linux-kernel - [tip:x86/urgent] x86/vdso: Fix lsl operand order

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Message-ID: <tip-e78e5a91456fcecaa2efbb3706572fe043766f4d@git.kernel.org>
Date:   Sat, 1 Sep 2018 14:06:50 -0700
From:   tip-bot for Samuel Neves <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, luto@...nel.org,
        sneves@....uc.pt, hpa@...or.com, mingo@...nel.org
Subject: [tip:x86/urgent] x86/vdso: Fix lsl operand order

Commit-ID:  e78e5a91456fcecaa2efbb3706572fe043766f4d
Gitweb:     https://git.kernel.org/tip/e78e5a91456fcecaa2efbb3706572fe043766f4d
Author:     Samuel Neves <sneves@....uc.pt>
AuthorDate: Sat, 1 Sep 2018 21:14:52 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sat, 1 Sep 2018 23:01:56 +0200

x86/vdso: Fix lsl operand order

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

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

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index fb856c9f0449..53748541c487 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -93,7 +93,7 @@ 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));