From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@amacapital.net>,
"H. Peter Anvin" <hpa@zytor.com>,
Andi Kleen <andi@firstfloor.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
libc-alpha <libc-alpha@sourceware.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Carlos O'Donell <carlos@redhat.com>, x86 <x86@kernel.org>
Subject: Re: rseq/x86: choosing rseq code signature
Date: Wed, 10 Apr 2019 08:54:17 +0200 [thread overview]
Message-ID: <20190410065417.GU11158@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <913288111.2663.1554842622822.JavaMail.zimbra@efficios.com>
On Tue, Apr 09, 2019 at 04:43:42PM -0400, Mathieu Desnoyers wrote:
> +/*
> + * RSEQ_SIG is used with the following privileged instructions, which trap in user-space:
> + * x86-32: 0f 01 3d 53 30 05 53 invlpg 0x53053053
> + * x86-64: 0f 01 3d 53 30 05 53 invlpg 0x53053053(%rip)
> + */
Right, and the alternative is: 0f b9 3d $SIG, which decodes to:
UD1 $SIG(%rip),%edi
which will trap unconditionally. The only problem is that gas will not
actually assemble it, but since we're .byte coding it, it doesn't
matter.
UD1 is specified by both AMD and Intel to take a ModR/M, unlike UD0
where they disagree on the ModR/M.
next prev parent reply other threads:[~2019-04-10 6:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-09 19:32 Mathieu Desnoyers
2019-04-09 20:43 ` Mathieu Desnoyers
2019-04-10 0:50 ` Zack Weinberg
2019-04-10 1:57 ` Andy Lutomirski
2019-04-10 4:19 ` Mathieu Desnoyers
2019-04-10 6:54 ` Peter Zijlstra [this message]
2019-04-10 15:47 ` Mathieu Desnoyers
2019-04-10 17:57 ` Peter Zijlstra
2019-04-10 18:05 ` Mathieu Desnoyers
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