Branch sync and push, reformated and made the OS look more "official"

kernel/arch/i386/boot.s

@@ -0,0 +1,72 @@
+.set ALIGN, 1<<0    /* align loaded modules on page boundaries */
+.set MEMINFO, 1<<1  /* provide memory map */
+.set FLAGS, ALIGN | MEMINFO /* Multiboot flag */
+.set MAGIC, 0x1BADB002 /* Magic number lets bootloader find the header */
+.set CHECKSUM, -(MAGIC + FLAGS) /* checksum of above, to prove we are multiboot (sanity check I think) */
+
+/* so this basically declares the multiboot header that defines this program as a kernel,
+   and the following values are in the multiboot standard. The bootloader will look for the
+   first 8KiB of the kernel file, aligned with the 32-bit boundary, this means that it won't
+   work with 64bit until I keep on learning or I create my own bootloader (without multiboot)
+*/
+.section .multiboot
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
+
+/* This is where my knowledge is not high enough but here is the summary:
+        - esp is NOT in the multiboot standard so the kernel has to provide it.
+          this basically means that it doesn't define the value of the stack register
+          (whatever that means)
+        - This allocates some room for a stack by creating a symbol at the bottom of it
+          then allocate 16 KiB and then creating a symbol on top.
+        - The stack grows downwards on x86.
+
+And many more, apparently it's re-aligned to System-V ABI standard as well? Not sure, but hopefully I can
+continue learning
+*/
+.section .bss
+.align 16
+stack_bottom:
+.skip 16384 # 16 KiB
+stack_top:
+
+/* linker specifies a _start as the entry point to the kernel and the bootloader will jump to the position
+however it doesn't make any sense to return to this after the bootloader is gone
+*/
+.section .text
+.global _start
+.type _start, @function
+_start:
+        /* We are now in... no printf and other things, kernel has FULL CONTROL of the cpu. No security also lol */
+
+        /* To set up a stack, this sets the esp to register to the point of the stack because it grows downwards on
+        on x86 systems. this is done in assembly because languages like C can't function without a stack */
+        mov $stack_top, %esp
+
+        /* so we need to initialize some critical processor states before the high-level kernel is entered.
+        interestingly a lot of things are done at the boot level, we should load GDT, enable paging, and add runtime
+        support (for C++). Crazy!
+        */
+
+        /* time to enter the kernel,
+        according to the guide, this is a well defined call as the stack was originally 16-byte aligned, we pushed a 
+        multiple of 16-bytes to the stack (since 0 bytes were pushed so far), so alignment has been perserved.
+        */
+        call kernel_main
+
+        /* If there is nothing else to do, the computer will be in an infinite loop 
+                - Disable interrupts with cli (they wil be disabled by the bootloader)
+                - Wait for next interrupt to arrive with halt instruction (hlt)
+                - Jump to hlt instruction if it ever wakes up due to a non-maskable
+                  interrupt occuring or due to system management mode.
+        */
+        cli
+1:      hlt
+        jmp 1b
+
+/* set the size of _start symbol to the current location minus its start.
+Useful for debugging or if I implement call tracing
+*/
+.size _start, . - _start