improve linker script

src/mbr_test.ld

@@ -1,35 +1,45 @@
 MEMORY
 {
-    BOOTLOADER  (RWX)   :   ORIGIN = 0x0000, LENGTH = 440
-    UNIQUE_ID   (R)     :   ORIGIN = 0x01B8, LENGTH = 4
-    RESERVED    (R)     :   ORIGIN = 0x01BC, LENGTH = 2
-    PTABLE      (R)     :   ORIGIN = 0x01BE, LENGTH = 64
-    MBR_MAGIC   (R)     :   ORIGIN = 0x01FE, LENGTH = 2
+    RAM         (RWX)   :   ORIGIN = 0x0000, LENGTH = 492032
 }
 
 SECTIONS
 {
-    .text 0x0000 : {
+    RAM = 0x7E00;
+    RAM_SEGMENT = (RAM >> 8);
+
+    .text       0x0000 : {
         BOOTLOADER_START = .;
         *(.text)
         *(.rodata)
         BOOTLOADER_END = .;
-        *(.bss)
         BOOTLOADER_SIZE = BOOTLOADER_END - BOOTLOADER_START;
+    } > RAM
 
-        RAM = 0x7E00;
-        RAM_SEGMENT = (RAM >> 8);
-    }
+    .stack (NOLOAD): {
+        . = ALIGN(8);
+        STACK_SIZE = 0x100;
         
-    .unique_id 0x01B8 : {
+        STACK_START = .;
+        . = . + STACK_SIZE;
+        . = ALIGN(8);
+        STACK_END = .;
+    } > RAM
+
+    .bss (NOLOAD) : {
+        . = ALIGN(8);
+        *(.bss)
+    } > RAM
+
+    .unique_id  0x01B8 : {
         SHORT(0x1234)
     }
 
-    .reserved 0x01BC : {
+    .reserved   0x01BC : {
         SHORT(0x0000)
     }
 
-    .mbr_magic 0x01FE : {
+    .mbr_magic  0x01FE : {
         SHORT(0xAA55)
     }
 }

src/mbr_test.s

@@ -1,17 +1,20 @@
 .section .text
 .code16
 
-    # we're moving to 0050, 0x7C00 -> 0x0500
-    # so, DS is 0x07C0 and ES is 0x0050  
-    mov $0x07C0, %ax
-    mov %ax, %ds
-    mov $0x0050, %ax
-    mov %ax, %es
+    # initialize stack
+    mov $RAM_SEGMENT, %ax
+    mov %ax, %ss
+    mov $STACK_END, %sp
+
+    # we're moving to 0x7C00 -> 0x7E00
+    push $0x07C0
+    pop %ds
+    push %ss
+    pop %es
 
     # set both source and destination pointers to zero, since we using segments
-    xor %ax, %ax
-    mov %ax, %si
-    mov %ax, %di
+    xor %si, %si
+    xor %di, %di
 
     # set counter with determined size by linker
     mov $BOOTLOADER_SIZE, %cx
@@ -22,16 +25,11 @@
     loop .copy
 
     # far jump to new memory region
-    jmp $0x0050,$.bootloader
+    jmp $RAM_SEGMENT,$.bootloader
 .bootloader:
-    # initialize stack
-    mov $0x07DF, %ax
-    mov %ax, %ss
-    xor %sp, %sp
-
-    # set ES segment
-    push %ds
-    pop %es
+    # set DS segment
+    push %es
+    pop %ds
 
 .entry:
     call serial_init