BaseUefiCpuLib: Preserve EBX register in InitializeFloatingPointUnits

The EBX register should be preserved for the IA32 C calling convention.
The use of the CPUID instruction was modifying the EBX register, so
we push and pop EBX.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9573 6f19259b-4bc3-4df7-8a09-765794883524

UefiCpuPkg/Library/BaseUefiCpuLib/Ia32/InitializeFpu.S

@@ -1,19 +1,19 @@
-#------------------------------------------------------------------------------
-#*
-#*   Copyright 2009, 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.
-#*
-#*
-#------------------------------------------------------------------------------
-
-
-
+#------------------------------------------------------------------------------
+#*
+#*   Copyright 2009, 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.
+#*
+#*
+#------------------------------------------------------------------------------
+
+
+
 #
 # Float control word initial value: 
 # all exceptions masked, double-precision, round-to-nearest
@@ -23,18 +23,21 @@ ASM_PFX(mFpuControlWord): .word     0x027F
 # Multimedia-extensions control word:
 # all exceptions masked, round-to-nearest, flush to zero for masked underflow
 #
-ASM_PFX(mMmxControlWord): .long     0x01F80
-
-#
+ASM_PFX(mMmxControlWord): .long     0x01F80
+
+#
 # Initializes floating point units for requirement of UEFI specification.
 #
 # This function initializes floating-point control word to 0x027F (all exceptions
 # masked,double-precision, round-to-nearest) and multimedia-extensions control word
 # (if supported) to 0x1F80 (all exceptions masked, round-to-nearest, flush to zero
-# for masked underflow).
-#
-ASM_GLOBAL ASM_PFX(InitializeFloatingPointUnits)
-ASM_PFX(InitializeFloatingPointUnits):
+# for masked underflow).
+#
+ASM_GLOBAL ASM_PFX(InitializeFloatingPointUnits)
+ASM_PFX(InitializeFloatingPointUnits):
+
+    pushl   %ebx
+
     #
     # Initialize floating point units
     #
@@ -49,22 +52,24 @@ ASM_PFX(InitializeFloatingPointUnits):
     cpuid
     btl     $25, %edx
     jnc     Done
-    
-    #
-    # Set OSFXSR bit 9 in CR4
-    #
-    movl    %cr4, %eax 
-    or      $200, %eax
-    movl    %eax, %cr4
-    
+    
+    #
+    # Set OSFXSR bit 9 in CR4
+    #
+    movl    %cr4, %eax 
+    or      $200, %eax
+    movl    %eax, %cr4
+    
     #
     # The processor should support SSE instruction and we can use
     # ldmxcsr instruction
     #
-    ldmxcsr ASM_PFX(mMmxControlWord)
-
-Done:
-    ret
-
-#END
-
+    ldmxcsr ASM_PFX(mMmxControlWord)
+
+Done:
+    popl    %ebx
+
+    ret
+
+#END
+

UefiCpuPkg/Library/BaseUefiCpuLib/Ia32/InitializeFpu.asm

@@ -30,15 +30,18 @@ mMmxControlWord       DD      01F80h
     .xmm
     .code
 
-;
+;
 ; Initializes floating point units for requirement of UEFI specification.
 ;
 ; This function initializes floating-point control word to 0x027F (all exceptions
 ; masked,double-precision, round-to-nearest) and multimedia-extensions control word
 ; (if supported) to 0x1F80 (all exceptions masked, round-to-nearest, flush to zero
-; for masked underflow).
+; for masked underflow).
 ;
 InitializeFloatingPointUnits PROC PUBLIC
+
+    push    ebx
+
     ;
     ; Initialize floating point units
     ;
@@ -67,6 +70,7 @@ InitializeFloatingPointUnits PROC PUBLIC
     ;
     ldmxcsr mMmxControlWord
 Done:
+    pop     ebx
 
     ret