From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Brian Gerst <brgerst@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Kees Cook <keescook@chromium.org>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Byungchul Park <byungchul.park@lge.com>
Subject: Re: [PATCH 10/19] x86/dumpstack: add get_stack_info() interface
Date: Tue, 26 Jul 2016 13:59:41 -0500 [thread overview]
Message-ID: <20160726185941.rpldgeban5m66r2d@treble> (raw)
In-Reply-To: <CAMzpN2ivhVynevNrbMarccWEa7=PbRsrbJ=weeFdCez2A5A8fw@mail.gmail.com>
On Tue, Jul 26, 2016 at 01:49:06PM -0400, Brian Gerst wrote:
> On Tue, Jul 26, 2016 at 12:47 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > On Mon, Jul 25, 2016 at 05:09:44PM -0700, Andy Lutomirski wrote:
> >> On Sat, Jul 23, 2016 at 7:04 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >> > Am I correct in understanding that there can only be one level of NMI
> >> > nesting at any given time? If so, could we make it easier on the
> >> > unwinder by putting the nested NMI on a separate software stack, so the
> >> > "next stack" pointers are always in the same place? Or am I just being
> >> > naive?
> >>
> >> I think you're being naive :)
> >
> > Another dumb question: since NMIs are reentrant, have you considered
> > removing the NMI IST entry, and instead just have NMIs keep using the
> > current stack?
> >
> > The first NMI could then be switched to an NMI software stack, like IRQs
> > (assuming there's a way to do that atomically!). And then determining
> > the context of subsequent NMIs would be straightforward, and we'd no
> > longer need to jump through all those horrible hoops in the entry code
> > to deal with NMI nesting.
> >
> > Now you can tell me what else I'm missing...
>
> There are several places (most notably SYSCALL entry) where the kernel
> stack pointer is unsafe/user controlled for a brief time. Since an
> NMI can interrupt anywhere in the kernel, you have to use an IST to
> protect against that case.
Ah, that makes sense. Thanks.
--
Josh
next prev parent reply other threads:[~2016-07-26 18:59 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-21 21:21 [PATCH 00/19] x86/dumpstack: rewrite x86 stack dump code Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 01/19] x86/dumpstack: remove show_trace() Josh Poimboeuf
2016-07-21 21:49 ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 02/19] x86/dumpstack: add get_stack_pointer() and get_frame_pointer() Josh Poimboeuf
2016-07-21 21:53 ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments Josh Poimboeuf
2016-07-21 21:56 ` Andy Lutomirski
2016-07-22 1:41 ` Josh Poimboeuf
2016-07-22 2:29 ` Andy Lutomirski
2016-07-22 3:08 ` Brian Gerst
2016-07-21 21:21 ` [PATCH 04/19] x86/dumpstack: make printk_stack_address() more generally useful Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 05/19] x86/dumpstack: fix function graph tracing stack dump reliability issues Josh Poimboeuf
2016-07-29 22:55 ` Steven Rostedt
2016-07-30 0:50 ` Josh Poimboeuf
2016-07-30 2:20 ` Steven Rostedt
2016-07-30 13:51 ` Josh Poimboeuf
2016-08-01 14:28 ` Steven Rostedt
2016-08-01 15:36 ` Josh Poimboeuf
2016-08-02 21:00 ` Josh Poimboeuf
2016-08-02 21:16 ` Steven Rostedt
2016-08-02 22:13 ` Josh Poimboeuf
2016-08-02 23:16 ` Steven Rostedt
2016-08-03 1:56 ` Josh Poimboeuf
2016-08-03 2:30 ` Steven Rostedt
2016-08-03 2:50 ` Josh Poimboeuf
2016-08-03 2:59 ` Steven Rostedt
