User:Johnburger/Demo/Exec/User/TSS

There's not much to this code, since Demo/Exec/Alloc/TSS does most of the hard work for me. After CALLing it, the rest of the code initialises the other important registers, as well as filling in the User Code's expected parameters, and then activates the TSS.

That's it! The User Code is now ready to run!

Demo/Exec/User/TSS.inc

;
; Exec/User/TSS.inc
;
 
; This module creates a User-mode Program's TSS and populates it.
 
Exec.User.TSS:
; This function creates a TSS for the LDT, and populates it ready for a User Task
; Input:  AX  = LDT
; Output: EAX = Non-zero on success
 
                CALL            Exec.Alloc.TSS
                TEST            EAX,EAX
                JZ              .End
 
; Initialise fields in new TSS for User Task
                MOV             CL,Window.Width
                MOV             CH,Window.Height
 
                MOV             EDX,[%$Pos]
 
                MOV     WORD    [ES:x86.TSS.CS],  Selector(User.LDT.Code,   LDT, RPL3)
                MOV    DWORD    [ES:x86.TSS.EIP], User.Entry
                MOV     WORD    [ES:x86.TSS.SS0], Selector(User.LDT.Stack0, LDT, RPL0)
;               MOV    DWORD    [ES:x86.TSS.ESP0],0
                MOV     WORD    [ES:x86.TSS.SS],  Selector(User.LDT.Stack3, LDT, RPL3)
;               MOV    DWORD    [ES:x86.TSS.ESP], 0
                MOV     WORD    [ES:x86.TSS.ES],  Selector(GDT.VGA,         GDT, RPL3)
                MOV     WORD    [ES:x86.TSS.DS],  Selector(User.LDT.Data,   LDT, RPL3)
                MOV    DWORD    [ES:x86.TSS.EBX], VGA.Cols * 2
                MOV             [ES:x86.TSS.ECX], ECX
                MOV             [ES:x86.TSS.EDX], EDX
 
                MOV             AH,0            ; Not a System TSS
                CALL            Exec.Alloc.TSS.Enable
.End:
                RET