From 06d05938cc828901703112b99740c2e90a392b88 Mon Sep 17 00:00:00 2001
From: Alexey Gavrilov <rebovas@yahoo.com>
Date: Tue, 8 Aug 2023 18:38:07 +0700
Subject: First commit

---
 .gitignore             |  5 +++++
 README.md              | 41 +++++++++++++++++++++++++++++++++++++++++
 iso/boot/grub/grub.cfg |  3 +++
 kernel/boot.s          | 28 ++++++++++++++++++++++++++++
 kernel/kernel.c        |  4 ++++
 kernel/linker.ld       | 28 ++++++++++++++++++++++++++++
 makefile               | 30 ++++++++++++++++++++++++++++++
 7 files changed, 139 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 README.md
 create mode 100644 iso/boot/grub/grub.cfg
 create mode 100644 kernel/boot.s
 create mode 100644 kernel/kernel.c
 create mode 100644 kernel/linker.ld
 create mode 100644 makefile

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5fdcd7a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+# Directory where project build
+build
+
+# Operarting system's files needed to boot
+iso/os/*
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..2e7ba67
--- /dev/null
+++ b/README.md
@@ -0,0 +1,41 @@
+## Object Operating System
+
+----
+
+## Install dependencies
+
+#### Ubuntu
+
+'''sh
+sudo apt update -y  
+sudo apt -y install build-essential binutils nasm xorriso grub-common qemu-system-i386 mtools
+'''
+
+## Build and run
+
+#### Ubuntu
+
+'''sh
+# Build and create iso image
+make install  
+make run
+''''
+
+## Docs
+
+-   [1][Link on collection of articles "How startup app without OS"]
+-   [2][The GNU GRUB manual]
+-   [3][Executable and linkable format ELF]
+-   [4][NASM documentation]
+-   [5][Article where creating a simple OS]
+-   [6][Multiboot specification]
+-   [7][GCC compiler documentation]
+-   [8][Using NASM in a Hello World kernel]
+
+[1]:https://habr.com/ru/companies/neobit/articles/173263/
+[2]:https://www.gnu.org/software/grub/manual/grub/grub.pdf
+[3]:https://www.cs.cmu.edu/afs/cs/academic/class/15213-f00/docs/elf.pdf
+[4]:https://www.nasm.us/xdoc/2.16.01/nasmdoc.pdf
+[5]:https://wiki.osdev.org/Bare_Bones#Writing_a_kernel_in_C.2B.2B
+[6]:https://www.gnu.org/software/grub/manual/multiboot/multiboot.pdf
+[7]:https://gcc.gnu.org/onlinedocs/gcc.pdf
diff --git a/iso/boot/grub/grub.cfg b/iso/boot/grub/grub.cfg
new file mode 100644
index 0000000..fd0f925
--- /dev/null
+++ b/iso/boot/grub/grub.cfg
@@ -0,0 +1,3 @@
+menuentry "myos" {
+    multiboot /os/kernel.bin
+}
diff --git a/kernel/boot.s b/kernel/boot.s
new file mode 100644
index 0000000..2fd1c55
--- /dev/null
+++ b/kernel/boot.s
@@ -0,0 +1,28 @@
+MBALIGN equ 1 << 0
+MEMINFO equ 1 << 1
+MBFLAGS equ MBALIGN | MEMINFO
+MAGIC equ 0x1BADB002
+CHECKSUM equ -(MAGIC + MBFLAGS)
+
+section .multiboot
+align 4
+    dd MAGIC
+    dd MBFLAGS
+    dd CHECKSUM
+
+section .bss
+align 16
+stack_bottom:
+resb 16384
+stack_top:
+
+section .text
+global _start:function (_start.end - _start)
+_start:
+            mov esp, stack_top
+            extern main
+            call main
+            cli
+.hang:      hlt
+            jmp .hang
+.end:
diff --git a/kernel/kernel.c b/kernel/kernel.c
new file mode 100644
index 0000000..1d734c9
--- /dev/null
+++ b/kernel/kernel.c
@@ -0,0 +1,4 @@
+int main()
+{
+    return 0;
+};
diff --git a/kernel/linker.ld b/kernel/linker.ld
new file mode 100644
index 0000000..e490e6a
--- /dev/null
+++ b/kernel/linker.ld
@@ -0,0 +1,28 @@
+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)
+    }
+}
diff --git a/makefile b/makefile
new file mode 100644
index 0000000..1e07743
--- /dev/null
+++ b/makefile
@@ -0,0 +1,30 @@
+CC = gcc# compiler
+LD = ld# linker
+ASM = nasm# assembler
+# what is the flag -O2 
+CFLAGS = -c -Wall -ffreestanding -nostdinc -nostdlib -lgcc# c compiler flags
+# flag elf32 allow decrease object file size
+AFLAGS = -f elf64# asm compiler flags
+BDIR = build# build directory
+
+.PHONY: install
+
+install: build
+	@echo "Creating an iso image of OS"
+	cp ./$(BDIR)/kernel.bin ./iso/os/
+	grub-mkrescue -o ./$(BDIR)/kernel.iso ./iso
+
+build:
+	mkdir $(BDIR) 
+	@echo "Compile source files..."
+	$(CC) $(CFLAGS) -o ./$(BDIR)/kernel.o ./kernel/kernel.c
+	$(ASM) $(AFLAGS) -o ./$(BDIR)/boot.o ./kernel/boot.s
+	@echo "Link object files..."
+	$(LD) -m elf_x86_64 -o ./$(BDIR)/kernel.bin -T ./kernel/linker.ld ./$(BDIR)/*.o
+	@echo "Project was built"
+
+clean:
+	rm -rf ./build
+
+run:
+	 qemu-system-i386 -cdrom ./$(BDIR)/kernel.iso
-- 
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