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().

Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Link: http://lkml.kernel.org/r/alpine.LNX.2.00.1307121120250.29788@pobox.suse.cz
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 2889b3d43882..460f5d9ceebb 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();
 }