Leaked source code of windows server 2003
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subttl emlsenv.asm - Emulator Save/Restore
page
;***
;emlsenv.asm - Emulator Save/Restore
;
;
; Copyright (c) Microsoft Corporation 1991
;
; All Rights Reserved
;
;Purpose:
; FLDCW, FSTCW, FSTSW, FSTENV, FLDENV, FSAVE, FRSTOR instructions
;
;Revision History:
;
; [] 09/05/91 TP Initial 32-bit version.
;
;
;*******************************************************************************
;When setting the control word, the [RoundMode] vector must be set
;according to the rounding and precision modes.
tRoundMode label dword
irp RC,<near,down,up,chop>
irp PC,<24,24,53,64>
dd Round&&PC&&RC
endm
endm
EM_ENTRY eFLDCW
eFLDCW:
;Uses only eax and ebx
mov ax, dseg:[esi] ; Fetch control word from user memory
SetControlWord:
and ax,0F3FH ; Limit to valid values
mov EMSEG:[ControlWord], ax ; Store in the emulated control word
not al ;Flip mask bits for fast compare
and al,3FH ;Limit to valid mask bits
mov EMSEG:[ErrMask],al
and eax,(RoundControl + PrecisionControl) shl 8
.erre RoundControl eq 1100B
.erre PrecisionControl eq 0011B
shr eax,6 ;Put PC and RC in bits 2-5
mov ebx,tRoundMode[eax] ;Get correct RoundMode vector
mov EMSEG:[RoundMode],ebx
mov EMSEG:[SavedRoundMode],ebx
and eax,RoundControl shl (8-6) ;Mask off precision control
mov ebx,tRoundMode[eax+PC64 shl (8-6)];Get correct RoundMode vector
mov EMSEG:[TransRound],ebx ;Round mode w/o precision
ret
EM_ENTRY eFSTCW
eFSTCW:
;Uses only eax
mov ax, EMSEG:[ControlWord] ; Fetch user control word
mov dseg:[esi], ax ; Store into user memory
ret
EM_ENTRY eFSTSW
eFSTSW:
;Uses only eax and ebx
call GetStatusWord ; Fetch emulated Status word
mov dseg:[esi], ax ; Store into user memory
ret
eFSTSWax:
;Uses only eax and ebx
call GetStatusWord ; Fetch emulated Status word
mov [esp+4].regAX,ax
ret
EM_ENTRY eFDECSTP
eFDECSTP:
;edi = [CURstk]
cmp edi,BEGstk
jbe DecWrap
sub EMSEG:[CURstk],Reg87Len
ret
DecWrap:
mov EMSEG:[CURstk],INITstk
ret
EM_ENTRY eFINCSTP
eFINCSTP:
;edi = [CURstk]
cmp edi,INITstk
jae IncWrap
add EMSEG:[CURstk],Reg87Len
ret
IncWrap:
mov EMSEG:[CURstk],BEGstk
ret
eFCLEX:
mov EMSEG:[SWerr],0
and [esp+4].OldLongStatus,0FFFF00FFH ; clear saved SWerr
ret
;*** eFSTENV - emulate FSTENV [address]
;
; ARGUMENTS
; dseg:esi = where to store environment
;
;
; DESCRIPTION
; This routine emulates an 80387 FSTENV (store environment)
;
EM_ENTRY eFSTENV
eFSTENV:
mov ax,[esp+4].OldStatus
mov EMSEG:[StatusWord],ax
SaveEnv:
xor ax,ax
mov dseg:[esi.reserved1],ax
mov dseg:[esi.reserved2],ax
mov dseg:[esi.reserved3],ax
mov dseg:[esi.reserved4],ax
mov dseg:[esi.reserved5],ax
mov ax,EMSEG:[ControlWord]
mov dseg:[esi.E32_ControlWord],ax
call GetEMSEGStatusWord
mov dseg:[esi.E32_StatusWord],ax
call GetTagWord
mov dseg:[esi.E32_TagWord],ax
mov ax,cs
mov dseg:[esi.E32_CodeSeg],ax
mov ax,ss
mov dseg:[esi.E32_DataSeg],ax
mov eax,EMSEG:[PrevCodeOff]
mov dseg:[esi.E32_CodeOff],eax
mov eax,EMSEG:[PrevDataOff]
mov dseg:[esi.E32_DataOff],eax
mov EMSEG:[CWmask],03FH ;Set all mask bits
mov EMSEG:[ErrMask],0
ret
;*** eFSAVE - emulate FSAVE [address]
;
; ARGUMENTS
; dseg:esi = where to store environment
;
;
; DESCRIPTION
; This routine emulates an 80387 FSAVE (store environment)
; Once the data is stored an finit is executed.
