linux-kernel - [RFC PATCH 12/14] powerpc/ftrace: Drop saving LR to stack save area for -mprofile-kernel

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Message-Id: <b40cb303a22f75b85ec0c8d45160e983baff9299.1606412433.git.naveen.n.rao@linux.vnet.ibm.com>
Date:   Thu, 26 Nov 2020 23:38:49 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     <linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: [RFC PATCH 12/14] powerpc/ftrace: Drop saving LR to stack save area for -mprofile-kernel

In -mprofile-kernel variant of ftrace_graph_caller(), we save the
optionally-updated LR address into the stack save area at the end. This
is likely an offshoot of the initial -mprofile-kernel implementation in
gcc emitting the same as part of the -mprofile-kernel instruction
sequence. However, this is not required. Drop it.

Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
 arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
index bbe871b47ade58..c5602e9b07faa3 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
@@ -310,7 +310,5 @@ _GLOBAL(ftrace_graph_caller)
 	ld	r2, 24(r1)
 
 	addi	r1, r1, SWITCH_FRAME_SIZE
-	mflr	r0
-	std	r0, LRSAVE(r1)
 	bctr
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-- 
2.25.4