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|
;------------------------------------------------------------------------------
; @file
; An entry point use by Xen when a guest is started in PVH mode.
;
; Copyright (c) 2019, Citrix Systems, Inc.
;
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
;------------------------------------------------------------------------------
BITS 32
xenPVHMain:
;
; 'BP' to indicate boot-strap processor
;
mov di, 'BP'
;
; Store "Start of day" struct pointer for later use
;
mov dword[PVH_SPACE (0)], ebx
mov dword[PVH_SPACE (4)], 'XPVH'
;
; calculate delta between build-addr and run position
;
mov esp, PVH_SPACE(16) ; create a temporary stack
call .delta
.delta:
pop edx ; get addr of .delta
sub edx, ADDR_OF(.delta) ; calculate delta
;
; Find address of GDT and gdtr and fix the later
;
mov ebx, ADDR_OF(gdtr)
add ebx, edx ; add delta gdtr
mov eax, ADDR_OF(GDT_BASE)
add eax, edx ; add delta to GDT_BASE
mov dword[ebx + 2], eax ; fix GDT_BASE addr in gdtr
lgdt [ebx]
mov eax, SEC_DEFAULT_CR0
mov cr0, eax
;
; push return addr to the stack, then return far
;
push dword LINEAR_CODE_SEL ; segment to select
mov eax, ADDR_OF(.jmpToNewCodeSeg) ; return addr
add eax, edx ; add delta to return addr
push eax
retf
.jmpToNewCodeSeg:
mov eax, SEC_DEFAULT_CR4
mov cr4, eax
mov ax, LINEAR_SEL
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
;
; ESP will be used as initial value of the EAX register
; in Main.asm
;
xor esp, esp
;
; parameter for Flat32SearchForBfvBase
;
mov eax, 0 ; ADDR_OF(fourGigabytes)
add eax, edx ; add delta
;
; Jump to the main routine of the pre-SEC code
; skiping the 16-bit part of the routine and
; into the 32-bit flat mode part
;
OneTimeCallRet TransitionFromReal16To32BitFlat
|
