linux-kernel - [PATCH v3 22/28] x86: Use RCU in all users of __module

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Message-ID: <20250108090457.512198-23-bigeasy@linutronix.de>
Date: Wed,  8 Jan 2025 10:04:51 +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>,
	"H. Peter Anvin" <hpa@...or.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	x86@...nel.org
Subject: [PATCH v3 22/28] x86: Use RCU in all users of __module_address().

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

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

Cc: H. Peter Anvin <hpa@...or.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 arch/x86/kernel/callthunks.c | 3 +--
 arch/x86/kernel/unwind_orc.c | 4 +---
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index f17d166078823..276b5368ff6b0 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -98,11 +98,10 @@ static inline bool within_module_coretext(void *addr)
 #ifdef CONFIG_MODULES
 	struct module *mod;
 
-	preempt_disable();
+	guard(rcu)();
 	mod = __module_address((unsigned long)addr);
 	if (mod && within_module_core((unsigned long)addr, mod))
 		ret = true;
-	preempt_enable();
 #endif
 	return ret;
 }
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index d4705a348a804..977ee75e047c8 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -476,7 +476,7 @@ bool unwind_next_frame(struct unwind_state *state)
 		return false;
 
 	/* Don't let modules unload while we're reading their ORC data. */
-	preempt_disable();
+	guard(rcu)();
 
 	/* End-of-stack check for user tasks: */
 	if (state->regs && user_mode(state->regs))
@@ -669,14 +669,12 @@ bool unwind_next_frame(struct unwind_state *state)
 		goto err;
 	}
 
-	preempt_enable();
 	return true;
 
 err:
 	state->error = true;
 
 the_end:
-	preempt_enable();
 	state->stack_info.type = STACK_TYPE_UNKNOWN;
 	return false;
 }
-- 
2.47.1