From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Borislav Petkov <bp@alien8.de>
Cc: x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: WARNING: kernel stack frame pointer at ffffffff82e03f40 in swapper:0 has bad value (null)
Date: Tue, 13 Dec 2016 08:34:55 -0600 [thread overview]
Message-ID: <20161213143455.kj5siigmad4f3xim@treble> (raw)
In-Reply-To: <20161212230511.22dusz7bwrvmtjd3@treble>
On Mon, Dec 12, 2016 at 05:05:11PM -0600, Josh Poimboeuf wrote:
> On Mon, Dec 12, 2016 at 11:33:54PM +0100, Borislav Petkov wrote:
> > On Mon, Dec 12, 2016 at 04:11:47PM -0600, Josh Poimboeuf wrote:
> > > Yes, please.
> >
> > Attached.
>
> Thanks, I was able to recreate. Will take a look tomorrow.
Figured it out. Your config has CONFIG_PARAVIRT=n, which convinces gcc
to create the following preamble for x86_64_start_kernel():
0000000000000124 <x86_64_start_kernel>:
124: 4c 8d 54 24 08 lea 0x8(%rsp),%r10
129: 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
12d: 41 ff 72 f8 pushq -0x8(%r10)
131: 55 push %rbp
132: 48 89 e5 mov %rsp,%rbp
It's an unusual pattern which aligns rsp (though in this case it's
already aligned) and saves the start_cpu() return address again on the
stack before storing the frame pointer.
The unwinder assumes the last stack frame header is at a certain offset,
but the above code breaks that assumption. I still need to think about
the best way to fix it.
--
Josh
next prev parent reply other threads:[~2016-12-13 14:35 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-10 16:17 WARNING: kernel stack frame pointer at ffffffff82e03f40 in swapper:0 has bad value (null) Borislav Petkov
2016-12-10 17:04 ` Josh Poimboeuf
2016-12-10 17:28 ` Borislav Petkov
2016-12-12 15:45 ` Josh Poimboeuf
2016-12-12 17:50 ` Borislav Petkov
2016-12-12 18:10 ` Josh Poimboeuf
2016-12-12 21:16 ` Josh Poimboeuf
2016-12-12 21:34 ` Borislav Petkov
2016-12-12 22:11 ` Josh Poimboeuf
2016-12-12 22:33 ` Borislav Petkov
2016-12-12 23:05 ` Josh Poimboeuf
2016-12-13 14:34 ` Josh Poimboeuf [this message]
2016-12-13 16:55 ` Andy Lutomirski
2016-12-13 17:26 ` Josh Poimboeuf
2016-12-13 17:51 ` Borislav Petkov
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