linux-kernel - [tip: perf/urgent] arm/ftrace: Fix BE text poking

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Date:   Tue, 11 Feb 2020 12:01:43 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Dmitry Osipenko <digetx@...il.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: perf/urgent] arm/ftrace: Fix BE text poking

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     be993e44badc448add6a18d6f12b20615692c4c3
Gitweb:        https://git.kernel.org/tip/be993e44badc448add6a18d6f12b20615692c4c3
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 07 Feb 2020 12:57:36 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 11 Feb 2020 12:56:26 +01:00

arm/ftrace: Fix BE text poking

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>
---
 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 2a5ff69..10499d4 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -78,13 +78,10 @@ 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))