linux-kernel - [tip:core/core] x86/jump_label: Switch to jump

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Message-ID: <tip-9fc0f798ab8a6c042d811e45086260eb59be45c1@git.kernel.org>
Date:   Thu, 27 Sep 2018 09:03:08 -0700
From:   tip-bot for Ard Biesheuvel <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, will.deacon@....com, keescook@...omium.org,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        catalin.marinas@....com, arnd@...db.de,
        linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        peterz@...radead.org, ard.biesheuvel@...aro.org, hpa@...or.com,
        mingo@...nel.org, jeyu@...nel.org
Subject: [tip:core/core] x86/jump_label: Switch to jump_entry accessors

Commit-ID:  9fc0f798ab8a6c042d811e45086260eb59be45c1
Gitweb:     https://git.kernel.org/tip/9fc0f798ab8a6c042d811e45086260eb59be45c1
Author:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
AuthorDate: Tue, 18 Sep 2018 23:51:40 -0700
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 27 Sep 2018 17:56:48 +0200

x86/jump_label: Switch to jump_entry accessors

In preparation of switching x86 to use place-relative references for
the code, target and key members of struct jump_entry, replace direct
references to the struct members with invocations of the new accessors.
This will allow us to make the switch by modifying the accessors only.

This incorporates a cleanup of __jump_label_transform() proposed by
Peter.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-s390@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Will Deacon <will.deacon@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Jessica Yu <jeyu@...nel.org>
Link: https://lkml.kernel.org/r/20180919065144.25010-6-ard.biesheuvel@linaro.org

---
 arch/x86/kernel/jump_label.c | 62 ++++++++++++++++++--------------------------
 1 file changed, 25 insertions(+), 37 deletions(-)

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index eeea935e9bb5..aac0c1f7e354 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -42,55 +42,40 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 					 void *(*poker)(void *, const void *, size_t),
 					 int init)
 {
-	union jump_code_union code;
+	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;
+	int line;
+
+	jmp.jump = 0xe9;
+	jmp.offset = jump_entry_target(entry) -
+		     (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 
 	if (early_boot_irqs_disabled)
 		poker = text_poke_early;
 
 	if (type == JUMP_LABEL_JMP) {
 		if (init) {
-			/*
-			 * Jump label is enabled for the first time.
-			 * So we expect a default_nop...
-			 */
-			if (unlikely(memcmp((void *)entry->code, default_nop, 5)
-				     != 0))
-				bug_at((void *)entry->code, __LINE__);
+			expect = default_nop; line = __LINE__;
 		} else {
-			/*
-			 * ...otherwise expect an ideal_nop. Otherwise
-			 * something went horribly wrong.
-			 */
-			if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
-				     != 0))
-				bug_at((void *)entry->code, __LINE__);
+			expect = ideal_nop; line = __LINE__;
 		}
 
-		code.jump = 0xe9;
-		code.offset = entry->target -
-				(entry->code + JUMP_LABEL_NOP_SIZE);
+		code = &jmp.code;
 	} else {
-		/*
-		 * We are disabling this jump label. If it is not what
-		 * we think it is, then something must have gone wrong.
-		 * If this is the first initialization call, then we
-		 * are converting the default nop to the ideal nop.
-		 */
 		if (init) {
-			if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
-				bug_at((void *)entry->code, __LINE__);
+			expect = default_nop; line = __LINE__;
 		} else {
-			code.jump = 0xe9;
-			code.offset = entry->target -
-				(entry->code + JUMP_LABEL_NOP_SIZE);
-			if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
-				bug_at((void *)entry->code, __LINE__);
+			expect = &jmp.code; line = __LINE__;
 		}
-		memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
+
+		code = ideal_nop;
 	}
 
+	if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
+		bug_at((void *)jump_entry_code(entry), line);
+
 	/*
 	 * Make text_poke_bp() a default fallback poker.
 	 *
@@ -99,11 +84,14 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 	 * 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);
+	if (poker) {
+		(*poker)((void *)jump_entry_code(entry), code,
+			 JUMP_LABEL_NOP_SIZE);
+		return;
+	}
+
+	text_poke_bp((void *)jump_entry_code(entry), code, JUMP_LABEL_NOP_SIZE,
+		     (void *)jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 }
 
 void arch_jump_label_transform(struct jump_entry *entry,