Changeset beb3926a in mainline for kernel/arch/sparc64/src/trap/trap_table.S

Timestamp:

2006-08-31T11:05:30Z (18 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

e0b241f

Parents:

ee454eb

Message:

sparc64 work.
Handle situation when there are more valid windows than NWINDOW - 2 during
the return to userspace in preemtpible_handler().

File:

• kernel/arch/sparc64/src/trap/trap_table.S (modified) (3 diffs)

kernel/arch/sparc64/src/trap/trap_table.S

@@ -492 +492 @@
         bnz 1f                                  ! ...skip restoring userspace windows
         nop
+
+        /*
+         * Spills and fills will be processed by the {spill,fill}_1_normal
+         * handlers.
+         */
+        wrpr %g0, WSTATE_OTHER(0) | WSTATE_NORMAL(1), %wstate
         
         rdpr %cwp, %g1
@@ -546 +552 @@
         wrpr %g1, 0, %cwp
         add %g4, %g2, %g2
-        mov NWINDOW - 2, %g1
+        cmp %g2, NWINDOW - 2
+        bg 2f                                   ! fix the CANRESTORE=NWINDOW-1 anomaly
+        mov NWINDOW - 2, %g1                    ! use dealy slot for both cases
         sub %g1, %g2, %g1
         
@@ -554 +562 @@
         wrpr %g2, 0, %cleanwin                  ! avoid information leak
 
-        /*
-         * Spills and fills will be processed by the {spill,fill}_1_normal
-         * handlers.
-         */
-        wrpr %g0, WSTATE_OTHER(0) | WSTATE_NORMAL(1), %wstate
-
 1:
         restore
         retry
+
+        /*
+         * We got here in order to avoid inconsistency of the window state registers.
+         * If the:
+         *
+         *      save %g6, -PREEMPTIBLE_HANDLER_STACK_FRAME_SIZE, %sp
+         *
+         * instruction trapped and spilled a register window into the userspace
+         * window buffer, we have just restored NWINDOW - 1 register windows.
+         * However, CANRESTORE can be only NWINDOW - 2 at most.
+         *
+         * The solution is to manually switch to (CWP - 1) mod NWINDOW
+         * and set the window state registers so that:
+         *
+         *      CANRESTORE      = NWINDOW - 2
+         *      CLEANWIN        = NWINDOW - 2
+         *      CANSAVE         = 0
+         *      OTHERWIN        = 0
+         *
+         * The RESTORE isntruction is therfore to be skipped.
+         */
+2:
+        wrpr %g0, 0, %otherwin
+        wrpr %g0, 0, %cansave
+        wrpr %g1, 0, %canrestore
+        wrpr %g1, 0, %cleanwin
+
+        rdpr %cwp, %g1
+        dec %g1
+        and %g1, NWINDOW - 1, %g1
+        wrpr %g1, 0, %cwp                       ! CWP--
+        
+        retry