linux-kernel - [PATCH v2 06/13] powerpc/ftrace: Simplify PPC32's return_to

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Message-ID: <aab39b77b34fb2c4ed08ed01c547b6ed13643788.1640017960.git.christophe.leroy@csgroup.eu>
Date:   Mon, 20 Dec 2021 16:38:19 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>
CC:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>
Subject: [PATCH v2 06/13] powerpc/ftrace: Simplify PPC32's return_to_handler()

return_to_handler() was copied from PPC64. For PPC32 it
just needs to save r3 and r4, and doesn't require any nop
after the bl.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/trace/ftrace_32.S | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/trace/ftrace_32.S b/arch/powerpc/kernel/trace/ftrace_32.S
index 7e2fd729116b..95ffea2bdc29 100644
--- a/arch/powerpc/kernel/trace/ftrace_32.S
+++ b/arch/powerpc/kernel/trace/ftrace_32.S
@@ -162,22 +162,18 @@ _GLOBAL(ftrace_graph_caller)
 
 _GLOBAL(return_to_handler)
 	/* need to save return values */
-	stwu	r1, -32(r1)
-	stw	r3, 20(r1)
-	stw	r4, 16(r1)
-	stw	r31, 12(r1)
-	mr	r31, r1
+	stwu	r1, -16(r1)
+	stw	r3, 8(r1)
+	stw	r4, 12(r1)
 
 	bl	ftrace_return_to_handler
-	nop
 
 	/* return value has real return address */
 	mtlr	r3
 
-	lwz	r3, 20(r1)
-	lwz	r4, 16(r1)
-	lwz	r31,12(r1)
-	lwz	r1, 0(r1)
+	lwz	r3, 8(r1)
+	lwz	r4, 12(r1)
+	addi	r1, r1, 16
 
 	/* Jump back to real return address */
 	blr
-- 
2.33.1