system76-edk2/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm

;------------------------------------------------------------------------------ ;
; Copyright (c) 2016 - 2018, Intel Corporation. All rights reserved.<BR>
; This program and the accompanying materials
; are licensed and made available under the terms and conditions of the BSD License
; which accompanies this distribution.  The full text of the license may be found at
; http://opensource.org/licenses/bsd-license.php.
;
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;
; Module Name:
;
;   SmiEntry.nasm
;
; Abstract:
;
;   Code template of the SMI handler for a particular processor
;
;-------------------------------------------------------------------------------

;
; Variables referrenced by C code
;

%define MSR_IA32_MISC_ENABLE 0x1A0
%define MSR_EFER      0xc0000080
%define MSR_EFER_XD   0x800

;
; Constants relating to PROCESSOR_SMM_DESCRIPTOR
;
%define DSC_OFFSET 0xfb00
%define DSC_GDTPTR 0x30
%define DSC_GDTSIZ 0x38
%define DSC_CS 14
%define DSC_DS 16
%define DSC_SS 18
%define DSC_OTHERSEG 20
;
; Constants relating to CPU State Save Area
;
%define SSM_DR6 0xffd0
%define SSM_DR7 0xffc8

%define PROTECT_MODE_CS 0x8
%define PROTECT_MODE_DS 0x20
%define LONG_MODE_CS 0x38
%define TSS_SEGMENT 0x40
%define GDT_SIZE 0x50

extern ASM_PFX(SmiRendezvous)
extern ASM_PFX(gSmiHandlerIdtr)
extern ASM_PFX(CpuSmmDebugEntry)
extern ASM_PFX(CpuSmmDebugExit)

global ASM_PFX(gPatchSmbase)
extern ASM_PFX(mXdSupported)
global ASM_PFX(gPatchXdSupported)
global ASM_PFX(gPatchSmiStack)
global ASM_PFX(gPatchSmiCr3)
global ASM_PFX(gcSmiHandlerTemplate)
global ASM_PFX(gcSmiHandlerSize)

    DEFAULT REL
    SECTION .text

BITS 16
ASM_PFX(gcSmiHandlerTemplate):
_SmiEntryPoint:
    mov     bx, _GdtDesc - _SmiEntryPoint + 0x8000
    mov     ax,[cs:DSC_OFFSET + DSC_GDTSIZ]
    dec     ax
    mov     [cs:bx], ax
    mov     eax, [cs:DSC_OFFSET + DSC_GDTPTR]
    mov     [cs:bx + 2], eax
o32 lgdt    [cs:bx]                       ; lgdt fword ptr cs:[bx]
    mov     ax, PROTECT_MODE_CS
    mov     [cs:bx-0x2],ax
    mov     edi, strict dword 0           ; source operand will be patched
ASM_PFX(gPatchSmbase):
    lea     eax, [edi + (@ProtectedMode - _SmiEntryPoint) + 0x8000]
    mov     [cs:bx-0x6],eax
    mov     ebx, cr0
    and     ebx, 0x9ffafff3
    or      ebx, 0x23
    mov     cr0, ebx
    jmp     dword 0x0:0x0
_GdtDesc:
    DW 0
    DD 0

BITS 32
@ProtectedMode:
    mov     ax, PROTECT_MODE_DS
o16 mov     ds, ax
o16 mov     es, ax
o16 mov     fs, ax
o16 mov     gs, ax
o16 mov     ss, ax
    mov esp, strict dword 0               ; source operand will be patched
ASM_PFX(gPatchSmiStack):
    jmp     ProtFlatMode

BITS 64
ProtFlatMode:
    mov eax, strict dword 0               ; source operand will be patched
ASM_PFX(gPatchSmiCr3):
    mov     cr3, rax
    mov     eax, 0x668                   ; as cr4.PGE is not set here, refresh cr3
    mov     cr4, rax                    ; in PreModifyMtrrs() to flush TLB.
; Load TSS
    sub     esp, 8                      ; reserve room in stack
    sgdt    [rsp]
    mov     eax, [rsp + 2]              ; eax = GDT base
    add     esp, 8
    mov     dl, 0x89
    mov     [rax + TSS_SEGMENT + 5], dl ; clear busy flag
    mov     eax, TSS_SEGMENT
    ltr     ax

