[xtensa-cvscommit] linux/arch/xtensa/kernel vectors.S,1.4,1.5 handlers.S,1.9,1.10 sys.S,1.1.1.1,1.2

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Update of /cvsroot/xtensa/linux/arch/xtensa/kernel
In directory sc8-pr-cvs1:/tmp/cvs-serv30731/arch/xtensa/kernel

Modified Files:
	vectors.S handlers.S sys.S 
Log Message:

Fixed a bug that hangs the kernel.  We were improperly handling double exceptions that occurred during the handling of a window underflow exception.

Index: vectors.S
===================================================================
RCS file: /cvsroot/xtensa/linux/arch/xtensa/kernel/vectors.S,v
retrieving revision 1.4
retrieving revision 1.5
diff -C2 -d -r1.4 -r1.5
*** vectors.S	29 Jan 2003 06:18:00 -0000	1.4
--- vectors.S	30 Jan 2003 23:55:26 -0000	1.5
***************
*** 131,135 ****
  	_bltu	a0, a2, 1f
  	addi	a2, a2, XSHAL_WINDOW_VECTORS_SIZE
! 	_bltu	a0, a2, find_handler

  	/* Occasionally, the kernel expects a double exception to
--- 131,135 ----
  	_bltu	a0, a2, 1f
  	addi	a2, a2, XSHAL_WINDOW_VECTORS_SIZE
! 	_bltu	a0, a2, .Ldouble_in_wvec

  	/* Occasionally, the kernel expects a double exception to
***************
*** 147,151 ****
  	 * fixup routine.  If the variable TABLE_FIXUP is zero, the
  	 * kernel is in trouble.  If the variable is nonzero, this
! 	 * handler jumps to the instruction that the variable
  	 * addresses.
  	 *
--- 147,151 ----
  	 * fixup routine.  If the variable TABLE_FIXUP is zero, the
  	 * kernel is in trouble.  If the variable is nonzero, this
! 	 * handler jumps to the instruction that the TABLE_FIXUP
  	 * addresses.
  	 *
***************
*** 165,208 ****
  	 */

! 1:	l32i	a2, a1, TABLE_FIXUP
! 	beqz	a2, CriticalExc
! 	jx	a2

! 	/* The double exception did occur within a window exception
! 	 * handler.  All entry conditions below say "All other
! 	 * registers contain their original values."  These values
! 	 * usually are not user values, but kernel values, since
! 	 * the double exception will return to the kernel handler,
! 	 * not the user code.
  	 *
  	 * find_handler has some entry conditions, but these are met
! 	 * by the Double Exception Vector code, not the routines that
! 	 * register find_handler with TABLE_FIXUP.  They are:
  	 *
  	 *	a0 is undefined
  	 *	a1 = &exception_handlers[0]
  	 *	EXCSAVE_1 contains original a1
! 	 *	a2 is undefined
  	 *	[ EXCSAVE_1 + TABLE_SAVEA2 ] contains original a2
  	 *	All other registers contain their original values.
  	 *
  	 * We setup the following conditions for the registered
! 	 * handler:
  	 *
  	 *	a0 is undefined
  	 *	DEPC contains original a0
  	 *	DEPC saved in [ EXCSAVE_1 + TABLE_SAVEA0 ]
  	 *	All other registers contain their original values.
  	 */

  	.global	find_handler
  find_handler:
  	rsr	a0, EXCCAUSE
- 	l32i	a2, a1, TABLE_SAVEA2	// restore a2 (in slot)
  	addx4	a0, a0, a1
  	l32i	a0, a0, TABLE_OFS + EXC_CODE_DOUBLE*4	// load handler addr
  	xsr	a1, EXCSAVE_1		// restore a1
  	jx	a0			// jump to handler
- 

--- 165,218 ----
  	 */

! 1:	l32i	a0, a1, TABLE_FIXUP
! 	beqz	a0, CriticalExc
! 	movi	a2, ( 0 << EXCTYPE_DOUBLE_WIND_SHIFT )
! 	jx	a0

