xtensa: add fixup for double exception raised in window overflow

	beqz	a2, 1f		# if at start of vector, don't restore

	addi	a0, a0, -128

	bbsi	a0, 8, 1f	# don't restore except for overflow 8 and 12

	bbsi	a0, 7, 2f

	bbsi.l	a0, 8, 1f	# don't restore except for overflow 8 and 12

	/*

	 * This fixup handler is for the extremely unlikely case where the

	 * overflow handler's reference thru a0 gets a hardware TLB refill

	 * that bumps out the (distinct, aliasing) TLB entry that mapped its

	 * prior references thru a9/a13, and where our reference now thru

	 * a9/a13 gets a 2nd-level miss exception (not hardware TLB refill).

	 */

	movi	a2, window_overflow_restore_a0_fixup

	s32i	a2, a3, EXC_TABLE_FIXUP

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	xsr	a3, excsave1

	bbsi.l	a0, 7, 2f

	/*

	 * Restore a0 as saved by _WindowOverflow8().

	 *

	 * FIXME:  we really need a fixup handler for this L32E,

	 * for the extremely unlikely case where the overflow handler's

	 * reference thru a0 gets a hardware TLB refill that bumps out

	 * the (distinct, aliasing) TLB entry that mapped its prior

	 * references thru a9, and where our reference now thru a9

	 * gets a 2nd-level miss exception (not hardware TLB refill).

	 */

	l32e	a2, a9, -16

	wsr	a2, depc	# replace the saved a0

	j	1f

	l32e	a0, a9, -16

	wsr	a0, depc	# replace the saved a0

	j	3f

2:

	/*

	 * Restore a0 as saved by _WindowOverflow12().

	 *

	 * FIXME:  we really need a fixup handler for this L32E,

	 * for the extremely unlikely case where the overflow handler's

	 * reference thru a0 gets a hardware TLB refill that bumps out

	 * the (distinct, aliasing) TLB entry that mapped its prior

	 * references thru a13, and where our reference now thru a13

	 * gets a 2nd-level miss exception (not hardware TLB refill).

	 */

	l32e	a2, a13, -16

	wsr	a2, depc	# replace the saved a0

	l32e	a0, a13, -16

	wsr	a0, depc	# replace the saved a0

3:

	xsr	a3, excsave1

	movi	a0, 0

	s32i	a0, a3, EXC_TABLE_FIXUP

	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

1:

	/*

	 * Restore WindowBase while leaving all address registers restored.

	s32i	a0, a2, PT_DEPC

_DoubleExceptionVector_handle_exception:

	addx4	a0, a0, a3

	l32i	a0, a0, EXC_TABLE_FAST_USER

	xsr	a3, excsave1

	rotw	-3

	j	1b

	.end literal_prefix

ENDPROC(_DoubleExceptionVector)

/*

 * Fixup handler for TLB miss in double exception handler for window owerflow.

 * We get here with windowbase set to the window that was being spilled and

 * a0 trashed. a0 bit 7 determines if this is a call8 (bit clear) or call12

 * (bit set) window.

 *

 * We do the following here:

 * - go to the original window retaining a0 value;

 * - set up exception stack to return back to appropriate a0 restore code

 *   (we'll need to rotate window back and there's no place to save this

 *    information, use different return address for that);

 * - handle the exception;

 * - go to the window that was being spilled;

 * - set up window_overflow_restore_a0_fixup as a fixup routine;

 * - reload a0;

 * - restore the original window;

 * - reset the default fixup routine;

 * - return to user. By the time we get to this fixup handler all information

 *   about the conditions of the original double exception that happened in

 *   the window overflow handler is lost, so we just return to userspace to

 *   retry overflow from start.

 *

 * a0: value of depc, original value in depc

 * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE

 * a3: exctable, original value in excsave1

 */

ENTRY(window_overflow_restore_a0_fixup)

	rsr	a0, ps

	extui	a0, a0, PS_OWB_SHIFT, PS_OWB_WIDTH

	rsr	a2, windowbase

	sub	a0, a2, a0

	extui	a0, a0, 0, 3

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	xsr	a3, excsave1

	_beqi	a0, 1, .Lhandle_1

	_beqi	a0, 3, .Lhandle_3

	.macro	overflow_fixup_handle_exception_pane n

	rsr	a0, depc

	rotw	-\n

	xsr	a3, excsave1

	wsr	a2, depc

	l32i	a2, a3, EXC_TABLE_KSTK

	s32i	a0, a2, PT_AREG0

	movi	a0, .Lrestore_\n

	s32i	a0, a2, PT_DEPC

	rsr	a0, exccause

	j	_DoubleExceptionVector_handle_exception

	.endm

	overflow_fixup_handle_exception_pane 2

.Lhandle_1:

	overflow_fixup_handle_exception_pane 1

.Lhandle_3:

	overflow_fixup_handle_exception_pane 3

	.macro	overflow_fixup_restore_a0_pane n

	rotw	\n

	/* Need to preserve a0 value here to be able to handle exception

	 * that may occur on a0 reload from stack. It may occur because

	 * TLB miss handler may not be atomic and pointer to page table

	 * may be lost before we get here. There are no free registers,

	 * so we need to use EXC_TABLE_DOUBLE_SAVE area.

	 */

	xsr	a3, excsave1

	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	movi	a2, window_overflow_restore_a0_fixup

	s32i	a2, a3, EXC_TABLE_FIXUP

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	xsr	a3, excsave1

	bbsi.l	a0, 7, 1f

	l32e	a0, a9, -16

	j	2f

1:

	l32e	a0, a13, -16

2:

	rotw	-\n

	.endm

.Lrestore_2:

	overflow_fixup_restore_a0_pane 2

.Lset_default_fixup:

	xsr	a3, excsave1

	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	movi	a2, 0

	s32i	a2, a3, EXC_TABLE_FIXUP

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	xsr	a3, excsave1

	rfe

.Lrestore_1:

	overflow_fixup_restore_a0_pane 1

	j	.Lset_default_fixup

.Lrestore_3:

	overflow_fixup_restore_a0_pane 3

	j	.Lset_default_fixup

ENDPROC(window_overflow_restore_a0_fixup)

	.end literal_prefix

/*

 * Debug interrupt vector

 *

		  .UserExceptionVector.literal)

  SECTION_VECTOR (_DoubleExceptionVector_literal,

		  .DoubleExceptionVector.literal,

		  DOUBLEEXC_VECTOR_VADDR - 16,

		  DOUBLEEXC_VECTOR_VADDR - 40,

		  SIZEOF(.UserExceptionVector.text),

		  .UserExceptionVector.text)

  SECTION_VECTOR (_DoubleExceptionVector_text,

		  .DoubleExceptionVector.text,

		  DOUBLEEXC_VECTOR_VADDR,

		  32,

		  40,

		  .DoubleExceptionVector.literal)

  . = (LOADADDR( .DoubleExceptionVector.text ) + SIZEOF( .DoubleExceptionVector.text ) + 3) & ~ 3;