From: Andy Lutomirski <luto@kernel.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
moritz.lipp@iaik.tugraz.at,
Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
michael.schwarz@iaik.tugraz.at,
richard.fellner@student.tugraz.at,
Linus Torvalds <torvalds@linux-foundation.org>,
Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>,
X86 ML <x86@kernel.org>
Subject: Re: [PATCH 24/30] x86, kaiser: disable native VSYSCALL
Date: Sun, 12 Nov 2017 19:52:34 -0800 [thread overview]
Message-ID: <CALCETrWyagW0YV_-4xhiCxrxDBXTW7MBfZbSDbMY_mBYtsPRaA@mail.gmail.com> (raw)
In-Reply-To: <7ec56785-8e18-4ac8-ebe8-ebdd3ac265da@linux.intel.com>
On Fri, Nov 10, 2017 at 3:04 PM, Dave Hansen
<dave.hansen@linux.intel.com> wrote:
> On 11/10/2017 02:06 PM, Andy Lutomirski wrote:
>> On Thu, Nov 9, 2017 at 10:31 PM, Dave Hansen
>> <dave.hansen@linux.intel.com> wrote:
>>> On 11/09/2017 06:25 PM, Andy Lutomirski wrote:
>>>> Here are two proposals to address this without breaking vsyscalls.
>>>>
>>>> 1. Set NX on low mappings that are _PAGE_USER. Don't set NX on high
>>>> mappings but, optionally, warn if you see _PAGE_USER on any address
>>>> that isn't the vsyscall page.
>>>>
>>>> 2. Ignore _PAGE_USER entirely and just mark the EFI mm as special so
>>>> KAISER doesn't muck with it.
>>>
>>> These are totally doable. But, what's the big deal with breaking native
>>> vsyscall? We can still do the emulation so nothing breaks: it is just slow.
>>
>> I have nothing against disabling native. I object to breaking the
>> weird binary tracing behavior in the emulation mode, especially if
>> it's tangled up with KAISER. I got all kinds of flak in an earlier
>> version of the vsyscall emulation patches when I broke that use case.
>> KAISER may get very widely backported -- let's not make changes that
>> are already known to break things.
>
> Is the thing that broke a "user mode program that actually looks at the
> vsyscall page"? Like Linus is referring to here:
>
Yes. But I disagree with Linus. I think it would be perfectly
reasonable to enable KAISER and to use a tool like pin on a legacy
binary from some enterprise distribution. I bet there are lots of
enterprise distributions that are still supported that use vsyscalls.
next prev parent reply other threads:[~2017-11-13 3:52 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-08 19:46 [PATCH 00/30] [v2] KAISER: unmap most of the kernel from userspace page tables Dave Hansen
2017-11-08 19:46 ` [PATCH 01/30] x86, mm: do not set _PAGE_USER for init_mm " Dave Hansen
2017-11-08 19:52 ` Linus Torvalds
2017-11-08 20:11 ` Dave Hansen
2017-11-09 10:29 ` Borislav Petkov
2017-11-08 19:46 ` [PATCH 02/30] x86, tlb: make CR4-based TLB flushes more robust Dave Hansen
2017-11-09 10:48 ` Borislav Petkov
2017-11-09 10:51 ` Thomas Gleixner
2017-11-09 11:02 ` Borislav Petkov
2017-11-08 19:46 ` [PATCH 03/30] x86, mm: document X86_CR4_PGE toggling behavior Dave Hansen
2017-11-09 12:21 ` Borislav Petkov
2017-11-08 19:46 ` [PATCH 04/30] x86, kaiser: disable global pages by default with KAISER Dave Hansen
2017-11-09 12:51 ` Borislav Petkov
2017-11-09 22:19 ` Thomas Gleixner
2017-11-08 19:46 ` [PATCH 05/30] x86, kaiser: prepare assembly for entry/exit CR3 switching Dave Hansen
2017-11-09 13:20 ` Borislav Petkov
2017-11-09 15:34 ` Dave Hansen