! 
! 	/* Control branches to .Ldouble_in_wvec when the double
! 	 * exception occurred within a window exception.  This entry
! 	 * point sets a2 to indicate this condition for handle_double,
! 	 * then falls through to find_handler.  Exceptions that occur
! 	 * outside a window exception will fall into the TABLE_FIXUP
! 	 * code, which always clears a2 for the handler.
! 	 *
! 	 * The entry conditions below say "All other registers contain
! 	 * their original values."  These values usually are not user
! 	 * values, but kernel values, since the double exception will
! 	 * return to some kernel handler, not the user code.
  	 *
  	 * find_handler has some entry conditions, but these are met
! 	 * by the Double Exception Vector code above, not the routines
! 	 * that register handlers with TABLE_FIXUP.  They are:
  	 *
  	 *	a0 is undefined
  	 *	a1 = &exception_handlers[0]
  	 *	EXCSAVE_1 contains original a1
! 	 *	a2 sets the EXCTYPE_DOUBLE_WIND_SHIFT bit if in window vector, 0 otherwise.
  	 *	[ EXCSAVE_1 + TABLE_SAVEA2 ] contains original a2
  	 *	All other registers contain their original values.
  	 *
  	 * We setup the following conditions for the registered
! 	 * handler (probably handle_double):
  	 *
  	 *	a0 is undefined
+ 	 *	a2 sets the EXCTYPE_DOUBLE_WIND_SHIFT bit if in window vector, 0 otherwise.
  	 *	DEPC contains original a0
  	 *	DEPC saved in [ EXCSAVE_1 + TABLE_SAVEA0 ]
+ 	 *	[ EXCSAVE_1 + TABLE_SAVEA2 ] contains original a2
  	 *	All other registers contain their original values.
  	 */

  	.global	find_handler
+ 
+ .Ldouble_in_wvec:
+ 	movi	a2, ( 1 << EXCTYPE_DOUBLE_WIND_SHIFT )
  find_handler:
  	rsr	a0, EXCCAUSE
  	addx4	a0, a0, a1
  	l32i	a0, a0, TABLE_OFS + EXC_CODE_DOUBLE*4	// load handler addr
  	xsr	a1, EXCSAVE_1		// restore a1
  	jx	a0			// jump to handler

Index: handlers.S
===================================================================
RCS file: /cvsroot/xtensa/linux/arch/xtensa/kernel/handlers.S,v
retrieving revision 1.9
retrieving revision 1.10
diff -C2 -d -r1.9 -r1.10
*** handlers.S	29 Jan 2003 06:17:59 -0000	1.9
--- handlers.S	30 Jan 2003 23:55:26 -0000	1.10
***************
*** 128,133 ****
--- 128,135 ----
   *
   *	a0 is undefined (okay, it contains handle_double)
+  *	a2 sets the EXCTYPE_DOUBLE_WIND_SHIFT bit if in window vector, 0 otherwise.
   *	DEPC contains original a0
   *	DEPC saved in [ EXCSAVE_1 + TABLE_SAVEA0 ]
+  *	[ EXCSAVE_1 + TABLE_SAVEA2 ] contains original a2
   *	All other register contain their original values.
   */
***************
*** 145,149 ****
  	bbci.l	a0, PS_PROGSTACK_SHIFT, doubleram_kernel	// stacked (kernel) mode?

! 	/* Program (user) mode, so switch stack pointers.  Get pointer
  	 * to kernel stack, pre-decremented by 16+PT_SIZE */

--- 147,151 ----
  	bbci.l	a0, PS_PROGSTACK_SHIFT, doubleram_kernel	// stacked (kernel) mode?

! 	/* User mode, so switch stack pointers.  Get pointer
  	 * to kernel stack, pre-decremented by 16+PT_SIZE */

***************
*** 166,180 ****
  	mov	a1, a0			// set sp to system stack

  	/*  Now unshuffle the way state was saved in the vector, and save
! 	 *  state that is specific to exceptions in window handlers.
! 	 */

  	xsr	a1, EXCSAVE_1		// a1 <-- ptr to handler table, save a1
! 	/* slot */
  	l32i	a0, a1, TABLE_SAVEA0	// get saved DEPC
  	xsr	a1, EXCSAVE_1		// restore a1, save table ptr
  	/* slot */
  	s32i	a0, a1, PT_DEPC		// store DEPC in exc stack frame

  #if 0
  	/* XTFIXME: For now, don't restart anything.  Just get it to
--- 168,253 ----
  	mov	a1, a0			// set sp to system stack

