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powerpc/kprobe: Complete kprobe and migrate exception frame

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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: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Tiejun Chen 2012-09-16 23:54:30 +00:00 committed by Benjamin Herrenschmidt
parent f0d1128fcb
commit a9c4e541ea
2 changed files with 76 additions and 6 deletions
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47
arch/powerpc/kernel/entry_32.S
View File

@ -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 */

35
arch/powerpc/kernel/entry_64.S
View File

@ -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