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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [PATCH] x86-64/entry: add instruction suffix to SYSRET
Date:   Tue, 10 Dec 2019 07:29:52 -0800
Message-Id: <08B92B44-CCA9-4B83-B9CC-F1601D44B73F@amacapital.net>
References: <cbecab05-9e95-5dec-ef81-499617c153a6@suse.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
In-Reply-To: <cbecab05-9e95-5dec-ef81-499617c153a6@suse.com>
To:     Jan Beulich <JBeulich@suse.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Dec 10, 2019, at 2:48 AM, Jan Beulich <JBeulich@suse.com> wrote:
>=20
> =EF=BB=BFOmitting suffixes from instructions in AT&T mode is bad practice w=
hen
> operand size cannot be determined by the assembler from register
> operands, and is likely going to be warned about by upstream gas in the
> future. Add the missing suffix here.
>=20
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>=20
> --- 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

Isn=E2=80=99t the default sysretq?  sysretl looks more correct, but that sug=
gests that your changelog is wrong.

Is this code even reachable?

> SYM_CODE_END(ignore_sysret)
> #endif
>=20