Implemented simple Multiboot1 kernel

README

@@ -1,7 +1,7 @@
 kern.
 =====
 
-_Idk why i called it that it was 3am and i needed sleep._
+Idk why i called it that it was 3am and i needed sleep.
 
 !! WARNING !!
 Kern is broken at the moment. The last working commit is: '11feab5'
@@ -13,8 +13,6 @@ Kern is a 32-bit OS based on the x86 architecture written in NASM Assembly and C
 I'm working on a basic command line as well as a custom unix-esque filesystem.
 It has a simple shell with some commands (use 'help' for a list of available ones).
 
-Since there's always more to do, here are the TODO.
-
 Features
 --------
 * Shell

boot/makefile

@@ -0,0 +1,7 @@
+.PHONY: all clean
+
+all:
+	@echo "TODO: Write this makefile..."
+
+clean:
+

defaults.mk

@@ -1,3 +1,30 @@
 #
 # kern. makefile defaults
 #
+
+# Tools
+HOSTCC = cc
+CC = i686-elf-gcc
+LD = i686-elf-ld
+AS = nasm
+MAKE = make
+
+# Flags
+CFLAGS 	= -Wall -Wextra -Wpedantic -Wno-pointer-arith\
+	  -ffreestanding -fno-stack-protector -fno-builtin -fno-pie -fcommon\
+	  -O2 -std=c17 -nostdinc -nostdlib -z notext -march=i386
+LDFLAGS	= -melf_i386
+ASFLAGS	=
+
+# Directories
+KERNEL_DIR = ./kernel
+BOOT_DIR = ./boot
+LIBC_DIR = ./libc
+USER_DIR = ./user
+
+# Modules
+MODULES	= $(KERNEL_DIR)	\
+	  $(BOOT_DIR)	\
+	  $(LIBC_DIR) 	\
+	  $(USER_DIR)
+

docs/modules.txt

@@ -7,8 +7,10 @@ Independant Modules
 * Each MAY have their own internal independant submodules (eg. userspace programs in 'usr/')
 * A module MAY be dependant on it's own submodules, but it's submodules MUST be independant of each other
 * Each MUST have a makefile in their directory (eg. 'libc/makefile')
+* Each module makefile MUST implement the 'all' and 'clean' targets
 * Each module MUST be listed in the 'make.defaults' directory
 * Each module MUST be self-contained and independentally compilable
+* A module SHOULD output binaries into the 'bin/' directory
 
 kern (Root "module", is dependant on all of it's submodules)
  |- boot

kernel/header.c

@@ -0,0 +1,15 @@
+#include "multiboot.h"
+
+#define FLAGS	(MBH_PAGE_ALIGN | MBH_GRAPH_INFO)
+
+__attribute__ ((section(".multiboot")))
+struct multiboot_header mbh = {
+	.magic = HEAD_MAGIC,
+	.flags = FLAGS,
+	.checksum = -(HEAD_MAGIC + FLAGS),
+	// We don't need the a.out format fields
+	.mode_type = 0,
+	.width = 1920,
+	.height = 1080,
+	.depth = 32,
+};

