From: Dave Hansen <dave@sr71.net>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
X86 ML <x86@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@google.com>
Subject: Re: [PATCH 31/31] x86, pkeys: execute-only support
Date: Thu, 7 Jan 2016 14:13:11 -0800 [thread overview]
Message-ID: <568EE2F7.5000902@sr71.net> (raw)
In-Reply-To: <CALCETrUUS=jHCwmeQ5iUeTAq15PAGZO8Js57ZBLKPM6oEDz3Qg@mail.gmail.com>
On 01/07/2016 01:10 PM, Andy Lutomirski wrote:
> On Wed, Jan 6, 2016 at 4:01 PM, Dave Hansen <dave@sr71.net> wrote:
>> From: Dave Hansen <dave.hansen@linux.intel.com>
>> Protection keys provide new page-based protection in hardware.
>> But, they have an interesting attribute: they only affect data
>> accesses and never affect instruction fetches. That means that
>> if we set up some memory which is set as "access-disabled" via
>> protection keys, we can still execute from it.
>> could lose the bits in PKRU that enforce execute-only
>> permissions. To avoid this, we suggest avoiding ever calling
>> mmap() or mprotect() when the PKRU value is expected to be
>> stable.
>
> This may be a bit unfortunate for people who call mmap from signal
> handlers. Admittedly, the failure mode isn't that bad.
mmap() isn't in the list of async-signal-safe functions, so it's bad
already.
> Out of curiosity, do you have timing information for WRPKRU and
> RDPKRU? If they're fast and if anyone ever implements my deferred
> xstate restore idea, then the performance issue goes away and we can
> stop caring about whether PKRU is in the init state.
I don't have timing information that I can share. From my perspective,
they're pretty fast, *not* like an MSR write or something. I think
they're fast enough to use in the context switch path. I'd say PKRU is
in XSAVE for consistency more than for performance.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-01-07 22:13 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-07 0:01 [PATCH 00/31] x86: Memory Protection Keys (v8) Dave Hansen
2016-01-07 0:01 ` [PATCH 01/31] mm, gup: introduce concept of "foreign" get_user_pages() Dave Hansen
2016-01-13 19:00 ` Vlastimil Babka
2016-01-13 19:16 ` Dave Hansen
2016-01-07 0:01 ` [PATCH 02/31] x86, fpu: add placeholder for Processor Trace XSAVE state Dave Hansen
2016-01-07 0:01 ` [PATCH 03/31] x86, pkeys: Add Kconfig option Dave Hansen
2016-01-07 0:01 ` [PATCH 04/31] x86, pkeys: cpuid bit definition Dave Hansen
2016-01-07 0:01 ` [PATCH 05/31] x86, pkeys: define new CR4 bit Dave Hansen
2016-01-07 0:01 ` [PATCH 06/31] x86, pkeys: add PKRU xsave fields and data structure(s) Dave Hansen
2016-01-07 0:01 ` [PATCH 07/31] x86, pkeys: PTE bits for storing protection key Dave Hansen
2016-01-07 0:01 ` [PATCH 08/31] x86, pkeys: new page fault error code bit: PF_PK Dave Hansen
2016-01-07 0:01 ` [PATCH 09/31] x86, pkeys: store protection in high VMA flags Dave Hansen
2016-01-07 0:01 ` [PATCH 10/31] x86, pkeys: arch-specific protection bits Dave Hansen
2016-01-08 19:31 ` Thomas Gleixner
2016-01-07 0:01 ` [PATCH 11/31] x86, pkeys: pass VMA down in to fault signal generation code Dave Hansen
2016-01-07 0:01 ` [PATCH 12/31] signals, pkeys: notify userspace about protection key faults Dave Hansen
2016-01-07 0:01 ` [PATCH 13/31] x86, pkeys: fill in pkey field in siginfo Dave Hansen
2016-01-07 0:01 ` [PATCH 14/31] x86, pkeys: add functions to fetch PKRU Dave Hansen
2016-01-08 19:32 ` Thomas Gleixner
2016-01-07 0:01 ` [PATCH 15/31] mm: factor out VMA fault permission checking Dave Hansen
2016-01-07 0:01 ` [PATCH 16/31] x86, mm: simplify get_user_pages() PTE bit handling Dave Hansen
2016-01-07 0:01 ` [PATCH 17/31] x86, pkeys: check VMAs and PTEs for protection keys Dave Hansen
2016-01-07 0:01 ` [PATCH 18/31] mm: add gup flag to indicate "foreign" mm access Dave Hansen
2016-01-07 0:01 ` [PATCH 19/31] x86, pkeys: optimize fault handling in access_error() Dave Hansen
2016-01-07 0:01 ` [PATCH 20/31] x86, pkeys: differentiate instruction fetches Dave Hansen
2016-01-07 0:01 ` [PATCH 21/31] x86, pkeys: dump PKRU with other kernel registers Dave Hansen
2016-01-07 0:01 ` [PATCH 22/31] x86, pkeys: dump pkey from VMA in /proc/pid/smaps Dave Hansen
2016-01-07 0:01 ` [PATCH 23/31] x86, pkeys: add Kconfig prompt to existing config option Dave Hansen
2016-01-07 0:01 ` [PATCH 24/31] x86, pkeys: actually enable Memory Protection Keys in CPU Dave Hansen
2016-01-07 0:01 ` [PATCH 25/31] mm, multi-arch: pass a protection key in to calc_vm_flag_bits() Dave Hansen
2016-01-07 0:01 ` [PATCH 26/31] x86, pkeys: add arch_validate_pkey() Dave Hansen
2016-01-08 19:34 ` Thomas Gleixner
2016-01-07 0:01 ` [PATCH 27/31] x86: separate out LDT init from context init Dave Hansen
2016-01-07 0:01 ` [PATCH 28/31] x86, fpu: allow setting of XSAVE state Dave Hansen
2016-01-07 0:01 ` [PATCH 29/31] x86, pkeys: allow kernel to modify user pkey rights register Dave Hansen
2016-01-08 19:40 ` Thomas Gleixner
2016-01-07 0:01 ` [PATCH 30/31] x86, pkeys: create an x86 arch_calc_vm_prot_bits() for VMA flags Dave Hansen
2016-01-08 19:40 ` Thomas Gleixner
2016-01-07 0:01 ` [PATCH 31/31] x86, pkeys: execute-only support Dave Hansen
2016-01-07 21:02 ` Kees Cook
2016-01-07 22:25 ` Dave Hansen
2016-01-07 21:10 ` Andy Lutomirski
2016-01-07 22:13 ` Dave Hansen [this message]
2016-01-07 22:44 ` Andy Lutomirski
2016-01-08 19:51 ` Thomas Gleixner
2016-01-29 18:16 [PATCH 00/31] x86: Memory Protection Keys (v9) Dave Hansen
2016-01-29 18:17 ` [PATCH 31/31] x86, pkeys: execute-only support Dave Hansen
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=568EE2F7.5000902@sr71.net \
--to=dave@sr71.net \
--cc=akpm@linux-foundation.org \
--cc=dave.hansen@linux.intel.com \
--cc=keescook@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@amacapital.net \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/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