Initial commit. We have a booting kernel

kernel/.gitignore

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+*.d
+*.kernel
+*.o

kernel/Makefile

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+DEFAULT_HOST!=../default-host.sh
+HOST?=DEFAULT_HOST
+HOSTARCH!=../target-triplet-to-arch.sh $(HOST)
+ 
+CFLAGS?=-O2 -g
+CPPFLAGS?=
+LDFLAGS?=
+LIBS?=
+ 
+DESTDIR?=
+PREFIX?=/usr/local
+EXEC_PREFIX?=$(PREFIX)
+BOOTDIR?=$(EXEC_PREFIX)/boot
+INCLUDEDIR?=$(PREFIX)/include
+ 
+CFLAGS:=$(CFLAGS) -ffreestanding -Wall -Wextra
+CPPFLAGS:=$(CPPFLAGS) -D__is_kernel -Iinclude
+LDFLAGS:=$(LDFLAGS)
+LIBS:=$(LIBS) -nostdlib -lk -lgcc
+ 
+ARCHDIR=arch/$(HOSTARCH)
+ 
+include $(ARCHDIR)/make.config
+ 
+CFLAGS:=$(CFLAGS) $(KERNEL_ARCH_CFLAGS)
+CPPFLAGS:=$(CPPFLAGS) $(KERNEL_ARCH_CPPFLAGS)
+LDFLAGS:=$(LDFLAGS) $(KERNEL_ARCH_LDFLAGS)
+LIBS:=$(LIBS) $(KERNEL_ARCH_LIBS)
+ 
+KERNEL_OBJS=\
+$(KERNEL_ARCH_OBJS) \
+kernel/kernel.o \
+ 
+OBJS=\
+$(ARCHDIR)/crti.o \
+$(ARCHDIR)/crtbegin.o \
+$(KERNEL_OBJS) \
+$(ARCHDIR)/crtend.o \
+$(ARCHDIR)/crtn.o \
+ 
+LINK_LIST=\
+$(LDFLAGS) \
+$(ARCHDIR)/crti.o \
+$(ARCHDIR)/crtbegin.o \
+$(KERNEL_OBJS) \
+$(LIBS) \
+$(ARCHDIR)/crtend.o \
+$(ARCHDIR)/crtn.o \
+ 
+.PHONY: all clean install install-headers install-kernel
+.SUFFIXES: .o .c .cpp .S
+ 
+all: banan-os.kernel
+ 
+banan-os.kernel: $(OBJS) $(ARCHDIR)/linker.ld
+	$(CC) -T $(ARCHDIR)/linker.ld -o $@ $(CFLAGS) $(LINK_LIST)
+	grub-file --is-x86-multiboot banan-os.kernel
+ 
+$(ARCHDIR)/crtbegin.o $(ARCHDIR)/crtend.o:
+	OBJ=`$(CC) $(CFLAGS) $(LDFLAGS) -print-file-name=$(@F)` && cp "$$OBJ" $@
+ 
+.c.o:
+	$(CC) -MD -c $< -o $@ -std=gnu11 $(CFLAGS) $(CPPFLAGS)
+ 
+.S.o:
+	$(CC) -MD -c $< -o $@ $(CFLAGS) $(CPPFLAGS)
+ 
+clean:
+	rm -f banan-os.kernel
+	rm -f $(OBJS) *.o */*.o */*/*.o
+	rm -f $(OBJS:.o=.d) *.d */*.d */*/*.d
+ 
+install: install-headers install-kernel
+ 
+install-headers:
+	mkdir -p $(DESTDIR)$(INCLUDEDIR)
+	cp -R --preserve=timestamps include/. $(DESTDIR)$(INCLUDEDIR)/.
+ 
+install-kernel: banan-os.kernel
+	mkdir -p $(DESTDIR)$(BOOTDIR)
+	cp banan-os.kernel $(DESTDIR)$(BOOTDIR)
+ 
+-include $(OBJS:.o=.d)

