From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
mingo@kernel.org, joel@joelfernandes.org,
gregkh@linuxfoundation.org, gustavo@embeddedor.com,
tglx@linutronix.de, josh@joshtriplett.org,
mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
luto@kernel.org, tony.luck@intel.com, frederic@kernel.org,
dan.carpenter@oracle.com, mhiramat@kernel.org
Subject: Re: [PATCH v3 04/22] x86/doublefault: Make memmove() notrace/NOKPROBE
Date: Wed, 19 Feb 2020 17:34:09 +0100 [thread overview]
Message-ID: <20200219163409.GI18400@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200219162747.GX2935@paulmck-ThinkPad-P72>
On Wed, Feb 19, 2020 at 08:27:47AM -0800, Paul E. McKenney wrote:
> On Wed, Feb 19, 2020 at 11:12:28AM -0500, Steven Rostedt wrote:
> > On Wed, 19 Feb 2020 17:04:42 +0100
> > Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > > > - memmove(&gpregs->ip, (void *)regs->sp, 5*8);
> > > > + for (i = 0; i < count; i++) {
> > > > + int idx = (dst <= src) ? i : count - i;
> > >
> > > That's an off-by-one for going backward; 'count - 1 - i' should work
> > > better, or I should just stop typing for today ;-)
> >
> > Or, we could just cut and paste the current memmove and make a notrace
> > version too. Then we don't need to worry bout bugs like this.
>
> OK, I will bite...
>
> Can we just make the core be an inline function and make a notrace and
> a trace caller? Possibly going one step further and having one call
> the other? (Presumably the traceable version invoking the notrace
> version, but it has been one good long time since I have looked at
> function preambles.)
One complication is that GCC (and others) are prone to stick their own
implementation of memmove() (and other string functions) in at 'random'.
That is, it is up to the compiler's discretion wether or not to put a
call to memmove() in or just emit some random giberish they feel has the
same effect.
So if we go play silly games like that, we need be careful (or just call
__memmove I suppose, which is supposed to avoid that IIRC).
next prev parent reply other threads:[~2020-02-19 16:34 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 14:47 [PATCH v3 00/22] tracing vs world Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 01/22] hardirq/nmi: Allow nested nmi_enter() Peter Zijlstra
2020-02-19 15:31 ` Steven Rostedt
2020-02-19 16:56 ` Borislav Petkov
2020-02-19 17:07 ` Peter Zijlstra
2020-02-20 8:41 ` Will Deacon
2020-02-20 9:19 ` Marc Zyngier
2020-02-20 13:18 ` Petr Mladek
2020-02-19 14:47 ` [PATCH v3 02/22] x86,mce: Delete ist_begin_non_atomic() Peter Zijlstra
2020-02-19 17:13 ` Borislav Petkov
2020-02-19 17:21 ` Andy Lutomirski
2020-02-19 17:33 ` Peter Zijlstra
2020-02-19 22:12 ` Andy Lutomirski
2020-02-19 22:33 ` Luck, Tony
2020-02-19 22:48 ` Andy Lutomirski
2020-02-20 7:39 ` Peter Zijlstra
2020-02-19 17:42 ` Borislav Petkov
2020-02-19 17:46 ` Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 03/22] x86: Replace ist_enter() with nmi_enter() Peter Zijlstra
2020-02-20 10:54 ` Borislav Petkov
2020-02-20 12:11 ` Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 04/22] x86/doublefault: Make memmove() notrace/NOKPROBE Peter Zijlstra
2020-02-19 15:36 ` Steven Rostedt
2020-02-19 15:40 ` Peter Zijlstra
2020-02-19 15:55 ` Steven Rostedt
2020-02-19 15:57 ` Peter Zijlstra
2020-02-19 16:04 ` Peter Zijlstra
2020-02-19 16:12 ` Steven Rostedt
2020-02-19 16:27 ` Paul E. McKenney
2020-02-19 16:34 ` Peter Zijlstra [this message]
2020-02-19 16:46 ` Paul E. McKenney
2020-02-19 17:05 ` Steven Rostedt
2020-02-20 12:17 ` Borislav Petkov