2017-11-09 15:59 ` Borislav Petkov
2017-11-08 19:46 ` [PATCH 06/30] x86, kaiser: introduce user-mapped percpu areas Dave Hansen
2017-11-08 19:46 ` [PATCH 07/30] x86, kaiser: mark percpu data structures required for entry/exit Dave Hansen
2017-11-08 19:47 ` [PATCH 08/30] x86, kaiser: unmap kernel from userspace page tables (core patch) Dave Hansen
2017-11-10 12:57 ` Ingo Molnar
2017-11-08 19:47 ` [PATCH 09/30] x86, kaiser: only populate shadow page tables for userspace Dave Hansen
2017-11-08 19:47 ` [PATCH 10/30] x86, kaiser: allow NX to be set in p4d/pgd Dave Hansen
2017-11-08 19:47 ` [PATCH 11/30] x86, kaiser: make sure static PGDs are 8k in size Dave Hansen
2017-11-08 19:47 ` [PATCH 12/30] x86, kaiser: map GDT into user page tables Dave Hansen
2017-11-08 19:47 ` [PATCH 13/30] x86, kaiser: map dynamically-allocated LDTs Dave Hansen
2017-11-08 19:47 ` [PATCH 14/30] x86, kaiser: map espfix structures Dave Hansen
2017-11-08 19:47 ` [PATCH 15/30] x86, kaiser: map entry stack variables Dave Hansen
2017-11-08 19:47 ` [PATCH 16/30] x86, kaiser: map trace interrupt entry Dave Hansen
2017-11-08 19:47 ` [PATCH 17/30] x86, kaiser: map debug IDT tables Dave Hansen
2017-11-08 19:47 ` [PATCH 18/30] x86, kaiser: map virtually-addressed performance monitoring buffers Dave Hansen
2017-11-10 12:17 ` Peter Zijlstra
2017-11-08 19:47 ` [PATCH 19/30] x86, mm: Move CR3 construction functions Dave Hansen
2017-11-08 19:47 ` [PATCH 20/30] x86, mm: remove hard-coded ASID limit checks Dave Hansen
2017-11-10 12:20 ` Peter Zijlstra
2017-11-10 18:41 ` Dave Hansen
2017-11-08 19:47 ` [PATCH 21/30] x86, mm: put mmu-to-h/w ASID translation in one place Dave Hansen
2017-11-08 19:47 ` [PATCH 22/30] x86, pcid, kaiser: allow flushing for future ASID switches Dave Hansen
2017-11-10 12:25 ` Peter Zijlstra
2017-11-08 19:47 ` [PATCH 23/30] x86, kaiser: use PCID feature to make user and kernel switches faster Dave Hansen
2017-11-08 19:47 ` [PATCH 24/30] x86, kaiser: disable native VSYSCALL Dave Hansen
2017-11-09 19:04 ` Andy Lutomirski
2017-11-09 19:26 ` Dave Hansen
2017-11-10 0:53 ` Andy Lutomirski
2017-11-10 0:57 ` Dave Hansen
2017-11-10 1:04 ` Andy Lutomirski
2017-11-10 1:22 ` Dave Hansen
2017-11-10 2:25 ` Andy Lutomirski
2017-11-10 6:31 ` Dave Hansen
2017-11-10 22:06 ` Andy Lutomirski
2017-11-10 23:04 ` Dave Hansen
2017-11-13 3:52 ` Andy Lutomirski [this message]
2017-11-13 21:07 ` Dave Hansen
2017-11-14 2:15 ` Andy Lutomirski
2017-11-08 19:47 ` [PATCH 25/30] x86, kaiser: add debugfs file to turn KAISER on/off at runtime Dave Hansen
2017-11-08 19:47 ` [PATCH 26/30] x86, kaiser: add a function to check for KAISER being enabled Dave Hansen
2017-11-08 19:47 ` [PATCH 27/30] x86, kaiser: un-poison PGDs at runtime Dave Hansen
2017-11-08 19:47 ` [PATCH 28/30] x86, kaiser: allow KAISER to be enabled/disabled " Dave Hansen
2017-11-08 19:47 ` [PATCH 29/30] x86, kaiser: add Kconfig Dave Hansen
2017-11-08 19:47 ` [PATCH 30/30] x86, kaiser, xen: Dynamically disable KAISER when running under Xen PV Dave Hansen
2017-11-09 15:01 ` Juergen Gross
2017-11-10 19:30 [PATCH 00/30] [v3] KAISER: unmap most of the kernel from userspace page tables Dave Hansen
2017-11-10 19:31 ` [PATCH 24/30] x86, kaiser: disable native VSYSCALL Dave Hansen
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