+ 	/* Branch if the double exception happened during a window
+ 	 * exception handler. */
+ 
+ 	bnez	a2, double_convert
+ 
+ double_noconversion:
+ 	/* Compute the exception type.  PS (in a0) indicates user vs
+ 	 * kernel.  MISC_REG_0 indicates whether the double exception
+ 	 * occurred in the window vector. */
+ 
+ 	movi	a0, EXCTYPE_DOUBLE_KERNEL
+ 	bbci.l	a0, PS_PROGSTACK_SHIFT, 1f	// branch if kernel mode
+ 	movi	a0, EXCTYPE_DOUBLE_USER
+ 1:	or	a2, a2, a0			// add in window vector bit
+ 						//  (may be zero)
+ 
  	/*  Now unshuffle the way state was saved in the vector, and save
! 	 *  state that is specific to exceptions in window handlers. */

  	xsr	a1, EXCSAVE_1		// a1 <-- ptr to handler table, save a1
! 	wsr	a2, MISC_REG_0		// save off exctype
  	l32i	a0, a1, TABLE_SAVEA0	// get saved DEPC
+ 	l32i	a2, a1, TABLE_SAVEA2	// get original a2
  	xsr	a1, EXCSAVE_1		// restore a1, save table ptr
  	/* slot */
  	s32i	a0, a1, PT_DEPC		// store DEPC in exc stack frame

+ 	/* Load up the exctype and jump to common exception handling. */
+ 
+ 	rsr	a0, MISC_REG_0
+ 	j	_excCommonException
+ 
+ 
+ double_convert:
+ 	/* We need DEPC to distinguish between overflows and
+ 	 * underflows.  It is currently saved in TABLE_SAVEA0.
+ 	 * Did the double exception occur in a window overflow or
+ 	 * underflow?  We restart underflows, but not overflows. */
+ 
+ 	xsr	a1, EXCSAVE_1		// a1 <-- exception_handlers
+ 	l32i	a0, a1, TABLE_SAVEA0	// load DEPC
+ 	xsr	a1, EXCSAVE_1		// a1 <-- kernel stack pointer
+ 	bbci.l	a0, 6, double_noconversion // branch if window overflow
+ 
+ 	/*  Restart window underflow exception.
+ 	 *  Just set WINDOWBASE to PS.OWB.  This is feasible for underflows
+ 	 *  because registers are available to do this. */
+ 
+ 	wsr	a1, DEPC		// save kernel stack ptr across window change
+ 					// (out of scope a0 is clobbered)
+ 	rsr	a0, PS			// get PS
+ 	l32i	a1, a1, PT_AREG1	// restore a1 of this window
+     					// (not needed but might help debugging)
+ 	extui	a0, a0, XCHAL_PS_OWB_SHIFT, XCHAL_PS_OWB_BITS
+ 	wsr	a0, WINDOWBASE		// WB <-- PS.OWB
+ 	rsync
+ 	xsr	a0, DEPC		// save a0 in DEPC, restore kernel stack ptr
+ 	/* slot */
+ 	s32i	a1, a0, PT_AREG1	// save a1 of active window
+ 	mov	a1, a0			// set kernel stack ptr
+ 
+ 	/* We ignore the out-of-scope value of a2 still in TABLE_SAVEA2. */
+ 
+ 	/* Use PS to mark proper exception type.  Note that since we
+ 	 * are restarting the window underflow, we want to change the
+ 	 * exception type from double to user or kernel.  This change
+ 	 * will trigger the use of "rfe" instead of "rfde" when
+ 	 * exception processing is complete.
+ 	 */
+ 
+ 	rsr	a0, PS			// get PS
+ 	/* slot */
+ 	bbci.l	a0, PS_PROGSTACK_SHIFT, 1f	// stacked (kernel) mode?
+ 
+ 	movi	a0, EXCTYPE_USER	// mark exception as "double-window-user"
+ 	j	_excCommonException	// jump to common exception handling
+ 
+ 1:	movi	a0, EXCTYPE_KERNEL	// mark exception as "double-window-kernel"
+ 	j	_excCommonException	// jump to common exception handling
+ 
+ 
+ 
  #if 0
  	/* XTFIXME: For now, don't restart anything.  Just get it to
***************
*** 237,256 ****

