asmfuncs.asm

Next BIOS Source code : Extensible Firmware Interface

;******************************************************************************
;*
;*        Copyright (c) 2000-2001  Intel Corporation. All rights reserved
;*
;*    This software and associated documenation (if any) is furnished
;*    under a license and may only be used or copied in accordance
;*    with the terms of the license. Except as permitted by such
;*    license, no part of this software or documentation may be
;*    reproduced, stored in a retrieval system, or transmitted in any
;*    form or by any means without the express written consent of
;*    Intel Corporation.
;*
;******************************************************************************

.586p
.MODEL          FLAT, C

EXCPT32_DIVIDE_ERROR     EQU    0
EXCPT32_DEBUG            EQU    1
EXCPT32_NMI              EQU    2
EXCPT32_BREAKPOINT       EQU    3
EXCPT32_OVERFLOW         EQU    4
EXCPT32_BOUND            EQU    5
EXCPT32_INVALID_OPCODE   EQU    6
EXCPT32_DOUBLE_FAULT     EQU    8
EXCPT32_INVALID_TSS      EQU   10
EXCPT32_SEG_NOT_PRESENT  EQU   11
EXCPT32_STACK_FAULT      EQU   12
EXCPT32_GP_FAULT         EQU   13
EXCPT32_PAGE_FAULT       EQU   14
EXCPT32_FP_ERROR         EQU   16
EXCPT32_ALIGNMENT_CHECK  EQU   17
EXCPT32_MACHINE_CHECK    EQU   18
EXCPT32_SIMD             EQU   19

FXSTOR_FLAG              EQU   01000000h         ; bit cpuid 24 of feature flags

;; The FXSTOR and FXRSTOR commands are used for saving and restoring the x87,
;; MMX, SSE, SSE2, etc registers.  The initialization of the debugsupport driver
;; MUST check the CPUID feature flags to see that these instructions are available
;; and fail to init if they are not.

;; fxstor [edi]
FXSTOR_EDI               MACRO
                         db 0fh, 0aeh, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [edi]
ENDM

;; fxrstor [esi]
FXRSTOR_ESI              MACRO
                         db 0fh, 0aeh, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [esi]
ENDM
.DATA

public          OrigVector, InterruptEntryStub, StubSize, CommonIdtEntry, FxStorSupport

StubSize        dd      InterruptEntryStubEnd - InterruptEntryStub
AppEsp          dd      11111111h ; ?
DebugEsp        dd      22222222h ; ?
ExtraPush       dd      33333333h ; ?
ExceptData      dd      44444444h ; ?
Eflags          dd      55555555h ; ?
OrigVector      dd      66666666h ; ?

;; The declarations below define the memory region that will be used for the debug stack.
;; The context record will be built by pushing register values onto this stack.
;; It is imparitive that alignment be carefully managed, since the FXSTOR and
;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
;;
;; The stub will switch stacks from the application stack to the debuger stack
;; and pushes the exception number.
;;
;; Then we building the context record on the stack. Since the stack grows down,
;; we push the fields of the context record from the back to the front.  There
;; are 132 bytes of stack used prior allocating the 512 bytes of stack to be
;; used as the memory buffer for the fxstor instruction. Therefore address of
;; the buffer used for the FXSTOR instruction is &Eax - 132 - 512, which
;; must be 16 byte aligned.
;;
;; We carefully locate the stack to make this happen.
;;
;; For reference, the context structure looks like this:
;;      struct {
;;        UINT32        ExceptionData;
;;        FX_SAVE_STATE FxSaveState;    // 512 bytes, must be 16 byte aligned
;;        UINT32        Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
;;        UINT32        Cr0, Cr1, Cr2, Cr3, Cr4;
;;        UINT32        Ldtr, Tr;
;;        UINT64        Gdtr, Idtr;
;;        UINT32        EFlags;
;;        UINT32        Eip;
;;        UINT32        SegGs, SegFs, SegEs, SegDs, SegCs, SegSs;
;;        UINT32        Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
;;      } SYSTEM_CONTEXT_IA32;  // 32 bit system context record


align           16
DebugStackEnd   db      "DbgStkEnd >>>>>>"      ;; 16 byte long string - must be 16 bytes to preserve alignment
                dd      1ffdh dup (000000000h)  ;; 32K should be enough stack
                                                ;;   This allocation is coocked to insure 
                                                ;;   that the the buffer for the FXSTORE instruction
                                                ;;   will be 16 byte aligned also.
                                                ;;
ExceptionNumber dd      ?                       ;; first entry will be the vector number pushed by the stub

DebugStackBegin db      "<<<< DbgStkBegin"      ;; initial debug ESP == DebugStackBegin, set in stub

