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From: Dmitry Vyukov <dvyukov@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@kernel.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Josh Triplett <josh@joshtriplett.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Andy Lutomirski <luto@kernel.org>,
	tony.luck@intel.com, Frederic Weisbecker <frederic@kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [PATCH v3 22/22] x86/int3: Ensure that poke_int3_handler() is not sanitized
Date: Thu, 20 Feb 2020 17:22:14 +0100	[thread overview]
Message-ID: <CACT4Y+bj_Onff8jUP97AVRhmdeN0QRrGcd9KRPSfnFTHAHyxtA@mail.gmail.com> (raw)
In-Reply-To: <20200220120631.GX18400@hirez.programming.kicks-ass.net>

On Thu, Feb 20, 2020 at 1:06 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Thu, Feb 20, 2020 at 11:37:32AM +0100, Dmitry Vyukov wrote:
> > On Wed, Feb 19, 2020 at 6:20 PM Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > On Wed, Feb 19, 2020 at 05:30:25PM +0100, Peter Zijlstra wrote:
> > >
> > > > By inlining everything in poke_int3_handler() (except bsearch :/) we can
> > > > mark the whole function off limits to everything and call it a day. That
> > > > simplicity has been the guiding principle so far.
> > > >
> > > > Alternatively we can provide an __always_inline variant of bsearch().
> > >
> > > This reduces the __no_sanitize usage to just the exception entry
> > > (do_int3) and the critical function: poke_int3_handler().
> > >
> > > Is this more acceptible?
> >
> > Let's say it's more acceptable.
> >
> > Acked-by: Dmitry Vyukov <dvyukov@google.com>
>
> Thanks, I'll go make it happen.
>
> > I guess there is no ideal solution here.
> >
> > Just a straw man proposal: expected number of elements is large enough
> > to make bsearch profitable, right? I see 1 is a common case, but the
> > other case has multiple entries.
>
> Latency was the consideration; the linear search would dramatically
> increase the runtime of the exception.
>
> The current limit is 256 entries and we're hitting that quite often.
>
> (we can trivially increase, but nobody has been able to show significant
> benefits for that -- as of yet)

I see. Thanks for explaining. Just wanted to check because inlining a
linear search would free us from all these unpleasant problems.

      reply	other threads:[~2020-02-20 16:22 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
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 [this message]

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