linux-kernel - Re: [patch V4 part 1 22/36] tracing: Provide lockdep less trace_hardirqs

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: <87eervefx9.fsf@nanos.tec.linutronix.de>
Date:   Thu, 07 May 2020 20:52:18 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 1 22/36] tracing: Provide lockdep less trace_hardirqs_on/off() variants

Andy Lutomirski <luto@...nel.org> writes:

> On Tue, May 5, 2020 at 7:13 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>> trace_hardirqs_on/off() is only partially safe vs. RCU idle. The tracer
>> core itself is safe, but the resulting tracepoints can be utilized by
>> e.g. BPF which is unsafe.
>>
>> Provide variants which do not contain the lockdep invocation so the lockdep
>> and tracer invocations can be split at the call site and placed properly.
>>
>> The new variants also do not use rcuidle as they are going to be called
>> from entry code after/before context tracking.
>
> I can't quite follow this.  Are you saying that the new variants are
> intended to be called by the entry code in a context where tracing is
> acceptable and that the lockdep part will still be called in a context
> where tracing is not acceptable?

Yes. Before RCU is reestablished and after. I'll rephrase.