From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Andy Lutomirski <luto@kernel.org>
Subject: Re: [patch 15/14] x86/dumpstack/64: Speedup in_exception_stack()
Date: Wed, 3 Apr 2019 18:26:06 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1904031823100.1967@nanos.tec.linutronix.de> (raw)
In-Reply-To: <6205D576-694A-4C7D-B1B7-A9FF2E1F9E77@amacapital.net>
[-- Attachment #1: Type: text/plain, Size: 1064 bytes --]
On Tue, 2 Apr 2019, Andy Lutomirski wrote:
> > On Apr 2, 2019, at 1:29 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> >>> How about a much better fix: make the DB stack be the same size as all
> >>> the others and just have 4 of them (DB0, DB1, DB2, and DB3. After all,
> >>> overflowing from one debug stack into another is just as much of a bug as
> >>> overflowing into a different IST stack.
> >>
> >> That makes sense.
> >
> > Except that we just have two not four.
> >
> > It needs some tweaking of the ist_shift stuff in entry_64.S but that's not
> > rocket science. Famous last words....
> >
>
> The ist_shift mess should probably be in C, but that’s a big can of
> worms. That being said, why do we have it at all? Once upon a time, we’d
> do ICEBP from user mode (or a legit breakpoint), then send a signal and
> hit a data breakpoint, and we’d recurse. But we don’t run user debug
> handlers on the IST stack at all anymore.
>
> Maybe we can convince ourselves it’s safe?
Maybe. Need to think about it for a while.
Thanks,
tglx
next prev parent reply other threads:[~2019-04-03 16:26 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-31 21:40 [patch 00/14] x86/exceptions: Add guard patches to IST stacks Thomas Gleixner
2019-03-31 21:40 ` [patch 01/14] x86/irq/64: Limit IST stack overflow check to #DB stack Thomas Gleixner
2019-04-01 18:03 ` Borislav Petkov
2019-04-02 16:34 ` Sean Christopherson
2019-03-31 21:40 ` [patch 02/14] x86/idt: Remove unused macro SISTG Thomas Gleixner
2019-04-01 4:04 ` Andy Lutomirski
2019-03-31 21:40 ` [patch 03/14] x86/exceptions: Remove unused stack defines on 32bit Thomas Gleixner
2019-03-31 21:40 ` [patch 04/14] x86/exceptions: Make IST index zero based Thomas Gleixner
2019-04-01 7:30 ` Peter Zijlstra
2019-04-01 7:33 ` Thomas Gleixner
2019-04-02 16:49 ` Sean Christopherson
2019-04-03 16:35 ` Borislav Petkov
2019-03-31 21:40 ` [patch 05/14] x86/cpu_entry_area: Cleanup setup functions Thomas Gleixner
2019-03-31 21:40 ` [patch 06/14] x86/exceptions: Add structs for exception stacks Thomas Gleixner
2019-03-31 21:40 ` [patch 07/14] x86/cpu_entry_area: Prepare for IST guard pages Thomas Gleixner
2019-03-31 21:40 ` [patch 08/14] x86/cpu_entry_area: Provide exception stack accessor Thomas Gleixner
2019-03-31 21:40 ` [patch 09/14] x86/traps: Use cpu_entry_area instead of orig_ist Thomas Gleixner
2019-03-31 21:40 ` [patch 10/14] x86/irq/64: Use cpu entry area " Thomas Gleixner
2019-03-31 21:40 ` [patch 11/14] x86/dumpstack/64: Use cpu_entry_area " Thomas Gleixner
2019-03-31 21:40 ` [patch 12/14] x86/cpu: Prepare TSS.IST setup for guard pages Thomas Gleixner
2019-04-02 16:57 ` Sean Christopherson
2019-03-31 21:40 ` [patch 13/14] x86/cpu: Remove orig_ist array Thomas Gleixner
2019-03-31 21:40 ` [patch 14/14] x86/exceptions: Enable IST guard pages Thomas Gleixner
2019-04-02 10:19 ` [patch 15/14] x86/dumpstack/64: Speedup in_exception_stack() Thomas Gleixner
2019-04-02 15:43 ` Josh Poimboeuf
2019-04-02 15:48 ` Thomas Gleixner
2019-04-02 15:51 ` Josh Poimboeuf
2019-04-02 15:53 ` Josh Poimboeuf
2019-04-03 8:08 ` Peter Zijlstra
2019-04-03 8:10 ` Peter Zijlstra
2019-04-03 15:11 ` Josh Poimboeuf
2019-04-02 16:11 ` Andy Lutomirski
2019-04-02 18:27 ` Thomas Gleixner
2019-04-02 19:29 ` Thomas Gleixner
2019-04-03 0:36 ` Andy Lutomirski
2019-04-03 16:26 ` Thomas Gleixner [this message]
2019-04-03 19:42 ` Thomas Gleixner
2019-04-04 0:03 ` Andy Lutomirski
2019-04-02 19:02 ` Rasmus Villemoes
2019-04-02 19:21 ` Thomas Gleixner
2019-04-03 8:02 ` Peter Zijlstra
2019-04-01 4:03 ` [patch 00/14] x86/exceptions: Add guard patches to IST stacks Andy Lutomirski
2019-04-03 16:30 ` Thomas Gleixner
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