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.c...@windriver.com>
---
arch/powerpc/kernel/entry_32.S | 43 +++++++++++++++++++++++++++++++++------
1 files changed, 36 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index ba3aeb4..e7eefdf 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -829,19 +829,50 @@ 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 */
rlwinm r9,r1,0,0,(31-THREAD_SHIFT)
- lwz r0,TI_PREEMPT(r9)
- cmpwi 0,r0,0 /* if non-zero, just restore regs and return */
- bne restore
lwz r0,TI_FLAGS(r9)
+ andis. r0,r0,_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 */
+ li r5,INT_FRAME_SIZE /* size: INT_FRAME_SIZE */
+ mr r1,r3 /* Reroute the trampoline frame to r1 */
+ bl memcpy /* Copy from the original to the
trampoline */
+
+ /* Do real store operation to complete stwu */
+ lwz r5,GPR1(r1)
+ stw r8,0(r5)
+
+ /* Clear _TIF_EMULATE_STACK_STORE flag */
+ rlwinm r9,r1,0,0,(31-THREAD_SHIFT)
+ 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 r8,TI_PREEMPT(r9)
+ cmpwi 0,r8,0 /* if non-zero, just restore regs and return */
+ bne restore
andi. r0,r0,_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
@@ -862,8 +893,6 @@ resume_kernel:
*/
bl trace_hardirqs_on
#endif
-#else
-resume_kernel:
#endif /* CONFIG_PREEMPT */
/* interrupts are hard-disabled at this point */
--
1.5.6
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