kernel/kernel.c

@@ -0,0 +1,200 @@
+#include "stdint.h"
+#include "multiboot.h"
+
+/* Constants */
+#define COLS	80
+#define ROWS	24
+#define ATTR	0x0f
+#define VID_MEM	0xb8000
+
+/* Variables */
+static int xpos;
+static int ypos;
+static uint8_t* video;
+
+/* Forward Declarations */
+void cls(void);
+void itoa(char* buf, int base, int d);
+void putc(int c);
+void printf(const char* fmt, ...);
+
+/* Entry Point */
+void kmain(void) {
+	uint32_t magic, addr;
+	__asm__ volatile ("movl %%eax, %0; movl %%ebx, %1" : "=m"(magic), "=m"(addr));
+	struct multiboot_info* mbi;
+  	video = (uint8_t*)VID_MEM;
+
+	// Clear Screen
+	cls();
+
+	// Didn't boot with Multiboot
+	if (magic != BOOT_MAGIC) {
+		printf("Invalid Magic Number: 0x%x\n", magic);
+		while (1);
+	}
+	
+	mbi = (struct multiboot_info*)addr;
+
+	printf("flags: 0x%x\n", mbi->flags);
+
+	if (mbi->flags & MBI_MEMORY) {
+		printf("mem_lower: %ukB, mem_upper: %ukB\n", 
+			mbi->mem_lower, mbi->mem_upper);
+	}
+
+	if (mbi->flags & MBI_BOOT_DEV) {
+		printf("boot_device: 0x%x\n", mbi->boot_device);
+	}
+
+	if (mbi->flags & MBI_CMDLINE) {
+		printf("cmdline: %s\n", mbi->cmdline);
+	}
+
+	if (mbi->flags & MBI_MODS) {
+		printf("mods_count: %d, mods_addr: 0x%x\n",
+			mbi->mods_count, mbi->mods_addr);
+
+		struct multiboot_module* mod = 
+			(struct multiboot_module*)mbi->mods_addr;
+
+		for (size_t i = 0; i < mbi->mods_count; i++) {
+			printf("  start 0x%x, end: 0x%x, cmdline: %s\n",
+				mod->start, mod->end, mod->cmdline);
+			mod++;
+		}
+	}
+
+	if (mbi->flags & MBI_SYMBOLS &&
+	    mbi->flags & MBI_ELF_HEAD) {
+		printf("Flag SYMBOLS and ELF HEADER are both set!\n");
+		while (1);
+	}
+
+	if (mbi->flags & MBI_MEMMAP) {
+		printf("mmap_addr: 0x%x, mmap_length: 0x%x\n",
+			mbi->mmap_addr, mbi->mmap_length);
+
+		struct multiboot_memmap* mmap = 
+			(struct multiboot_memmap*)mbi->mmap_addr;
+
+		while ((uint32_t)mmap < mbi->mmap_addr + mbi->mmap_length) {
+			printf(	"  size: 0x%x, base: 0x%08x, "
+				"length: 0x%08x, type: 0x%x\n",
+				mmap->size, mmap->base, mmap->len, mmap->type);
+
+			mmap = (struct multiboot_memmap*)
+				((uint32_t)mmap + mmap->size + (sizeof(mmap->size)));
+		}
+	}
+
+	while (1);
+}
+
+void cls(void) {
+	for (int i = 0; i < COLS * ROWS * 2; i++) video[i] = 0;
+	xpos = 0;
+	ypos = 0;
+}
+
+void itoa(char* buf, int base, int d) {
+	char* p = buf;
+	char* p1;
+	char* p2;
+	uint32_t ud = d;
+	int divisor = 10;
+
+	if (base == 'd' && d < 0) {
+		*p++ = '-';
+		buf++;
+		ud = -d;
+	} else if (base == 'x') divisor = 16;
+
+	do {
+		int remainder = ud % divisor;
+		*p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
+	} while (ud /= divisor);
+
+	*p = 0;
+
+	p1 = buf;
+	p2 = p - 1;
+	while (p1 < p2) {
+		char tmp = *p1;
+		*p1 = *p2;
+		*p2 = tmp;
+		p1++;
+		p2--;
+	}
+}
+
+/* Put the character C on the screen. */
+void putc(int c) {
+	if (c == '\n' || c == '\r') {
+	newline:
+		xpos = 0;
+		ypos++;
+		if (ypos >= ROWS)
+		ypos = 0;
+		return;
+	}
+
+	video[(xpos + ypos * COLS) * 2] = c & 0xFF;
+	video[(xpos + ypos * COLS) * 2 + 1] = ATTR;
+
+	xpos++;
+	if (xpos >= COLS)
+	goto newline;
+}
+
+void printf(const char *format, ...) {
+	char** arg = (char**)&format;
+	int c;
+	char buf[20];
+
+	arg++;
+
+	while ((c = *format++) != 0) {
+		if (c != '%') { 
+			putc (c);
+			continue;
+		}
+		
+		char *p, *p2;
+		int pad0 = 0, pad = 0;
+		
+		c = *format++;
+		
+		if (c == '0') {
+			pad0 = 1;
+			c = *format++;
+		}
+
+		if (c >= '0' && c <= '9') {
+			pad = c - '0';
+			c = *format++;
+		}
+
+		switch (c) {
+		case 'd':
+		case 'u':
+		case 'x':
+			itoa(buf, c, *((int *) arg++));
+			p = buf;
+			goto string;
+			break;
+		case 's':
+			p = *arg++;
+			if (! p) p = "(null)";
+		string:
+			for (p2 = p; *p2; p2++);
+			for (; p2 < p + pad; p2++) putc (pad0 ? '0' : ' ');
+			while (*p) putc (*p++);
+			break;
+		default:
+			putc(*((int *) arg++));
+			break;
+		}
+	}
+}
+

