linux-kernel - [PATCH AUTOSEL 4.4 4/7] arm/ftrace: Fix BE text poking

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Message-Id: <20200223022459.2594-4-sashal@kernel.org>
Date:   Sat, 22 Feb 2020 21:24:56 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 4.4 4/7] arm/ftrace: Fix BE text poking

From: Peter Zijlstra <peterz@...radead.org>

[ Upstream commit be993e44badc448add6a18d6f12b20615692c4c3 ]

The __patch_text() function already applies __opcode_to_mem_*(), so
when __opcode_to_mem_*() is not the identity (BE*), it is applied
twice, wrecking the instruction.

Fixes: 42e51f187f86 ("arm/ftrace: Use __patch_text()")
Reported-by: Dmitry Osipenko <digetx@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Tested-by: Dmitry Osipenko <digetx@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm/kernel/ftrace.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index faa9a905826ee..7982409e5c27f 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -105,13 +105,10 @@ static int ftrace_modify_code(unsigned long pc, unsigned long old,
 {
 	unsigned long replaced;
 
-	if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
+	if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
 		old = __opcode_to_mem_thumb32(old);
-		new = __opcode_to_mem_thumb32(new);
-	} else {
+	else
 		old = __opcode_to_mem_arm(old);
-		new = __opcode_to_mem_arm(new);
-	}
 
 	if (validate) {
 		if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
-- 
2.20.1