xtensa/kernel/entry.S

2  * Low-level exception handling
99 /* ----------------- DEFAULT FIRST LEVEL EXCEPTION HANDLERS ----------------- */
102  * First-level exception handler for user exceptions.
105  * exception code.
118  *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
119  *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
243 2:	/* Now, jump to the common exception handler. */
253  *	 MOVSP here, as we do that when we return from the exception.
254  *	 (See comment in the kernel exception exit code)
265  *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
266  *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
330 	 * in order to keep exception stack continuous
350  * This is the common exception handler.
351  * We get here from the user exception handler or simply by falling through
352  * from the kernel exception handler.
354  * to the second-level exception handler.
403 	 * - in case of exception or level-1 interrupt it's in the PS,
460 	 * exception handler and call the exception handler.
473 	/* Jump here for exception exit */
495 	/* Specific to a user exception exit:
581 	/* Restore the state of the task and return from the exception. */
646 	/* This is the kernel exception exit.
647 	 * We avoided to do a MOVSP when we entered the exception, but we
656 	 * been spilled to the *temporary* exception stack instead of the
670 	 *        different from the time the exception occurred.)
673 	/* Test WINDOWSTART before and after the exception.
678 	_beqi	a2, 1, common_exception_exit	# Spilled before exception,jump
699 	/* Common exception exit.
701 	 * return from the exception.
750 	/* Check if it was double exception. */
771  * Debug exception handler.
783 	bbsi.l	a0, PS_EXCM_BIT, 1f	# exception mode
810 	s32i	a0, a2, PT_DEPC		# mark it as a regular exception
817 	/* Debug exception is handled as an exception, so interrupts will
818 	 * likely be enabled in the common exception handler. Disable
838 	/* Debug exception while in exception mode. This may happen when
839 	 * window overflow/underflow handler or fast exception handler hits
888 	/* Debug exception while in exception mode. Should not happen. */
895  * We get here in case of an unrecoverable exception.
917 	.ascii "Unrecoverable error in exception handler\0"
945 /* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */
961  * double exceptions. The 'movsp' instruction will only cause an exception if
962  * the next window needs to be loaded. In fact this ALLOCA exception may be
963  * replaced at some point by changing the hardware to do a underflow exception
967  * exception handler, makes it appear that we have started a window underflow
971  * active AR registers it won't cause an exception.
974  * the partial WindowUnderflow will be handled in the double exception
986  *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
987  *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1018  * This is used to fix up user PS.WOE on the exception caused
1020  * already set it goes directly to the common user exception handler.
1119  *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1120  *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1368 	/* Advance PC, restore registers and SAR, and return from exception. */
1424  * We get here if the spill routine causes an exception, e.g. tlb miss.
1426  * we entered the spill routine and jump to the user exception handler.
1448 	 * in WS, so that the exception handlers save them to the task stack.
1452 	 * the exception handler call.
1487 	 *  depc: exception address
1502 	/* Jump to the exception handler. */
1517 	wsr	a2, depc		# exception address
1529 	/* Load WB at the time the exception occurred. */
1584  *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1585  *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1590 	/* Save a1 and a3. Note: we don't expect a double exception. */
1684 	/* Return from double exception. */
1709 	/* We shouldn't be in a double exception */
1714 	/* Make sure the exception originated in the special functions */
1767 2:	/* Invalid PGD, default exception handling */
1794  *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1795  *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1855 	/* Double exception. Restore FIXUP handler and return. */