From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>,
Greg KH <gregkh@linuxfoundation.org>,
gustavo@embeddedor.com, Thomas Gleixner <tglx@linutronix.de>,
paulmck@kernel.org, Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Tony Luck <tony.luck@intel.com>,
Frederic Weisbecker <frederic@kernel.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH v4 05/27] x86: Replace ist_enter() with nmi_enter()
Date: Mon, 24 Feb 2020 17:34:09 +0100 [thread overview]
Message-ID: <20200224163409.GJ18400@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200224112708.4f307ba3@gandalf.local.home>
On Mon, Feb 24, 2020 at 11:27:08AM -0500, Steven Rostedt wrote:
> On Mon, 24 Feb 2020 11:43:46 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > -dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
> > +dotraplinkage notrace void do_int3(struct pt_regs *regs, long error_code)
> > {
> > if (poke_int3_handler(regs))
> > return;
> >
> > /*
> > - * Use ist_enter despite the fact that we don't use an IST stack.
> > - * We can be called from a kprobe in non-CONTEXT_KERNEL kernel
> > - * mode or even during context tracking state changes.
> > - *
> > - * This means that we can't schedule. That's okay.
> > + * Unlike any other non-IST entry, we can be called from pretty much
> > + * any location in the kernel through kprobes -- text_poke() will most
> > + * likely be handled by poke_int3_handler() above. This means this
> > + * handler is effectively NMI-like.
> > */
> > - ist_enter(regs);
> > + nmi_enter();
>
> Hmm, note that nmi_enter() calls other functions. Did you make sure
> all of them are not able to be kprobed. This is different than just
> being "NMI like", it's that if they are kprobed, then this will go into
> an infinite loop because nothing can have a kprobe before the kprobe
> int3 handler is called here.
I did not audit that; I went with the fact that hitting kprobes before
in_nmi() is true is a bug.
Looking at nmi_enter(), that leaves trace_hardirq_enter(), since we know
we marked rcu_nmi_enter() as NOKPROBES, per the patches elsewhere in
this series.
next prev parent reply other threads:[~2020-02-24 16:34 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 13:34 [PATCH v4 00/27] tracing vs world Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 01/27] lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions Peter Zijlstra
2020-02-21 15:08 ` Steven Rostedt
2020-02-21 20:25 ` Peter Zijlstra
2020-02-21 20:28 ` Steven Rostedt
2020-02-21 22:01 ` Frederic Weisbecker
2020-02-22 3:08 ` Joel Fernandes
2020-02-24 10:10 ` Peter Zijlstra
2020-02-25 2:12 ` Joel Fernandes
2020-03-20 12:58 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 02/27] hardirq/nmi: Allow nested nmi_enter() Peter Zijlstra
2020-02-21 22:21 ` Frederic Weisbecker
2020-02-24 12:13 ` Petr Mladek
2020-02-25 1:30 ` Frederic Weisbecker
2020-02-24 16:13 ` Peter Zijlstra
2020-02-25 3:09 ` Frederic Weisbecker
2020-02-25 15:41 ` Peter Zijlstra
2020-02-25 16:21 ` Frederic Weisbecker
2020-02-25 22:10 ` Frederic Weisbecker
2020-02-27 9:10 ` Peter Zijlstra
2020-02-27 13:34 ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 03/27] x86/entry: Flip _TIF_SIGPENDING and _TIF_NOTIFY_RESUME handling Peter Zijlstra
2020-02-21 16:14 ` Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 04/27] x86/mce: Delete ist_begin_non_atomic() Peter Zijlstra
2020-02-21 19:07 ` Andy Lutomirski
2020-02-21 23:40 ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 05/27] x86: Replace ist_enter() with nmi_enter() Peter Zijlstra
2020-02-21 19:05 ` Andy Lutomirski
2020-02-21 20:22 ` Peter Zijlstra
2020-02-24 10:43 ` Peter Zijlstra
2020-02-24 16:27 ` Steven Rostedt
2020-02-24 16:34 ` Peter Zijlstra [this message]
2020-02-24 16:47 ` Steven Rostedt
2020-02-24 21:31 ` Peter Zijlstra
2020-02-24 22:02 ` Steven Rostedt
2020-02-26 10:25 ` Peter Zijlstra
2020-02-26 13:16 ` Peter Zijlstra
2020-02-26 10:27 ` Peter Zijlstra
2020-02-26 15:20 ` Steven Rostedt
2020-03-07 1:53 ` Masami Hiramatsu
2020-02-21 13:34 ` [PATCH v4 06/27] x86/doublefault: Remove memmove() call Peter Zijlstra
2020-02-21 19:10 ` Andy Lutomirski
2020-02-21 13:34 ` [PATCH v4 07/27] rcu: Make RCU IRQ enter/exit functions rely on in_nmi() Peter Zijlstra
2020-02-26 0:23 ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 08/27] rcu/kprobes: Comment why rcu_nmi_enter() is marked NOKPROBE Peter Zijlstra
2020-02-26 0:27 ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 09/27] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-21 20:21 ` Steven Rostedt
2020-02-24 10:24 ` Peter Zijlstra
2020-02-26 0:35 ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 10/27] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 11/27] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-03-06 11:50 ` Peter Zijlstra
2020-03-06 12:40 ` Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 12/27] sched,rcu,tracing: Avoid tracing before in_nmi() is correct Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 13/27] x86,tracing: Add comments to do_nmi() Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 14/27] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 15/27] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 16/27] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-03-06 10:43 ` Peter Zijlstra
2020-03-06 11:31 ` Peter Zijlstra
2020-03-06 15:51 ` Alexei Starovoitov
2020-03-06 16:04 ` Mathieu Desnoyers
2020-03-06 17:55 ` Steven Rostedt
2020-03-06 18:45 ` Joel Fernandes
2020-03-06 18:59 ` Steven Rostedt
2020-03-06 19:14 ` Joel Fernandes
2020-03-06 20:22 ` Mathieu Desnoyers
2020-03-06 20:45 ` Steven Rostedt
2020-03-06 20:55 ` Mathieu Desnoyers
2020-03-06 21:06 ` Steven Rostedt
2020-03-06 23:10 ` Alexei Starovoitov
2020-03-06 17:21 ` Joel Fernandes
2020-02-21 13:34 ` [PATCH v4 17/27] perf,tracing: Allow function tracing when !RCU Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 18/27] x86/int3: Ensure that poke_int3_handler() is not traced Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 19/27] locking/atomics, kcsan: Add KCSAN instrumentation Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 20/27] asm-generic/atomic: Use __always_inline for pure wrappers Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 21/27] asm-generic/atomic: Use __always_inline for fallback wrappers Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 22/27] compiler: Simple READ/WRITE_ONCE() implementations Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 23/27] locking/atomics: Flip fallbacks and instrumentation Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 24/27] x86/int3: Avoid atomic instrumentation Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 25/27] lib/bsearch: Provide __always_inline variant Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 26/27] x86/int3: Inline bsearch() Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 27/27] x86/int3: Ensure that poke_int3_handler() is not sanitized Peter Zijlstra
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