linux-kernel - [PATCH v3 4/4] LoongArch: ftrace: Adjust register stack restore order in direct call trampolines

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Message-Id: <20251216094753.1317231-5-duanchenghao@kylinos.cn>
Date: Tue, 16 Dec 2025 17:47:53 +0800
From: Chenghao Duan <duanchenghao@...inos.cn>
To: yangtiezhu@...ngson.cn,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mark.rutland@....com,
	hengqi.chen@...il.com,
	chenhuacai@...nel.org
Cc: kernel@...0n.name,
	zhangtianyang@...ngson.cn,
	masahiroy@...nel.org,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	bpf@...r.kernel.org,
	duanchenghao@...inos.cn,
	youling.tang@...ux.dev,
	jianghaoran@...inos.cn,
	vincent.mc.li@...il.com,
	linux-trace-kernel@...r.kernel.org,
	Youling Tang <tangyouling@...inos.cn>
Subject: [PATCH v3 4/4] LoongArch: ftrace: Adjust register stack restore order in direct call trampolines

Ensure that in the ftrace direct call logic, the CPU register state
(with ra = parent return address) is restored to the correct state
after the execution of the custom trampoline function and before
returning to the traced function. Additionally, guarantee the
correctness of the jump logic for jr t0 (traced function address).

Reported-by: Youling Tang <tangyouling@...inos.cn>
Signed-off-by: Chenghao Duan <duanchenghao@...inos.cn>
---
 samples/ftrace/ftrace-direct-modify.c       | 8 ++++----
 samples/ftrace/ftrace-direct-multi-modify.c | 8 ++++----
 samples/ftrace/ftrace-direct-multi.c        | 4 ++--
 samples/ftrace/ftrace-direct-too.c          | 4 ++--
 samples/ftrace/ftrace-direct.c              | 4 ++--
 5 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
index da3a9f2091f5..1ba1927b548e 100644
--- a/samples/ftrace/ftrace-direct-modify.c
+++ b/samples/ftrace/ftrace-direct-modify.c
@@ -176,8 +176,8 @@ asm (
 "	st.d	$t0, $sp, 0\n"
 "	st.d	$ra, $sp, 8\n"
 "	bl	my_direct_func1\n"
-"	ld.d	$t0, $sp, 0\n"
-"	ld.d	$ra, $sp, 8\n"
+"	ld.d	$ra, $sp, 0\n"
+"	ld.d	$t0, $sp, 8\n"
 "	addi.d	$sp, $sp, 16\n"
 "	jr	$t0\n"
 "	.size		my_tramp1, .-my_tramp1\n"
@@ -189,8 +189,8 @@ asm (
 "	st.d	$t0, $sp, 0\n"
 "	st.d	$ra, $sp, 8\n"
 "	bl	my_direct_func2\n"
-"	ld.d	$t0, $sp, 0\n"
-"	ld.d	$ra, $sp, 8\n"
+"	ld.d	$ra, $sp, 0\n"
+"	ld.d	$t0, $sp, 8\n"
 "	addi.d	$sp, $sp, 16\n"
 "	jr	$t0\n"
 "	.size		my_tramp2, .-my_tramp2\n"
diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
index 8f7986d698d8..7a7822dfeb50 100644
--- a/samples/ftrace/ftrace-direct-multi-modify.c
+++ b/samples/ftrace/ftrace-direct-multi-modify.c
@@ -199,8 +199,8 @@ asm (
 "	move	$a0, $t0\n"
 "	bl	my_direct_func1\n"
 "	ld.d	$a0, $sp, 0\n"
-"	ld.d	$t0, $sp, 8\n"
-"	ld.d	$ra, $sp, 16\n"
+"	ld.d	$ra, $sp, 8\n"
+"	ld.d	$t0, $sp, 16\n"
 "	addi.d	$sp, $sp, 32\n"
 "	jr	$t0\n"
 "	.size		my_tramp1, .-my_tramp1\n"
@@ -215,8 +215,8 @@ asm (
 "	move	$a0, $t0\n"
 "	bl	my_direct_func2\n"
 "	ld.d	$a0, $sp, 0\n"
-"	ld.d	$t0, $sp, 8\n"
-"	ld.d	$ra, $sp, 16\n"
+"	ld.d	$ra, $sp, 8\n"
+"	ld.d	$t0, $sp, 16\n"
 "	addi.d	$sp, $sp, 32\n"
 "	jr	$t0\n"
 "	.size		my_tramp2, .-my_tramp2\n"
diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
index db326c81a27d..3fe6ddaf0b69 100644
--- a/samples/ftrace/ftrace-direct-multi.c
+++ b/samples/ftrace/ftrace-direct-multi.c
@@ -131,8 +131,8 @@ asm (
 "	move	$a0, $t0\n"
 "	bl	my_direct_func\n"
 "	ld.d	$a0, $sp, 0\n"
-"	ld.d	$t0, $sp, 8\n"
-"	ld.d	$ra, $sp, 16\n"
+"	ld.d	$ra, $sp, 8\n"
+"	ld.d	$t0, $sp, 16\n"
 "	addi.d	$sp, $sp, 32\n"
 "	jr	$t0\n"
 "	.size		my_tramp, .-my_tramp\n"
diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
index 3d0fa260332d..bf2411aa6fd7 100644
--- a/samples/ftrace/ftrace-direct-too.c
+++ b/samples/ftrace/ftrace-direct-too.c
@@ -143,8 +143,8 @@ asm (
 "	ld.d	$a0, $sp, 0\n"
 "	ld.d	$a1, $sp, 8\n"
 "	ld.d	$a2, $sp, 16\n"
-"	ld.d	$t0, $sp, 24\n"
-"	ld.d	$ra, $sp, 32\n"
+"	ld.d	$ra, $sp, 24\n"
+"	ld.d	$t0, $sp, 32\n"
 "	addi.d	$sp, $sp, 48\n"
 "	jr	$t0\n"
 "	.size		my_tramp, .-my_tramp\n"
diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
index 956834b0d19a..5368c8c39cbb 100644
--- a/samples/ftrace/ftrace-direct.c
+++ b/samples/ftrace/ftrace-direct.c
@@ -124,8 +124,8 @@ asm (
 "	st.d	$ra, $sp, 16\n"
 "	bl	my_direct_func\n"
 "	ld.d	$a0, $sp, 0\n"
-"	ld.d	$t0, $sp, 8\n"
-"	ld.d	$ra, $sp, 16\n"
+"	ld.d	$ra, $sp, 8\n"
+"	ld.d	$t0, $sp, 16\n"
 "	addi.d	$sp, $sp, 32\n"
 "	jr	$t0\n"
 "	.size		my_tramp, .-my_tramp\n"
-- 
2.25.1