Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   David Laight <David.Laight@ACULAB.COM>
To:     'Peter Zijlstra' <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
CC:     LKML <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "Kenneth R. Crudup" <kenny@panix.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Jessica Yu <jeyu@kernel.org>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Xiaoyao Li <xiaoyao.li@intel.com>,
        Nadav Amit <namit@vmware.com>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        "Steven Rostedt" <rostedt@goodmis.org>
Subject: RE: [patch v2 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect
Thread-Topic: [patch v2 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect
Thread-Index: AQHWCQK4i0gO2diBOkK6XKhOFlCL2qhnC2Fg
Date:   Fri, 3 Apr 2020 08:09:03 +0000
Message-ID: <9b95fe9e81c14370859e19f081cc23e4@AcuMS.aculab.com>
References: <20200402123258.895628824@linutronix.de>
 <20200402124205.242674296@linutronix.de>
 <20200402152340.GL20713@hirez.programming.kicks-ass.net>
In-Reply-To: <20200402152340.GL20713@hirez.programming.kicks-ass.net>
Accept-Language: en-GB, en-US
Content-Language: en-US
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Peter Zijlstra
> Sent: 02 April 2020 16:24
> 
> I picked VMXOFF (which also appears in vmmon.ko) instead of VMXON
> because that latter takes an argument is therefore more difficult to
> decode.
...
> +	while (text < text_end) {
> +		kernel_insn_init(&insn, text, text_end - text);
> +		insn_get_length(&insn);
> +
> +		if (WARN_ON_ONCE(!insn_complete(&insn)))
> +			break;
> +
> +		if (insn.length == 3 &&
> +		    (!memcmp(text, vmlaunch, sizeof(vmlaunch)) ||
> +		     !memcmp(text, vmxoff, sizeof(vmxoff))))
> +				goto bad_module;
> +
> +		text += insn.length;
> +	}

How long is that going to take on a module with (say) 400k of text?

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)