linux-kernel - [PATCH v6 07/17] powerpc/ftrace: Skip instruction patching if the instructions are the same

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Message-ID: <20241018173632.277333-8-hbathini@linux.ibm.com>
Date: Fri, 18 Oct 2024 23:06:22 +0530
From: Hari Bathini <hbathini@...ux.ibm.com>
To: linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, bpf@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc: Michael Ellerman <mpe@...erman.id.au>, "Naveen N. Rao" <naveen@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Vishal Chourasia <vishalc@...ux.ibm.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>
Subject: [PATCH v6 07/17] powerpc/ftrace: Skip instruction patching if the instructions are the same

From: Naveen N Rao <naveen@...nel.org>

To simplify upcoming changes to ftrace, add a check to skip actual
instruction patching if the old and new instructions are the same. We
still validate that the instruction is what we expect, but don't
actually patch the same instruction again.

Signed-off-by: Naveen N Rao <naveen@...nel.org>
---
 arch/powerpc/kernel/trace/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index fe0546fbac8e..719517265d39 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -82,7 +82,7 @@ static inline int ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_
 {
 	int ret = ftrace_validate_inst(ip, old);
 
-	if (!ret)
+	if (!ret && !ppc_inst_equal(old, new))
 		ret = patch_instruction((u32 *)ip, new);
 
 	return ret;
-- 
2.47.0