From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@amacapital.net>,
Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
Brian Gerst <brgerst@gmail.com>, Juergen Gross <JGross@suse.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code
Date: Wed, 26 Feb 2020 20:51:01 +0100 [thread overview]
Message-ID: <87sgixb00q.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <83D8A083-792A-4A82-985C-CAC33BC702DB@amacapital.net>
Andy Lutomirski <luto@amacapital.net> writes:
>> On Feb 26, 2020, at 12:17 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>> On Tue, Feb 25, 2020 at 09:43:46PM -0800, Andy Lutomirski wrote:
>>> Your earlier patches suggest quite strongly that tracing isn't safe
>>> until enter_from_user_mode(). But trace_hardirqs_off() calls
>>> trace_irq_disable_rcuidle(), which looks [0] like a tracepoint.
>>>
>>> Did you perhaps mean to do this *after* enter_from_user_mode()?
>>
>> aside from the fact that enter_from_user_mode() itself also has a
>> tracepoint, the crucial detail is that we must not trace/kprobe the
>> function calling this.
>>
>> Specifically for #PF, because we need read_cr2() before this. See later
>> patches.
>
> Indeed. I’m fine with this patch, but I still don’t understand what
> the changelog is about.
Yeah, the changelog is not really helpful. Let me fix that.
> And I’m still rather baffled by most of the notrace annotations in the
> series.
As discussed on IRC, this might be too broad, but then I rather have the
actual C-entry points neither traceable nor probable in general and
relax this by calling functions which can be traced and probed.
My rationale for this decision was that enter_from_user_mode() is marked
notrace/noprobe as well, so I kept the protection scope the same as we
had in the ASM maze which is marked noprobe already.
Thanks,
tglx
next prev parent reply other threads:[~2020-02-26 19:51 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 22:08 [patch 0/8] x86/entry: Consolidation - Part II Thomas Gleixner
2020-02-25 22:08 ` [patch 1/8] x86/entry/64: Trace irqflags unconditionally on when returing to user space Thomas Gleixner
2020-02-27 19:49 ` Borislav Petkov
2020-02-27 22:45 ` Frederic Weisbecker
2020-02-28 8:58 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 2/8] x86/entry/common: Consolidate syscall entry code Thomas Gleixner
2020-02-27 19:57 ` Borislav Petkov
2020-02-27 22:52 ` Frederic Weisbecker
2020-02-28 8:59 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 3/8] x86/entry/common: Mark syscall entry points notrace/nokprobe Thomas Gleixner
2020-02-27 23:15 ` Frederic Weisbecker
2020-02-28 8:59 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code Thomas Gleixner
2020-02-26 5:43 ` Andy Lutomirski
2020-02-26 8:17 ` Peter Zijlstra
2020-02-26 11:20 ` Andy Lutomirski
2020-02-26 19:51 ` Thomas Gleixner [this message]
2020-02-29 14:44 ` Thomas Gleixner
2020-02-29 19:25 ` Andy Lutomirski
2020-02-29 23:58 ` Steven Rostedt
2020-03-01 10:16 ` Thomas Gleixner
2020-03-01 14:37 ` Andy Lutomirski
2020-03-01 15:21 ` Thomas Gleixner
2020-03-01 16:00 ` Andy Lutomirski
2020-03-01 18:12 ` Thomas Gleixner
2020-03-01 18:26 ` Paul E. McKenney
2020-03-01 18:54 ` Andy Lutomirski
2020-03-01 19:30 ` Paul E. McKenney
2020-03-01 19:39 ` Andy Lutomirski
2020-03-01 20:18 ` Paul E. McKenney
2020-03-02 0:35 ` Steven Rostedt
2020-03-02 6:47 ` Masami Hiramatsu
2020-03-02 1:10 ` Joel Fernandes
2020-03-02 2:18 ` Andy Lutomirski
2020-03-02 2:36 ` Joel Fernandes
2020-03-02 5:40 ` Andy Lutomirski
2020-03-02 8:10 ` Thomas Gleixner
2020-03-01 18:23 ` Steven Rostedt
2020-03-01 18:20 ` Steven Rostedt
2020-02-27 23:11 ` Frederic Weisbecker
2020-02-28 9:00 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 5/8] x86/entry/common: Provide trace/kprobe safe exit to user space functions Thomas Gleixner
2020-02-26 5:45 ` Andy Lutomirski
2020-02-26 8:15 ` Peter Zijlstra
2020-02-27 15:43 ` Alexandre Chartre
2020-02-27 15:53 ` Thomas Gleixner
2020-02-25 22:08 ` [patch 6/8] x86/entry: Move irq tracing to syscall_slow_exit_work Thomas Gleixner
2020-02-26 5:47 ` Andy Lutomirski
2020-02-27 16:12 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 7/8] x86/entry: Move irq tracing to prepare_exit_to_user_mode() Thomas Gleixner
2020-02-26 5:50 ` Andy Lutomirski
2020-02-26 19:53 ` Thomas Gleixner
2020-02-26 20:07 ` Andy Lutomirski
2020-02-25 22:08 ` [patch 8/8] x86/entry: Move irqflags tracing to do_int80_syscall_32() Thomas Gleixner
2020-02-27 16:46 ` Alexandre Chartre
2020-02-28 13:49 ` Thomas Gleixner
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