- #ifndef RESTART_OVERFLOW
- restart_overflow:
- #endif
- 
- 	/*  Use PS to mark proper exception type:  */
- 	rsr	a0, PS			// get PS
- 	/* slot */
- 	bbci.l	a0, PS_PROGSTACK_SHIFT, 1f	// stacked (kernel) mode?
- 
- 	movi	a0, EXCTYPE_DOUBLE_WIND_USER	// mark exception as "double-window-user"
- 	j	_excCommonException		// jump to common exception handling
- 
- 1:	movi	a0, EXCTYPE_DOUBLE_WIND_KERNEL	// mark exception as "double-window-kernel"
- 	j	_excCommonException		// jump to common exception handling
- 
- 
  #ifdef RESTART_OVERFLOW
  restart_overflow:
--- 310,313 ----
***************
*** 582,588 ****
  	 * interrupts which we don't currently do], for user
  	 * exceptions we might have more leeway but we leave it as is
! 	 * for now.) */
! 
! 	/* Here, a0 still contains exception type.  Type values are
  	 * such that bit EXCTYPE_QUICKSPILL_SHIFT of each value is
  	 * clear if all live register windows must be spilled for that
--- 639,645 ----
  	 * interrupts which we don't currently do], for user
  	 * exceptions we might have more leeway but we leave it as is
! 	 * for now.)
! 	 *
! 	 * Here, a0 still contains exception type.  Type values are
  	 * such that bit EXCTYPE_QUICKSPILL_SHIFT of each value is
  	 * clear if all live register windows must be spilled for that
***************
*** 610,617 ****
  	 *	PS.EXCM = 1
  	 *	a0 thru a3 saved already
! 	 *	a4 thru a15 valid
! 	 *	a0,a2,a3 undefined
  	 *	a1 = current PS pointing to exception frame
! 	 *	WINDOWSTART[WINDOWBASE] = 1 ???
  	 *	LCOUNT = 0
  	 *
--- 667,675 ----
  	 *	PS.EXCM = 1
  	 *	a0 thru a3 saved already
! 	 *	a0,a2 undefined
  	 *	a1 = current PS pointing to exception frame
! 	 *	a3 has WINDOWSTART
! 	 *	a4 thru a15 valid
! 	 *	WINDOWSTART[WINDOWBASE] = 1
  	 *	LCOUNT = 0
  	 *
***************
*** 807,810 ****
--- 865,869 ----
  	// a3 = 0 .. WSBITS-4 (number of panes to save, other than current window's 4)
  ut_save:
+ 
  	s32i	a3, a1, PT_WMASK	// save this number, rather than recompute it on restore

***************
*** 818,822 ****
  #if 1
  	j	simple_save_end
- 
  simple_save:
  	rotw	-1		// a2,a3 become a6,a7
--- 877,880 ----
***************
*** 1552,1563 ****
  excdone:

! 	/* Return from user/kernel exception, or double exception? 
! 	 * Branch if double exception occurred (uncommon case).
  	 */

! #if (EXCTYPE_DOUBLE_WIND_USER > EXCTYPE_DOUBLE_WIND_KERNEL)
! #error Bad assumption by next instruction.
! #endif
! 	bgeui	a0, EXCTYPE_DOUBLE_WIND_USER, 4f

  	l32i	a0, a1, PT_AREG0	// restore a0
--- 1610,1620 ----
  excdone:

! 	/* Return from the exception.  Two cases:
! 	 *
! 	 * 1.  Return from double exception
! 	 * 2.  Return from user or kernel exception (common case)
  	 */

! 	bbsi.l	a0, EXCTYPE_DOUBLE_SHIFT, 4f

  	l32i	a0, a1, PT_AREG0	// restore a0
***************
*** 1565,1582 ****
  	rfe

- 
- 	/* Control comes here only when returning from double
- 	 * exceptions that happened in a window-overflow handler.
- 	 * (Double exceptions occuring in window-underflow handlers
- 	 * are converted to EXCTYPE_{USER,KERNEL} exceptions.)
- 	 * Restarting window overflows is not yet implemented, so we
- 	 * must "return from double exception" (rfde) into the
- 	 * window-overflow handler.
- 	 */
- 
  4:	l32i	a0, a1, PT_AREG0	// restore a0
  	l32i	a1, a1, PT_AREG1	// restore a1
  	rfde
- 

--- 1622,1628 ----

Index: sys.S
===================================================================
RCS file: /cvsroot/xtensa/linux/arch/xtensa/kernel/sys.S,v
retrieving revision 1.1.1.1
retrieving revision 1.2
diff -C2 -d -r1.1.1.1 -r1.2
*** sys.S	28 Aug 2002 16:10:14 -0000	1.1.1.1
--- sys.S	30 Jan 2003 23:55:27 -0000	1.2
***************
*** 814,818 ****
  	s32i	a0, a1, PT_DEPC		// store DEPC in ESF

! 	movi	a0, EXCTYPE_DOUBLE_WIND_KERNEL
  	j	_excCommonException

--- 814,818 ----
  	s32i	a0, a1, PT_DEPC		// store DEPC in ESF

! 	movi	a0, EXCTYPE_DOUBLE_KERNEL
  	j	_excCommonException