linux-kernel - [RFC] [PATCH 2/2] x86: make jump

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Date:	Wed, 10 Jul 2013 22:25:58 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...hat.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [RFC] [PATCH 2/2] x86: make jump_label use int3-based patching

Make jump labels use text_poke_bp() for text patching instead of 
text_poke_smp(), avoiding the need for stop_machine().

Signed-off-by: Jiri Kosina <jkosina@...e.cz>
---
 arch/x86/kernel/jump_label.c |   16 ++++++++++++++--
 1 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 2889b3d..460f5d9 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -37,7 +37,19 @@ static void __jump_label_transform(struct jump_entry *entry,
 	} else
 		memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
 
-	(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
+	/*
+	 * Make text_poke_bp() a default fallback poker.
+	 *
+	 * At the time the change is being done, just ignore whether we
+	 * are doing nop -> jump or jump -> nop transition, and assume
+	 * always nop being the 'currently valid' instruction
+	 *
+	 */
+	if (poker)
+		(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
+	else
+		text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
+			     (void *)entry->code + JUMP_LABEL_NOP_SIZE);
 }
 
 void arch_jump_label_transform(struct jump_entry *entry,
@@ -45,7 +57,7 @@ void arch_jump_label_transform(struct jump_entry *entry,
 {
 	get_online_cpus();
 	mutex_lock(&text_mutex);
-	__jump_label_transform(entry, type, text_poke_smp);
+	__jump_label_transform(entry, type, NULL);
 	mutex_unlock(&text_mutex);
 	put_online_cpus();
 }
-- 
1.7.3.1

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