linux-kernel - Re: [tip:x86/asm] x86/entry/32: Switch INT80 to the new C syscall path

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Date:	Thu, 15 Oct 2015 12:09:16 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Gerst <brgerst@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [tip:x86/asm] x86/entry/32: Switch INT80 to the new C syscall path

On Thu, Oct 15, 2015 at 11:09 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Fri, Oct 09, 2015 at 06:12:44AM -0700, tip-bot for Andy Lutomirski wrote:
>> Commit-ID:  150ac78d63afb96360dab448b7b4d33c98c8266c
>> Gitweb:     http://git.kernel.org/tip/150ac78d63afb96360dab448b7b4d33c98c8266c
>> Author:     Andy Lutomirski <luto@...nel.org>
>> AuthorDate: Mon, 5 Oct 2015 17:48:14 -0700
>> Committer:  Ingo Molnar <mingo@...nel.org>
>> CommitDate: Fri, 9 Oct 2015 09:41:10 +0200
>>
>> x86/entry/32: Switch INT80 to the new C syscall path
>>
>> Signed-off-by: Andy Lutomirski <luto@...nel.org>
>> Cc: Andy Lutomirski <luto@...capital.net>
>> Cc: Borislav Petkov <bp@...en8.de>
>> Cc: Brian Gerst <brgerst@...il.com>
>> Cc: Denys Vlasenko <dvlasenk@...hat.com>
>> Cc: H. Peter Anvin <hpa@...or.com>
>> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: linux-kernel@...r.kernel.org
>> Link: http://lkml.kernel.org/r/a7e8d8df96838eae3208dd0441023f3ce7a81831.1444091585.git.luto@kernel.org
>> Signed-off-by: Ingo Molnar <mingo@...nel.org>
>> ---
>>  arch/x86/entry/entry_32.S | 34 +++++++++++++---------------------
>>  1 file changed, 13 insertions(+), 21 deletions(-)
>
> Just triggered this here on rc5+tip/master, 32-bit. Any ideas?
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 1 at /mnt/kernel/kernel/linux-2.6/kernel/locking/lockdep.c:2639 trace_hardirqs_off_caller+0xef/0x150()
> DEBUG_LOCKS_WARN_ON(!irqs_disabled())
> Modules linked in:
>
> CPU: 1 PID: 1 Comm: init Tainted: G        W       4.3.0-rc5+ #1
> Hardware name: LENOVO 30515QG/30515QG, BIOS 8RET30WW (1.12 ) 09/15/2011
>  00000000 00000000 f44fbf34 c1301072 f44fbf74 f44fbf64 c105658d c1819094
>  f44fbf90 00000001 c181f838 00000a4f c10a284f c10a284f f4520000 c1662048
>  00000009 f44fbf7c c10565f3 00000009 f44fbf74 c1819094 f44fbf90 f44fbf9c
> Call Trace:
>  [<c1301072>] dump_stack+0x4b/0x79
>  [<c105658d>] warn_slowpath_common+0x8d/0xc0
>  [<c10a284f>] ? trace_hardirqs_off_caller+0xef/0x150
>  [<c10a284f>] ? trace_hardirqs_off_caller+0xef/0x150
>  [<c1662048>] ? entry_INT80_32+0x28/0x2f

Can you turn that entry_INT80_32 address into either a line number of
some assembly code?  I'm not seeing the code path that could do this,
and there are two unlikely choices.

Based on the warning that triggered, I assume you have
CONFIG_PROVE_LOCKING=y, which means that the obvious failures that
would have blown up like this should also have warned earlier.

--Andy
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