1. Removed AsmSwitchStackAndBackingStore from BaseLib.h

[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / WriteDr5.asm

diff --git a/MdePkg/Library/BaseLib/Ia32/WriteDr5.asm b/MdePkg/Library/BaseLib/Ia32/WriteDr5.asm
index dc074244a1d5af53cbbaf4ff46533466a9103b51..e10434ef3d389662b0bde2436cc191d7e5aa39a1 100644 (file)
--- a/MdePkg/Library/BaseLib/Ia32/WriteDr5.asm
+++ b/MdePkg/Library/BaseLib/Ia32/WriteDr5.asm
@@ -22,20 +22,27 @@
 ;------------------------------------------------------------------------------\r
 \r
     .586p\r
-    .model  flat\r
+    .model  flat,C\r
     .code\r
 \r
 ;------------------------------------------------------------------------------\r
-; VOID\r
+; UINTN\r
 ; EFIAPI\r
 ; AsmWriteDr5 (\r
 ;   IN UINTN Value\r
 ;   );\r
 ;------------------------------------------------------------------------------\r
-_AsmWriteDr5    PROC\r
+AsmWriteDr5 PROC\r
     mov     eax, [esp + 4]\r
+    ;\r
+    ; DR5 is alias to DR7 only if DE (in CR4) is cleared. Otherwise, writing to\r
+    ; this register will cause a #UD exception.\r
+    ;\r
+    ; MS assembler doesn't support this instruction since no one would use it\r
+    ; under normal circustances. Here opcode is used.\r
+    ;\r
     DB      0fh, 23h, 0e8h\r
     ret\r
-_AsmWriteDr5    ENDP\r
+AsmWriteDr5 ENDP\r
 \r
     END\r