From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>
Subject: Re: [PATCH v10 01/26] Documentation/x86: Add CET description
Date: Mon, 18 May 2020 07:21:26 -0700 [thread overview]
Message-ID: <b3a0b0a404f1d1c588244889e71fe08508f0c31e.camel@intel.com> (raw)
In-Reply-To: <6f2ef0e5-d3bb-2b52-dc81-8228fec4a3f5@intel.com>
On Mon, 2020-05-18 at 06:41 -0700, Dave Hansen wrote:
> On 5/15/20 7:53 PM, Yu-cheng Yu wrote:
> > On Fri, 2020-05-15 at 16:56 -0700, Dave Hansen wrote:
> > > What's my recourse as an end user? I want to run my app and turn off
> > > CET for that app. How can I do that?
> >
> > GLIBC_TUNABLES=glibc.tune.hwcaps=-SHSTK,-IBT
>
> Like I mentioned to H.J., this is something that we need to at least
> acknowledge the existence of in the changelog and probably even the
> Documentation/.
Sure. I will do that.
>
> > > > > I think you're saying that the CET-enabled binary would do
> > > > > arch_setup_elf_property() when it was first exec()'d. Later, it could
> > > > > use the new prctl(ARCH_X86_CET_DISABLE) to disable its shadow stack,
> > > > > then fork() and the child would not be using CET. Right?
> > > > >
> > > > > What is ARCH_X86_CET_DISABLE used for, anyway?
> > > >
> > > > Both the parent and the child can do ARCH_X86_CET_DISABLE, if CET is
> > > > not locked.
> > >
> > > Could you please describe a real-world example of why
> > > ARCH_X86_CET_DISABLE exists? What kinds of apps will use it, or *are*
> > > using it? Why was it created in the first place?
> >
> > Currently, ld-linux turns off CET if the binary being loaded does not support
> > CET.
>
> Great! Could this please be immortalized in the documentation for the
> prctl()?
Yes.
>
> > > > > > > Does this *code* work? Could you please indicate which JITs have been
> > > > > > > enabled to use the code in this series? How much of the new ABI is in use?
> > > > > >
> > > > > > JIT does not necessarily use all of the ABI. The JIT changes mainly fix stack
> > > > > > frames and insert ENDBRs. I do not work on JIT. What I found is LLVM JIT fixes
> > > > > > are tested and in the master branch. Sljit fixes are in the release.
> > > > >
> > > > > Huh, so who is using the new prctl() ABIs?
> > > >
> > > > Any code can use the ABI, but JIT code CET-enabling part mostly do not use these
> > > > new prctl()'s, except, probably to get CET status.
> > >
> > > Which applications specifically are going to use the new prctl()s which
> > > this series adds? How are they going to use them?
> > >
> > > "Any code can use them" is not a specific enough answer.
> >
> > We have four arch_ptctl() calls. ARCH_X86_CET_DISABLE and ARCH_X86_CET_LOCK are
> > used by ld-linux. ARCH_X86_CET_STATUS are used in many places to determine if
> > CET is on. ARCH_X86_CET_ALLOC_SHSTK is used in ucontext related handling, but
> > it can be use by any application to switch shadow stacks.
>
> Could some of this information be added to the documentation, please?
> It would also be nice to have some more details about how apps end up
> using ARCH_X86_CET_STATUS. Why would they care that CET is on?
Yes.
Yu-cheng
next prev parent reply other threads:[~2020-05-18 14:21 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 22:07 [PATCH v10 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 01/26] Documentation/x86: Add CET description Yu-cheng Yu
2020-04-29 22:53 ` Dave Hansen
2020-04-29 23:02 ` Yu-cheng Yu
2020-05-12 23:20 ` Yu-cheng Yu
2020-05-15 18:39 ` Dave Hansen
2020-05-15 21:33 ` Yu-cheng Yu
2020-05-15 22:43 ` Dave Hansen
2020-05-15 23:29 ` Yu-cheng Yu
2020-05-15 23:56 ` Dave Hansen
2020-05-16 2:51 ` H.J. Lu
2020-05-17 23:09 ` Dave Hansen
2020-05-16 2:53 ` Yu-cheng Yu
2020-05-18 13:41 ` Dave Hansen
2020-05-18 14:01 ` H.J. Lu
2020-05-18 14:26 ` Dave Hansen
2020-05-18 14:21 ` Yu-cheng Yu [this message]
2020-05-18 23:47 ` Yu-cheng Yu
2020-05-19 0:38 ` Dave Hansen
2020-05-19 1:35 ` Andy Lutomirski
2020-05-20 1:04 ` Andy Lutomirski
2020-05-29 2:08 ` Yu-cheng Yu
2020-05-16 0:13 ` Andrew Cooper
2020-05-16 2:37 ` H.J. Lu
2020-05-16 14:09 ` Andrew Cooper
2020-05-22 16:49 ` Peter Zijlstra
2020-05-22 17:48 ` Andrew Cooper
2020-04-29 22:07 ` [PATCH v10 02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-07-23 16:10 ` Sean Christopherson
2020-07-23 16:21 ` Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 04/26] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-05-07 15:55 ` Dave Hansen
2020-05-07 16:59 ` Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 08/26] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 09/26] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 10/26] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 12/26] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 13/26] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 14/26] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 15/26] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 16/26] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 17/26] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 18/26] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 19/26] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 20/26] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 21/26] ELF: UAPI and Kconfig additions for ELF program properties Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 22/26] ELF: Add ELF program property parsing support Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 23/26] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 24/26] x86/cet/shstk: ELF header parsing for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 25/26] x86/cet/shstk: Handle thread " Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 26/26] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2020-05-21 22:42 ` Kees Cook
2020-05-22 17:17 ` Yu-cheng Yu
2020-05-22 17:29 ` Eugene Syromiatnikov
2020-05-22 18:13 ` Yu-cheng Yu
2020-05-21 15:15 ` [PATCH v10 00/26] Control-flow Enforcement: Shadow Stack Josh Poimboeuf
2020-05-21 15:57 ` Yu-cheng Yu
2020-05-21 18:50 ` Josh Poimboeuf
2020-05-21 19:08 ` Yu-cheng Yu
2020-07-23 16:25 ` Sean Christopherson
2020-07-23 16:41 ` Dave Hansen
2020-07-23 16:56 ` Sean Christopherson
2020-07-23 18:41 ` Dave Hansen
2020-07-24 3:40 ` Yu-cheng Yu
2020-07-24 4:50 ` Sean Christopherson
2020-07-24 4:59 ` Sean Christopherson
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