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From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Al Viro <viro@zeniv.linux.org.uk>, X86 ML <x86@kernel.org>,
	Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux API <linux-api@vger.kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls
Date: Mon, 18 Jul 2016 11:56:57 +0200	[thread overview]
Message-ID: <20160718095657.GA5374@gmail.com> (raw)
In-Reply-To: <CALCETrWPM_jrF6saHPxoUL4vkjhhGBfizATXrFOW=+z5xycToQ@mail.gmail.com>


* Andy Lutomirski <luto@amacapital.net> wrote:

> On Thu, Jul 14, 2016 at 1:07 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Andy Lutomirski <luto@amacapital.net> wrote:
> >
> >> On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >> >
> >> > * Andy Lutomirski <luto@amacapital.net> wrote:
> >> >
> >> >> > If we push a PKRU value into a thread between the rdpkru() and wrpkru(), we'll
> >> >> > lose the content of that "push".  I'm not sure there's any way to guarantee
> >> >> > this with a user-controlled register.
> >> >>
> >> >> We could try to insist that user code uses some vsyscall helper that tracks
> >> >> which bits are as-yet-unassigned.  That's quite messy, though.
> >> >
> >> > Actually, if we turned the vDSO into something more like a minimal user-space
> >> > library with the ability to run at process startup as well to prepare stuff
> >> > then it's painful to get right only *once*, and there will be tons of other
> >> > areas where a proper per thread data storage on the user-space side would be
> >> > immensely useful!
> >>
> >> Doing this could be tricky: how exactly is the vDSO supposed to find per-thread
> >> data without breaking existing glibc?
> >
> > So I think the way this could be done is by allocating it itself. The vDSO vma
> > itself is 'external' to glibc as well to begin with - this would be a small
> > extension to that concept.
> 
> But how does the vdso code find it?  FS and GS are both spoken for by existing 
> userspace.

Minimally relinking itself on a per mm basis?

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Al Viro <viro@zeniv.linux.org.uk>, X86 ML <x86@kernel.org>,
	Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux API <linux-api@vger.kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls
Date: Mon, 18 Jul 2016 11:56:57 +0200	[thread overview]
Message-ID: <20160718095657.GA5374@gmail.com> (raw)
In-Reply-To: <CALCETrWPM_jrF6saHPxoUL4vkjhhGBfizATXrFOW=+z5xycToQ@mail.gmail.com>


* Andy Lutomirski <luto@amacapital.net> wrote:

> On Thu, Jul 14, 2016 at 1:07 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Andy Lutomirski <luto@amacapital.net> wrote:
> >
> >> On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >> >
> >> > * Andy Lutomirski <luto@amacapital.net> wrote:
> >> >
> >> >> > If we push a PKRU value into a thread between the rdpkru() and wrpkru(), we'll
> >> >> > lose the content of that "push".  I'm not sure there's any way to guarantee
> >> >> > this with a user-controlled register.
> >> >>
> >> >> We could try to insist that user code uses some vsyscall helper that tracks
> >> >> which bits are as-yet-unassigned.  That's quite messy, though.
> >> >
> >> > Actually, if we turned the vDSO into something more like a minimal user-space
> >> > library with the ability to run at process startup as well to prepare stuff
> >> > then it's painful to get right only *once*, and there will be tons of other
> >> > areas where a proper per thread data storage on the user-space side would be
> >> > immensely useful!
> >>
> >> Doing this could be tricky: how exactly is the vDSO supposed to find per-thread
> >> data without breaking existing glibc?
> >
> > So I think the way this could be done is by allocating it itself. The vDSO vma
> > itself is 'external' to glibc as well to begin with - this would be a small
> > extension to that concept.
> 
> But how does the vdso code find it?  FS and GS are both spoken for by existing 
> userspace.

Minimally relinking itself on a per mm basis?

Thanks,

	Ingo

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  reply	other threads:[~2016-07-18  9:57 UTC|newest]

