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Commit a9c4e541 authored by Tiejun Chen's avatar Tiejun Chen Committed by Benjamin Herrenschmidt
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powerpc/kprobe: Complete kprobe and migrate exception frame 



We can't emulate stwu since that may corrupt current exception stack.
So we will have to do real store operation in the exception return code.

Firstly we'll allocate a trampoline exception frame below the kprobed
function stack and copy the current exception frame to the trampoline.
Then we can do this real store operation to implement 'stwu', and reroute
the trampoline frame to r1 to complete this exception migration.

Signed-off-by: default avatarTiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent f0d1128f

arch/powerpc/kernel/entry_32.S

+41 −6
Original line number Diff line number Diff line
@@ -831,19 +831,56 @@ restore_user: 
	bnel-	load_dbcr0

#endif



#ifdef CONFIG_PREEMPT

	b	restore



/* N.B. the only way to get here is from the beq following ret_from_except. */

resume_kernel:

	/* check current_thread_info->preempt_count */

	/* check current_thread_info, _TIF_EMULATE_STACK_STORE */

	CURRENT_THREAD_INFO(r9, r1)

	lwz	r8,TI_FLAGS(r9)

	andis.	r8,r8,_TIF_EMULATE_STACK_STORE@h

	beq+	1f



	addi	r8,r1,INT_FRAME_SIZE	/* Get the kprobed function entry */



	lwz	r3,GPR1(r1)

	subi	r3,r3,INT_FRAME_SIZE	/* dst: Allocate a trampoline exception frame */

	mr	r4,r1			/* src:  current exception frame */

	mr	r1,r3			/* Reroute the trampoline frame to r1 */



	/* Copy from the original to the trampoline. */

	li	r5,INT_FRAME_SIZE/4	/* size: INT_FRAME_SIZE */

	li	r6,0			/* start offset: 0 */

	mtctr	r5

2:	lwzx	r0,r6,r4

	stwx	r0,r6,r3

	addi	r6,r6,4

	bdnz	2b



	/* Do real store operation to complete stwu */

	lwz	r5,GPR1(r1)

	stw	r8,0(r5)



	/* Clear _TIF_EMULATE_STACK_STORE flag */

	lis	r11,_TIF_EMULATE_STACK_STORE@h

	addi	r5,r9,TI_FLAGS

0:	lwarx	r8,0,r5

	andc	r8,r8,r11

#ifdef CONFIG_IBM405_ERR77

	dcbt	0,r5

#endif

	stwcx.	r8,0,r5

	bne-	0b

1:



#ifdef CONFIG_PREEMPT

	/* check current_thread_info->preempt_count */

	lwz	r0,TI_PREEMPT(r9)

	cmpwi	0,r0,0		/* if non-zero, just restore regs and return */

	bne	restore

	lwz	r0,TI_FLAGS(r9)

	andi.	r0,r0,_TIF_NEED_RESCHED

	andi.	r8,r8,_TIF_NEED_RESCHED

	beq+	restore

	lwz	r3,_MSR(r1)

	andi.	r0,r3,MSR_EE	/* interrupts off? */

	beq	restore		/* don't schedule if so */

#ifdef CONFIG_TRACE_IRQFLAGS
@@ -864,8 +901,6 @@ resume_kernel: 
	 */

	bl	trace_hardirqs_on

#endif

#else

resume_kernel:

#endif /* CONFIG_PREEMPT */



	/* interrupts are hard-disabled at this point */

arch/powerpc/kernel/entry_64.S

+35 −0
Original line number Diff line number Diff line
@@ -593,6 +593,41 @@ _GLOBAL(ret_from_except_lite) 
	b	.ret_from_except



resume_kernel:

	/* check current_thread_info, _TIF_EMULATE_STACK_STORE */

	CURRENT_THREAD_INFO(r9, r1)

	ld	r8,TI_FLAGS(r9)

	andis.	r8,r8,_TIF_EMULATE_STACK_STORE@h

	beq+	1f



	addi	r8,r1,INT_FRAME_SIZE	/* Get the kprobed function entry */



	lwz	r3,GPR1(r1)

	subi	r3,r3,INT_FRAME_SIZE	/* dst: Allocate a trampoline exception frame */

	mr	r4,r1			/* src:  current exception frame */

	mr	r1,r3			/* Reroute the trampoline frame to r1 */



	/* Copy from the original to the trampoline. */

	li	r5,INT_FRAME_SIZE/8	/* size: INT_FRAME_SIZE */

	li	r6,0			/* start offset: 0 */

	mtctr	r5

2:	ldx	r0,r6,r4

	stdx	r0,r6,r3

	addi	r6,r6,8

	bdnz	2b



	/* Do real store operation to complete stwu */

	lwz	r5,GPR1(r1)

	std	r8,0(r5)



	/* Clear _TIF_EMULATE_STACK_STORE flag */

	lis	r11,_TIF_EMULATE_STACK_STORE@h

	addi	r5,r9,TI_FLAGS

	ldarx	r4,0,r5

	andc	r4,r4,r11

	stdcx.	r4,0,r5

	bne-	0b

1:



#ifdef CONFIG_PREEMPT

	/* Check if we need to preempt */

	andi.	r0,r4,_TIF_NEED_RESCHED