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 | 35 +++++++++++++++++++++++++++++++++++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 56212bc..0cdd27d 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -850,6 +850,41 @@ resume_kernel:
/* interrupts are hard-disabled at this point */
restore:
+ lwz r3,_MSR(r1) /* Returning to user mode? */
+ andi. r0,r3,MSR_PR
+ bne 1f
+ /* check current_thread_info, _TIF_EMULATE_STACK_STORE */
+ rlwinm r9,r1,0,0,(31-THREAD_SHIFT)
+ lwz r0,TI_FLAGS(r9)
+ andis. r0,r0,_TIF_EMULATE_STACK_STORE@h
+ beq+ 1f
+
+ addi r9,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 r9,0(r5)
+
+ /* Clear _TIF_EMULATE_STACK_STORE flag */
+ rlwinm r9,r1,0,0,(31-THREAD_SHIFT)
+ lis r11,_TIF_EMULATE_STACK_STORE@h
+ addi r9,r9,TI_FLAGS
+0: lwarx r8,0,r9
+ andc r8,r8,r11
+#ifdef CONFIG_IBM405_ERR77
+ dcbt 0,r9
+#endif
+ stwcx. r8,0,r9
+ bne- 0b
+1:
+
#ifdef CONFIG_44x
BEGIN_MMU_FTR_SECTION
b 1f
--
1.5.6
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