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Commit e1088430 authored by Chris Zankel's avatar Chris Zankel
Browse files

[XTENSA] Fix register corruption for certain processor configurations 



For processor configurations that have optional registers
(compiler-used but non-coprocessor), user space registers
might get corrupted when there are only 4 registers in
the current window-frame, ie. register a4 belongs to the
oldest frame in the register file.

Signed-off-by: default avatarChris Zankel <chris@zankel.net>
parent 9f8fcf38

arch/xtensa/kernel/entry.S

+15 −29
Original line number Diff line number Diff line
@@ -395,55 +395,49 @@ common_exception_return: 
	/* Jump if we are returning from kernel exceptions. */



1:	l32i	a3, a1, PT_PS

	_bbsi.l	a3, PS_UM_BIT, 2f

	j	kernel_exception_exit

	_bbci.l	a3, PS_UM_BIT, 4f



	/* Specific to a user exception exit:

	 * We need to check some flags for signal handling and rescheduling,

	 * and have to restore WB and WS, extra states, and all registers

	 * in the register file that were in use in the user task.

	 */



2:	wsr	a3, PS		/* disable interrupts */



	/* Check for signals (keep interrupts disabled while we read TI_FLAGS)

	 * Note: PS.INTLEVEL = 0, PS.EXCM = 1

	 * Note that we don't disable interrupts here. 

	 */



	GET_THREAD_INFO(a2,a1)

	l32i	a4, a2, TI_FLAGS



	/* Enable interrupts again.

	 * Note: When we get here, we certainly have handled any interrupts.

	 *       (Hint: There is only one user exception frame on stack)

	 */



	movi	a3, 1 << PS_WOE_BIT



	_bbsi.l	a4, TIF_NEED_RESCHED, 3f

	_bbci.l	a4, TIF_SIGPENDING, 4f



	l32i	a4, a1, PT_DEPC

	bgeui	a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f

	/* Reenable interrupts and call do_signal() */



	wsr	a3, PS

	/* Call do_signal() */



	movi	a4, do_signal	# int do_signal(struct pt_regs*, sigset_t*)

	mov	a6, a1

	movi	a7, 0

	callx4	a4

	j	1b



3:	/* Reenable interrupts and reschedule */

3:	/* Reschedule */



	wsr	a3, PS

	movi	a4, schedule	# void schedule (void)

	callx4	a4

	j	1b



	/* Restore the state of the task and return from the exception. */

4:	/* Restore optional registers. */



	load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT



4:	/* a2 holds GET_CURRENT(a2,a1)  */

	wsr	a3, PS		/* disable interrupts */



	_bbci.l	a3, PS_UM_BIT, kernel_exception_exit



user_exception_exit:



	/* Restore the state of the task and return from the exception. */



	/* Switch to the user thread WINDOWBASE. Save SP temporarily in DEPC */
@@ -509,10 +503,6 @@ common_exception_return: 


kernel_exception_exit:



	/* Disable interrupts (a3 holds PT_PS) */



	wsr	a3, PS



#ifdef PREEMPTIBLE_KERNEL



#ifdef CONFIG_PREEMPT
@@ -591,10 +581,6 @@ kernel_exception_exit: 


common_exception_exit:



	/* Restore optional registers. */



	load_xtregs_opt a1 a3 a4 a5 a6 a7 PT_XTREGS_OPT



	/* Restore address registers. */



	_bbsi.l	a2, 1, 1f