linux-kernel - [tip: x86/asm] x86/entry/64: Add instruction suffix to SYSRET

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Date:   Thu, 09 Jan 2020 11:37:19 -0000
From:   "tip-bot2 for Jan Beulich" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Jan Beulich <jbeulich@...e.com>, Borislav Petkov <bp@...e.de>,
        Andy Lutomirski <luto@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/asm] x86/entry/64: Add instruction suffix to SYSRET

The following commit has been merged into the x86/asm branch of tip:

Commit-ID:     b2b1d94cdfd4e906d3936dab2850096a4a0c2017
Gitweb:        https://git.kernel.org/tip/b2b1d94cdfd4e906d3936dab2850096a4a0c2017
Author:        Jan Beulich <jbeulich@...e.com>
AuthorDate:    Mon, 16 Dec 2019 11:40:03 +01:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Thu, 09 Jan 2020 12:33:43 +01:00

x86/entry/64: Add instruction suffix to SYSRET

ignore_sysret() contains an unsuffixed SYSRET instruction. gas correctly
interprets this as SYSRETL, but leaving it up to gas to guess when there
is no register operand that implies a size is bad practice, and upstream
gas is likely to warn about this in the future. Use SYSRETL explicitly.
This does not change the assembled output.

Signed-off-by: Jan Beulich <jbeulich@...e.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Acked-by: Andy Lutomirski <luto@...nel.org>
Link: https://lkml.kernel.org/r/038a7c35-062b-a285-c6d2-653b56585844@suse.com
---
 arch/x86/entry/entry_64.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 76942cb..f2bb91e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1728,7 +1728,7 @@ SYM_CODE_END(nmi)
 SYM_CODE_START(ignore_sysret)
 	UNWIND_HINT_EMPTY
 	mov	$-ENOSYS, %eax
-	sysret
+	sysretl
 SYM_CODE_END(ignore_sysret)
 #endif