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From: Andy Lutomirski <luto@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>, X86 ML <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 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
Date: Wed, 26 Feb 2020 07:10:01 -0800	[thread overview]
Message-ID: <CALCETrVXzwmwNOB6qUk7aM=LQRBySrMJPdRZ244T3y1bpRBzaQ@mail.gmail.com> (raw)
In-Reply-To: <20200226132850.GX18400@hirez.programming.kicks-ass.net>

On Wed, Feb 26, 2020 at 5:28 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Feb 25, 2020 at 09:29:00PM -0800, Andy Lutomirski wrote:
>
> > >> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
> > >>  {
> > >>    DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
> > >>    DECLARE_BITMAP(toclear, MAX_NR_BANKS);
> > >> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
> > >>    ist_exit(regs);
> > >>  }
> > >>  EXPORT_SYMBOL_GPL(do_machine_check);
> > >> +NOKPROBE_SYMBOL(do_machine_check);
> > >
> > > That won't protect all the function called by do_machine_check(), right?
> > > There are lots of them.
> > >
> >
> > It at least means we can survive to run actual C code in
> > do_machine_check(), which lets us try to mitigate this issue further.
> > PeterZ has patches for that, and maybe this series fixes it later on.
> > (I'm reading in order!)
>
> Yeah, I don't cover that either. Making the kernel completely kprobe
> safe is _lots_ more work I think.
>
> We really need some form of automation for this :/ The current situation
> is completely nonsatisfactory.

I've looked at too many patches lately and lost track a bit of which
is which.  Shouldn't a simple tracing_disable() or similar in
do_machine_check() be sufficient?  We'd maybe want automation to check
everything before it.  We still need to survive hitting a kprobe int3,
but that shouldn't have recursion issues.

(Yes, that function doesn't exist in current kernels.  And we'd need
to make sure that BPF respects it.)

  reply	other threads:[~2020-02-26 15:10 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
2020-02-26  1:00   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
2020-02-26  1:13   ` Frederic Weisbecker
2020-02-26  5:29     ` Andy Lutomirski
2020-02-26 13:28       ` Peter Zijlstra
2020-02-26 15:10         ` Andy Lutomirski [this message]
2020-02-26 16:08           ` Peter Zijlstra
2020-02-26 17:28             ` Andy Lutomirski
2020-02-26 18:42               ` Borislav Petkov
2020-02-26 18:59                 ` Peter Zijlstra
2020-02-26 19:09                   ` Andy Lutomirski
2020-02-26 20:59                     ` Steven Rostedt
2020-02-26 11:18   ` Borislav Petkov
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Andy Lutomirski
2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
2020-02-26  1:11   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Thomas Gleixner
2020-02-26  1:19   ` Frederic Weisbecker
2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
2020-02-26 17:08   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 07/10] x86/irq: Remove useless return value from do_IRQ() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries Thomas Gleixner
2020-02-26  5:34   ` Andy Lutomirski
2020-02-26 18:42     ` Thomas Gleixner
2020-02-26 18:57       ` Andy Lutomirski
2020-02-26 19:15         ` Thomas Gleixner
2020-02-27 14:24           ` [patch V2 " Thomas Gleixner
2020-02-29 11:49             ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
2020-02-26 17:35   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-27 14:33   ` tip-bot2 for Andy Lutomirski
2020-02-26  5:26 ` [patch 00/10] x86/entry: Consolidation - Part I Andy Lutomirski
2020-02-26  5:35 ` Andy Lutomirski
2020-02-27 11:01 ` Alexandre Chartre

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