;
; REGISTERS
; destroys ALL.
EM_ENTRY eFSAVE
eFSAVE:
mov ax,[esp+4].OldStatus
mov EMSEG:[StatusWord],ax
mov eax,[esp+4].OldCodeOff
mov EMSEG:[PrevCodeOff],eax
push offset eFINIT ; After fsave we must do a finit
SaveState: ; Enter here for debugger save state
call SaveEnv
add esi,size Env80x87_32 ;Skip over environment
mov ebp,NumLev ;Save entire stack
mov edi,EMSEG:[CURstk]
FsaveStoreLoop:
mov eax,EMSEG:[edi].ExpSgn
call StoreTempReal ;in emstore.asm
add esi,10
mov edi,EMSEG:[CURstk]
NextStackElem edi,FSave
mov EMSEG:[CURstk],edi
dec ebp
jnz FsaveStoreLoop
ret
WrapFSave: ; tied to NextStackElem above
mov edi, BEGstk
mov EMSEG:[CURstk],edi
dec ebp
jnz FsaveStoreLoop
ret
;*** eFRSTOR - emulate FRSTOR [address]
;
; ARGUMENTS
; dseg:esi = where to get the environment
;
; DESCRIPTION
; This routine emulates an 80387 FRSTOR (restore state)
NextStackWrap edi,Frstor
EM_ENTRY eFRSTOR
eFRSTOR:
;First we set up the status word so that [CURstk] is initialized.
;The floating-point registers are stored in logical ST(0) - ST(7) order,
;not physical register order. We don't do a full load of the environment
;because we're not ready to use the tag word yet.
and [esp+4].[OldLongStatus], NOT(LongSavedFlags) ;clear saved codes, errs
mov ax, dseg:[esi.E32_StatusWord]
call SetEmStatusWord ;Initialize [CURstk]
add esi,size Env80x87_32 ;Skip over environment
;Load of temp real has one difference from real math chip: it is an invalid
;operation to load an unsupported format. By ensuring the exception is
;masked, we will convert unsupported format to Indefinite. Note that the
;mask and [CURerr] will be completely restored by the FLDENV at the end.
mov EMSEG:[CWmask],3FH ;Mask off invalid operation exception
mov edi,EMSEG:[CURstk]
mov ebp,NumLev
FrstorLoadLoop:
push esi
call LoadTempReal ;In emload.asm
pop esi
add esi,10 ;Point to next temp real
NextStackElem edi,Frstor
dec ebp
jnz FrstorLoadLoop
sub esi,NumLev*10+size Env80x87_32 ;Point to start of env.
jmp eFLDENV ;Fall into eFLDENV
;*** eFLDENV - emulate FLDENV [address]
;
; ARGUMENTS
; dseg:si = where to store environment
;
; This routine emulates an 80387 FLDENV (load environment)
EM_ENTRY eFLDENV
eFLDENV:
and [esp+4].[OldLongStatus], NOT(LongSavedFlags) ;clear saved codes, errs
mov ax, dseg:[esi.E32_StatusWord]
call SetEmStatusWord ; set up status word
mov ax, dseg:[esi.E32_ControlWord]
call SetControlWord
mov ax, dseg:[esi.E32_TagWord]
call UseTagWord
mov eax, dseg:[esi.E32_CodeOff]
mov EMSEG:[PrevCodeOff], eax
mov eax, dseg:[esi.E32_DataOff]
mov EMSEG:[PrevDataOff], eax
ret
;*** GetTagWord - figures out what the tag word is from the numeric stack
; and returns the value of the tag word in ax.
;
GetTagWord:
push esi
xor eax, eax
mov ecx, NumLev ; get tags for regs. 0, 7 - 1
mov esi,INITstk
GetTagLoop:
mov bh, EMSEG:[esi.bTag] ; The top 2 bits of Tag are the X87 tag bits.
shld ax, bx, 2
sub esi, Reg87Len
loop GetTagLoop
rol ax, 2 ; This moves Tag(0) into the low 2 bits
pop esi
ret
;*** UseTagWord - Set up tags using tag word from environment
;
; ARGUMENTS
; ax - should contain the tag word
;
; Destroys ax,bx,cx,dx,di
UseTagWord:
ror ax, 2 ; mov Tag(0) into top bits of ax
mov edi,INITstk
mov ecx, NumLev
UseTagLoop:
mov dl,bTAG_EMPTY
cmp ah, 0c0h ;Is register to be tagged Empty?
jae SetTag ;Yes, go mark it
mov dl,EMSEG:[edi].bTag ;Get current tag
cmp dl,bTAG_EMPTY ;Is register currently Empty?
je SetTagNotEmpty ;If so, go figure out tag for it
SetTag:
mov EMSEG:[edi].bTag,dl
UseTagLoopCheck:
sub edi, Reg87Len
shl eax, 2
loop UseTagLoop
ret
SetTagEmpty:
mov EMSEG:[edi.bTag], bTAG_EMPTY
jmp UseTagLoopCheck
SetTagNotEmpty:
;Register is currently tagged empty, but new tag word says it is not empty.