kernel/linker.ld

@@ -0,0 +1,43 @@
+OUTPUT_FORMAT(elf32-i386)
+ENTRY(kmain)
+
+SECTIONS {
+	. = 0x00100000;
+
+	/* Multiboot Header */
+	.multiboot ALIGN(4) : {
+		*(.multiboot)
+	}
+
+	/* Kernel Code */
+	.text ALIGN(4) : {
+		*(.text)
+		*(.text.*)
+	}
+
+	/* Read-Only Data */
+	.rodata ALIGN(4) : {
+		*(.rodata)
+		*(.rodata.*)
+	}
+
+	/* Read/Write Data */
+	.data ALIGN(4) : {
+		*(.data)
+		*(.data.*)
+	}
+
+	/* BSS Section */
+	.bss ALIGN(4) : {
+		*(COMMON)
+		*(.bss)
+		*(.bss.*)
+	}
+
+	/* Discarded Sections */
+	/DISCARD/ : {
+		*(.note)
+		*(.note.*)
+		*(.comment)
+	}
+}

kernel/makefile

@@ -0,0 +1,19 @@
+include defaults.mk
+
+SRCS = $(shell find $(SRC) -name '**.c')
+OBJS = $(patsubst $(SRC)/%.c, $(BIN)/%.o, $(SRCS))
+LINKER = $(SRC)/linker.ld
+OUT = $(BIN)/kernel.elf
+
+.PHONY: all clean
+
+all: $(OUT)
+$(OUT): $(OBJS)
+	$(LD) $(LDFLAGS) -T $(LINKER) -o $@ $^
+
+$(BIN)/%.o: $(SRC)/%.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+clean:
+	rm -fr $(BIN)
+

kernel/multiboot.h

@@ -0,0 +1,96 @@
+#ifndef _MULTIBOOT_H
+#define _MULTIBOOT_H
+
+#include "stdint.h"
+
+#define __packed	__attribute__ ((packed))
+
+#define HEAD_MAGIC 	0x1BADB002
+#define BOOT_MAGIC	0x2BADB002
+
+// Multiboot Header Flags
+enum {
+	MBH_PAGE_ALIGN	= (1<<0),
+	MBH_MEMORY_INFO	= (1<<1),
+	MBH_GRAPH_INFO	= (1<<2),
+	MBH_ADDR_FIELDS = (1<<16),
+};
+
+struct multiboot_header {
+	uint32_t magic;
+	uint32_t flags;
+	uint32_t checksum;
+	uint32_t header_addr;
+	uint32_t load_addr;
+	uint32_t load_end_addr;
+	uint32_t bss_end_addr;
+	uint32_t entry_addr;
+	uint32_t mode_type;
+	uint32_t width;
+	uint32_t height;
+	uint32_t depth;
+} __packed;
+
+// Multiboot Info Flags
+enum {
+	MBI_MEMORY	= (1<<0),
+	MBI_BOOT_DEV	= (1<<1),
+	MBI_CMDLINE	= (1<<2),
+	MBI_MODS	= (1<<3),
+	MBI_SYMBOLS	= (1<<4),
+	MBI_ELF_HEAD	= (1<<5),
+	MBI_MEMMAP	= (1<<6),
+	MBI_DRIVES	= (1<<7),
+	MBI_CONF_TAB	= (1<<8),
+	MBI_BOOTLD_NAME	= (1<<9),
+	MBI_APM_TABLE	= (1<<10),
+	MBI_VBE_TABLE	= (1<<11),
+	MBI_FB_TABLE	= (1<<12),
+};
+
+struct multiboot_info {
+	uint32_t flags;
+	uint32_t mem_lower;
+	uint32_t mem_upper;
+	uint32_t boot_device;
+	uint32_t cmdline;
+	uint32_t mods_count;
+	uint32_t mods_addr;
+	uint32_t syms[4];
+	uint32_t mmap_length;
+	uint32_t mmap_addr;
+	uint32_t drives_length;
+	uint32_t drives_addr;
+	uint32_t config_table;
+	uint32_t bootloader_name;
+	uint32_t apm_table;
+	uint32_t vbe_control_info;
+	uint32_t vbe_mode_info;
+	uint32_t vbe_mode;   
+	uint32_t vbe_interface_seg;
+	uint32_t vbe_interface_off;
+	uint32_t vbe_interface_len;
+	uint32_t framebuffer_addr;
+	uint32_t framebuffer_pitch;
+	uint32_t framebuffer_width;
+	uint32_t framebuffer_height;
+	uint32_t framebuffer_bpp;
+	uint32_t framebuffer_type;
+	uint32_t color_info;
+} __packed;
+
+struct multiboot_module {
+	uint32_t start;
+	uint32_t end;
+	uint32_t cmdline;
+	uint32_t __reserved;
+} __packed;
+
+struct multiboot_memmap {
+	uint32_t size;
+	uint64_t base;
+	uint64_t len;
+	uint32_t type;
+} __packed;
+
+#endif

