xtensa/kernel/vectors.S

13  * Copyright (C) 2005 - 2008 Tensilica, Inc.
20  * We use a two-level table approach. The user and kernel exception vectors
21  * use a first-level dispatch table to dispatch the exception to a registered
23  * The default handler sets up a C-stack and dispatches the exception to a
24  * registerd C handler in the second-level dispatch table.
50 #include <asm/asm-offsets.h>
92  * jump to the first-level handler associated with the exception cause.
103 	addi	a2, a1, -16 - PT_KERNEL_SIZE	# adjust stack pointer
121  * Note that this vector is never invoked for level-1 interrupts, because such
124  * We decode the exception and take the appropriate action.  However, the
130  * happens when accessing user-space memory with the user's permissions
138  * EXC_TABLE_FIXUP is non-zero, this handler jumps to that address. A value of
141  * label, the kernel is in trouble. This mechanism is used to protect critical
153  *  - The original stack pointer (in a1) must not be modified. The fast
156  *  - If the fast handler manipulates the stack pointer (in a2), it has to
159  *  - The handler can use any other generic register from a3 to a15, but it
162  *  - These registers must be saved before a double exception can occur.
164  *  - If we ever implement handling signals while in double exceptions, the
170  *  - Fixup entry conditions differ from regular exceptions:
179  *  - When the kernel enters the fixup handler, it still assumes it is in a
180  *    critical section, so EXC_TABLE_FIXUP variable is set to exc_table.
181  *    The fixup handler, therefore, has to re-register itself as the fixup
184  *  - Fixup handler can share the same exception frame with the fast handler.
187  *  - Fixup handlers can jump to the default kernel and user exception
191  *    it instead of the exception address, so it can re-register itself as
194  * In case of a critical condition where the kernel cannot recover, we jump
225 	/* Note: We don't need to indicate that we enter a critical section. */
295 	addi	a3, a3, -EXCCAUSE_DTLB_MISS
303 	/* Critical! We can't handle this situation. PANIC! */
316 .Lfixup:/* Check for a fixup handler or if we were in a critical section. */
320 	/* Enter critical section. */
324 	beq	a2, a3, .Lunrecoverable_fixup	# critical section
334 	addi	a2, a2, -PT_USER_SIZE
382 	extui	a2, a0, 0, 6	# get offset into 64-byte vector handler
385 	addi	a0, a0, -128
393 	 * a9/a13 gets a 2nd-level miss exception (not hardware TLB refill).
406 	l32e	a0, a9, -16
415 	l32e	a0, a13, -16
444 	rotw	-2
464 	addi	a0, a0, -EXCCAUSE_UNALIGNED
477 	rotw	-1
482 	rotw	-3
497  * - go to the original window retaining a0 value;
498  * - set up exception stack to return back to appropriate a0 restore code
501  * - handle the exception;
502  * - go to the window that was being spilled;
503  * - set up window_overflow_restore_a0_fixup as a fixup routine;
504  * - reload a0;
505  * - restore the original window;
506  * - reset the default fixup routine;
507  * - return to user. By the time we get to this fixup handler all information
536 	rotw	-\n
572 	l32e	a0, a9, -16
575 	l32e	a0, a13, -16
577 	rotw	-\n
686  * handlers underflow-4 to underflow-12, then the overflow handlers
687  * overflow-4 to overflow-12.
703 /* 4-Register Window Overflow Vector (Handler) */
707 	s32e	a0, a5, -16
708 	s32e	a1, a5, -12
709 	s32e	a2, a5,  -8
710 	s32e	a3, a5,  -4
715 /* 4-Register Window Underflow Vector (Handler) */
719 	l32e	a0, a5, -16
720 	l32e	a1, a5, -12
721 	l32e	a2, a5,  -8
722 	l32e	a3, a5,  -4
727 /* 8-Register Window Overflow Vector (Handler) */
731 	s32e	a0, a9, -16
732 	l32e	a0, a1, -12
733 	s32e	a2, a9,  -8
734 	s32e	a1, a9, -12
735 	s32e	a3, a9,  -4
736 	s32e	a4, a0, -32
737 	s32e	a5, a0, -28
738 	s32e	a6, a0, -24
739 	s32e	a7, a0, -20
744 /* 8-Register Window Underflow Vector (Handler) */
748 	l32e	a1, a9, -12
749 	l32e	a0, a9, -16
750 	l32e	a7, a1, -12
751 	l32e	a2, a9,  -8
752 	l32e	a4, a7, -32
753 	l32e	a3, a9,  -4
754 	l32e	a5, a7, -28
755 	l32e	a6, a7, -24
756 	l32e	a7, a7, -20
761 /* 12-Register Window Overflow Vector (Handler) */
765 	s32e	a0,  a13, -16
766 	l32e	a0,  a1,  -12
767 	s32e	a1,  a13, -12
768 	s32e	a2,  a13,  -8
769 	s32e	a3,  a13,  -4
770 	s32e	a4,  a0,  -48
771 	s32e	a5,  a0,  -44
772 	s32e	a6,  a0,  -40
773 	s32e	a7,  a0,  -36
774 	s32e	a8,  a0,  -32
775 	s32e	a9,  a0,  -28
776 	s32e	a10, a0,  -24
777 	s32e	a11, a0,  -20
782 /* 12-Register Window Underflow Vector (Handler) */
786 	l32e	a1,  a13, -12
787 	l32e	a0,  a13, -16
788 	l32e	a11, a1,  -12
789 	l32e	a2,  a13,  -8
790 	l32e	a4,  a11, -48
791 	l32e	a8,  a11, -32
792 	l32e	a3,  a13,  -4
793 	l32e	a5,  a11, -44
794 	l32e	a6,  a11, -40
795 	l32e	a7,  a11, -36
796 	l32e	a9,  a11, -28
797 	l32e	a10, a11, -24
798 	l32e	a11, a11, -20