.CODE

externdef InterruptDistrubutionHub:near

;------------------------------------------------------------------------------
; BOOLEAN
; FxStorSupport (
;   void
;   )
;
; Abstract: Returns TRUE if FxStor instructions are supported
;
FxStorSupport   PROC    C PUBLIC

;
; cpuid corrupts ebx which must be preserved per the C calling convention
;
                push    ebx
                mov     eax, 1
                cpuid
                mov     eax, edx
                and     eax, FXSTOR_FLAG
                shr     eax, 24
                pop     ebx
                ret
FxStorSupport   ENDP


;------------------------------------------------------------------------------
; DESCRIPTOR *
; GetIdtr (
;   void
;   )
;
; Abstract: Returns physical address of IDTR
;
GetIdtr         PROC    C PUBLIC
                LOCAL   IdtrBuf:FWORD

                sidt    IdtrBuf
                mov     eax, DWORD PTR IdtrBuf + 2
                ret
GetIdtr         ENDP


;------------------------------------------------------------------------------
; BOOLEAN
; WriteInterruptFlag (
;   BOOLEAN NewState
;   )
;
; Abstract: Programs interrupt flag to the requested state and returns previous
;           state.
;
WriteInterruptFlag  PROC C PUBLIC State:DWORD

                pushfd
                pop     eax
                and     eax, 200h
                shr     eax, 9
                mov     ecx, State
                .IF     ecx == 0
                        cli
                .ELSE
                        sti
                .ENDIF
                ret

WriteInterruptFlag  ENDP



;------------------------------------------------------------------------------
; void
; Vect2Desc (
;   DESCRIPTOR * DestDesc,
;   void (*Vector) (void)
;   )
;
; Abstract: Encodes an IDT descriptor with the given physical address
;
Vect2Desc       PROC    C PUBLIC DestPtr:DWORD, Vector:DWORD

                mov     eax, Vector
                mov     ecx, DestPtr
                mov     word ptr [ecx], ax                  ; write bits 15..0 of offset
                mov     word ptr [ecx+2], 20h               ; SYS_CODE_SEL from GDT
                mov     word ptr [ecx+4], 0e00h OR 8000h    ; type = 386 interrupt gate, present
                shr     eax, 16
                mov     word ptr [ecx+6], ax                ; write bits 31..16 of offset

                ret

Vect2Desc       ENDP



;------------------------------------------------------------------------------
; InterruptEntryStub
;
; Abstract: This code is not a function, but is a small piece of code that is
;               copied and fixed up once for each IDT entry that is hooked.
;
InterruptEntryStub::
                mov     AppEsp, esp             ; save stack top
                mov     esp, offset DebugStackBegin  ; switch to debugger stack
                push    0                       ; push vector number - will be modified before installed
                db      0e9h                    ; jump rel32
                dd      0                       ; fixed up to relative address of CommonIdtEntry
InterruptEntryStubEnd:



;------------------------------------------------------------------------------
; CommonIdtEntry
;
; Abstract: This code is not a function, but is the common part for all IDT
;               vectors.
;
CommonIdtEntry::
;;
;; At this point, the stub has saved the current application stack esp into AppEsp
;; and switched stacks to the debug stack, where it pushed the vector number
;;
;; The application stack looks like this:
;;
;;              ...
;;              (last application stack entry)
;;              eflags from interrupted task
;;              CS from interrupted task
;;              EIP from interrupted task
;;              Error code <-------------------- Only present for some exeption types
;;
;;


;; The stub switched us to the debug stack and pushed the interrupt number.
;;
;; Next, construct the context record.  It will be build on the debug stack by
;; pushing the registers in the correct order so as to create the context structure
;; on the debug stack.  The context record must be built from the end back to the
;; beginning because the stack grows down...
;
;; For reference, the context record looks like this:
;;
;; typedef
;; struct {
;;   UINT32        ExceptionData;
;;   FX_SAVE_STATE FxSaveState;
;;   UINT32        Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
;;   UINT32        Cr0, Cr2, Cr3, Cr4;
;;   UINT32        Ldtr, Tr;
;;   UINT64        Gdtr, Idtr;
;;   UINT32        EFlags;
;;   UINT32        Eip;
;;   UINT32        SegGs, SegFs, SegEs, SegDs, SegCs, SegSs;
;;   UINT32        Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
;; } SYSTEM_CONTEXT_IA32;  // 32 bit system context record

;; UINT32  Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
                pushad

;; Save interrupt state eflags register...
                pushfd
                pop     eax
                mov     dword ptr Eflags, eax

;; We need to determine if any extra data was pushed by the exception, and if so, save it
;; To do this, we check the exception number pushed by the stub, and cache the