kernel/arch/i386/boot.s

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+/* Declare constants for the multiboot header. */
+.set ALIGN,    1<<0             /* align loaded modules on page boundaries */
+.set MEMINFO,  1<<1             /* provide memory map */
+.set MB_FLAGS,    ALIGN | MEMINFO  /* this is the Multiboot 'flag' field */
+.set MB_MAGIC,    0x1BADB002       /* 'magic number' lets bootloader find the header */
+.set MB_CHECKSUM, -(MB_MAGIC + MB_FLAGS) /* checksum of above, to prove we are multiboot */
+ 
+ /* Multiboot header */
+.section .multiboot
+	.align 4
+	.long MB_MAGIC
+	.long MB_FLAGS
+	.long MB_CHECKSUM
+ 
+ /* Create stack */
+.section .bss
+	.align 16
+	stack_bottom:
+	.skip 16384 # 16 KiB
+	stack_top:
+ 
+/* Entrypoint */
+.section .text
+.global _start
+.type _start, @function
+_start:
+	/* Setup stack */
+	mov $stack_top, %esp
+ 
+	/* Call into C code */
+	call kernel_main
+ 
+	/* Hang if kernel_main returns */
+	cli
+1:	hlt
+	jmp 1b
+ 
+.size _start, . - _start

kernel/arch/i386/crti.s

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+/* x86 crti.s */
+.section .init
+.global _init
+.type _init, @function
+_init:
+	push %ebp
+	movl %esp, %ebp
+	/* gcc will nicely put the contents of crtbegin.o's .init section here. */
+
+.section .fini
+.global _fini
+.type _fini, @function
+_fini:
+	push %ebp
+	movl %esp, %ebp
+	/* gcc will nicely put the contents of crtbegin.o's .fini section here. */

kernel/arch/i386/crtn.s

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+/* x86 crtn.s */
+.section .init
+	/* gcc will nicely put the contents of crtend.o's .init section here. */
+	popl %ebp
+	ret
+
+.section .fini
+	/* gcc will nicely put the contents of crtend.o's .fini section here. */
+	popl %ebp
+	ret

kernel/arch/i386/linker.ld

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+ENTRY(_start)
+ 
+SECTIONS
+{
+	. = 1M;
+ 
+	.text BLOCK(4K) : ALIGN(4K)
+	{
+		*(.multiboot)
+		*(.text)
+	}
+ 
+	.rodata BLOCK(4K) : ALIGN(4K)
+	{
+		*(.rodata)
+	}
+ 
+	.data BLOCK(4K) : ALIGN(4K)
+	{
+		*(.data)
+	}
+ 
+	.bss BLOCK(4K) : ALIGN(4K)
+	{
+		*(COMMON)
+		*(.bss)
+	}
+}

kernel/arch/i386/make.config

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+KERNEL_ARCH_CFLAGS=
+KERNEL_ARCH_CPPFLAGS=
+KERNEL_ARCH_LDFLAGS=
+KERNEL_ARCH_LIBS=
+ 
+KERNEL_ARCH_OBJS=\
+$(ARCHDIR)/boot.o \
+$(ARCHDIR)/tty.o \

