x86/jump_label: Add a __jump_label_set_jump_code() helper

Move the definition of the code to be written from
__jump_label_transform() to a specialized function. No functional
change.

Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris von Recklinghausen <crecklin@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Wood <swood@redhat.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/d2f52a0010ecd399cf9b02a65bcf5836571b9e52.1560325897.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Author: Daniel Bristot de Oliveira

arch/x86/kernel/jump_label.c

@@ -35,41 +35,43 @@ static void bug_at(unsigned char *ip, int line)
 	BUG();
 }
 
-static void __ref __jump_label_transform(struct jump_entry *entry,
-					 enum jump_label_type type,
-					 int init)
+static void __jump_label_set_jump_code(struct jump_entry *entry,
+				       enum jump_label_type type,
+				       union jump_code_union *code,
+				       int init)
 {
-	union jump_code_union jmp;
 	const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
 	const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
-	const void *expect, *code;
+	const void *expect;
 	int line;
 
-	jmp.jump = 0xe9;
-	jmp.offset = jump_entry_target(entry) -
-		     (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
-
-	if (type == JUMP_LABEL_JMP) {
-		if (init) {
-			expect = default_nop; line = __LINE__;
-		} else {
-			expect = ideal_nop; line = __LINE__;
-		}
+	code->jump = 0xe9;
+	code->offset = jump_entry_target(entry) -
+		       (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 
-		code = &jmp.code;
+	if (init) {
+		expect = default_nop; line = __LINE__;
+	} else if (type == JUMP_LABEL_JMP) {
+		expect = ideal_nop; line = __LINE__;
 	} else {
-		if (init) {
-			expect = default_nop; line = __LINE__;
-		} else {
-			expect = &jmp.code; line = __LINE__;
-		}
-
-		code = ideal_nop;
+		expect = code->code; line = __LINE__;
 	}
 
 	if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
 		bug_at((void *)jump_entry_code(entry), line);
 
+	if (type == JUMP_LABEL_NOP)
+		memcpy(code, ideal_nop, JUMP_LABEL_NOP_SIZE);
+}
+
+static void __ref __jump_label_transform(struct jump_entry *entry,
+					 enum jump_label_type type,
+					 int init)
+{
+	union jump_code_union code;
+
+	__jump_label_set_jump_code(entry, type, &code, init);
+
 	/*
 	 * As long as only a single processor is running and the code is still
 	 * not marked as RO, text_poke_early() can be used; Checking that
@@ -82,12 +84,12 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 	 * always nop being the 'currently valid' instruction
 	 */
 	if (init || system_state == SYSTEM_BOOTING) {
-		text_poke_early((void *)jump_entry_code(entry), code,
+		text_poke_early((void *)jump_entry_code(entry), &code,
 				JUMP_LABEL_NOP_SIZE);
 		return;
 	}
 
-	text_poke_bp((void *)jump_entry_code(entry), code, JUMP_LABEL_NOP_SIZE,
+	text_poke_bp((void *)jump_entry_code(entry), &code, JUMP_LABEL_NOP_SIZE,
 		     (void *)jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 }