1. Added comments to ASM files

2. Fixed a bug in 64-bit AsmDisablePaging64(), which may cause a #GP exception.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2206 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 10 insertions, 10 deletions

diff --git a/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm b/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm
index 61a53d1e3a..95e57efac1 100644
--- a/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm
+++ b/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm
@@ -36,13 +36,13 @@ EXTERN  InternalMathDivRemU64x32:PROC
 ;   );

 ;------------------------------------------------------------------------------

 InternalMathDivRemU64x64    PROC

-    mov     ecx, [esp + 16]

+    mov     ecx, [esp + 16]             ; ecx <- divisor[32..63]

     test    ecx, ecx

     jnz     _@DivRemU64x64              ; call _@DivRemU64x64 if Divisor > 2^32

     mov     ecx, [esp + 20]

     jecxz   @F

-    and     dword ptr [ecx + 4], 0

-    mov     [esp + 16], ecx

+    and     dword ptr [ecx + 4], 0      ; zero high dword of remainder

+    mov     [esp + 16], ecx             ; set up stack frame to match DivRemU64x32

 @@:

     jmp     InternalMathDivRemU64x32

 InternalMathDivRemU64x64    ENDP

@@ -61,11 +61,11 @@ _@DivRemU64x64  PROC    USES    ebx esi edi
     jnz     @B

     div     ebx

     mov     ebx, eax                    ; ebx <- quotient

-    mov     ecx, [esp + 28]

-    mul     dword ptr [esp + 24]

-    imul    ecx, ebx

-    add     edx, ecx

-    mov     ecx, dword ptr [esp + 32]

+    mov     ecx, [esp + 28]             ; ecx <- high dword of divisor

+    mul     dword ptr [esp + 24]        ; edx:eax <- quotient * divisor[0..31]

+    imul    ecx, ebx                    ; ecx <- quotient * divisor[32..63]

+    add     edx, ecx                    ; edx <- (quotient * divisor)[32..63]

+    mov     ecx, dword ptr [esp + 32]   ; ecx <- addr for Remainder

     jc      @TooLarge                   ; product > 2^64

     cmp     edi, edx                    ; compare high 32 bits

     ja      @Correct

@@ -76,7 +76,7 @@ _@DivRemU64x64  PROC    USES    ebx esi edi
     dec     ebx                         ; adjust quotient by -1

     jecxz   @Return                     ; return if Remainder == NULL

     sub     eax, dword ptr [esp + 24]

-    sbb     edx, dword ptr [esp + 28]

+    sbb     edx, dword ptr [esp + 28]   ; edx:eax <- (quotient - 1) * divisor

 @Correct:

     jecxz   @Return

     sub     esi, eax

@@ -85,7 +85,7 @@ _@DivRemU64x64  PROC    USES    ebx esi edi
     mov     [ecx + 4], edi

 @Return:

     mov     eax, ebx                    ; eax <- quotient

-    xor     edx, edx

+    xor     edx, edx                    ; quotient is 32 bits long

     ret

 _@DivRemU64x64  ENDP