From b3c18725a0eb7ea2458e9ae3b7e5a477f52e361f Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Wed, 17 Sep 2014 17:07:04 +1000 Subject: 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 Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/entry_32.S | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'arch/powerpc/kernel/entry_32.S') diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 22b45a4955cd..ad837d8a26d4 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -1424,12 +1424,18 @@ _GLOBAL(ftrace_graph_caller) 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 -- cgit v1.2.3