linux-kernel - [PATCH v2 17/28] arm64: module: Use RCU in all users of __module_text

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Message-ID: <20241220174731.514432-18-bigeasy@linutronix.de>
Date: Fri, 20 Dec 2024 18:41:31 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Daniel Gomez <da.gomez@...sung.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Mark Rutland <mark.rutland@....com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Will Deacon <will@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v2 17/28] arm64: module: Use RCU in all users of __module_text_address().

__module_text_address() can be invoked within a RCU section, there is no
requirement to have preemption disabled.

Replace the preempt_disable() section around __module_text_address()
with RCU.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-trace-kernel@...r.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 arch/arm64/kernel/ftrace.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 245cb419ca24d..2b76939b6304f 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -257,14 +257,13 @@ static bool ftrace_find_callable_addr(struct dyn_ftrace *rec,
 	 * dealing with an out-of-range condition, we can assume it
 	 * is due to a module being loaded far away from the kernel.
 	 *
-	 * NOTE: __module_text_address() must be called with preemption
-	 * disabled, but we can rely on ftrace_lock to ensure that 'mod'
+	 * NOTE: __module_text_address() must be called within a RCU read
+	 * section, but we can rely on ftrace_lock to ensure that 'mod'
 	 * retains its validity throughout the remainder of this code.
 	 */
 	if (!mod) {
-		preempt_disable();
+		guard(rcu)();
 		mod = __module_text_address(pc);
-		preempt_enable();
 	}
 
 	if (WARN_ON(!mod))
-- 
2.45.2