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From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Eugene Syromiatnikov <esyr@redhat.com>
Cc: Kees Cook <keescook@chromium.org>,
	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>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	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>,
	mtk.manpages@gmail.com
Subject: Re: [PATCH v10 26/26] x86/cet/shstk: Add arch_prctl functions for shadow stack
Date: Fri, 22 May 2020 11:13:24 -0700
Message-ID: <676f710b9747b091783aed38fb07259af3ca5b43.camel@intel.com> (raw)
In-Reply-To: <20200522172934.GI12341@asgard.redhat.com>

On Fri, 2020-05-22 at 19:29 +0200, Eugene Syromiatnikov wrote:
> On Fri, May 22, 2020 at 10:17:43AM -0700, Yu-cheng Yu wrote:
> > On Thu, 2020-05-21 at 15:42 -0700, Kees Cook wrote:
> > > On Wed, Apr 29, 2020 at 03:07:32PM -0700, Yu-cheng Yu wrote:
> > [...]
> > > > +
> > > > +int prctl_cet(int option, u64 arg2)
> > > > +{
> > > > +	struct cet_status *cet;
> > > > +
> > > > +	if (!IS_ENABLED(CONFIG_X86_INTEL_CET))
> > > > +		return -EINVAL;
> > > 
> > > Using -EINVAL here means userspace can't tell the difference between an
> > > old kernel and a kernel not built with CONFIG_X86_INTEL_CET. Perhaps
> > > -ENOTSUPP?
> > 
> > Looked into this.  The kernel and GLIBC are not in sync.  So maybe we still use
> > EINVAL here?
> > 
> > Yu-cheng
> > 
> > 
> > 
> > In kernel:
> > ----------
> > 
> > #define EOPNOTSUPP	95
> > #define ENOTSUPP 	524
> > 
> > In GLIBC:
> > ---------
> > 
> > printf("ENOTSUP=%d\n", ENOTSUP);
> > printf("EOPNOTSUPP=%d\n", EOPNOTSUPP);
> > printf("%s=524\n", strerror(524));
> >  
> > ENOTSUP=95
> > EOPNOTSUPP=95
> > Unknown error 524=524
> 
> EOPNOTSUPP/ENOTSUP/ENOTSUPP is actually a mess, it's summarized recently
> by Michael Kerrisk[1].  From the kernel's point of view, I think it
> would be reasonable to return EOPNOTSUPP, and expect that the userspace
> would use ENOTSUP to match against it.

Ok, use EOPNOTSUPP and add a comment why.

Yu-cheng


  reply index

Thread overview: 62+ 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
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
2020-04-29 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 [this message]
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

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