xnu-792.10.96.tar.gz

[apple/xnu.git] / osfmk / ppc / commpage / bcopy_970.s

diff --git a/osfmk/ppc/commpage/bcopy_970.s b/osfmk/ppc/commpage/bcopy_970.s
index 6294f16d7314fc6e5247c186f13cc5065d40de9a..8417fde741851df4d48a44bf579e89557e88d959 100644 (file)
--- a/osfmk/ppc/commpage/bcopy_970.s
+++ b/osfmk/ppc/commpage/bcopy_970.s
@@ -25,7 +25,6 @@
  *
  * Version of 6/11/2003, tuned for the IBM 970.
  *
- *
  * Register usage.  Note the rather delicate way we assign multiple uses
  * to the same register.  Beware.
  *   r0  = temp (NB: cannot use r0 for any constant such as "c16")
@@ -74,8 +73,22 @@
 #include <machine/commpage.h>
 
         .text
-        .globl EXT(bcopy_970)
-
+/*
+ * 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.
+ */
 
 #define        kShort          64
 #define        kVeryLong       (128*1024)
@@ -347,7 +360,7 @@ LFwdLongVectors:
         lis            w3,kVeryLong>>16        // cutoff for very-long-operand special case path
         cmplw  cr1,rc,w3                       // very long operand?
         rlwinm w3,rc,0,28,31           // move last 0-15 byte count to w3
-        bgea-- cr1,_COMM_PAGE_BIGCOPY  // handle big copies separately
+        bge--  cr1,LBigCopy        // handle big copies separately
         mtctr  r0                                      // set up loop count
         cmpwi  cr6,w3,0                        // set cr6 on leftover byte count
         oris   w4,rv,0xFFF8            // we use v0-v12
@@ -586,4 +599,23 @@ LReverseVecUnal:
         bne            cr6,LShortReverse16     // handle last 0-15 bytes iff any
         blr
 
-        COMMPAGE_DESCRIPTOR(bcopy_970,_COMM_PAGE_BCOPY,k64Bit+kHasAltivec,0,kCommPageMTCRF)
+        
+// Very Big Copy Path.  Save our return address in the stack for help decoding backtraces.
+// The conditions bigcopy expects are:
+//  r0 = return address (also stored in caller's SF)
+//     r4 = source ptr
+//     r5 = length (at least several pages)
+// r12 = dest ptr
+
+LBigCopy:
+               lis             r2,0x4000                       // r2 <- 0x40000000
+        mflr    r0                  // get our return address
+               add.    r2,r2,r2                        // set cr0_lt if running in 32-bit mode
+        stw     r0,8(r1)            // save return, assuming 32-bit mode ("crsave" if 64-bit mode)
+               blta    _COMM_PAGE_BIGCOPY  // 32-bit mode, join big operand copy
+               std             r0,16(r1)                       // save return in correct spot for 64-bit mode
+        ba      _COMM_PAGE_BIGCOPY  // then join big operand code
+        
+
+       COMMPAGE_DESCRIPTOR(bcopy_970,_COMM_PAGE_BCOPY,k64Bit+kHasAltivec,0, \
+                               kCommPageMTCRF+kCommPageBoth+kPort32to64)