[src/trunk]: src/sys/arch/sparc64/sparc64 Handle improperly aligned stack poi...

[eeh <eeh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9801168147c4
branches:  trunk
changeset: 532347:9801168147c4
user:      eeh <eeh%NetBSD.org@localhost>
date:      Wed Jun 05 18:11:18 2002 +0000

description:
Handle improperly aligned stack pointers more cleanly.

diffstat:

 sys/arch/sparc64/sparc64/locore.s |  79 ++++++++++++++++++++++++++++++--------
 1 files changed, 62 insertions(+), 17 deletions(-)

diffs (107 lines):

diff -r 0e6c7bb59d45 -r 9801168147c4 sys/arch/sparc64/sparc64/locore.s
--- a/sys/arch/sparc64/sparc64/locore.s Wed Jun 05 17:58:33 2002 +0000
+++ b/sys/arch/sparc64/sparc64/locore.s Wed Jun 05 18:11:18 2002 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.s,v 1.155 2002/06/04 15:04:08 eeh Exp $ */
+/*     $NetBSD: locore.s,v 1.156 2002/06/05 18:11:18 eeh Exp $ */
 
 /*
  * Copyright (c) 1996-2002 Eduardo Horvath
@@ -3422,9 +3422,17 @@
 /*
  * We're here because we took an alignment fault in NUCLEUS context.
  * This could be a kernel bug or it could be due to saving a user
- * window to an invalid stack pointer.  If the latter is the case,
- * we should emulate the save by storing all the user register windows 
- * to the PCB and returning.
+ * window to an invalid stack pointer.  
+ * 
+ * If the latter is the case, we could try to emulate unaligned accesses, 
+ * but we really don't know where to store the registers since we can't 
+ * determine if there's a stack bias.  Or we could store all the regs 
+ * into the PCB and punt, until the user program uses up all the CPU's
+ * register windows and we run out of places to store them.  So for
+ * simplicity we'll just blow them away and enter the trap code which
+ * will generate a bus error.  Debugging the problem will be a bit
+ * complicated since lots of register windows will be lost, but what
+ * can we do?
  */
 checkalign:
        rdpr    %tl, %g2
@@ -3448,8 +3456,8 @@
        !!
        !! Double data fault -- bad stack?
        !!
-       wrpr    %g2, %tl        ! Restore trap level.
-       sir                     ! Just issue a reset and don't try to recover.
+       wrpr    %g2, %tl                ! Restore trap level.
+       sir                             ! Just issue a reset and don't try to recover.
        mov     %fp, %l6                ! Save the frame pointer
        set     EINTSTACK+USPACE+CC64FSZ-STKB, %fp ! Set the frame pointer to the middle of the idle stack
        add     %fp, -CC64FSZ, %sp      ! Create a stackframe
@@ -3459,17 +3467,54 @@
        ba      slowtrap                !  all our register windows.
         wrpr   %g0, 0x101, %tt
 #endif
-checkalignspill:       
-       wr      %g0, ASI_DMMU, %asi                     ! We need to re-load trap info
-       ldxa    [SFSR] %asi, %g3                        ! get sync fault status register
-       stxa    %g0, [SFSR] %asi                        ! Clear out fault now
-       membar  #Sync                                   ! No real reason for this XXXX
-       /*
-        * Here we just jump to winfixspill and let it take care of
-        * saving the windows.
-        */
-       ba,pt   %icc, winfixspill       ! Continue with the winfix
-        orcc   %g0, %g0, %g0           ! Make sure we compare to zero
+checkalignspill:
+       /*
+         * %g1 -- current tl
+        * %g2 -- original tl
+        * %g4 -- tstate
+         * %g7 -- tt
+        */
+
+       and     %g4, CWP, %g5
+       wrpr    %g5, %cwp               ! Go back to the original register win
+
+       /*
+        * Remember:
+        * 
+        * %otherwin = 0
+        * %cansave = NWINDOWS - 2 - %canrestore
+        */
+
+       rdpr    %otherwin, %g6
+       rdpr    %canrestore, %g3
+       rdpr    %ver, %g5
+       sub     %g3, %g6, %g3           ! Calculate %canrestore - %g7
+       and     %g5, CWP, %g5           ! NWINDOWS-1
+       movrlz  %g3, %g0, %g3           ! Clamp at zero
+       wrpr    %g0, 0, %otherwin
+       wrpr    %g3, 0, %canrestore     ! This is the new canrestore
+       dec     %g5                     ! NWINDOWS-2
+       wrpr    %g5, 0, %cleanwin       ! Set cleanwin to max, since we're in-kernel
+       sub     %g5, %g3, %g5           ! NWINDOWS-2-%canrestore
+#ifdef xTRAPTRACE
+       wrpr    %g5, 0, %cleanwin       ! Force cleanwindow faults
+#endif
+       wrpr    %g5, 0, %cansave
+
+       wrpr    %g0, T_ALIGN, %tt       ! This was an alignment fault 
+       /*
+        * Now we need to determine if this was a userland store or not.
+        * Userland stores occur in anything other than the kernel spill
+        * handlers (trap type 09x).
+        */
+       and     %g7, 0xff0, %g5
+       cmp     %g5, 0x90
+       bz,pn   %icc, slowtrap
+        nop
+       bclr    TSTATE_PRIV, %g4
+       wrpr    %g4, 0, %tstate
+       ba,a,pt %icc, slowtrap
+        nop
        
 /*
  * slowtrap() builds a trap frame and calls trap().