powerpc/ftrace: simplify prepare_ftrace_return
Instead of passing in the stack address of the link register
to be modified, just pass in the old value and return the
new value and rely on ftrace_graph_caller to do the
modification.
This removes the exception handling around the stack update -
it isn't needed and we weren't consistent about it. Later on
we would do an unprotected modification:
if (!ftrace_graph_entry(&trace)) {
*parent = old;
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 22b45a4..ad837d8 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -1424,12 +1424,18 @@
lwz r4, 44(r1)
subi r4, r4, MCOUNT_INSN_SIZE
- /* get the parent address */
- addi r3, r1, 52
+ /* Grab the LR out of the caller stack frame */
+ lwz r3,52(r1)
bl prepare_ftrace_return
nop
+ /*
+ * prepare_ftrace_return gives us the address we divert to.
+ * Change the LR in the callers stack frame to this.
+ */
+ stw r3,52(r1)
+
MCOUNT_RESTORE_FRAME
/* old link register ends up in ctr reg */
bctr