refactor + wip bios call from protected mode

boot1/asm/prelude.s

@@ -1,4 +1,5 @@
 %include "defines.s"
+%include "ps2.s"
 
 [bits 16]
 
@@ -7,6 +8,12 @@ extern boot1_bin_sectors
 extern boot1_magic
 extern _start
 
+extern gdt_flat_slice
+extern gdt_flat
+extern GDT_FLAT_IDX_CODE_32
+extern GDT_FLAT_IDX_CODE_16
+extern GDT_FLAT_IDX_DATA
+
 section .prelude
 
 %macro copy_stack_var_to_globals 2
@@ -335,22 +342,22 @@ prelude_main:
   cli
 
   ; Load our flat-address-space GDT.
-  lgdt [flat_gdt_slice]
+  lgdt [gdt_flat_slice]
 
   ; Set the protected-mode bit in cr0.
   mov eax, cr0
   or al, 0x01
   mov cr0, eax
 
-  ; Long jump to set the code segment to flat_gdt.segment_code, and to clear the instruction
+  ; Long jump to set the code segment to gdt_flat.segment_code, and to clear the instruction
   ; pipeline.
-  jmp (flat_gdt.segment_code_32 - flat_gdt):.protected_mode
+  jmp GDT_FLAT_IDX_CODE_32:.protected_mode_32
 
 [bits 32]
-.protected_mode:
+.protected_mode_32:
 
-  ; Set the data segments to flat_gdt.segment_data.
-  mov eax, (flat_gdt.segment_data - flat_gdt)
+  ; Set the data segments to gdt_flat.segment_data.
+  mov eax, GDT_FLAT_IDX_DATA
   mov ds, eax
   mov es, eax
   mov fs, eax
@@ -363,87 +370,3 @@ prelude_main:
 
   jmp _start
   jmp panic_simple
-
-
-section .data
-flat_gdt_slice:
-  dw FLAT_GDT_LEN
-  dd flat_gdt
-
-; Segment descriptor layout
-; | Range (bits) | Field         |
-; |--------------|---------------|
-; |         0-16 | limit         |
-; |        16-32 | base          |
-; |        32-40 | base cont.    |
-; |        40-48 | access        |
-; |        48-52 | limit cont.   |
-; |        52-56 | flags         |
-; |        56-64 | base cont.    |
-;
-; Flags
-; - 0: reserved
-; - 1: long-mode code segment
-; - 2: size
-;   - unset: 16-bit
-;   - set: 32-bit
-; - 3: granularity
-;   - unset: limit is measured in bytes
-;   - set: limit is measured in 4KiB pages
-;
-; Access
-; - 0: accessed
-;   - unset: CPU will set it when the segment is accessed
-; - 1: readable / writable
-;   - data segments: is segment writable (data segments are always readable)
-;   - code segments: is segment readable (code segments are never writable)
-; - 2: direction / conforming
-;   - data segments: whether segment grows down
-;   - code segments: whether this can be executed from a lower-privilege ring
-; - 3: executable
-;   - unset: this is a data segment
-;   - set: this is a code segment
-; - 4: descriptor type
-;   - unset: this is a task state segment
-;   - set: this is a data or code segment
-; - 5-6: privilege level (ring number)
-; - 7: present (must be set)
-;
-align 8
-flat_gdt:
-; First GDT entry must be 0.
-.segment_null:
-  dq 0
-
-; 32-bit code segment.
-; Bytes 0x0000 - 0xffff.
-.segment_code_32:
-  db 0xff, 0xff, \
-     0x00, 0x00, \
-     0x00,       \
-     10011011b,  \
-     01000000b,  \
-     0x00
-
-; 16-bit code segment, to use if we want to switch back to real mode.
-; Bytes 0x0000 - 0xffff.
-.segment_code_16:
-  db 0xff, 0xff, \
-     0x00, 0x00, \
-     0x00,       \
-     10011011b,  \
-     00000000b,  \
-     0x00
-
-; Data segment.
-; Pages 0x000000 - 0x0fffff, which covers the entire 32-bit address space (start of 0xfffff-th page
-; is 0xfffff * 4096 = 0xfffff000, end of page exclusive is 0xfffff000 + 4096 = 0x100000000).
-.segment_data:
-  db 0xff, 0xff, \
-     0x00, 0x00, \
-     0x00,       \
-     10010011b,  \
-     11001111b,  \
-     0x00
-
-  FLAT_GDT_LEN equ ($ - flat_gdt)