linux-kernel - [PATCH v2 07/13] powerpc/ftrace: Prepare PPC32's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH

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Date:   Mon, 20 Dec 2021 16:38:22 +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 07/13] powerpc/ftrace: Prepare PPC32's ftrace_caller() for
 CONFIG_DYNAMIC_FTRACE_WITH_ARGS

In order to implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS, change
ftrace_caller() stack layout to match struct pt_regs.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/ftrace.h     | 39 +--------------------------
 arch/powerpc/kernel/trace/ftrace_32.S | 29 +++++++++++++++++---
 2 files changed, 26 insertions(+), 42 deletions(-)

diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index debe8c4f7062..b3f6184f77ea 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -10,44 +10,7 @@
 
 #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
-#ifdef __ASSEMBLY__
-
-/* Based off of objdump output from glibc */
-
-#define MCOUNT_SAVE_FRAME			\
-	stwu	r1,-48(r1);			\
-	stw	r3, 12(r1);			\
-	stw	r4, 16(r1);			\
-	stw	r5, 20(r1);			\
-	stw	r6, 24(r1);			\
-	mflr	r3;				\
-	lwz	r4, 52(r1);			\
-	mfcr	r5;				\
-	stw	r7, 28(r1);			\
-	stw	r8, 32(r1);			\
-	stw	r9, 36(r1);			\
-	stw	r10,40(r1);			\
-	stw	r3, 44(r1);			\
-	stw	r5, 8(r1)
-
-#define MCOUNT_RESTORE_FRAME			\
-	lwz	r6, 8(r1);			\
-	lwz	r0, 44(r1);			\
-	lwz	r3, 12(r1);			\
-	mtctr	r0;				\
-	lwz	r4, 16(r1);			\
-	mtcr	r6;				\
-	lwz	r5, 20(r1);			\
-	lwz	r6, 24(r1);			\
-	lwz	r0, 52(r1);			\
-	lwz	r7, 28(r1);			\
-	lwz	r8, 32(r1);			\
-	mtlr	r0;				\
-	lwz	r9, 36(r1);			\
-	lwz	r10,40(r1);			\
-	addi	r1, r1, 48
-
-#else /* !__ASSEMBLY__ */
+#ifndef __ASSEMBLY__
 extern void _mcount(void);
 
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
diff --git a/arch/powerpc/kernel/trace/ftrace_32.S b/arch/powerpc/kernel/trace/ftrace_32.S
index 95ffea2bdc29..c4055b41af5f 100644
--- a/arch/powerpc/kernel/trace/ftrace_32.S
+++ b/arch/powerpc/kernel/trace/ftrace_32.S
@@ -27,17 +27,38 @@ _GLOBAL(_mcount)
 EXPORT_SYMBOL(_mcount)
 
 _GLOBAL(ftrace_caller)
-	MCOUNT_SAVE_FRAME
-	/* r3 ends up with link register */
+	stwu	r1, -INT_FRAME_SIZE(r1)
+
+	SAVE_GPRS(3, 10, r1)
+
+	addi	r8, r1, INT_FRAME_SIZE
+	stw	r8, GPR1(r1)
+
+	mflr	r3
+	stw	r3, _NIP(r1)
 	subi	r3, r3, MCOUNT_INSN_SIZE
+
+	stw	r0, _LINK(r1)
+	mr	r4, r0
+
 	lis	r5,function_trace_op@ha
 	lwz	r5,function_trace_op@l(r5)
-	li	r6, 0
+
+	addi	r6, r1, STACK_FRAME_OVERHEAD
 .globl ftrace_call
 ftrace_call:
 	bl	ftrace_stub
 	nop
-	MCOUNT_RESTORE_FRAME
+
+	lwz	r3, _NIP(r1)
+	mtctr	r3
+
+	REST_GPRS(3, 10, r1)
+
+	lwz	r0, _LINK(r1)
+	mtlr	r0
+
+	addi	r1, r1, INT_FRAME_SIZE
 ftrace_caller_common:
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 .globl ftrace_graph_call
-- 
2.33.1