: %s", 0
+err_invalid_boot_magic db "[ERROR] Invalid boot magic (got: %x, expected: 0x2BADB002)", 0
+err_cannot_map_memory db "[ERROR] Can't map memory", 0
+
 file db __FILE__, 0

kernel/linker.ld

@@ -4,6 +4,7 @@ ENTRY(entry)
 SECTIONS
 {
 	. = 1M;
+	kernel_start = .;
 
 	.text : ALIGN(4) {
 		KEEP(*(.multiboot))
@@ -22,4 +23,6 @@ SECTIONS
 		*(COMMON)
 		*(.bss)
 	}
+
+	kernel_end = .;
 }

kernel/multiboot.inc

@@ -0,0 +1,66 @@
+struc mb_info
+	.flags: resd 1
+
+	;; flags[0] is set
+	.mem_lower: resd 1
+	.mem_upper: resd 1
+
+	;; flags[1] is set
+	.boot_device: resd 1
+
+	;; flags[2] is set
+	.cmdline: resd 1
+
+	;; flags[3] is set
+	.mods_count: resd 1
+	.mods_addr: resd 1
+
+	;; flags[4] || flags[4] is set
+	.syms: resd 4
+
+	;; flags[6] is set
+	.mmap_length: resd 1
+	.mmap_addr: resd 1
+
+	;; flags[7] is set
+	.drives_length: resd 1
+	.drives_addr: resd 1
+
+	;; flags[8] is set
+	.config_table: resd 1
+
+	;; flags[9] is set
+	.bootloader_name: resd 1
+
+	;; flags[10] is set
+	.apm_table: resd 1
+
+	;; 
+	.vbe_control_info: resd 1
+	.vbe_mode_info: resd 1
+	.vbe_mode: resw 1
+	.vbe_interface_seg: resw 1
+	.vbe_interface_off: resw 1
+	.vbe_interface_len: resw 1
+
+	.framebuffer_addr: resq 1
+	.framebuffer_pitch: resd 1
+	.framebuffer_width: resd 1
+	.framebuffer_height: resd 1
+	.framebuffer_bpp: resb 1
+	.framebuffer_type: resb 1
+	.framebuffer_misc: resw 3
+endstruc
+
+struc mb_mmap
+	.size: resd 1
+	.addr: resq 1
+	.length: resq 1
+	.type: resd 1
+endstruc
+
+%define MB_MEMORY_AVAILABLE 1
+%define MB_MEMORY_RESERVED 2
+%define MB_MEMORY_ACPI 3
+%define MB_MEMORY_NVS 4
+%define MB_MEMORY_BADRAM 5

kernel/paging.s

@@ -1,5 +1,11 @@
 [BITS 32]
 
+PE_PRESENT equ 1 << 0
+PE_WRITABLE equ 1 << 1
+PE_USERMODE equ 1 << 2
+PE_ACCESSED equ 1 << 5
+PE_DIRTY equ 1 << 6
+
 section .data
 align 4096
 

kernel/pmm.s

@@ -0,0 +1,74 @@
+[BITS 32]
+
+%include "base.inc"
+%include "multiboot.inc"
+
+section .text
+global setup_pmm
+setup_pmm:
+	push ebp
+	mov ebp, esp
+	push edi
+	push esi
+	push ebx
+
+	mov edi, [ebp + 8]
+
+	mov eax, [edi]
+	and eax, 0x40 ; (1 << 6)
+	jz .no_mmap
+	mov esi, [edi + mb_info.mmap_length]
+	mov ebx, [edi + mb_info.mmap_addr]
+.loop:
+	mov eax, ebx
+	LOG msg_mmap_entry, dword [eax + mb_mmap.addr + 4], \
+						dword [eax + mb_mmap.addr], \
+						dword [eax + mb_mmap.length + 4], \
+						dword [eax + mb_mmap.length], \
+						dword [eax + mb_mmap.type]
+	mov eax, [ebx + mb_mmap.size]
+	add eax, 0x4
+	add ebx, eax
+	sub esi, eax
+	jnz .loop
+
+	jmp .end_mem_detection
+
+.no_mmap:
+	LOG warn_no_mmap
+	mov eax, [edi]
+	and eax, 0x1
+	jz .err
+
+	xor eax, eax
+	mov ecx, [edi + mb_info.mem_lower]
+	shl ecx, 0xA ; ecx * 1KiB
+	LOG msg_mem_block, eax, ecx
+	mov eax, 0x100000
+	mov ecx, [edi + mb_info.mem_upper]
+	shl ecx, 0xA
+	LOG msg_mem_block, eax, ecx
+
+.end_mem_detection:
+
+	xor eax, eax
+	jmp .end
+.err:
+	mov eax, 1
+.end:
+	pop ebx
+	pop esi
+	pop ebx
+	leave
+	ret
+
+section .rodata
+warn_no_mmap db "[WARN] mmap flag not set", 0
+msg_mmap_entry db "Memory Map Entry:", 0xA
+	db 0x9, "Address: (hi): %x (lo): %x", 0xA
+	db 0x9, "Length: (hi): %x (lo): %x", 0xA
+	db 0x9, "Type: %x", 0
+msg_mem_block db "Free Memory:", 0xA
+	db 0x9, "Address: %x", 0xA
+	db 0x9, "Length: %x", 0
+file db __FILE__, 0

lib/base/log.s

@@ -30,7 +30,6 @@ putstr:
 	ret
 
 puthex:
-	xchg bx, bx
 	push ebp
 	mov ebp, esp
 	push edi