Message-ID: <20161005134357.GH20761@phenom.ffwll.local>
Date:   Wed, 5 Oct 2016 15:43:57 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>
Cc:     "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Cc Ma <cc.ma@...iatek.com>,
        Joakim Bech <joakim.bech@...aro.org>,
        Burt Lien <burt.lien@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linaro MM SIG Mailman List <linaro-mm-sig@...ts.linaro.org>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH v10 0/3] Secure Memory Allocation Framework

On Wed, Oct 05, 2016 at 03:40:14PM +0200, Benjamin Gaignard wrote:
> because with ion it is up to userland to decide which heap to use
> and until now userland doesn't have any way to get device constraints...
> 
> I will prefer let a central allocator (in kernel) decide from the
> attached devices
> which allocator is the best. It is what I have implemented in smaf.

And how does that work? Atm there's no interfaces at all in the kernel to
allocate a buffer suitable for 2 devices at the same time. Seems
incomplete if this is the direction you want to go to. Also, it's against
the direction we all discussed ad XDC, where the clear consensus was to
have most of that haggling in userspace (with the kernel exporting a
little bit more information to userspace than what it does now).
-Daniel

> 
> Benjamin
> 
> 
> 2016-10-05 15:19 GMT+02:00 Daniel Vetter <daniel@...ll.ch>:
> > On Tue, Oct 04, 2016 at 01:47:21PM +0200, Benjamin Gaignard wrote:
> >> version 10 changes:
> >>  - rebased on kernel 4.8 tag
> >>  - minor typo fix
> >>
> >> version 9 changes:
> >>  - rebased on 4.8-rc5
> >>  - struct dma_attrs doesn't exist anymore so update CMA allocator
> >>    to compile with new dma_*_attr functions
> >>  - add example SMAF use case in cover letter
> >>
> >> version 8 changes:
> >>  - rework of the structures used within ioctl
> >>    by adding a version field and padding to be futur proof
> >>  - rename fake secure moduel to test secure module
> >>  - fix the various remarks done on the previous patcheset
> >>
> >> version 7 changes:
> >>  - rebased on kernel 4.6-rc7
> >>  - simplify secure module API
> >>  - add vma ops to be able to detect mmap/munmap calls
> >>  - add ioctl to get number and allocator names
> >>  - update libsmaf with adding tests
> >>    https://git.linaro.org/people/benjamin.gaignard/libsmaf.git
> >>  - add debug log in fake secure module
> >>
> >> version 6 changes:
> >>  - rebased on kernel 4.5-rc4
> >>  - fix mmapping bug while requested allocation size isn't a a multiple of
> >>    PAGE_SIZE (add a test for this in libsmaf)
> >>
> >> version 5 changes:
> >>  - rebased on kernel 4.3-rc6
> >>  - rework locking schema and make handle status use an atomic_t
> >>  - add a fake secure module to allow performing tests without trusted
> >>    environment
> >>
> >> version 4 changes:
> >>  - rebased on kernel 4.3-rc3
> >>  - fix missing EXPORT_SYMBOL for smaf_create_handle()
> >>
> >> version 3 changes:
> >>  - Remove ioctl for allocator selection instead provide the name of
> >>    the targeted allocator with allocation request.
> >>    Selecting allocator from userland isn't the prefered way of working
> >>    but is needed when the first user of the buffer is a software component.
> >>  - Fix issues in case of error while creating smaf handle.
> >>  - Fix module license.
> >>  - Update libsmaf and tests to care of the SMAF API evolution
> >>    https://git.linaro.org/people/benjamin.gaignard/libsmaf.git
> >>
> >> version 2 changes:
> >>  - Add one ioctl to allow allocator selection from userspace.
> >>    This is required for the uses case where the first user of
> >>    the buffer is a software IP which can't perform dma_buf attachement.
> >>  - Add name and ranking to allocator structure to be able to sort them.
> >>  - Create a tiny library to test SMAF:
> >>    https://git.linaro.org/people/benjamin.gaignard/libsmaf.git
> >>  - Fix one issue when try to secure buffer without secure module registered
> >>
> >> SMAF aim to solve two problems: allocating memory that fit with hardware IPs
> >> constraints and secure those data from bus point of view.
> >>
> >> One example of SMAF usage is camera preview: on SoC you may use either an USB
