From: Thomas Gleixner <tglx@linutronix.de>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Andi Kleen <ak@linux.intel.com>
Cc: Sasha Levin <sashal@kernel.org>,
linux-kernel@vger.kernel.org, bp@alien8.de, luto@kernel.org,
hpa@zytor.com, dave.hansen@intel.com, tony.luck@intel.com,
ravi.v.shankar@intel.com, chang.seok.bae@intel.com
Subject: Re: [PATCH v12 00/18] Enable FSGSBASE instructions
Date: Tue, 19 May 2020 01:03:25 +0200 [thread overview]
Message-ID: <87v9ksvoaq.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <371e6a92cad25cbe7a8489785efa7d3457ecef3b.camel@linux.intel.com>
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> writes:
> On Mon, 2020-05-18 at 08:34 -0700, Andi Kleen wrote:
>> > Yes, for SGX this is functional feature because enclave entry points,
>> > thread control structures (aka TCS's), reset FSBASE and GSBASE registers
>> > to fixed (albeit user defined) values. And syscall's can be done only
>> > outside of enclave.
>> >
>> > This is a required feature for fancier runtimes (such as Graphene).
>>
>> Can you please explain a bit more? What do they need GS for?
>
> Apparently, uses only wrfsbase:
>
> https://raw.githubusercontent.com/oscarlab/graphene/master/Pal/src/host/Linux-SGX/db_misc.c
>
> I'm not too familiar with the codebase yet but by reading some research
> papers in the past the idea is to multiplex one TCS for multiple virtual
> threads inside the enclave.
>
> E.g. TCS could represent a vcpu for a libos type of container and on
> entry would pick on a thread and set fsbase accordingly for a thread
> control block.
That justifies to write books which recommend to load a kernel module
which creates a full unpriviledged root hole. I bet none of these papers
ever mentioned that.
Thanks,
tglx
next prev parent reply other threads:[~2020-05-18 23:03 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-11 4:52 Sasha Levin
2020-05-11 4:52 ` [PATCH v12 01/18] x86/ptrace: Prevent ptrace from clearing the FS/GS selector Sasha Levin
2020-05-11 4:52 ` [PATCH v12 02/18] selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write Sasha Levin
2020-05-11 4:52 ` [PATCH v12 03/18] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Sasha Levin
2020-05-11 4:52 ` [PATCH v12 04/18] x86/entry/64: Clean up paranoid exit Sasha Levin
2020-05-11 4:52 ` [PATCH v12 05/18] x86/entry/64: Switch CR3 before SWAPGS in paranoid entry Sasha Levin
2020-05-11 4:52 ` [PATCH v12 06/18] x86/entry/64: Introduce the FIND_PERCPU_BASE macro Sasha Levin
2020-05-11 4:53 ` [PATCH v12 07/18] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit Sasha Levin
2020-05-11 4:53 ` [PATCH v12 08/18] x86/entry/64: Document GSBASE handling in the paranoid path Sasha Levin
2020-05-11 4:53 ` [PATCH v12 09/18] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Sasha Levin
2020-05-11 4:53 ` [PATCH v12 10/18] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Sasha Levin
2020-05-18 18:20 ` Thomas Gleixner
2020-05-18 20:24 ` Sasha Levin
2020-05-18 22:59 ` Thomas Gleixner
2020-05-19 12:20 ` David Laight
2020-05-19 14:48 ` Thomas Gleixner
2020-05-20 9:13 ` David Laight
2020-05-11 4:53 ` [PATCH v12 11/18] x86/fsgsbase/64: Use FSGSBASE in switch_to() if available Sasha Levin
2020-05-11 4:53 ` [PATCH v12 12/18] x86/fsgsbase/64: move save_fsgs to header file Sasha Levin
2020-05-11 4:53 ` [PATCH v12 13/18] x86/fsgsbase/64: Use FSGSBASE instructions on thread copy and ptrace Sasha Levin
2020-05-11 4:53 ` [PATCH v12 14/18] x86/speculation/swapgs: Check FSGSBASE in enabling SWAPGS mitigation Sasha Levin
2020-05-11 4:53 ` [PATCH v12 15/18] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE Sasha Levin
2020-05-11 4:53 ` [PATCH v12 16/18] x86/fsgsbase/64: Enable FSGSBASE on 64bit by default and add a chicken bit Sasha Levin
2020-05-11 4:53 ` [PATCH v12 17/18] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Sasha Levin
2020-05-11 4:53 ` [PATCH v12 18/18] Documentation/x86/64: Add documentation for GS/FS addressing mode Sasha Levin
2020-05-15 9:24 ` [PATCH v12 00/18] Enable FSGSBASE instructions Jarkko Sakkinen
2020-05-15 16:40 ` Sasha Levin
2020-05-15 17:55 ` Andi Kleen
2020-05-15 23:07 ` Sasha Levin
2020-05-16 12:21 ` Jarkko Sakkinen
2020-05-16 9:50 ` Jarkko Sakkinen
2020-05-18 15:34 ` Andi Kleen
2020-05-18 20:01 ` Jarkko Sakkinen
2020-05-18 23:03 ` Thomas Gleixner [this message]
2020-05-19 16:48 ` Jarkko Sakkinen
2020-05-22 20:14 ` Don Porter
2020-05-22 20:55 ` Dave Hansen
2020-05-23 0:45 ` Thomas Gleixner
2020-05-24 19:45 ` hpa
2020-05-24 21:19 ` Sasha Levin
2020-05-24 23:44 ` hpa
2020-05-25 7:54 ` Richard Weinberger
2020-05-25 21:56 ` Tony Luck
2020-05-26 8:12 ` David Laight
2020-05-26 8:23 ` Richard Weinberger
2020-05-27 8:31 ` Jarkko Sakkinen
2020-05-26 12:42 ` Don Porter
2020-05-26 20:27 ` Sasha Levin
2020-05-26 22:03 ` Don Porter
2020-05-26 22:51 ` Sasha Levin
2020-05-28 17:37 ` Don Porter
2020-05-28 10:29 ` Thomas Gleixner
2020-05-28 17:40 ` Don Porter
2020-05-28 18:38 ` Andy Lutomirski
2020-05-29 15:27 ` Wojtek Porczyk
2020-06-25 15:27 ` Don Porter
2020-06-25 21:37 ` Jarkko Sakkinen
2020-07-18 18:19 ` Don Porter
2020-07-23 3:23 ` Jarkko Sakkinen
2020-05-28 19:19 ` Jarkko Sakkinen
2020-05-28 19:41 ` Sasha Levin
2020-05-29 3:07 ` Jarkko Sakkinen
2020-05-29 3:10 ` Jarkko Sakkinen
2020-06-25 15:30 ` Don Porter
2020-06-25 21:40 ` Jarkko Sakkinen
2020-05-23 4:19 ` Andi Kleen
2020-05-28 10:36 ` Thomas Gleixner
2020-05-27 8:20 ` Jarkko Sakkinen
2020-05-27 12:42 ` Wojtek Porczyk
2020-05-18 9:51 ` Thomas Gleixner
2020-05-18 15:16 ` Sasha Levin
2020-05-18 18:28 ` Thomas Gleixner
2020-05-18 19:36 ` Jarkko Sakkinen
2020-05-18 6:18 ` Christoph Hellwig
2020-05-18 12:33 ` Sasha Levin
2020-05-18 14:53 ` Thomas Gleixner
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