From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "bp@alien8.de" <bp@alien8.de>
Cc: "bsingharora@gmail.com" <bsingharora@gmail.com>,
"hpa@zytor.com" <hpa@zytor.com>,
"Syromiatnikov, Eugene" <esyr@redhat.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"rdunlap@infradead.org" <rdunlap@infradead.org>,
"keescook@chromium.org" <keescook@chromium.org>,
"Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"Eranian, Stephane" <eranian@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"fweimer@redhat.com" <fweimer@redhat.com>,
"nadav.amit@gmail.com" <nadav.amit@gmail.com>,
"jannh@google.com" <jannh@google.com>,
"dethoma@microsoft.com" <dethoma@microsoft.com>,
"kcc@google.com" <kcc@google.com>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"pavel@ucw.cz" <pavel@ucw.cz>,
"oleg@redhat.com" <oleg@redhat.com>,
"hjl.tools@gmail.com" <hjl.tools@gmail.com>,
"Yang, Weijiang" <weijiang.yang@intel.com>,
"Lutomirski, Andy" <luto@kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"arnd@arndb.de" <arnd@arndb.de>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"Schimpe, Christina" <christina.schimpe@intel.com>,
"mike.kravetz@oracle.com" <mike.kravetz@oracle.com>,
"x86@kernel.org" <x86@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"jamorris@linux.microsoft.com" <jamorris@linux.microsoft.com>,
"john.allen@amd.com" <john.allen@amd.com>,
"rppt@kernel.org" <rppt@kernel.org>,
"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"corbet@lwn.net" <corbet@lwn.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"gorcunov@gmail.com" <gorcunov@gmail.com>
Subject: Re: [PATCH v5 11/39] x86/mm: Update pte_modify for _PAGE_COW
Date: Thu, 9 Feb 2023 17:09:15 +0000 [thread overview]
Message-ID: <49d20fcd197e85e8475f5170db78780f06396cc0.camel@intel.com> (raw)
In-Reply-To: <Y+T+ZxydCZS1Yjmz@zn.tnic>
On Thu, 2023-02-09 at 15:08 +0100, Borislav Petkov wrote:
> On Thu, Jan 19, 2023 at 01:22:49PM -0800, Rick Edgecombe wrote:
> > From: Yu-cheng Yu <yu-cheng.yu@intel.com>
> >
> > The Write=0,Dirty=1 PTE has been used to indicate copy-on-write
> > pages.
> > However, newer x86 processors also regard a Write=0,Dirty=1 PTE as
> > a
> > shadow stack page. In order to separate the two, the software-
> > defined
> > _PAGE_DIRTY is changed to _PAGE_COW for the copy-on-write case, and
> > pte_*() are updated to do this.
>
> "In order to separate the two, change the software-defined ..."
>
> From section "2) Describe your changes" in
> Documentation/process/submitting-patches.rst:
>
> "Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
> instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
> to do frotz", as if you are giving orders to the codebase to change
> its behaviour."
Yea, this is ambiguous. It's actually trying to say that "the software-
defined..." *were* changed in previous patches. I'll change it to make
that clear.
>
> > +static inline pte_t __pte_mkdirty(pte_t pte, bool soft)
> > +{
> > + pteval_t dirty = _PAGE_DIRTY;
> > +
> > + if (soft)
> > + dirty |= _PAGE_SOFT_DIRTY;
> > +
> > + return pte_set_flags(pte, dirty);
> > +}
>
> Dunno, do you even need that __pte_mkdirty() helper?
>
> AFAIU, pte_mkdirty() will always set _PAGE_SOFT_DIRTY too so whatever
> the __pte_mkdirty() thing needs to do, you can simply do it by foot
> in
> the two callsites.
>
> And this way you won't have the confusion: should I use pte_mkdirty()
> or
> __pte_mkdirty()?
>
> Ditto for the pmd variants.
>
> Otherwise, this is starting to make more sense now.
The thing is it would need to duplicate the pte_write() and shadow
stack enablement check and know when to set the Cow(soon to be
SavedDirty) bit.
I see that having a similar helper is not ideal, but isn't it nice that
this special critical logic for setting the Cow bit is all in one
place? I actually tried it the other way, but thought that it was nicer
to have a helper that might drive future people to not miss the Cow bit
part.