kernel/stdint.h

@@ -0,0 +1,23 @@
+#ifndef _STDINT_H
+#define _STDINT_H
+
+#define NULL ((void*)0)
+
+// Naitive width
+typedef unsigned int size_t;
+typedef signed int ssize_t;
+
+// Signed ints
+typedef signed char int8_t;
+typedef signed short int16_t;
+typedef signed int int32_t;
+typedef signed long long int64_t;
+
+// Unsigned ints
+typedef unsigned char uint8_t;
+typedef unsigned short uint16_t;
+typedef unsigned int uint32_t;
+typedef unsigned long long uint64_t;
+
+
+#endif

libc/include/ctype.h

@@ -1,17 +1,19 @@
 #ifndef _CTYPE_H
 #define _CTYPE_H
 
-/* Bitfield values
+/* 
-     Property   | Bit 
+ * Bitfield values
-    ------------|-----
+ *
-     Digit      |  0
+ *  Property   | Bit 
-     Letter     |  1
+ * ------------|-----
-     Lowercase  |  2
+ *  Digit      |  0
-     Punct      |  3
+ *  Letter     |  1
-     Space      |  4
+ *  Lowercase  |  2
-     Control    |  5
+ *  Punct      |  3
-     Printable  |  6
+ *  Space      |  4
-     Hex digit  |  7
+ *  Control    |  5
+ *  Printable  |  6
+ *  Hex digit  |  7
  */
 #define _DIGIT_MASK (1<<0)
 #define _ALPHA_MASK (1<<1)

libc/makefile

@@ -1,14 +1,7 @@
-#
+.PHONY: all clean
-# C Standard library
-#
 
-include make.defaults
+all:
+	@echo "TODO: Write this makefile..."
 
-$(LIBC): $(LIBC_SRC)
+clean:
-	@echo "Building $(LIBC)..."
-	for f in $(LIBC_SRC); do\
-		filename=$$(basename $$f .c);\
-		$(CC) $(CFLAGS) -I$(LIBC_INC) -o $(BIN)/libc/$$filename.o -c $$f;\
-	done
-	$(LD) $(LDFLAGS) -r -o $(LIBC) $(BIN)/libc/**.o
 

makefile

@@ -3,7 +3,38 @@
 # (c) 2023-2025 Tomas Kubecek
 #
 
+export VERSION = 0.3.0
+
+# Configurable variables
 include defaults.mk
 
+BIN = ./bin
+IMG = ./kern.img
 
+.PHONY: all clean qemu msg $(MODULES)
+
+all: msg $(IMG)
+$(IMG): $(MODULES)
+	@echo "\nDone!\n"
+
+# Build each module
+$(MODULES): 
+	mkdir -p $(BIN)/$@
+	$(MAKE) BIN=$(BIN)/$@ SRC=$@ -f $@/makefile all
+
+clean:
+	for m in $(MODULES); do $(MAKE) BIN=$(BIN)/$$m SRC=$$m -C . -f $$m/makefile clean; done
+	rm -fr $(BIN)
+	rm -fr $(IMG)
+
+msg:
+	@echo "\x1b[36mBuilding \x1b[1mkern.\x1b[22m V$(VERSION)\x1b[0m\n"
+
+# Core Audio only works on MacOS
+qemu:
+	qemu-system-x86_64\
+		-drive format=raw,file=$(IMG),index=0,media=disk\
+		-m 256M -accel tcg -monitor stdio\
+		-rtc base=localtime,clock=host,driftfix=slew\
+		-audiodev coreaudio,id=audio0 -machine pcspk-audiodev=audio0
 

user/makefile

@@ -0,0 +1,7 @@
+.PHONY: all clean
+
+all:
+	@echo "TODO: Write this makefile..."
+
+clean:
+