[RFC] [PATCH 2/2] x86: make jump_label use int3-based patching

From: Jiri Kosina
Date: Wed Jul 10 2013 - 16:26:10 EST


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@xxxxxxx>
---
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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