From: Joshua Wise Date: Sat, 6 Sep 2008 07:57:16 +0000 (-0400) Subject: Remove an entry from the GDT that is no longer necessary. Add a few comments. X-Git-Url: http://git.joshuawise.com/netwatch.git/commitdiff_plain/1458b27545d4e447e751a3baa653bb9641027a24?ds=inline;hp=-c Remove an entry from the GDT that is no longer necessary. Add a few comments. --- 1458b27545d4e447e751a3baa653bb9641027a24 diff --git a/aseg/aseg.asm b/aseg/aseg.asm index b9ae424..c086b83 100644 --- 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