;Figure out a new tag for it. The rules are:
;
;1. Everything is either normalized or zero--unnormalized formats cannot
;get in. So if the high half mantissa is zero, the number is zero.
;
;2. Although the exponent bias is different, NANs and Infinities are in
;standard IEEE format - exponent is TexpMax, mantissa indicates NAN vs.
;infinity (mantissa for infinity is 800..000H).
;
;3. Denormals have an exponent less than TexpMin.
;
;4. If the low half of the mantissa is zero, it is tagged bTAG_SNGL
;
;5. Everything else is bTAG_VALID
mov ebx,EMSEG:[edi].lManHi
mov dl,bTAG_ZERO ;Try zero first
or ebx,ebx ;Is mantissa zero?
jz SetTag
mov edx,EMSEG:[edi].ExpSgn
mov dl,bTAG_DEN
cmp edx,TexpMin shl 16 ;Is it denormal?
jl SetTag
cmp EMSEG:[edi].lManLo,0 ;Is low half zero?
.erre bTAG_VALID eq 1
.erre bTAG_SNGL eq 0
setnz dl ;if low half==0 then dl=0 else dl=1
cmp edx,TexpMax shl 16 ;Is it NAN or Infinity?
jl SetTag ;If not, it's valid
.erre (bTAG_VALID - bTAG_SNGL) shl TAG_SHIFT eq (bTAG_NAN - bTAG_INF)
shl dl,TAG_SHIFT
add dl,bTAG_INF - bTAG_SNGL
;If the low bits were zero we have just changed bTAG_SNGL to bTAG_INF
;If the low bits weren't zero, we changed bTAG_VALID to bTAG_NAN
;See if infinity is really possible: is high half 80..00H?
cmp ebx,1 shl 31 ;Is it infinity?
jz SetTag ;Store tag for infinity or NAN
mov dl,bTAG_NAN
jmp SetTag
;*** GetStatusWord -
;
; User status word returned in ax.
; Destroys ebx only.
GetStatusWord:
mov eax, EMSEG:[CURstk]
sub eax, BEGstk
mov bl,Reg87Len
div bl
inc eax ; adjust for emulator's stack layout
and eax, 7 ; eax is now the stack number
shl ax, 11
or ax,[esp+8].OldStatus ; or in the rest of the status word.
ret
;*** GetEMSEGStatusWord -
;
; User status word returned in ax.
; Destroys ebx only.
; Uses status word in per-thread data area, otherwise
; identical to GetStatusWord
EM_ENTRY eGetStatusWord
GetEMSEGStatusWord:
mov eax, EMSEG:[CURstk]
sub eax, BEGstk
mov bl,Reg87Len
div bl
inc eax ; adjust for emulator's stack layout
and eax, 7 ; eax is now the stack number
shl ax, 11
or ax, EMSEG:[StatusWord] ; or in the rest of the status word.
ret
;*** SetEmStatusWord -
;
; Given user status word in ax, set into emulator.
; Destroys ebx only.
SetEmStatusWord:
and ax,7F7FH
mov bx,ax
and bx,3FH ; set up CURerr in case user
mov EMSEG:[CURerr],bl ; wants to force an exception
mov ebx, eax
and ebx, not (7 shl 11) ; remove stack field.
mov EMSEG:[StatusWord], bx
sub ah, 8 ; adjust for emulator's stack layout
and ah, 7 shl 3
mov al, ah
shr ah, 1
add al, ah ; stack field * 3 * 4
.erre Reg87Len eq 12
and eax, 255 ; eax is now 12*stack number
add eax, BEGstk
mov EMSEG:[CURstk], eax
ret
public _SaveEm87Context
_SaveEm87Context PROC
push ebp
mov ebp, esp
push ebx
push edi
push esi
mov esi, [ebp+8]
call SaveState
test EMSEG:[CURErr], Summary
jne RetSaveEmIdle
mov eax, Em87Busy
jmp RetSaveEm
RetSaveEmIdle:
mov eax, Em87Idle
RetSaveEm:
pop esi
pop edi
pop ebx
pop ebp
ret
_SaveEm87Context ENDP
public _RestoreEm87Context
_RestoreEm87Context PROC
push ebp
mov ebp, esp
push ebx
push edi
push esi
mov esi, [ebp+8]
call eFRSTOR
pop esi
pop edi
pop ebx
pop ebp
ret
_RestoreEm87Context ENDP