linux-kernel - Re: [PATCH] x86/asm/entry/64: Clean up entry

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Date:	Mon, 6 Jul 2015 18:43:30 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>, linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/asm/entry/64: Clean up entry_64.S


* Sasha Levin <sasha.levin@...cle.com> wrote:

> On 07/06/2015 12:23 PM, Ingo Molnar wrote:
> > 
> > * Sasha Levin <sasha.levin@...cle.com> wrote:
> > 
> >> On 07/06/2015 12:07 PM, Ingo Molnar wrote:
> >>>
> >>> * Sasha Levin <sasha.levin@...cle.com> wrote:
> >>>
> >>>> Hey Ingo,
> >>>>
> >>>> I've started seeing the fuzzer hitting the BUG() at arch/x86/kernel/nmi.c:533. git
> >>>> blame pointed to this patch. I know that you didn't see any changes in the compiled
> >>>> file in your testcase, but I do see changes in mine.
> >>>
> >>> Hm, weird - could you send me your .config please?
> >>
> >> Attached.
> > 
> > It's still weird: I copied your config to 4d7321381e5c and made 'make oldconfig' - 
> > and it asked a couple of questions, which suggests that your config does not come 
> > from 4d7321381e5c?
> 
> Right, sorry, this is my base config for -next. I just did 'yes "" | make oldconfig'
> for the build test.
> 
> I've attached it.
> 
> > Furthermore, building 4d7321381e5c and 4d7321381e5c^1 gives me:
> > 
> >   # arch/x86/entry/entry_64.o:
> > 
> >    text    data     bss     dec     hex filename
> >   11530       0       0   11530    2d0a entry_64.o.before
> >   11530       0       0   11530    2d0a entry_64.o.after
> > 
> > md5:
> >    1430e793250d5d8572bc2df2997d3929  entry_64.o.before.asm
> >    1430e793250d5d8572bc2df2997d3929  entry_64.o.after.asm
> > 
> > i.e. I have trouble reproducing the discrepancy you are seeing. (I also tried 
> > allmodconfig/allyesconfig again for good measure - no luck.)
> 
> With allyesconfig I don't actually see a change. Only with the config I've attached.

So I still cannot reproduce it even with your latest config:

  # arch/x86/entry/entry_64.o:

   text    data     bss     dec     hex filename
  11530       0       0   11530    2d0a entry_64.o.before
  11530       0       0   11530    2d0a entry_64.o.after

md5:
   1430e793250d5d8572bc2df2997d3929  entry_64.o.before.asm
   1430e793250d5d8572bc2df2997d3929  entry_64.o.after.asm

but I saw this during the build:

  scripts/Makefile.kasan:23: CONFIG_KASAN: compiler does not support all options. Trying minimal configuration

is your KASAN build more fully enabled, and does the problem reproduce with 
CONFIG_KASAN turned off?

Thanks,

	Ingo
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