#      TITLE   CpuAsm.asm: 

#------------------------------------------------------------------------------
#*
#*   Copyright 2008 - 2011, Intel Corporation
#*   All rights reserved. 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.
#*
#*    CpuAsm.S
#*
#*   Abstract:
#*
#------------------------------------------------------------------------------


#text  SEGMENT


#EXTRN ASM_PFX(mErrorCodeFlag):DWORD # Error code flags for exceptions


#
# point to the external interrupt vector table
#
ExternalVectorTablePtr:
    .byte      0, 0, 0, 0, 0, 0, 0, 0

.intel_syntax
ASM_GLOBAL ASM_PFX(InitializeExternalVectorTablePtr)
ASM_PFX(InitializeExternalVectorTablePtr):
    lea     %rax, [%rip+ExternalVectorTablePtr] # save vector number
    mov     [%rax], %rcx
    ret


#------------------------------------------------------------------------------
# VOID
# SetCodeSelector (
#   UINT16 Selector
#   );
#------------------------------------------------------------------------------
.intel_syntax
ASM_GLOBAL ASM_PFX(SetCodeSelector)
ASM_PFX(SetCodeSelector):
    sub     %rsp, 0x10
    lea     %rax, [%rip+setCodeSelectorLongJump]
    mov     [%rsp], %rax
    mov     [%rsp+4], %cx
    jmp     fword ptr [%rsp]
setCodeSelectorLongJump:
    add     %rsp, 0x10
    ret

#------------------------------------------------------------------------------
# VOID
# SetDataSelectors (
#   UINT16 Selector
#   );
#------------------------------------------------------------------------------
.intel_syntax
ASM_GLOBAL ASM_PFX(SetDataSelectors)
ASM_PFX(SetDataSelectors):
    mov     %ss, %cx
    mov     %ds, %cx
    mov     %es, %cx
    mov     %fs, %cx
    mov     %gs, %cx
    ret

#---------------------------------------;
# CommonInterruptEntry                  ;
#---------------------------------------;
# The follow algorithm is used for the common interrupt routine.

.intel_syntax
ASM_GLOBAL ASM_PFX(CommonInterruptEntry)
ASM_PFX(CommonInterruptEntry):
    cli
    #
    # All interrupt handlers are invoked through interrupt gates, so
    # IF flag automatically cleared at the entry point
    #
    #
    # Calculate vector number
    #
    xchg    %rcx, [%rsp] # get the return address of call, actually, it is the address of vector number.
    movzx   %ecx, word ptr [%rcx]
    cmp     %ecx, 32         # Intel reserved vector for exceptions?
    jae     NoErrorCode
    push    %rax
    lea     %rax, [%rip+ASM_PFX(mErrorCodeFlag)]
    bt      dword ptr [%rax], %ecx
    pop     %rax
    jc      CommonInterruptEntry_al_0000

NoErrorCode:

    #
    # Push a dummy error code on the stack
    # to maintain coherent stack map
    #
    push    [%rsp]
    mov     qword ptr [%rsp + 8], 0
CommonInterruptEntry_al_0000:
    push    %rbp
    mov     %rbp, %rsp

    #
    # Stack:
    # +---------------------+ <-- 16-byte aligned ensured by processor
    # +    Old SS           +
    # +---------------------+
    # +    Old RSP          +
    # +---------------------+
    # +    RFlags           +
    # +---------------------+
    # +    CS               +
    # +---------------------+
    # +    RIP              +
    # +---------------------+
    # +    Error Code       +
    # +---------------------+
    # + RCX / Vector Number +
    # +---------------------+
    # +    RBP              +
    # +---------------------+ <-- RBP, 16-byte aligned
    #


    #
    # Since here the stack pointer is 16-byte aligned, so
    # EFI_FX_SAVE_STATE_X64 of EFI_SYSTEM_CONTEXT_x64
    # is 16-byte aligned
    #

#; UINT64  Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
#; UINT64  R8, R9, R10, R11, R12, R13, R14, R15;
    push    %r15
    push    %r14
    push    %r13
    push    %r12
    push    %r11
    push    %r10
    push    %r9
    push    %r8
    push    %rax
    push    qword ptr [%rbp + 8]   # RCX
    push    %rdx
    push    %rbx
    push    qword ptr [%rbp + 48]  # RSP
    push    qword ptr [%rbp]       # RBP
    push    %rsi
    push    %rdi

#; UINT64  Gs, Fs, Es, Ds, Cs, Ss;  insure high 16 bits of each is zero
    movzx   %rax, word ptr [%rbp + 56]
    push    %rax                      # for ss
    movzx   %rax, word ptr [%rbp + 32]
    push    %rax                      # for cs
    mov     %rax, %ds
    push    %rax
    mov     %rax, %es
    push    %rax
    mov     %rax, %fs
    push    %rax
    mov     %rax, %gs
    push    %rax

    mov     [%rbp + 8], %rcx               # save vector number

#; UINT64  Rip;
    push    qword ptr [%rbp + 24]

