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From: Ingo Molnar <mingo@kernel.org>
To: lkp@lists.01.org
Subject: Re: [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##]
Date: Fri, 18 May 2018 09:15:59 +0200	[thread overview]
Message-ID: <20180518071559.GA26358@gmail.com> (raw)
In-Reply-To: <CA+55aFzTpkn_fokmm+ddi+cgk5K3EOftRmPad+NkUb5W2z0Fqg@mail.gmail.com>

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* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Tue, May 15, 2018 at 3:43 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> 
> > Glancing through the 32-bit and 64-bit entry code, I didn't see any more
> > cases.  At least it will fail loudly if any such cases do still exist.
> 
> \Will it? Do we have objtool checks for it now?
> 
> Because without static checks, there could be things hiding that just don't
> happen normally (think compat code etc that for most people is just dead
> code).

And it's not just about infrequent uses, it's also about hard to debug crashes 
like in suspend/resume code, where people can only report "machine is dead".

So I'm not sure this side effect of turning padding into crashes is good for 
overall robustness, without static analysis finding such bugs.

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Peter Anvin <h.peter.anvin@intel.com>,
	kernel test robot <xiaolong.ye@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Lutomirski <luto@kernel.org>,
	Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Peter Anvin <hpa@zytor.com>, tipbuild@zytor.com, LKP <lkp@01.org>
Subject: Re: [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##]
Date: Fri, 18 May 2018 09:15:59 +0200	[thread overview]
Message-ID: <20180518071559.GA26358@gmail.com> (raw)
In-Reply-To: <CA+55aFzTpkn_fokmm+ddi+cgk5K3EOftRmPad+NkUb5W2z0Fqg@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Tue, May 15, 2018 at 3:43 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> 
> > Glancing through the 32-bit and 64-bit entry code, I didn't see any more
> > cases.  At least it will fail loudly if any such cases do still exist.
> 
> \Will it? Do we have objtool checks for it now?
> 
> Because without static checks, there could be things hiding that just don't
> happen normally (think compat code etc that for most people is just dead
> code).

And it's not just about infrequent uses, it's also about hard to debug crashes 
like in suspend/resume code, where people can only report "machine is dead".

So I'm not sure this side effect of turning padding into crashes is good for 
overall robustness, without static analysis finding such bugs.

Thanks,

	Ingo

  parent reply	other threads:[~2018-05-18  7:15 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-15  8:00 [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##] kernel test robot
2018-05-15  8:00 ` kernel test robot
2018-05-15 21:07 ` Alexey Dobriyan
2018-05-15 21:07   ` Alexey Dobriyan
2018-05-15 21:25   ` Anvin, H Peter
2018-05-15 21:43     ` Alexey Dobriyan
2018-05-15 21:43       ` Alexey Dobriyan
2018-05-15 22:22       ` Josh Poimboeuf
2018-05-15 22:22         ` Josh Poimboeuf
2018-05-15 22:26         ` Thomas Gleixner
2018-05-15 22:26           ` Thomas Gleixner
2018-05-15 22:28         ` Linus Torvalds
2018-05-15 22:28           ` Linus Torvalds
2018-05-15 22:43           ` Josh Poimboeuf
2018-05-15 22:43             ` Josh Poimboeuf
2018-05-15 22:52             ` Linus Torvalds
2018-05-15 22:52               ` Linus Torvalds
2018-05-15 23:05               ` Linus Torvalds
2018-05-15 23:05                 ` Linus Torvalds
2018-05-16  3:30                 ` Josh Poimboeuf
2018-05-16  3:30                   ` Josh Poimboeuf
2018-05-17 13:49                   ` [PATCH] objtool: Detect assembly code falling through to INT3 padding Josh Poimboeuf
2018-05-17 13:49                     ` Josh Poimboeuf
2018-05-17 14:01                     ` Peter Zijlstra
2018-05-17 14:01                       ` Peter Zijlstra
2018-05-18  7:24                       ` Ingo Molnar
2018-05-18  7:24                         ` Ingo Molnar
2018-05-18  7:18                     ` Ingo Molnar
2018-05-18  7:18                       ` Ingo Molnar
2018-05-18  7:27                       ` H. Peter Anvin
2018-05-18 16:06                         ` Borislav Petkov
2018-05-18 16:06                           ` Borislav Petkov
2018-05-18  7:27                       ` Ingo Molnar
2018-05-18  7:27                         ` Ingo Molnar
2018-05-18 17:51                       ` Alexey Dobriyan
2018-05-18 17:51                         ` Alexey Dobriyan
2018-05-19  8:18                         ` hpa
2018-05-19  7:00                 ` "interesting" entry in hibernation code was Re: [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##] Pavel Machek
2018-05-19  7:00                   ` Pavel Machek
2018-05-19  8:35                   ` Rafael J. Wysocki
2018-05-19  8:35                     ` Rafael J. Wysocki
2018-05-18  7:15               ` Ingo Molnar [this message]
2018-05-18  7:15                 ` Ingo Molnar
2018-05-15 22:25       ` Thomas Gleixner
2018-05-15 22:25         ` Thomas Gleixner
2018-05-15 22:29         ` Andy Lutomirski
2018-05-15 22:29           ` Andy Lutomirski
2018-05-15 22:27       ` Linus Torvalds
2018-05-15 22:27         ` Linus Torvalds
2018-05-15 22:50         ` Alexey Dobriyan
2018-05-15 22:50           ` Alexey Dobriyan
2018-05-15 22:58           ` [PATCH v2] x86/asm: Pad assembly functions with INT3 instructions Alexey Dobriyan
2018-05-15 22:58             ` Alexey Dobriyan
2018-05-15 23:28             ` Linus Torvalds
2018-05-15 23:28               ` Linus Torvalds
2018-05-18  7:36             ` Ingo Molnar
2018-05-18  7:36               ` Ingo Molnar
2018-05-18 13:02               ` Josh Poimboeuf
2018-05-18 13:02                 ` Josh Poimboeuf
2018-05-18 17:34                 ` Alexey Dobriyan
2018-05-18 17:34                   ` Alexey Dobriyan

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