xnu-1228.tar.gz

[apple/xnu.git] / osfmk / ppc / commpage / bzero_128.s

diff --git a/osfmk/ppc/commpage/bzero_128.s b/osfmk/ppc/commpage/bzero_128.s
index f97db603de97000f697d672ef5118f800a186694..f22198478d9f5739c1be499cb24ccea87d2705d8 100644 (file)
--- a/osfmk/ppc/commpage/bzero_128.s
+++ b/osfmk/ppc/commpage/bzero_128.s
@@ -1,16 +1,19 @@
 /*
  * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
- * 
- * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ * 
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
  * 
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
@@ -20,10 +23,9 @@
  * Please see the License for the specific language governing rights and
  * limitations under the License.
  * 
- * @APPLE_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 
-#define        ASSEMBLER
 #include <sys/appleapiopts.h>
 #include <ppc/asm.h>
 #include <machine/cpu_capabilities.h>
@@ -31,12 +33,26 @@
 
         .text
         .align 2
-        .globl EXT(bzero_128)
-        
+/*
+ * WARNING: this code is written for 32-bit mode, and ported by the kernel if necessary
+ * to 64-bit mode for use in the 64-bit commpage.  This "port" consists of the following
+ * simple transformations:
+ *      - all word compares are changed to doubleword
+ *      - all "srwi[.]" opcodes are changed to "srdi[.]"                      
+ * Nothing else is done.  For this to work, the following rules must be
+ * carefully followed:
+ *      - do not use carry or overflow
+ *      - only use record mode if you are sure the results are mode-invariant
+ *        for example, all "andi." and almost all "rlwinm." are fine
+ *      - do not use "slwi", "slw", or "srw"
+ * An imaginative programmer could break the porting model in other ways, but the above
+ * are the most likely problem areas.  It is perhaps surprising how well in practice
+ * this simple method works.
+ */        
 
-// *********************
-// * B Z E R O _ 1 2 8 *
-// *********************
+// **********************
+// * B Z E R O _ 1 2 8  *
+// **********************
 //
 // For 64-bit processors with a 128-byte cache line.
 //
@@ -45,7 +61,7 @@
 //             r3 = original ptr, not changed since memset returns it
 //             r4 = count of bytes to set
 //             r9 = working operand ptr
-// We do not touch r2 and r10-r12, which some callers depend on.
+// WARNING: We do not touch r2 and r10-r12, which some callers depend on.
 
         .align 5
 bzero_128:                                             // void bzero(void *b, size_t len);
@@ -153,4 +169,5 @@ Ltail:
         stb            r0,0(r9)
         blr
 
-        COMMPAGE_DESCRIPTOR(bzero_128,_COMM_PAGE_BZERO,kCache128+k64Bit,0,kCommPageMTCRF)
+       COMMPAGE_DESCRIPTOR(bzero_128,_COMM_PAGE_BZERO,kCache128+k64Bit,0, \
+                               kCommPageMTCRF+kCommPageBoth+kPort32to64)