[lwip-devel] [patch #7885] modification of api modules to support FreeRTOS-MPU (NO_SYS = 0)

[Artem Pisarenko]

URL:
  <http://savannah.nongnu.org/patch/?7885>

                 Summary: modification of api modules to support FreeRTOS-MPU
(NO_SYS = 0)
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: jblackarty
            Submitted on: Wed 14 Nov 2012 11:08:13 AM OMST
                Category: None
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

The patch makes lwip support system architectures (ports) based on
FreeRTOS-MPU (with memory protection unit) where tcpip thread must be run in
user mode. (Modification support lwip usage in all cases but I didn't
considered PPP. Maybe PPP module doesn't require modifications ever and will
work.)

FreeRTOS-MPU doesn't allow user-mode tasks to get access to other threads'
stacks. Current lwip code violates this rule because tcpip_thread accesses
local variables located on stack of api function (which belongs to application
thread) being passed by pointer via tcpip_msg. Based on static analysis of
code (manual, no special instruments :)) I followed all references to local
variables and moved them on heap/pool. This increases heap/pool usage but
decreases stack usage in application and tcpip threads.

There are also other MPU constraints which isn't being meet by lwip design.
They may be solved by means of port and application configuration. But this is
topic of separate discussion. This patch only makes strictly required changes
to lwip code itself.

"Release notes":
- LWIP_TCPIP_CORE_LOCKING option wasn't mentioned although I tried to consider
it
- new MEMP_NUM_SOCKET_API option added
- struct dns_api_msg (in api_msg.h) changed
- struct api_msg_msg (in api_msg.h) changed
- struct netifapi_msg_msg (in netifapi.h) changed
- some definitions of socket structures from sockets.c moved to header

I made some basic tests which covering code I modified except
lwip_getsockopt()/lwip_setsockopt() because I don't know sockets API so much.
Everything seems to work stable for me.
I expect project maintainers provide me with support to pass modified code
through all your internal tests and I'll report results.
I have STM3220G-EVAL board and from-scratch-made sys arch port and ethernet
driver designed to work in mem-pools configuration of lwip.

You can read discussion on this topic was started on mailing list
"[lwip-users] lwip and MPU (FreeRTOS-MPU)".



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File Attachments:


-------------------------------------------------------
Date: Wed 14 Nov 2012 11:08:13 AM OMST  Name: lwip_mpu_redesign__draft2.patch 
Size: 39kB   By: jblackarty

<http://savannah.nongnu.org/patch/download.php?file_id=26912>

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