linux-kernel - [PATCH 4.9 125/125] x86/vdso: Fix lsl operand order

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Date:   Wed, 22 Apr 2020 11:57:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Samuel Neves <sneves@....uc.pt>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "Nobuhiro Iwamatsu (CIP)" <nobuhiro1.iwamatsu@...hiba.co.jp>
Subject: [PATCH 4.9 125/125] x86/vdso: Fix lsl operand order

From: Samuel Neves <sneves@....uc.pt>

commit e78e5a91456fcecaa2efbb3706572fe043766f4d upstream.

In the __getcpu function, lsl is using the wrong target and destination
registers. Luckily, the compiler tends to choose %eax for both variables,
so it has been working so far.

Fixes: a582c540ac1b ("x86/vdso: Use RDPID in preference to LSL when available")
Signed-off-by: Samuel Neves <sneves@....uc.pt>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Andy Lutomirski <luto@...nel.org>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180901201452.27828-1-sneves@dei.uc.pt
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@...hiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/vgtod.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -92,7 +92,7 @@ static inline unsigned int __getcpu(void
 	 *
 	 * If RDPID is available, use it.
 	 */
-	alternative_io ("lsl %[p],%[seg]",
+	alternative_io ("lsl %[seg],%[p]",
 			".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
 			X86_FEATURE_RDPID,
 			[p] "=a" (p), [seg] "r" (__PER_CPU_SEG));