From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
X86 ML <x86@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH RFC V2 17/17] x86/entry: Preserve PKRS MSR across exceptions
Date: Fri, 24 Jul 2020 00:14:28 +0200 [thread overview]
Message-ID: <874kpxx4jf.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrUdxpVP3dZgsZBpCODxW8yaiHguxTu=aHg_AkRbs91dWg@mail.gmail.com>
Andy Lutomirski <luto@kernel.org> writes:
>> On Jul 23, 2020, at 1:22 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> Andy Lutomirski <luto@amacapital.net> writes:
>>> My suggestion is to enlarge pt_regs. The save and restore logic can
>>> probably be in C, but pt_regs is the logical place to put a register
>>> that is saved and restored across all entries.
>>
>> Kinda, but that still sucks because schedule from #PF will get it wrong
>> unless you do extra nasties.
>
> This seems like we’re reinventing the wheel. PKRS is not
> fundamentally different from, say, RSP. If we want to save it across
> exceptions, we save it on entry and context-switch-out and restore it
> on exit and context-switch-in.
It's fundamentally different from RSP because it has state (refcount)
attached, which RSP clearly has not. If you get rid of the state then
yes.
>>> Whoever does this work will have the delightful job of figuring out
>>> whether BPF thinks that the layout of pt_regs is ABI and, if so,
>>> fixing the resulting mess.
>>>
>>> The fact the new fields will go at the beginning of pt_regs will make
>>> this an entertaining prospect.
>>
>> Good luck with all of that.
>
> We can always cheat like this:
>
> struct real_pt_regs {
> unsigned long pkrs;
> struct pt_regs regs;
> };
>
> and pass a pointer to regs around. What BPF doesn't know about can't hurt it.
Yes, but that's the easy part of the problem :)
Thanks,
tglx
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next prev parent reply other threads:[~2020-07-23 22:14 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 7:20 [PATCH RFC V2 00/17] PKS: Add Protection Keys Supervisor (PKS) support ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 01/17] x86/pkeys: Create pkeys_internal.h ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 02/17] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support ira.weiny
2020-07-17 8:54 ` Peter Zijlstra
2020-07-17 20:52 ` Ira Weiny
2020-07-20 9:14 ` Peter Zijlstra
2020-07-17 22:36 ` Dave Hansen
2020-07-20 9:13 ` Peter Zijlstra
2020-07-17 7:20 ` [PATCH RFC V2 03/17] x86/pks: Enable Protection Keys Supervisor (PKS) ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 04/17] x86/pks: Preserve the PKRS MSR on context switch ira.weiny
2020-07-17 8:31 ` Peter Zijlstra
2020-07-17 21:39 ` Ira Weiny
2020-07-17 8:59 ` Peter Zijlstra
2020-07-17 22:34 ` Ira Weiny
2020-07-20 9:15 ` Peter Zijlstra
2020-07-20 18:35 ` Ira Weiny
2020-07-17 7:20 ` [PATCH RFC V2 05/17] x86/pks: Add PKS kernel API ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 06/17] x86/pks: Add a debugfs file for allocated PKS keys ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 07/17] Documentation/pkeys: Update documentation for kernel pkeys ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 08/17] x86/pks: Add PKS Test code ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 09/17] memremap: Convert devmap static branch to {inc,dec} ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 10/17] fs/dax: Remove unused size parameter ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 11/17] drivers/dax: Expand lock scope to cover the use of addresses ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 12/17] memremap: Add zone device access protection ira.weiny
2020-07-17 9:10 ` Peter Zijlstra
2020-07-18 5:06 ` Ira Weiny
2020-07-20 9:16 ` Peter Zijlstra
2020-07-17 9:17 ` Peter Zijlstra
2020-07-18 5:51 ` Ira Weiny
2020-07-17 9:20 ` Peter Zijlstra
2020-07-17 7:20 ` [PATCH RFC V2 13/17] kmap: Add stray write protection for device pages ira.weiny
2020-07-17 9:21 ` Peter Zijlstra
2020-07-19 4:13 ` Ira Weiny
2020-07-20 9:17 ` Peter Zijlstra
2020-07-21 16:31 ` Ira Weiny
2020-07-17 7:20 ` [PATCH RFC V2 14/17] dax: Stray write protection for dax_direct_access() ira.weiny
2020-07-17 9:22 ` Peter Zijlstra
2020-07-19 4:41 ` Ira Weiny
2020-07-17 7:20 ` [PATCH RFC V2 15/17] nvdimm/pmem: Stray write protection for pmem->virt_addr ira.weiny
2020-07-17 7:20 ` [PATCH RFC V2 16/17] [dax|pmem]: Enable stray write protection ira.weiny
2020-07-17 9:25 ` Peter Zijlstra
2020-07-17 7:20 ` [PATCH RFC V2 17/17] x86/entry: Preserve PKRS MSR across exceptions ira.weiny
2020-07-17 9:30 ` Peter Zijlstra
2020-07-21 18:01 ` Ira Weiny
2020-07-21 19:11 ` Peter Zijlstra
2020-07-17 9:34 ` Peter Zijlstra
2020-07-17 10:06 ` Peter Zijlstra
2020-07-22 5:27 ` Ira Weiny
2020-07-22 9:48 ` Peter Zijlstra
2020-07-22 21:24 ` Ira Weiny
2020-07-23 20:08 ` Thomas Gleixner
2020-07-23 20:15 ` Thomas Gleixner
2020-07-24 17:23 ` Ira Weiny
2020-07-24 17:29 ` Andy Lutomirski
2020-07-24 19:43 ` Ira Weiny
2020-07-22 16:21 ` Andy Lutomirski
2020-07-23 16:18 ` Fenghua Yu
2020-07-23 16:23 ` Dave Hansen
2020-07-23 16:52 ` Fenghua Yu
2020-07-23 17:08 ` Andy Lutomirski
2020-07-23 17:30 ` Dave Hansen
2020-07-23 20:23 ` Thomas Gleixner
2020-07-23 20:22 ` Thomas Gleixner
2020-07-23 21:30 ` Andy Lutomirski
2020-07-23 22:14 ` Thomas Gleixner [this message]
2020-07-23 19:53 ` Thomas Gleixner
2020-07-23 22:04 ` Ira Weiny
2020-07-23 23:41 ` Thomas Gleixner
2020-07-24 21:24 ` Thomas Gleixner
2020-07-24 21:31 ` Thomas Gleixner
2020-07-25 0:09 ` Andy Lutomirski
2020-07-27 20:59 ` Ira Weiny
2020-07-24 22:19 ` [PATCH RFC V2 00/17] PKS: Add Protection Keys Supervisor (PKS) support Kees Cook
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