l4-hackers Digest, Vol 105, Issue 9

[jangwoo]

Hi all.

I have similar problem.
Currently  applications on linux can't use mmap of framebuffer(/dev/fb0).
When apps access memory to get through mmap, it occurs page fault.

Without goos, fbdrv of L4 cell, mag, l4fb drv in linux, etc on,
Is there ways that it modify <linux lcd device driver> little bit as other
linux device drivers

In other words, could Apps use allocated  memory in linux kernel?

As a guide,
Because of using dedicated frame buffer only in one cell(linux), it mustn't
use things like goos, mag.

thanks
------------------------------
Message: 1
Date: Tue, 24 Jan 2012 20:03:36 +0100
From: Adam Lackorzynski <adam at os.inf.tu-dresden.de>
To: l4-hackers at os.inf.tu-dresden.de
Subject: Re: Fiasco.OC x86 IO port permission bitmap
Message-ID: <20120124190336.GE2897 at os.inf.tu-dresden.de>
Content-Type: text/plain; charset=iso-8859-1

Hi,

On Mon Jan 23, 2012 at 15:54:29 -0800, Daniel Waddington wrote:
> I want to use the TSS I/O permission bit map to support fine grained
> control of I/O access for user-level apps (x86 32 bit target).  From
> looking at the kernel code, I believe the bit map is switched out
> per-process as part of the Context class (Space::_io_space) -
> correct me if I am wrong.  My query is how to set/clear the bits for
> a given target task from a "root" task with sufficient privileges
> (e.g., base caps and sigma0 caps).  I could extend the kernel
> scheduler protocol, but I don't want to do this if there is already
> a clean way in place.

IO-ports are handled similar to page-faults, i.e. they can be mapped to
other tasks, and the pager receives io-page-faults when one of its
clients accesses an IO-port without having it. For example look for
L4_PROTO_IO_PAGE_FAULT and l4_iofpage().


Adam
-- 
Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/



------------------------------

Message: 2
Date: Tue, 24 Jan 2012 13:12:03 -0800
From: Daniel Waddington <d.waddington at samsung.com>
To: Adam Lackorzynski <adam at os.inf.tu-dresden.de>
Cc: l4-hackers at os.inf.tu-dresden.de
Subject: Re: Fiasco.OC x86 IO port permission bitmap
Message-ID: <4F1F1EA3.7060309 at samsung.com>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"

Hi Adam,

I see. So it seems that you have to map all of the IO port space before 
getting IOPL raised to 3 (assuming Kconfig IO_PROT & !IO_PROT_3) and 
therefore the default mode of operation is a driver will map the whole 
space if it wants to use IO instructions directly.  Is it right that you 
currently don't use the TSS IO bitmap to allow access to only specific 
IO ports with CPL > IOPL?

Thanks
Daniel

On 01/24/2012 11:03 AM, Adam Lackorzynski wrote:
> Hi,
>
> On Mon Jan 23, 2012 at 15:54:29 -0800, Daniel Waddington wrote:
>> I want to use the TSS I/O permission bit map to support fine grained
>> control of I/O access for user-level apps (x86 32 bit target).  From
>> looking at the kernel code, I believe the bit map is switched out
>> per-process as part of the Context class (Space::_io_space) -
>> correct me if I am wrong.  My query is how to set/clear the bits for
>> a given target task from a "root" task with sufficient privileges
>> (e.g., base caps and sigma0 caps).  I could extend the kernel
>> scheduler protocol, but I don't want to do this if there is already
>> a clean way in place.
> IO-ports are handled similar to page-faults, i.e. they can be mapped to
> other tasks, and the pager receives io-page-faults when one of its
> clients accesses an IO-port without having it. For example look for
> L4_PROTO_IO_PAGE_FAULT and l4_iofpage().
>
>
> Adam
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