2016-08-03 3:12 ` Josh Poimboeuf
2016-08-03 3:18 ` Steven Rostedt
2016-08-03 3:21 ` Steven Rostedt
2016-08-03 3:31 ` Josh Poimboeuf
2016-08-03 3:45 ` Steven Rostedt
2016-08-03 14:13 ` Josh Poimboeuf
2016-08-03 3:30 ` Josh Poimboeuf
2016-08-01 15:59 ` Josh Poimboeuf
2016-08-01 16:05 ` Steven Rostedt
2016-08-01 16:19 ` Josh Poimboeuf
2016-08-01 16:24 ` Josh Poimboeuf
2016-08-01 16:56 ` Steven Rostedt
2016-07-21 21:21 ` [PATCH 06/19] x86/dumpstack: remove extra brackets around "EOE" Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 07/19] x86/dumpstack: add IRQ_USABLE_STACK_SIZE define Josh Poimboeuf
2016-07-21 22:01 ` Andy Lutomirski
2016-07-22 1:48 ` Josh Poimboeuf
2016-07-22 8:24 ` Ingo Molnar
2016-07-21 21:21 ` [PATCH 08/19] x86/dumpstack: don't disable preemption in show_stack_log_lvl() and dump_trace() Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 09/19] x86/dumpstack: simplify in_exception_stack() Josh Poimboeuf
2016-07-21 22:05 ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 10/19] x86/dumpstack: add get_stack_info() interface Josh Poimboeuf
2016-07-22 23:26 ` Andy Lutomirski
2016-07-22 23:52 ` Andy Lutomirski
2016-07-23 13:09 ` Josh Poimboeuf
2016-07-22 23:54 ` Josh Poimboeuf
2016-07-23 0:15 ` Andy Lutomirski
2016-07-23 14:04 ` Josh Poimboeuf
2016-07-26 0:09 ` Andy Lutomirski
2016-07-26 16:26 ` Josh Poimboeuf
2016-07-26 17:51 ` Steven Rostedt
2016-07-26 18:56 ` Josh Poimboeuf
2016-07-26 20:59 ` Andy Lutomirski
2016-07-26 22:24 ` Josh Poimboeuf
2016-07-26 22:31 ` Steven Rostedt
2016-07-26 22:37 ` Andy Lutomirski
2016-07-26 16:47 ` Josh Poimboeuf
2016-07-26 17:49 ` Brian Gerst
2016-07-26 18:59 ` Josh Poimboeuf [this message]
2016-07-21 21:21 ` [PATCH 11/19] x86/dumptrace: add new unwind interface and implementations Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 12/19] perf/x86: convert perf_callchain_kernel() to the new unwinder Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 13/19] x86/stacktrace: convert save_stack_trace_*() " Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 14/19] oprofile/x86: convert x86_backtrace() " Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 15/19] x86/dumpstack: convert show_trace_log_lvl() " Josh Poimboeuf
2016-07-21 21:49 ` Byungchul Park
2016-07-22 1:38 ` Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 16/19] x86/dumpstack: remove dump_trace() Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 17/19] x86/entry/dumpstack: encode pt_regs pointer in frame pointer Josh Poimboeuf
2016-07-21 22:27 ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 18/19] x86/dumpstack: print stack identifier on its own line Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 19/19] x86/dumpstack: print any pt_regs found on the stack Josh Poimboeuf
2016-07-21 22:32 ` Andy Lutomirski
2016-07-22 3:30 ` Josh Poimboeuf
2016-07-22 5:13 ` Andy Lutomirski
2016-07-22 15:57 ` Josh Poimboeuf
2016-07-22 21:46 ` Andy Lutomirski
2016-07-22 22:20 ` Josh Poimboeuf
2016-07-22 23:18 ` Andy Lutomirski
2016-07-22 23:30 ` Josh Poimboeuf
2016-07-22 23:39 ` Andy Lutomirski
2016-07-23 0:00 ` Josh Poimboeuf
2016-07-23 0:22 ` [PATCH 00/19] x86/dumpstack: rewrite x86 stack dump code Linus Torvalds
2016-07-23 0:31 ` Andy Lutomirski
2016-07-23 5:35 ` Josh Poimboeuf
2016-07-23 5:39 ` Linus Torvalds
2016-07-23 12:53 ` Josh Poimboeuf
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