What do you think, can we leave it or give it a new name? Maybe
pte_set_dirty() to be more like the x86-only pte_set_flags() family of
functions? Then we have:
static inline pte_t pte_mkdirty(pte_t pte)
{
pte = pte_set_flags(pte, _PAGE_SOFT_DIRTY);
return pte_set_dirty(pte);
}
And...
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
...
/*
* Dirty bit is not preserved above so it can be done
* in a special way for the shadow stack case, where it
* may need to set _PAGE_SAVED_DIRTY. __pte_mkdirty() will do
* this in the case of shadow stack.
*/
if (oldval & _PAGE_DIRTY)
pte_result = pte_set_dirty(pte_result);
return pte_result;
}
next prev parent reply other threads:[~2023-02-09 17:09 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-19 21:22 [PATCH v5 00/39] Shadow stacks for userspace Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 01/39] Documentation/x86: Add CET shadow stack description Rick Edgecombe
2023-01-20 0:38 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 02/39] x86/shstk: Add Kconfig option for shadow stack Rick Edgecombe
2023-01-20 0:40 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks Rick Edgecombe
2023-01-20 0:44 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack Rick Edgecombe
2023-01-20 0:46 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 05/39] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2023-01-20 0:46 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 06/39] x86/fpu: Add helper for modifying xstate Rick Edgecombe
2023-01-20 0:47 ` Kees Cook
2023-02-01 11:01 ` Borislav Petkov
2023-02-01 17:31 ` Edgecombe, Rick P
2023-02-01 18:18 ` Borislav Petkov
2023-01-19 21:22 ` [PATCH v5 07/39] x86: Add user control-protection fault handler Rick Edgecombe
2023-01-20 0:50 ` Kees Cook
2023-02-03 19:09 ` Borislav Petkov
2023-02-03 19:24 ` Edgecombe, Rick P
2023-02-03 19:44 ` Borislav Petkov
2023-02-03 23:01 ` Edgecombe, Rick P
2023-02-04 10:37 ` Borislav Petkov
2023-01-19 21:22 ` [PATCH v5 08/39] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2023-01-20 0:52 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 09/39] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 10/39] x86/mm: Introduce _PAGE_COW Rick Edgecombe
2023-01-20 0:55 ` Kees Cook
2023-01-23 9:16 ` David Hildenbrand
2023-01-23 9:28 ` David Hildenbrand
2023-01-23 20:56 ` Edgecombe, Rick P
2023-01-24 16:28 ` David Hildenbrand
2023-01-19 21:22 ` [PATCH v5 11/39] x86/mm: Update pte_modify for _PAGE_COW Rick Edgecombe
2023-01-20 0:57 ` Kees Cook
2023-02-09 14:08 ` Borislav Petkov
2023-02-09 17:09 ` Edgecombe, Rick P [this message]
2023-02-10 13:57 ` Borislav Petkov
2023-02-10 17:00 ` Edgecombe, Rick P
2023-02-17 16:11 ` Borislav Petkov
2023-02-17 16:53 ` Edgecombe, Rick P
2023-01-19 21:22 ` [PATCH v5 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Rick Edgecombe
2023-01-20 0:58 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 13/39] x86/mm: Start actually marking _PAGE_COW Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 14/39] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 15/39] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 16/39] x86/mm: Check shadow stack page fault errors Rick Edgecombe
2023-01-20 0:59 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 17/39] x86/mm: Update maybe_mkwrite() for shadow stack Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk Rick Edgecombe
2023-01-23 9:50 ` David Hildenbrand
2023-01-23 20:47 ` Edgecombe, Rick P
2023-01-24 16:24 ` David Hildenbrand
2023-01-24 18:14 ` Edgecombe, Rick P
2023-01-25 9:27 ` David Hildenbrand
2023-01-25 18:43 ` Edgecombe, Rick P
2023-01-26 0:59 ` Edgecombe, Rick P
2023-01-26 8:46 ` David Hildenbrand
2023-01-26 20:19 ` Edgecombe, Rick P
2023-01-27 16:12 ` David Hildenbrand
2023-01-28 0:51 ` Edgecombe, Rick P
2023-01-31 8:46 ` David Hildenbrand
2023-01-31 23:33 ` Edgecombe, Rick P
2023-02-01 9:03 ` David Hildenbrand
2023-02-01 17:32 ` Edgecombe, Rick P
2023-02-01 18:03 ` David Hildenbrand
2023-01-26 8:57 ` David Hildenbrand
2023-01-26 20:16 ` Edgecombe, Rick P
2023-01-27 16:19 ` David Hildenbrand
