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>
---
v4:
* improve register usage
* use copy_and_flush() to replace memcpy since that only clobber r0, r6
and LR explicitly.
* retest
arch/powerpc/kernel/entry_32.S | 44 ++++++++++++++++++++++++++++++++++------
arch/powerpc/kernel/entry_64.S | 32 +++++++++++++++++++++++++++++
2 files changed, 70 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 1536d2c..b18e494 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -832,19 +832,53 @@ 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 */
+ li r5,INT_FRAME_SIZE /* size: INT_FRAME_SIZE */
+ li r6,0 /* start offset: 0 */
+ mr r1,r3 /* Reroute the trampoline frame to r1 */
+ /* Copy from the original to the trampoline.
+ * Its safe since copy_and_flush *only* clobbers r0, r6 and lr.
+ */
+ bl copy_and_flush
+
+ /* 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
@@ -865,8 +899,6 @@ resume_kernel:
*/
bl trace_hardirqs_on
#endif
-#else
-resume_kernel:
#endif /* CONFIG_PREEMPT */
/* interrupts are hard-disabled at this point */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index b40e0b4..d060f4d 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -593,6 +593,38 @@ _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 */
+ li r5,INT_FRAME_SIZE /* size: INT_FRAME_SIZE */
+ li r6,0 /* start offset: 0 */
+ mr r1,r3 /* Reroute the trampoline frame to r1 */
+ /* Copy from the original to the trampoline.
+ * Its safe since copy_and_flush *only* clobbers r0, r6 and lr
+ */
+ bl .copy_and_flush
+
+ /* 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
--
1.7.9.5
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