; enable NXE if supported
    mov     al, strict byte 1           ; source operand may be patched
ASM_PFX(gPatchXdSupported):
    cmp     al, 0
    jz      @SkipXd
;
; Check XD disable bit
;
    mov     ecx, MSR_IA32_MISC_ENABLE
    rdmsr
    sub     esp, 4
    push    rdx                        ; save MSR_IA32_MISC_ENABLE[63-32]
    test    edx, BIT2                  ; MSR_IA32_MISC_ENABLE[34]
    jz      .0
    and     dx, 0xFFFB                 ; clear XD Disable bit if it is set
    wrmsr
.0:
    mov     ecx, MSR_EFER
    rdmsr
    or      ax, MSR_EFER_XD            ; enable NXE
    wrmsr
    jmp     @XdDone
@SkipXd:
    sub     esp, 8
@XdDone:

; Switch into @LongMode
    push    LONG_MODE_CS                ; push cs hardcore here
    call    Base                       ; push return address for retf later
Base:
    add     dword [rsp], @LongMode - Base; offset for far retf, seg is the 1st arg

    mov     ecx, MSR_EFER
    rdmsr
    or      ah, 1                      ; enable LME
    wrmsr
    mov     rbx, cr0
    or      ebx, 0x80010023            ; enable paging + WP + NE + MP + PE
    mov     cr0, rbx
    retf
@LongMode:                              ; long mode (64-bit code) starts here
    mov     rax, strict qword 0         ;  mov     rax, ASM_PFX(gSmiHandlerIdtr)
SmiHandlerIdtrAbsAddr:
    lidt    [rax]
    lea     ebx, [rdi + DSC_OFFSET]
    mov     ax, [rbx + DSC_DS]
    mov     ds, eax
    mov     ax, [rbx + DSC_OTHERSEG]
    mov     es, eax
    mov     fs, eax
    mov     gs, eax
    mov     ax, [rbx + DSC_SS]
    mov     ss, eax
    mov     rax, strict qword 0         ;   mov     rax, _SmiHandler
_SmiHandlerAbsAddr:
    jmp     rax

_SmiHandler:
    mov     rbx, [rsp + 0x8]             ; rcx <- CpuIndex

    ;
    ; Save FP registers
    ;
    sub     rsp, 0x200
    DB      0x48                         ; FXSAVE64
    fxsave  [rsp]

    add     rsp, -0x20

    mov     rcx, rbx
    call    ASM_PFX(CpuSmmDebugEntry)

    mov     rcx, rbx
    call    ASM_PFX(SmiRendezvous)

    mov     rcx, rbx
    call    ASM_PFX(CpuSmmDebugExit)

    add     rsp, 0x20

    ;
    ; Restore FP registers
    ;
    DB      0x48                         ; FXRSTOR64
    fxrstor [rsp]

    add     rsp, 0x200

    lea     rax, [ASM_PFX(mXdSupported)]
    mov     al, [rax]
    cmp     al, 0
    jz      .1
    pop     rdx                       ; get saved MSR_IA32_MISC_ENABLE[63-32]
    test    edx, BIT2
    jz      .1
    mov     ecx, MSR_IA32_MISC_ENABLE
    rdmsr
    or      dx, BIT2                  ; set XD Disable bit if it was set before entering into SMM
    wrmsr

.1:
    rsm

ASM_PFX(gcSmiHandlerSize)    DW      $ - _SmiEntryPoint

global ASM_PFX(PiSmmCpuSmiEntryFixupAddress)
ASM_PFX(PiSmmCpuSmiEntryFixupAddress):
    lea    rax, [ASM_PFX(gSmiHandlerIdtr)]
    lea    rcx, [SmiHandlerIdtrAbsAddr]
    mov    qword [rcx - 8], rax

    lea    rax, [_SmiHandler]
    lea    rcx, [_SmiHandlerAbsAddr]
    mov    qword [rcx - 8], rax
    ret