linux-kernel - [PATCH V6 2/6] x86/jump_label: Add a __jump_label_set_jump

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Message-Id: <d2f52a0010ecd399cf9b02a65bcf5836571b9e52.1560325897.git.bristot@redhat.com>
Date:   Wed, 12 Jun 2019 11:57:27 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Chris von Recklinghausen <crecklin@...hat.com>,
        Jason Baron <jbaron@...mai.com>, Scott Wood <swood@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Clark Williams <williams@...hat.com>, x86@...nel.org
Subject: [PATCH V6 2/6] 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@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: Chris von Recklinghausen <crecklin@...hat.com>
Cc: Jason Baron <jbaron@...mai.com>
Cc: Scott Wood <swood@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Clark Williams <williams@...hat.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
 arch/x86/kernel/jump_label.c | 41 +++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index e631c358f7f4..d3328062b8cf 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -35,19 +35,19 @@ 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);
+	code->jump = 0xe9;
+	code->offset = jump_entry_target(entry) -
+		       (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 
 	if (type == JUMP_LABEL_JMP) {
 		if (init) {
@@ -56,19 +56,30 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 			expect = ideal_nop; line = __LINE__;
 		}
 
-		code = &jmp.code;
+		if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
+			bug_at((void *)jump_entry_code(entry), line);
+
 	} else {
 		if (init) {
 			expect = default_nop; line = __LINE__;
 		} else {
-			expect = &jmp.code; line = __LINE__;
+			expect = code->code; line = __LINE__;
 		}
 
-		code = ideal_nop;
+		if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
+			bug_at((void *)jump_entry_code(entry), line);
+
+		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;
 
-	if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
-		bug_at((void *)jump_entry_code(entry), line);
+	__jump_label_set_jump_code(entry, type, &code, init);
 
 	/*
 	 * As long as only a single processor is running and the code is still
@@ -82,12 +93,12 @@ 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);
 }
 
-- 
2.20.1