> >> webcam or the built-in camera interface and the frames could be send directly
> >> to the dipslay Ip or handle by GPU.
> >> Most of USB interfaces and GPU have mmu but almost all built-in camera
> >> interace and display Ips don't have mmu so when selecting how allocate
> >> buffer you need to be aware of each devices constraints (contiguous memroy,
> >> stride, boundary, alignment ...).
> >> ION has solve this problem by let userland decide which allocator (heap) to use
> >> but this require to adapt userland for each platform and sometime for each
> >> use case.
> >>
> >> To be sure to select the best allocation method for devices SMAF implement
> >> deferred allocation mechanism: memory allocation is only done when the first
> >> device effectively required it.
> >> Allocator modules have to implement a match() to let SMAF know if they are
> >> compatibles with devices needs.
> >> This patch set provide an example of allocator module which use
> >> dma_{alloc/free/mmap}_attrs() and check if at least one device have
> >> coherent_dma_mask set to DMA_BIT_MASK(32) in match function.
> >>
> >> In the same camera preview use case, SMAF allow to protect the data from being
> >> read by unauthorized IPs (i.e. a malware to dump camera stream).
> >> Until now I have only see access rights protection at process/thread level
> >> (PKeys/MPK) or on file (SELinux) but nothing allow to drive data bus firewalls.
> >> SMAF propose an interface to control and implement those firewalls.
> >> Like IOMMU, firewalls IPs can help to protect memory from malicious/faulty devices
> >> that are attempting DMA attacks.
> >>
> >> Secure modules are responsibles of granting and revoking devices access rights
> >> on the memory. Secure module is also called to check if CPU map memory into
> >> kernel and user address spaces.
> >> An example of secure module implementation can be found here:
> >> http://git.linaro.org/people/benjamin.gaignard/optee-sdp.git
> >> This code isn't yet part of the patch set because it depends on generic TEE
> >> which is still under discussion (https://lwn.net/Articles/644646/)
> >>
> >> For allocation part of SMAF code I get inspirated by Sumit Semwal work about
> >> constraint aware allocator.
> >
> > semi-random review comment, and a bit late: Why not implement smaf as a
> > new heap in ion? I think consensus is pretty much that we'll be stuck with
> > ion forever, and I think it's better to have 1 central buffer allocater
> > than lots of them ...
> > -Daniel
> >
> >>
> >> Benjamin Gaignard (3):
> >>   create SMAF module
> >>   SMAF: add CMA allocator
> >>   SMAF: add test secure module
> >>
> >>  drivers/Kconfig                |   2 +
> >>  drivers/Makefile               |   1 +
> >>  drivers/smaf/Kconfig           |  17 +
> >>  drivers/smaf/Makefile          |   3 +
> >>  drivers/smaf/smaf-cma.c        | 186 ++++++++++
> >>  drivers/smaf/smaf-core.c       | 818 +++++++++++++++++++++++++++++++++++++++++
> >>  drivers/smaf/smaf-testsecure.c |  90 +++++
> >>  include/linux/smaf-allocator.h |  45 +++
> >>  include/linux/smaf-secure.h    |  65 ++++
> >>  include/uapi/linux/smaf.h      |  85 +++++
> >>  10 files changed, 1312 insertions(+)
> >>  create mode 100644 drivers/smaf/Kconfig
> >>  create mode 100644 drivers/smaf/Makefile
> >>  create mode 100644 drivers/smaf/smaf-cma.c
> >>  create mode 100644 drivers/smaf/smaf-core.c
> >>  create mode 100644 drivers/smaf/smaf-testsecure.c
> >>  create mode 100644 include/linux/smaf-allocator.h
> >>  create mode 100644 include/linux/smaf-secure.h
> >>  create mode 100644 include/uapi/linux/smaf.h
> >>
> >> --
> >> 1.9.1
> >>
> >> _______________________________________________
> >> dri-devel mailing list
> >> dri-devel@...ts.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch
> 
> 
> 
> -- 
> Benjamin Gaignard
> 
> Graphic Study Group
> 
> Linaro.org │ Open source software for ARM SoCs
> 
> Follow Linaro: Facebook | Twitter | Blog
> _______________________________________________
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> dri-devel@...ts.freedesktop.org
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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