Commit c58ce2b1 authored by Tiejun Chen's avatar Tiejun Chen Committed by Benjamin Herrenschmidt
Browse files

ppc64: fix missing to check all bits of _TIF_USER_WORK_MASK in preempt 



In entry_64.S version of ret_from_except_lite, you'll notice that
in the !preempt case, after we've checked MSR_PR we test for any
TIF flag in _TIF_USER_WORK_MASK to decide whether to go to do_work
or not. However, in the preempt case, we do a convoluted trick to
test SIGPENDING only if PR was set and always test NEED_RESCHED ...
but we forget to test any other bit of _TIF_USER_WORK_MASK !!! So
that means that with preempt, we completely fail to test for things
like single step, syscall tracing, etc...

This should be fixed as the following path:

 - Test PR. If not set, go to resume_kernel, else continue.

 - If go resume_kernel, to do that original do_work.

 - If else, then always test for _TIF_USER_WORK_MASK to decide to do
that original user_work, else restore directly.

Signed-off-by: default avatarTiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 82b2521d

arch/powerpc/kernel/entry_64.S

+40 −57
Original line number Diff line number Diff line
@@ -558,27 +558,54 @@ _GLOBAL(ret_from_except_lite) 
	mtmsrd	r10,1		  /* Update machine state */

#endif /* CONFIG_PPC_BOOK3E */



#ifdef CONFIG_PREEMPT

	clrrdi	r9,r1,THREAD_SHIFT	/* current_thread_info() */

	li	r0,_TIF_NEED_RESCHED	/* bits to check */

	ld	r3,_MSR(r1)

	ld	r4,TI_FLAGS(r9)

	/* Move MSR_PR bit in r3 to _TIF_SIGPENDING position in r0 */

	rlwimi	r0,r3,32+TIF_SIGPENDING-MSR_PR_LG,_TIF_SIGPENDING

	and.	r0,r4,r0	/* check NEED_RESCHED and maybe SIGPENDING */

	bne	do_work



#else /* !CONFIG_PREEMPT */

	ld	r3,_MSR(r1)	/* Returning to user mode? */

	andi.	r3,r3,MSR_PR

	beq	restore		/* if not, just restore regs and return */

	beq	resume_kernel



	/* Check current_thread_info()->flags */

	andi.	r0,r4,_TIF_USER_WORK_MASK

	beq	restore



	andi.	r0,r4,_TIF_NEED_RESCHED

	beq	1f

	bl	.restore_interrupts

	bl	.schedule

	b	.ret_from_except_lite



1:	bl	.save_nvgprs

	bl	.restore_interrupts

	addi	r3,r1,STACK_FRAME_OVERHEAD

	bl	.do_notify_resume

	b	.ret_from_except



resume_kernel:

#ifdef CONFIG_PREEMPT

	/* Check if we need to preempt */

	andi.	r0,r4,_TIF_NEED_RESCHED

	beq+	restore

	/* Check that preempt_count() == 0 and interrupts are enabled */

	lwz	r8,TI_PREEMPT(r9)

	cmpwi	cr1,r8,0

	ld	r0,SOFTE(r1)

	cmpdi	r0,0

	crandc	eq,cr1*4+eq,eq

	bne	restore



	/*

	 * Here we are preempting the current task. We want to make

	 * sure we are soft-disabled first

	 */

	SOFT_DISABLE_INTS(r3,r4)

1:	bl	.preempt_schedule_irq



	/* Re-test flags and eventually loop */

	clrrdi	r9,r1,THREAD_SHIFT

	ld	r4,TI_FLAGS(r9)

	andi.	r0,r4,_TIF_USER_WORK_MASK

	bne	do_work

#endif /* !CONFIG_PREEMPT */

	andi.	r0,r4,_TIF_NEED_RESCHED

	bne	1b

#endif /* CONFIG_PREEMPT */



	.globl	fast_exc_return_irq

fast_exc_return_irq:
@@ -759,50 +786,6 @@ restore_check_irq_replay: 
#endif /* CONFIG_PPC_BOOK3E */

1:	b	.ret_from_except /* What else to do here ? */

 





3:

do_work:

#ifdef CONFIG_PREEMPT

	andi.	r0,r3,MSR_PR	/* Returning to user mode? */

	bne	user_work

	/* Check that preempt_count() == 0 and interrupts are enabled */

	lwz	r8,TI_PREEMPT(r9)

	cmpwi	cr1,r8,0

	ld	r0,SOFTE(r1)

	cmpdi	r0,0

	crandc	eq,cr1*4+eq,eq

	bne	restore



	/*

	 * Here we are preempting the current task. We want to make

	 * sure we are soft-disabled first

	 */

	SOFT_DISABLE_INTS(r3,r4)

1:	bl	.preempt_schedule_irq



	/* Re-test flags and eventually loop */

	clrrdi	r9,r1,THREAD_SHIFT

	ld	r4,TI_FLAGS(r9)

	andi.	r0,r4,_TIF_NEED_RESCHED

	bne	1b

	b	restore



user_work:

#endif /* CONFIG_PREEMPT */



	andi.	r0,r4,_TIF_NEED_RESCHED

	beq	1f

	bl	.restore_interrupts

	bl	.schedule

	b	.ret_from_except_lite



1:	bl	.save_nvgprs

	bl	.restore_interrupts

	addi	r3,r1,STACK_FRAME_OVERHEAD

	bl	.do_notify_resume

	b	.ret_from_except



unrecov_restore:

	addi	r3,r1,STACK_FRAME_OVERHEAD

	bl	.unrecoverable_exception

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