2023-01-19 21:22 ` [PATCH v5 19/39] mm: Fixup places that call pte_mkwrite() directly Rick Edgecombe
2023-01-20 1:01 ` Kees Cook
2023-02-14 0:09 ` Deepak Gupta
2023-02-14 1:07 ` Edgecombe, Rick P
2023-02-14 6:10 ` Deepak Gupta
2023-02-14 18:24 ` Edgecombe, Rick P
2023-02-15 6:37 ` Deepak Gupta
2023-01-19 21:22 ` [PATCH v5 20/39] mm: Add guard pages around a shadow stack Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 21/39] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 22/39] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory Rick Edgecombe
2023-01-23 9:10 ` David Hildenbrand
2023-01-23 10:45 ` Florian Weimer
2023-01-23 20:46 ` Edgecombe, Rick P
2023-01-24 16:26 ` David Hildenbrand
2023-01-24 18:42 ` Edgecombe, Rick P
2023-01-24 23:08 ` Kees Cook
2023-01-24 23:41 ` Edgecombe, Rick P
2023-01-25 9:29 ` David Hildenbrand
2023-01-25 15:23 ` Kees Cook
2023-01-25 15:36 ` Schimpe, Christina
2023-01-25 16:43 ` Schimpe, Christina
2023-01-19 21:23 ` [PATCH v5 24/39] x86/mm: Introduce MAP_ABOVE4G Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 25/39] mm: Warn on shadow stack memory in wrong vma Rick Edgecombe
2023-01-20 1:01 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 26/39] x86: Introduce userspace API for shadow stack Rick Edgecombe
2023-01-20 1:04 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 27/39] x86/shstk: Add user-mode shadow stack support Rick Edgecombe
2023-01-20 1:05 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 28/39] x86/shstk: Handle thread shadow stack Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 29/39] x86/shstk: Introduce routines modifying shstk Rick Edgecombe
2023-01-20 1:05 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 30/39] x86/shstk: Handle signals for shadow stack Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 31/39] x86/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2023-01-20 1:07 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 32/39] x86/shstk: Support WRSS for userspace Rick Edgecombe
2023-01-20 1:06 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 33/39] x86: Expose thread features in /proc/$PID/status Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 34/39] x86/shstk: Wire in shadow stack interface Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 35/39] selftests/x86: Add shadow stack test Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 36/39] x86/fpu: Add helper for initing features Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 37/39] x86: Add PTRACE interface for shadow stack Rick Edgecombe
2023-01-20 1:08 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 38/39] x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 39/39] x86/shstk: Add ARCH_SHSTK_STATUS Rick Edgecombe
2023-01-20 1:08 ` Kees Cook
2023-01-19 22:26 ` [PATCH v5 00/39] Shadow stacks for userspace Andrew Morton
2023-01-20 17:27 ` Edgecombe, Rick P
2023-01-20 19:19 ` Kees Cook
2023-01-25 19:46 ` Edgecombe, Rick P
2023-01-20 17:48 ` John Allen
2023-01-22 8:20 ` Mike Rapoport
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=49d20fcd197e85e8475f5170db78780f06396cc0.camel@intel.com \
--to=rick.p.edgecombe@intel.com \
--cc=akpm@linux-foundation.org \
--cc=andrew.cooper3@citrix.com \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=bsingharora@gmail.com \
--cc=christina.schimpe@intel.com \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=dethoma@microsoft.com \
--cc=eranian@google.com \
--cc=esyr@redhat.com \
--cc=fweimer@redhat.com \
--cc=gorcunov@gmail.com \
--cc=hjl.tools@gmail.com \
--cc=hpa@zytor.com \
--cc=jamorris@linux.microsoft.com \
--cc=jannh@google.com \
--cc=john.allen@amd.com \
--cc=kcc@google.com \
--cc=keescook@chromium.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mike.kravetz@oracle.com \
--cc=mingo@redhat.com \
--cc=nadav.amit@gmail.com \
--cc=oleg@redhat.com \
--cc=pavel@ucw.cz \
--cc=peterz@infradead.org \
--cc=rdunlap@infradead.org \
--cc=rppt@kernel.org \
--cc=tglx@linutronix.de \
--cc=weijiang.yang@intel.com \
--cc=x86@kernel.org \
--cc=yu-cheng.yu@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).