From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
"davej@codemonkey.org.uk" <davej@codemonkey.org.uk>,
"dvyukov@google.com" <dvyukov@google.com>,
Stephane Eranian <eranian@gmail.com>
Subject: Re: perf: fuzzer KASAN unwind_get_return_address
Date: Wed, 16 Nov 2016 08:58:40 -0600 [thread overview]
Message-ID: <20161116145840.gvh5wwycmdkluhuy@treble> (raw)
In-Reply-To: <20161116144943.GB3117@twins.programming.kicks-ass.net>
On Wed, Nov 16, 2016 at 03:49:43PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 16, 2016 at 08:37:46AM -0600, Josh Poimboeuf wrote:
> > On Wed, Nov 16, 2016 at 02:03:37PM +0100, Peter Zijlstra wrote:
> > > On Tue, Nov 15, 2016 at 02:57:48PM -0600, Josh Poimboeuf wrote:
> > > > Would you mind posting a disassembly of unwind_get_return_address()?
> > > > Any idea how recreatable it is? (In particular I'd be interested in
> > > > seeing this dump with the latest unwinder improvements in the -tip tree,
> > > > which dump the pt_regs associated with an interrupt.)
> > >
> > > Fairly reproducable it seems, doesn't seem to include pt_regs dumps
> > > though :/
> > >
> > > tip/master as of this morning.
> >
> > Thanks. This is actually a different issue than the one reported by
> > Vince. In this case FRAME_POINTER is disabled, so it uses the "guess"
> > unwinder which scans every address on the stack, looking for text
> > addresses. So the kasan errors are expected.
> >
> > (The missing pt_regs are also expected: the guess unwinder doesn't show
> > them.)
> >
> > I'll work up a patch to fix this. I still have no idea what's causing
> > Vince's bug in the frame pointer unwinder.
>
> Hurm,.. by the number of '?' entries in Vince's backtrace I was assuming
> it was without frame pointers.
When frame pointers are disabled, *all* the addresses are prefixed with
'?'.
When frame pointers are enabled, and there are a lot of '?' addresses,
it usually means the containing functions reserved a lot of stack space
and the printed addresses are mostly leftovers from previous runs.
> Let me enable those and run again, it didn't insta-trigger like it does
> without.
Thanks!
--
Josh
next prev parent reply other threads:[~2016-11-16 14:58 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-15 17:43 perf: fuzzer KASAN unwind_get_return_address Vince Weaver
2016-11-15 18:57 ` Peter Zijlstra
2016-11-15 19:04 ` Dmitry Vyukov
2016-11-15 20:56 ` Josh Poimboeuf
2016-11-15 19:05 ` Vince Weaver
2016-11-15 20:57 ` Josh Poimboeuf
2016-11-16 13:03 ` Peter Zijlstra
2016-11-16 13:18 ` Dmitry Vyukov
2016-11-16 14:37 ` Josh Poimboeuf
2016-11-16 14:49 ` Peter Zijlstra
2016-11-16 14:58 ` Josh Poimboeuf [this message]
2016-11-16 14:58 ` Peter Zijlstra
2016-11-17 4:48 ` Josh Poimboeuf
2016-11-17 9:04 ` Peter Zijlstra
2016-11-17 9:13 ` Peter Zijlstra
2016-11-17 9:30 ` Peter Zijlstra
2016-11-17 9:48 ` Dmitry Vyukov
2016-11-17 14:01 ` Josh Poimboeuf
2016-11-17 14:25 ` Vince Weaver
2016-11-17 14:36 ` Josh Poimboeuf
2016-11-17 14:58 ` Dmitry Vyukov
2016-11-17 17:15 ` Vince Weaver
2016-11-17 15:18 ` Josh Poimboeuf
2016-11-17 16:07 ` Peter Zijlstra
2016-11-17 17:17 ` Peter Zijlstra
2016-11-22 12:30 ` [tip:perf/urgent] perf/x86/intel: Cure bogus unwind from PEBS entries tip-bot for Peter Zijlstra
2016-11-16 15:06 ` perf: fuzzer KASAN unwind_get_return_address Vince Weaver
2016-11-17 15:57 ` [PATCH 1/2] unwind: prevent KASAN false positive warnings in guess unwinder Josh Poimboeuf
2016-11-17 15:57 ` [PATCH 2/2] dumpstack: prevent KASAN false positive warnings Josh Poimboeuf
2016-11-18 9:04 ` [tip:x86/urgent] x86/dumpstack: Prevent " tip-bot for Josh Poimboeuf
2016-11-17 20:26 ` [PATCH 1/2] unwind: prevent KASAN false positive warnings in guess unwinder Josh Poimboeuf
2016-11-18 8:38 ` Ingo Molnar
2016-11-18 9:04 ` [tip:x86/urgent] x86/unwind: Prevent " tip-bot for Josh Poimboeuf
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