define startup stack in linker script, not assembly

Rsconscript

@@ -97,6 +97,7 @@ EOF
     env["LIBS"] += %w[gcc]
     env["OBJDUMP"] = "i686-elf-objdump"
     env.Program("^/hos.elf", glob("src/**/*.{S,c}"))
+    env.depends("#{env.build_root}/hos.elf", "src/link.ld")
     env.Disassemble("^/hos.elf.txt", "^/hos.elf")
     env.EfiImage("build/hos-efi.img", %w[^/hos.elf])
     env.BiosImage("build/hos-bios.img", %w[^/hos.elf])

src/boot.S

@@ -1,21 +1,3 @@
-/*
-The multiboot standard does not define the value of the stack pointer register
-(esp) and it is up to the kernel to provide a stack. This allocates room for a
-small stack by creating a symbol at the bottom of it, then allocating 16384
-bytes for it, and finally creating a symbol at the top. The stack grows
-downwards on x86. The stack is in its own section so it can be marked nobits,
-which means the kernel file is smaller because it does not contain an
-uninitialized stack. The stack on x86 must be 16-byte aligned according to the
-System V ABI standard and de-facto extensions. The compiler will assume the
-stack is properly aligned and failure to align the stack will result in
-undefined behavior.
-*/
-.section .bss
-.align 16
-stack_bottom:
-.skip 16384 # 16 KiB
-stack_top:
- 
 /*
 The linker script specifies _start as the entry point to the kernel and the
 bootloader will jump to this position once the kernel has been loaded. It
@@ -25,25 +7,7 @@ doesn't make sense to return from this function as the bootloader is gone.
 .global _start
 .type _start, @function
 _start:
-    /*
-    The bootloader has loaded us into 32-bit protected mode on a x86
-    machine. Interrupts are disabled. Paging is disabled. The processor
-    state is as defined in the multiboot standard. The kernel has full
-    control of the CPU. The kernel can only make use of hardware features
-    and any code it provides as part of itself. There's no printf
-    function, unless the kernel provides its own <stdio.h> header and a
-    printf implementation. There are no security restrictions, no
-    safeguards, no debugging mechanisms, only what the kernel provides
-    itself. It has absolute and complete power over the
-    machine.
-    */
- 
-    /*
-    To set up a stack, we set the esp register to point to the top of the
-    stack (as it grows downwards on x86 systems). This is necessarily done
-    in assembly as languages such as C cannot function without a stack.
-    */
-    mov $stack_top, %esp
+    mov $_stack_end, %esp
  
     /*
     This is a good place to initialize crucial processor state before the

src/link.ld

@@ -20,6 +20,14 @@ SECTIONS
         *(.data)
     }
 
+    _stack_size = 16K;
+    .stack (NOLOAD) : ALIGN(4K)
+    {
+        _stack_start = .;
+        . = . + _stack_size;
+        _stack_end = .;
+    }
+
     .bss BLOCK(4K) : ALIGN(4K)
     {
         *(COMMON)