linux-kernel - [PATCH 1/2] x86/asm/suspend: Get rid of bogus_64

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Message-Id: <20190906075550.23435-1-jslaby@suse.cz>
Date:   Fri,  6 Sep 2019 09:55:49 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     bp@...en8.de
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Jiri Slaby <jslaby@...e.cz>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
        linux-pm@...r.kernel.org
Subject: [PATCH 1/2] x86/asm/suspend: Get rid of bogus_64_magic

bogus_64_magic is only a dead-end loop. There is no need for an
out-of-order function (and unannotated local label), so just handle it
in-place and also store 0xbad-m-a-g-i-c to rcx beforehand.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <lenb@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: linux-pm@...r.kernel.org
---
 arch/x86/kernel/acpi/wakeup_64.S | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index b0715c3ac18d..7f9ade13bbcf 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -18,8 +18,13 @@ ENTRY(wakeup_long64)
 	movq	saved_magic, %rax
 	movq	$0x123456789abcdef0, %rdx
 	cmpq	%rdx, %rax
-	jne	bogus_64_magic
+	je	2f
 
+	/* stop here on a saved_magic mismatch */
+	movq $0xbad6d61676963, %rcx
+1:
+	jmp 1b
+2:
 	movw	$__KERNEL_DS, %ax
 	movw	%ax, %ss	
 	movw	%ax, %ds
@@ -37,9 +42,6 @@ ENTRY(wakeup_long64)
 	jmp	*%rax
 ENDPROC(wakeup_long64)
 
-bogus_64_magic:
-	jmp	bogus_64_magic
-
 ENTRY(do_suspend_lowlevel)
 	FRAME_BEGIN
 	subq	$8, %rsp
-- 
2.23.0