linux-kernel - Re: Direct rdtsc call side-effect

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230601085602.GR4253@hirez.programming.kicks-ass.net>
Date:   Thu, 1 Jun 2023 10:56:02 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Steven Noonan <steven@...inklabs.net>, kernel@...labora.com
Subject: Re: Direct rdtsc call side-effect

On Thu, Jun 01, 2023 at 01:45:35PM +0500, Muhammad Usama Anjum wrote:
> Hi,
> 
> I've been looking into a problem where Windows applications misbehave
> across suspend/resume when run on Wine on x86. These applications see time
> going backwards. The timestamp counter (TSC) is reset when system resumes.
> In case of Windows on Intel and AMD, the timestamp is saved and restored
> when the system resumes from suspend.
> 
> These applications read timestamp by rdtsc directly. These calls cannot be
> intercepted by Wine. The application should be fixed such that it handles
> these scenarios correctly. But there are hundreds of applications which
> cannot be fixed. So some support is required in Wine or kernel. There isn't
> anything which Wine can do as rdtsc call directly reads the timestamp. The
> only option is that we support something in kernel.
> 
> As more and more things are being added to Wine, Windows application can be
> run pretty easily on Linux. But this rdtsc is a big hurdle. What are your
> thoughts on solving this problem?
> 
> We are thinking of saving and restoring the timestamp counter at suspend
> and resume time respectively. In theory it can work on Intel because of
> TSC_ADJUST register. But it'll never work on AMD until:
> * AMD supports the same kind of adjust register. (AMD has said that the
> adjust register cannot be implemented in their firmware. They'll have to
> add it to their hardware.)
> * by manual synchronization in kernel (I know you don't like this idea. But
> there is something Windows is doing to save/restore and sync the TSC)

Wine could set TIF_NOTSC, which will cause it to run with CR4.TSD
cleared and cause RDTSC to #GP, at which point you can emulate it.