linux-kernel - [PATCH v2] x86-64/entry: add instruction suffix to SYSRET

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Date:   Mon, 16 Dec 2019 11:40:03 +0100
From:   Jan Beulich <jbeulich@...e.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     the arch/x86 maintainers <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] x86-64/entry: 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>
Acked-by: Andy Lutomirski <luto@...nel.org>
---
v2: Use re-written description from Andy.

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1728,7 +1728,7 @@ END(nmi)
 SYM_CODE_START(ignore_sysret)
 	UNWIND_HINT_EMPTY
 	mov	$-ENOSYS, %eax
-	sysret
+	sysretl
 SYM_CODE_END(ignore_sysret)
 #endif