Thread overview: 103+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-07 12:47 [PATCH 0/9] [REVIEW-REQUEST] [v4] System Calls for Memory Protection Keys Dave Hansen
2016-07-07 12:47 ` Dave Hansen
2016-07-07 12:47 ` [PATCH 1/9] x86, pkeys: add fault handling for PF_PK page fault bit Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 14:40   ` Mel Gorman
2016-07-07 14:40     ` Mel Gorman
2016-07-07 15:42     ` Dave Hansen
2016-07-07 15:42       ` Dave Hansen
2016-07-07 12:47 ` [PATCH 2/9] mm: implement new pkey_mprotect() system call Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 14:40   ` Mel Gorman
2016-07-07 14:40     ` Mel Gorman
2016-07-07 16:51     ` Dave Hansen
2016-07-07 16:51       ` Dave Hansen
2016-07-08 10:15       ` Mel Gorman
2016-07-08 10:15         ` Mel Gorman
2016-07-07 12:47 ` [PATCH 3/9] x86, pkeys: make mprotect_key() mask off additional vm_flags Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 12:47 ` [PATCH 4/9] x86: wire up mprotect_key() system call Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 12:47 ` [PATCH 5/9] x86, pkeys: allocation/free syscalls Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 14:40   ` Mel Gorman
2016-07-07 14:40     ` Mel Gorman
2016-07-07 15:38     ` Dave Hansen
2016-07-07 15:38       ` Dave Hansen
2016-07-07 12:47 ` [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 14:45   ` Mel Gorman
2016-07-07 14:45     ` Mel Gorman
2016-07-07 17:33     ` Dave Hansen
2016-07-07 17:33       ` Dave Hansen
2016-07-08  7:18       ` Ingo Molnar
2016-07-08  7:18         ` Ingo Molnar
2016-07-08 16:32         ` Dave Hansen
2016-07-08 16:32           ` Dave Hansen
2016-07-08 16:32           ` Dave Hansen
2016-07-09  8:37           ` Ingo Molnar
2016-07-09  8:37             ` Ingo Molnar
2016-07-09  8:37             ` Ingo Molnar
2016-07-11  4:25             ` Andy Lutomirski
2016-07-11  4:25               ` Andy Lutomirski
2016-07-11  7:35               ` Ingo Molnar
2016-07-11  7:35                 ` Ingo Molnar
2016-07-11  7:35                 ` Ingo Molnar
2016-07-11 14:28                 ` Dave Hansen
2016-07-11 14:28                   ` Dave Hansen
2016-07-12  7:13                   ` Ingo Molnar
2016-07-12  7:13                     ` Ingo Molnar
2016-07-12 15:39                     ` Dave Hansen
2016-07-12 15:39                       ` Dave Hansen
2016-07-11 14:50                 ` Andy Lutomirski
2016-07-11 14:50                   ` Andy Lutomirski
2016-07-11 14:34               ` Dave Hansen
2016-07-11 14:34                 ` Dave Hansen
2016-07-11 14:34                 ` Dave Hansen
2016-07-11 14:45                 ` Andy Lutomirski
2016-07-11 14:45                   ` Andy Lutomirski
2016-07-11 15:48                   ` Dave Hansen
2016-07-11 15:48                     ` Dave Hansen
2016-07-12 16:32                     ` Andy Lutomirski
2016-07-12 16:32                       ` Andy Lutomirski
2016-07-12 17:12                       ` Dave Hansen
2016-07-12 17:12                         ` Dave Hansen
2016-07-12 22:55                         ` Andy Lutomirski
2016-07-12 22:55                           ` Andy Lutomirski
2016-07-13  7:56                       ` Ingo Molnar
2016-07-13  7:56                         ` Ingo Molnar
2016-07-13 18:43                         ` Andy Lutomirski
2016-07-13 18:43                           ` Andy Lutomirski
2016-07-14  8:07                           ` Ingo Molnar
2016-07-14  8:07                             ` Ingo Molnar
2016-07-18  4:43                             ` Andy Lutomirski
2016-07-18  4:43                               ` Andy Lutomirski
2016-07-18  9:56                               ` Ingo Molnar [this message]
2016-07-18  9:56                                 ` Ingo Molnar
2016-07-18 18:02             ` Dave Hansen
2016-07-18 18:02               ` Dave Hansen
2016-07-18 18:02               ` Dave Hansen
2016-07-18 20:12             ` Dave Hansen
2016-07-18 20:12               ` Dave Hansen
2016-07-18 20:12               ` Dave Hansen
2016-07-08 19:26         ` Dave Hansen
2016-07-08 19:26           ` Dave Hansen
2016-07-08 10:22       ` Mel Gorman
2016-07-08 10:22         ` Mel Gorman
2016-07-08 10:22         ` Mel Gorman
2016-07-07 12:47 ` [PATCH 7/9] generic syscalls: wire up memory protection keys syscalls Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 12:47 ` [PATCH 8/9] pkeys: add details of system call use to Documentation/ Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 12:47 ` [PATCH 9/9] x86, pkeys: add self-tests Dave Hansen
2016-07-07 12:47   ` Dave Hansen
2016-07-07 14:47 ` [PATCH 0/9] [REVIEW-REQUEST] [v4] System Calls for Memory Protection Keys Mel Gorman
2016-07-07 14:47   ` Mel Gorman
2016-07-07 14:47   ` Mel Gorman
2016-07-08 18:38 ` Hugh Dickins
2016-07-08 18:38   ` Hugh Dickins
2016-07-08 18:38   ` Hugh Dickins
  -- strict thread matches above, loose matches on Subject: below --
2016-06-09  0:01 [PATCH 0/9] [v3] " Dave Hansen
2016-06-09  0:01 ` [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen
2016-06-09  0:01   ` Dave Hansen
2016-06-07 20:47 [PATCH 0/9] [v2] System Calls for Memory Protection Keys Dave Hansen
2016-06-07 20:47 ` [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen
2016-06-07 20:47   ` Dave Hansen

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