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|
;------------------------------------------------------------------------------
;
; Copyright (c) 2022 - 2025, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Abstract:
;
; Switch the stack from temporary memory to permanent memory.
;
;------------------------------------------------------------------------------
DEFAULT REL
SECTION .text
%include "PushPopRegsNasm.inc"
; Page table related bits in CR0/CR4/EFER
%define CR0_PG_MASK 0x80010000 ; CR0.PG and CR0.WP
%define CR4_PG_MASK 0x10B0 ; CR4.PSE, CR4.PAE, CR4.PGE and CR4.LA57
%define EFER_PG_MASK 0x800 ; EFER.NXE
extern ASM_PFX(SwapStack)
extern ASM_PFX(FeaturePcdGet (PcdFspSaveRestorePageTableEnable))
;------------------------------------------------------------------------------
; UINT32
; EFIAPI
; Pei2LoaderSwitchStack (
; VOID
; )
;------------------------------------------------------------------------------
global ASM_PFX(Pei2LoaderSwitchStack)
ASM_PFX(Pei2LoaderSwitchStack):
xor rax, rax
jmp ASM_PFX(FspSwitchStack)
;------------------------------------------------------------------------------
; UINT32
; EFIAPI
; Loader2PeiSwitchStack (
; VOID
; )
;------------------------------------------------------------------------------
global ASM_PFX(Loader2PeiSwitchStack)
ASM_PFX(Loader2PeiSwitchStack):
jmp ASM_PFX(FspSwitchStack)
;------------------------------------------------------------------------------
; UINT32
; EFIAPI
; FspSwitchStack (
; VOID
; )
;------------------------------------------------------------------------------
global ASM_PFX(FspSwitchStack)
ASM_PFX(FspSwitchStack):
; Save current contexts. The format must align with CONTEXT_STACK_64.
push rdx ; Reserved QWORD for stack alignment
push rdx ; ApiParam2
push rcx ; ApiParam1
push rax ; FspInfoHeader
pushfq
cli
PUSHA_64
;
; Allocate 4x8 bytes on the stack.
;
sub rsp, 32
lea rdx, [ASM_PFX(FeaturePcdGet (PcdFspSaveRestorePageTableEnable))]
mov dl, byte [rdx]
cmp dl, 0
jz SkipPagetableSave
add rsp, 32
; Save EFER MSR
push rcx
push rax
mov rcx, 0xC0000080
rdmsr
shl rdx, 0x20
or rdx, rax
pop rax
pop rcx
push rdx
; Save CR registers
mov rdx, cr4
push rdx
mov rdx, cr3
push rdx
mov rdx, cr0
push rdx
SkipPagetableSave:
; Enable FSGSBASE instructions via CR4.FSGSBASE (bit 16)
mov rbx, cr4 ; Save original CR4 in rbx, SwapStack() doesn't change it
mov rdx, rbx
bts rdx, 16 ; Set CR4.FSGSBASE
mov cr4, rdx
; Save GsBase
rdgsbase rdx
push rdx
; Save FsBase
rdfsbase rdx
push rdx
; Save Segment registers
mov rdx, ss
push rdx
mov rdx, gs
push rdx
mov rdx, fs
push rdx
mov rdx, es
push rdx
mov rdx, ds
push rdx
mov rdx, cs
push rdx
; Reserve 16 bytes for GDT save/restore
sub rsp, 16
sgdt [rsp]
; Reserve 16 bytes for IDT save/restore
sub rsp, 16
sidt [rsp]
; Load new stack
mov rcx, rsp
sub rsp, 0x20
call ASM_PFX(SwapStack)
add rsp, 0x20
mov rsp, rax
; Restore previous contexts
lidt [rsp]
add rsp, 16
; Restore GDTR
lgdt [rsp]
add rsp, 16
; Restore Segment registers
lea rdx, [.0]
push rdx ; Push return address
retfq ; Far return to restore CS (uses CS from stack + return address)
.0:
pop rdx
mov ds, dx
pop rdx
mov es, dx
pop rdx
mov fs, dx
pop rdx
mov gs, dx
pop rdx
mov ss, dx
; Restore FsBase (CR4.FSGSBASE still set from save path)
pop rdx
wrfsbase rdx
; Restore GsBase
pop rdx
wrgsbase rdx
; Restore original CR4 (clear FSGSBASE bit)
mov cr4, rbx
lea rax, [ASM_PFX(FeaturePcdGet (PcdFspSaveRestorePageTableEnable))]
mov al, byte [rax]
cmp al, 0
jz SkipPagetableRestore
; [rsp] stores new cr0
; [rsp+8] stores new cr3
; [rsp+16] stores new cr4
; [rsp+24] stores new Efer
;
; When new EFER.NXE == 1, the restore flow is: EFER --> CRx
; Otherwise: CRx --> EFER
;
; If NXE bit is changed to 1, change NXE before CR register
; This is because Nx bit in page table entry in new CR3 will be invalid
; if updating CR3 before EFER MSR.
;
mov rax, [rsp + 24]
bt rax, 11
jnc SkipEferLabel1
; Restore EFER MSR
mov ecx, 0xC0000080
rdmsr
and eax, ~EFER_PG_MASK
mov ebx, [rsp + 24]
and ebx, EFER_PG_MASK
or eax, ebx
wrmsr
SkipEferLabel1:
mov rbx, [rsp]
mov rdx, cr0
and rdx, ~CR0_PG_MASK
and rbx, CR0_PG_MASK
or rdx, rbx
mov cr0, rdx
mov rbx, [rsp + 8]
mov cr3, rbx
mov rbx, [rsp + 16]
mov rdx, cr4
and rdx, ~CR4_PG_MASK
and rbx, CR4_PG_MASK
or rdx, rbx
mov cr4, rdx
;
; If NXE bit is changed to 0, change NXE after than CR regiser
;
mov rax, [rsp + 24]
bt rax, 11
jc SkipEferLabel2
; Restore EFER MSR
mov ecx, 0xC0000080
rdmsr
and eax, ~EFER_PG_MASK
mov ebx, [rsp + 24]
and ebx, EFER_PG_MASK
or eax, ebx
wrmsr
SkipEferLabel2:
SkipPagetableRestore:
; pop page table related registers.
add rsp, 32
POPA_64
popfq
add rsp, 32 ; FspInfoHeader + ApiParam[2] + Reserved QWORD
ret
|
