linux-kernel - Re: [PATCH 33/33] x86, pkeys: execute-only support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALCETrV7t7Dc9UjNzhwN-MSO1Z0005dypOYFSt8FBzpNQcTEgA@mail.gmail.com>
Date:	Wed, 17 Feb 2016 16:46:39 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Dave Hansen <dave@...1.net>
Cc:	Kees Cook <keescook@...gle.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	X86 ML <x86@...nel.org>, Linux-MM <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 33/33] x86, pkeys: execute-only support

On Wed, Feb 17, 2016 at 2:53 PM, Dave Hansen <dave@...1.net> wrote:
> On 02/17/2016 02:17 PM, Andy Lutomirski wrote:
>>> > Is there a way to detect this feature's availability without userspace
>>> > having to set up a segv handler and attempting to read a
>>> > PROT_EXEC-only region? (i.e. cpu flag for protection keys, or a way to
>>> > check the protection to see if PROT_READ got added automatically,
>>> > etc?)
>>> >
>> We could add an HWCAP.
>
> I'll bite.  What's an HWCAP?

It's a CPU capability vector that's passed to every program as an auxv
entry.  On x86, ELF_HWCAP is useless (it's already fully used up for
pointless purposes for CPUID stuff), but ELF_HWCAP2 could be added and
a bit could be defined like HWCAP2_PROT_EXEC_ONLY.

Some day, WRFSBASE, etc will be advertised via ELF_HWCAP2, I suspect.

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC