Remove an entry from the GDT that is no longer necessary. Add a few comments.

diff --git a/aseg/aseg.asm b/aseg/aseg.asm
index b9ae4245a31b84556fd84ee572a72eb4d443e031..c086b83b0971ebe211e3e9940fe900063fd65d93 100644 (file)
--- a/aseg/aseg.asm
+++ b/aseg/aseg.asm
@@ -1,9 +1,9 @@
        org 0xA8000
 [bits 16]
 entry:
-       mov ax, 0xA800
-       mov ds, ax              ; Take us out of flat unreal mode, and
-       mov es, ax              ; put us in true real mode.
+       mov ax, 0xA800                  ; Take us out of flat unreal mode,
+       mov ds, ax                      ; and put us in true real mode.
+       mov es, ax
        mov fs, ax
        mov gs, ax
        mov ss, ax
@@ -21,33 +21,32 @@ continue:
        mov fs, ax
        mov gs, ax
        mov ss, ax
-       mov esp, [dataptr]
+       mov esp, [dataptr]              ; Load stack pointer.
 
-       mov al, [needclear]
-       cmp al, 0
-       jz noclear
-       mov al, 0                       ; clear BSS
+       mov al, [needclear]             ; Has the aseg been run before?
+       cmp al, 0                       ; If so,
+       jz noclear                      ; don't clear BSS.
+       mov al, 0                       ; Otherwise, clear BSS.
        mov edi, [dataptr+4]
        mov ecx, [dataptr+8]
        rep stosb
        mov [needclear], al
        
 noclear:
-       mov eax, [dataptr+12]           ; jump into C
-       call eax
+       mov eax, [dataptr+12]           ; Load target jump address
+       call eax                        ; then jump into C.
 
        rsm                             ; and leave SMM
 
        align 0x4
 gdtr:
-       db 0x27, 0x00
+       db 0x1F, 0x00
        dd gdt
        align 0x4
 gdt:
-       db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+       db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00       ; initial null entry
        db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x93, 0xCF, 0x00       ; data segment
        db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x9B, 0xCF, 0x00       ; code segment
-       db 0xFF, 0xFF, 0x00, 0x80, 0x0A, 0x9B, 0xCF, 0x00       ; code segment for trampoline
 
 needclear:
        db 0x01