From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: paulmck <paulmck@kernel.org>, Masami Hiramatsu <mhiramat@kernel.org>
Cc: rostedt <rostedt@goodmis.org>,
"Joel Fernandes, Google" <joel@joelfernandes.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>
Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()
Date: Tue, 18 Feb 2020 11:15:30 -0500 (EST) [thread overview]
Message-ID: <1841874582.7975.1582042530726.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20200218161231.GD2935@paulmck-ThinkPad-P72>
----- On Feb 18, 2020, at 11:12 AM, paulmck paulmck@kernel.org wrote:
> On Tue, Feb 18, 2020 at 01:33:35PM +0900, Masami Hiramatsu wrote:
>> On Mon, 17 Feb 2020 08:31:12 -0800
>> "Paul E. McKenney" <paulmck@kernel.org> wrote:
>> >
>> > > BTW, if you consider the x86 specific code is in the generic file,
>> > > we can move NOKPROBE_SYMBOL() in arch/x86/kernel/traps.c.
>> > > (Sorry, I've hit this idea right now)
>> >
>> > Might this affect other architectures with NMIs and probe-like things?
>> > If so, it might make sense to leave it where it is.
>>
>> Yes, git grep shows that arm64 is using rcu_nmi_enter() in
>> debug_exception_enter().
>> OK, let's keep it, but maybe it is good to update the comment for
>> arm64 too. What about following?
>>
>> +/*
>> + * All functions in do_int3() on x86, do_debug_exception() on arm64 must be
>> + * marked NOKPROBE before kprobes handler is called.
>> + * ist_enter() on x86 and debug_exception_enter() on arm64 which is called
>> + * before kprobes handle happens to call rcu_nmi_enter() which means
>> + * that rcu_nmi_enter() must be marked NOKRPOBE.
>> + */
>
> Would it work to describe the general problem, then give x86 details
> as a specific example, as follows?
>
> /*
> * On some architectures, certain exceptions prohibit use of kprobes until
> * the exception code path reaches a certain point. For example, on x86 all
> * functions called by do_int3() must be marked NOKPROBE. However, once
> * kprobe_int3_handler() is called, kprobing is permitted. Specifically,
> * ist_enter() is called in do_int3() before kprobe_int3_handle().
> * Furthermore, ist_enter() calls rcu_nmi_enter(), which means that
> * rcu_nmi_enter() must be marked NOKRPOBE.
> */
>
> That way, I don't feel like I need to update the commment each time
> a new architecture adds this capability. ;-)
I suspect this kind of comment would belong in a new
Documentation/features/kprobes/annotations.txt or something
similar. You might want to look at other "features" files to see
the expected layout.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2020-02-18 16:15 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 21:01 [PATCH v2 0/9] tracing vs rcu vs nmi Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 1/9] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-12 22:38 ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 2/9] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-12 22:38 ` Joel Fernandes
2020-02-13 1:41 ` Steven Rostedt
2020-02-13 14:25 ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12 23:20 ` Joel Fernandes
2020-02-13 8:27 ` Peter Zijlstra
2020-02-13 13:31 ` Joel Fernandes
2020-02-13 13:51 ` Paul E. McKenney
2020-02-13 16:40 ` Peter Zijlstra
2020-02-13 18:56 ` Paul E. McKenney
2020-02-13 20:44 ` Joel Fernandes
2020-02-13 20:54 ` Paul E. McKenney
2020-02-13 21:19 ` Joel Fernandes
2020-02-13 21:38 ` Steven Rostedt
2020-02-13 21:50 ` Paul E. McKenney
2020-02-13 22:04 ` Steven Rostedt
2020-02-13 22:39 ` Paul E. McKenney
2020-02-14 6:19 ` Masami Hiramatsu
2020-02-15 14:59 ` Paul E. McKenney
2020-02-17 8:55 ` Masami Hiramatsu
2020-02-17 16:31 ` Paul E. McKenney
2020-02-18 4:33 ` Masami Hiramatsu
2020-02-18 16:12 ` Paul E. McKenney
2020-02-18 16:15 ` Mathieu Desnoyers [this message]
2020-02-18 16:35 ` Steven Rostedt
2020-02-18 17:46 ` Steven Rostedt
2020-02-18 20:18 ` Paul E. McKenney
2020-02-19 2:45 ` Masami Hiramatsu
2020-03-06 18:01 ` Masami Hiramatsu
2020-03-06 18:47 ` Joel Fernandes
2020-03-06 19:11 ` Joel Fernandes
2020-03-07 1:58 ` Masami Hiramatsu
2020-03-06 0:42 ` Thomas Gleixner
2020-02-13 21:48 ` Paul E. McKenney
2020-02-13 22:58 ` Joel Fernandes
2020-02-13 23:55 ` Steven Rostedt
2020-02-18 19:58 ` Peter Zijlstra
2020-02-18 20:17 ` Paul E. McKenney
2020-02-18 20:40 ` Peter Zijlstra
2020-02-18 21:39 ` Paul E. McKenney
2020-02-19 9:57 ` Peter Zijlstra
2020-02-19 12:46 ` Paul E. McKenney
2020-02-12 23:27 ` Joel Fernandes
2020-02-13 8:28 ` Peter Zijlstra
2020-02-13 18:39 ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 4/9] sched,rcu,tracing: Avoid tracing before in_nmi() is correct Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 5/9] x86,tracing: Add comments to do_nmi() Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 6/9] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-12 23:28 ` Joel Fernandes
2020-02-13 8:29 ` Peter Zijlstra
2020-02-13 18:38 ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 7/9] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 8/9] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 9/9] perf,tracing: Allow function tracing when !RCU Peter Zijlstra
2020-02-14 2:28 ` Sergey Senozhatsky
2020-02-14 2:42 ` Sergey Senozhatsky
2020-02-14 3:32 ` Steven Rostedt
2020-02-14 20:38 ` Kim Phillips
2020-02-14 22:48 ` Steven Rostedt
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