Subject: [PATCH 22/28] x86: Use RCU in all users of __module_address().
From: Sebastian Andrzej Siewior <[email-masked]>
Date: Wed, 8 Jan 2025 10:04:51 +0100

__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 <[email-masked]>
Cc: Borislav Petkov <[email-masked]>
Cc: Dave Hansen <[email-masked]>
Cc: Ingo Molnar <[email-masked]>
Cc: Josh Poimboeuf <[email-masked]>
Cc: Peter Zijlstra <[email-masked]>
Cc: Thomas Gleixner <[email-masked]>
Cc: [email-masked]
Acked-by: Peter Zijlstra (Intel) <[email-masked]>
Link: https://lore.kernel.org/r/[email-masked]
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 arch/x86/kernel/callthunks.c |    3 +--
 arch/x86/kernel/unwind_orc.c |    4 +---
 2 files changed, 2 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -98,11 +98,10 @@ static inline bool within_module_coretex
 #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;
 }
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -476,7 +476,7 @@ bool unwind_next_frame(struct unwind_sta
 		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_sta
 		goto err;
 	}
 
-	preempt_enable();
 	return true;
 
 err:
 	state->error = true;
 
 the_end:
-	preempt_enable();
 	state->stack_info.type = STACK_TYPE_UNKNOWN;
 	return false;
 }