2020-02-20 12:37 ` Peter Zijlstra
2020-02-19 15:47 ` Steven Rostedt
2020-02-19 14:47 ` [PATCH v3 05/22] rcu: Make RCU IRQ enter/exit functions rely on in_nmi() Peter Zijlstra
2020-02-19 16:31 ` Paul E. McKenney
2020-02-19 16:37 ` Peter Zijlstra
2020-02-19 16:45 ` Paul E. McKenney
2020-02-19 17:03 ` Peter Zijlstra
2020-02-19 17:42 ` Paul E. McKenney
2020-02-19 17:16 ` [PATCH] rcu/kprobes: Comment why rcu_nmi_enter() is marked NOKPROBE Steven Rostedt
2020-02-19 17:18 ` Joel Fernandes
2020-02-19 17:41 ` Paul E. McKenney
2020-02-20 5:54 ` Masami Hiramatsu
2020-02-19 14:47 ` [PATCH v3 06/22] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-19 16:38 ` Paul E. McKenney
2020-02-19 14:47 ` [PATCH v3 07/22] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-19 16:39 ` Paul E. McKenney
2020-02-19 17:19 ` Steven Rostedt
2020-02-19 14:47 ` [PATCH v3 08/22] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-19 15:49 ` Steven Rostedt
2020-02-19 15:58 ` Peter Zijlstra
2020-02-19 16:15 ` Steven Rostedt
2020-02-19 16:35 ` Peter Zijlstra
2020-02-19 16:44 ` Paul E. McKenney
2020-02-20 10:34 ` Peter Zijlstra
2020-02-20 13:58 ` Paul E. McKenney
2020-02-19 14:47 ` [PATCH v3 09/22] sched,rcu,tracing: Avoid tracing before in_nmi() is correct Peter Zijlstra
2020-02-19 15:50 ` Steven Rostedt
2020-02-19 15:50 ` Steven Rostedt
2020-02-19 14:47 ` [PATCH v3 10/22] x86,tracing: Add comments to do_nmi() Peter Zijlstra
2020-02-19 15:51 ` Steven Rostedt
2020-02-19 14:47 ` [PATCH v3 11/22] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 12/22] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-19 15:52 ` Steven Rostedt
2020-02-19 14:47 ` [PATCH v3 13/22] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-02-19 15:53 ` Steven Rostedt
2020-02-19 16:43 ` Paul E. McKenney
2020-02-19 16:47 ` Peter Zijlstra
2020-02-19 17:05 ` Peter Zijlstra
2020-02-19 17:21 ` Steven Rostedt
2020-02-19 17:40 ` Paul E. McKenney
2020-02-19 18:00 ` Steven Rostedt
2020-02-19 19:05 ` Paul E. McKenney
2020-02-19 14:47 ` [PATCH v3 14/22] perf,tracing: Allow function tracing when !RCU Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 15/22] x86/int3: Ensure that poke_int3_handler() is not traced Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 16/22] locking/atomics, kcsan: Add KCSAN instrumentation Peter Zijlstra
2020-02-19 15:46 ` Steven Rostedt
2020-02-19 16:03 ` Peter Zijlstra
2020-02-19 16:50 ` Paul E. McKenney
2020-02-19 16:54 ` Peter Zijlstra
2020-02-19 17:36 ` Paul E. McKenney
2020-02-19 14:47 ` [PATCH v3 17/22] asm-generic/atomic: Use __always_inline for pure wrappers Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 18/22] asm-generic/atomic: Use __always_inline for fallback wrappers Peter Zijlstra
2020-02-19 16:55 ` Paul E. McKenney
2020-02-19 17:06 ` Peter Zijlstra
2020-02-19 17:35 ` Paul E. McKenney
2020-02-19 14:47 ` [PATCH v3 19/22] compiler: Simple READ/WRITE_ONCE() implementations Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 20/22] locking/atomics: Flip fallbacks and instrumentation Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 21/22] x86/int3: Avoid atomic instrumentation Peter Zijlstra
2020-02-19 14:47 ` [PATCH v3 22/22] x86/int3: Ensure that poke_int3_handler() is not sanitized Peter Zijlstra
2020-02-19 16:06 ` Dmitry Vyukov
2020-02-19 16:30 ` Peter Zijlstra
2020-02-19 16:51 ` Peter Zijlstra
2020-02-19 17:20 ` Peter Zijlstra
2020-02-20 10:37 ` Dmitry Vyukov
2020-02-20 12:06 ` Peter Zijlstra
2020-02-20 16:22 ` Dmitry Vyukov
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