kernel/arch/i386/tty.c

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+#include <kernel/tty.h>
+
+#include "vga.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+static uint16_t* const VGA_MEMORY = (uint16_t*)0xB8000;
+
+static size_t terminal_row;
+static size_t terminal_col;
+static uint8_t terminal_color;
+static uint16_t* terminal_buffer;
+
+void terminal_putentryat(unsigned char c, uint8_t color, size_t x, size_t y)
+{
+	const size_t index = y * VGA_WIDTH + x;
+	terminal_buffer[index] = vga_entry(c, color);
+}
+
+void terminal_clear(void)
+{
+	for (size_t y = 0; y < VGA_HEIGHT; y++)
+		for (size_t x = 0; x < VGA_WIDTH; x++)
+			terminal_putentryat(' ', terminal_color, x, y);
+}
+
+void terminal_initialize(void)
+{
+	terminal_row = 0;
+	terminal_col = 0;
+	terminal_color = vga_entry_color(VGA_COLOR_WHITE, VGA_COLOR_BLACK);
+	terminal_buffer = VGA_MEMORY;
+	terminal_clear();
+}
+
+void terminal_setcolor(uint8_t color)
+{
+	terminal_color = color;
+}
+
+void terminal_scroll_line(size_t line)
+{
+	for (size_t x = 0; x < VGA_WIDTH; x++)
+	{
+		const size_t index = line * VGA_WIDTH + x;
+		terminal_buffer[index - VGA_WIDTH] = terminal_buffer[index];
+	}
+}
+
+void terminal_clear_line(size_t line)
+{
+	for (size_t x = 0; x < VGA_WIDTH; x++)
+		terminal_putentryat(' ', terminal_color, x, line);
+}
+
+void terminal_putchar(char c)
+{
+	if (c == '\n')
+	{
+		terminal_col = 0;
+		terminal_row++;
+	}
+	else
+	{
+		terminal_putentryat(c, terminal_color, terminal_col, terminal_row);
+		terminal_col++;
+	}
+
+	if (terminal_col == VGA_WIDTH)
+	{
+		terminal_col = 0;
+		terminal_row++;
+	}
+
+	if (terminal_row == VGA_HEIGHT)
+	{
+		for (size_t line = 1; line < VGA_HEIGHT; line++)
+			terminal_scroll_line(line);
+		terminal_clear_line(VGA_HEIGHT - 1);
+
+		terminal_col = 0;
+		terminal_row = VGA_HEIGHT - 1;
+	}
+}
+
+void terminal_write(const char* data, size_t size)
+{
+	for (size_t i = 0; i < size; i++)
+		terminal_putchar(data[i]);
+}
+
+void terminal_writestring(const char* data)
+{
+	size_t len = 0;
+	while (data[len])
+		len++;
+	terminal_write(data, len);
+}

kernel/arch/i386/vga.h

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+#pragma once
+
+#include <stdint.h>
+ 
+enum vga_color 
+{
+	VGA_COLOR_BLACK = 0,
+	VGA_COLOR_BLUE = 1,
+	VGA_COLOR_GREEN = 2,
+	VGA_COLOR_CYAN = 3,
+	VGA_COLOR_RED = 4,
+	VGA_COLOR_MAGENTA = 5,
+	VGA_COLOR_BROWN = 6,
+	VGA_COLOR_LIGHT_GREY = 7,
+	VGA_COLOR_DARK_GREY = 8,
+	VGA_COLOR_LIGHT_BLUE = 9,
+	VGA_COLOR_LIGHT_GREEN = 10,
+	VGA_COLOR_LIGHT_CYAN = 11,
+	VGA_COLOR_LIGHT_RED = 12,
+	VGA_COLOR_LIGHT_MAGENTA = 13,
+	VGA_COLOR_LIGHT_BROWN = 14,
+	VGA_COLOR_WHITE = 15,
+};
+ 
+static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg)
+{
+	return fg | bg << 4;
+}
+ 
+static inline uint16_t vga_entry(unsigned char uc, uint8_t color)
+{
+	return (uint16_t) uc | (uint16_t) color << 8;
+}

kernel/include/kernel/tty.h

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+#pragma once
+
+#include <stddef.h>
+
+void terminal_initialize(void);
+void terminal_putchar(char c);
+void terminal_write(const char* data, size_t size);
+void terminal_writestring(const char* data);

kernel/kernel/kernel.c

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+#include <kernel/tty.h>
+
+#include <stdio.h>
+
+void kernel_main()
+{
+	terminal_initialize();
+	printf("Hello from the kernel!\n");
+}