#; UINT64  Gdtr[2], Idtr[2];
    xor     %rax, %rax
    push    %rax
    push    %rax
    sidt    [%rsp]
    xchg    %rax, [%rsp + 2]
    xchg    %rax, [%rsp]
    xchg    %rax, [%rsp + 8]

    xor     %rax, %rax
    push    %rax
    push    %rax
    sgdt    [%rsp]
    xchg    %rax, [%rsp + 2]
    xchg    %rax, [%rsp]
    xchg    %rax, [%rsp + 8]

#; UINT64  Ldtr, Tr;
    xor     %rax, %rax
    str     %ax
    push    %rax
    sldt    %ax
    push    %rax

#; UINT64  RFlags;
    push    qword ptr [%rbp + 40]

#; UINT64  Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
    mov     %rax, %cr8
    push    %rax
    mov     %rax, %cr4
    or      %rax, 0x208
    mov     %cr4, %rax
    push    %rax
    mov     %rax, %cr3
    push    %rax
    mov     %rax, %cr2
    push    %rax
    xor     %rax, %rax
    push    %rax
    mov     %rax, %cr0
    push    %rax

#; UINT64  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
    mov     %rax, %dr7
    push    %rax
#; clear Dr7 while executing debugger itself
    xor     %rax, %rax
    mov     %dr7, %rax

    mov     %rax, %dr6
    push    %rax
#; insure all status bits in dr6 are clear...
    xor     %rax, %rax
    mov     %dr6, %rax

    mov     %rax, %dr3
    push    %rax
    mov     %rax, %dr2
    push    %rax
    mov     %rax, %dr1
    push    %rax
    mov     %rax, %dr0
    push    %rax

#; FX_SAVE_STATE_X64 FxSaveState;
    sub     %rsp, 512
    mov     %rdi, %rsp
    .byte 0x0f, 0x0ae, 0x07 #fxsave [rdi]

#; UEFI calling convention for x64 requires that Direction flag in EFLAGs is clear
    cld

#; UINT32  ExceptionData;
    push    qword ptr [%rbp + 16]

#; call into exception handler
    mov     %rcx, [%rbp + 8]
    lea     %rax, [%rip+ExternalVectorTablePtr]
    mov     %eax, [%eax]
    mov     %rax, [%rax + %rcx * 8]
    or      %rax, %rax                        # NULL?

    je    nonNullValue#

#; Prepare parameter and call
#  mov     rcx, [rbp + 8]
    mov     %rdx, %rsp
    #
    # Per X64 calling convention, allocate maximum parameter stack space
    # and make sure RSP is 16-byte aligned
    #
    sub     %rsp, 4 * 8 + 8
    call    %rax
    add     %rsp, 4 * 8 + 8

nonNullValue:
    cli
#; UINT64  ExceptionData;
    add     %rsp, 8

#; FX_SAVE_STATE_X64 FxSaveState;

    mov     %rsi, %rsp
    .byte   0x0f, 0x0ae, 0x0E # fxrstor [rsi]
    add     %rsp, 512

#; UINT64  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
    pop     %rax
    mov     %dr0, %rax
    pop     %rax
    mov     %dr1, %rax
    pop     %rax
    mov     %dr2, %rax
    pop     %rax
    mov     %dr3, %rax
#; skip restore of dr6.  We cleared dr6 during the context save.
    add     %rsp, 8
    pop     %rax
    mov     %dr7, %rax

#; UINT64  Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
    pop     %rax
    mov     %cr0, %rax
    add     %rsp, 8   # not for Cr1
    pop     %rax
    mov     %cr2, %rax
    pop     %rax
    mov     %cr3, %rax
    pop     %rax
    mov     %cr4, %rax
    pop     %rax
    mov     %cr8, %rax

#; UINT64  RFlags;
    pop     qword ptr [%rbp + 40]

#; UINT64  Ldtr, Tr;
#; UINT64  Gdtr[2], Idtr[2];
#; Best not let anyone mess with these particular registers...
    add     %rsp, 48

#; UINT64  Rip;
    pop     qword ptr [%rbp + 24]

#; UINT64  Gs, Fs, Es, Ds, Cs, Ss;
    pop     %rax
    # mov     gs, rax ; not for gs
    pop     %rax
    # mov     fs, rax ; not for fs
    # (X64 will not use fs and gs, so we do not restore it)
    pop     %rax
    mov     %es, %rax
    pop     %rax
    mov     %ds, %rax
    pop     qword ptr [%rbp + 32]  # for cs
    pop     qword ptr [%rbp + 56]  # for ss

#; UINT64  Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
#; UINT64  R8, R9, R10, R11, R12, R13, R14, R15;
    pop     %rdi
    pop     %rsi
    add     %rsp, 8               # not for rbp
    pop     qword ptr [%rbp + 48] # for rsp
    pop     %rbx
    pop     %rdx
    pop     %rcx
    pop     %rax
    pop     %r8
    pop     %r9
    pop     %r10
    pop     %r11
    pop     %r12
    pop     %r13
    pop     %r14
    pop     %r15

    mov     %rsp, %rbp
    pop     %rbp
    add     %rsp, 16
    iretq


#text  ENDS

#END