From: Borislav Petkov <bp@alien8.de>
To: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Cc: 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>,
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>,
Pengfei Xu <pengfei.xu@intel.com>
Subject: Re: [PATCH v15 08/26] x86/mm: Introduce _PAGE_COW
Date: Tue, 8 Dec 2020 19:47:27 +0100 [thread overview]
Message-ID: <20201208184727.GF27920@zn.tnic> (raw)
In-Reply-To: <218503f6-eec1-94b0-8404-6f92c55799e3@intel.com>
On Tue, Dec 08, 2020 at 10:25:15AM -0800, Yu, Yu-cheng wrote:
> > Both are "R/O + _PAGE_COW". Where's the difference? The dirty bit?
>
> The PTEs are the same for both (a) and (b), but come from different routes.
Do not be afraid to go into detail and explain to me what those routes
are please.
> > > (e) A page where the processor observed a Write=1 PTE, started a write, set
> > > Dirty=1, but then observed a Write=0 PTE.
> >
> > How does that happen? Something changed the PTE's W bit to 0 in-between?
>
> Yes.
Also do not scare from going into detail and explaining what you mean
here. Example?
> > Does _PAGE_COW mean dirty too?
>
> Yes. Basically [read-only & dirty] is created by software. Now the
> software uses a different bit.
That convention:
"[read-only & dirty] is created by software."
needs some prominent writeup somewhere explaining what it is.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-12-08 20:23 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 16:21 [PATCH v15 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 01/26] Documentation/x86: Add CET description Yu-cheng Yu
2020-11-30 18:26 ` Nick Desaulniers
2020-11-30 18:34 ` Yu, Yu-cheng
2020-11-30 19:38 ` Fāng-ruì Sòng
2020-11-30 19:47 ` Yu, Yu-cheng
2020-11-10 16:21 ` [PATCH v15 02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-11-26 11:02 ` Borislav Petkov
2020-11-30 17:45 ` [NEEDS-REVIEW] " Dave Hansen
2020-11-30 18:06 ` Yu, Yu-cheng
2020-11-30 18:12 ` Dave Hansen
2020-11-30 18:17 ` Yu, Yu-cheng
2020-11-30 23:16 ` Yu, Yu-cheng
2020-12-01 22:26 ` Dave Hansen
2020-12-01 22:35 ` Yu, Yu-cheng
2020-11-10 16:21 ` [PATCH v15 04/26] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-11-26 18:49 ` Borislav Petkov
2020-11-10 16:21 ` [PATCH v15 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-11-27 17:10 ` Borislav Petkov
2020-11-28 16:23 ` Yu, Yu-cheng
2020-11-30 18:15 ` Borislav Petkov
2020-11-30 22:48 ` Yu, Yu-cheng
2020-12-01 16:02 ` Borislav Petkov
2020-11-30 19:56 ` Nick Desaulniers
2020-11-30 20:30 ` Yu, Yu-cheng
2020-11-10 16:21 ` [PATCH v15 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-12-03 9:19 ` Borislav Petkov
2020-12-03 15:12 ` Dave Hansen
2020-12-03 15:56 ` Yu, Yu-cheng
2020-11-10 16:21 ` [PATCH v15 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-12-07 16:36 ` Borislav Petkov
2020-12-07 17:11 ` Yu, Yu-cheng
2020-11-10 16:21 ` [PATCH v15 08/26] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2020-12-08 17:50 ` Borislav Petkov
2020-12-08 18:25 ` Yu, Yu-cheng
2020-12-08 18:47 ` Borislav Petkov [this message]
2020-12-08 19:24 ` Yu, Yu-cheng
2020-12-10 17:41 ` Borislav Petkov
2020-12-10 18:10 ` Yu, Yu-cheng
2020-11-10 16:21 ` [PATCH v15 09/26] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 10/26] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 12/26] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 13/26] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-11-10 16:21 ` [PATCH v15 14/26] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 15/26] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 16/26] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 17/26] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 18/26] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 19/26] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 20/26] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 21/26] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 22/26] binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND properties Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 23/26] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 24/26] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 25/26] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2020-11-10 16:22 ` [PATCH v15 26/26] mm: Introduce PROT_SHSTK " Yu-cheng Yu
2020-11-27 9:29 ` [PATCH v15 00/26] Control-flow Enforcement: Shadow Stack Balbir Singh
2020-11-28 16:31 ` Yu, Yu-cheng
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