Devel November 2017

devel@sel4.systems

13 participants
14 discussions

loading and booting seL4test on a zynq7000
by Joel Svensson 13 Nov '17

13 Nov '17

Hello, I want to learn about seL4 so I am trying to get is started on the hardware I already have (a zynq 7000). I have generated the image: sel4test-driver-image-arm-zynq7000 Now I try to load that onto the zynq by executing these commands in XMD: connect arm hw rst fpga -f design_1_wrapper.bit source ps7_init.tcl ps7_init ps7_post_config dow sel4test-driver-image-arm-zynq7000 run All of the above seem to be successful. Then, I have a serial link hooked up to the board (uart) and there I get the following output (screen /dev/ttyUSB1 115200) : ELF-loader started on CPU: ARM Ltd. Cortex-A9 r3p0 paddr=[10000000..103c881f] ELF-loading image 'kernel' paddr=[0..2afff] vaddr=[e0000000..e002afff] virt_entry=e0000000 But then nothing more. I am lost what to do from this position in order to continue exploring seL4. I don't even know if what I see is an indication of a problem or not. If anyone has experience in running seL4 on zynq and if you sit on knowledge you want to share, please fill me in. Thank you

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CAmkES mutex Question
by Brandon, Jeffrey - 0553 - MITLL 06 Nov '17

06 Nov '17

Hi, I've been taking a look at mutex implementations in the camkes-app example and I had a question. In the mutex example here https://github.com/seL4/camkes/tree/master/apps/mutex suppose I wanted to extend to add a third component C I need to add the corresponding camkes, source, Kbuild, and Kconfig files and then I need to add connections to the master mutex.camkes file correct? My first intuition was to add a connector: Assembly { Composition{ . Connection seL4MyConnector connection(from c.lock, to b.lock); . } } But this yields and error saying something to the effect "seL4MyConnector expects one from endpoint and two are specified" To remedy this I added another lock component to B, and made a connection between C and this new lock B provides. The new lock being implemented by the same template. My Questions: In this scenario do A B and C still have access to the same mutex? If A has a lock on the mutex, then C requests a lock, will this cause A to be unable to release the lock? In my mental model I have three threads of control, one each for A B and C, if A has a lock and then C requests a lock, does this block B (when it receives a message from C and is now blocked on requesting the mutex)? Then when A tries to release, B is blocked and cannot release the mutex on A's behalf. To put it another way, does this mutex example rely on B having direct access to the templated code and there only being two components? Secondarily, in the lockserver example https://github.com/seL4/camkes/tree/master/apps/lockserver a situation is presented where three clients access a single mutex through a single server. Would there be an issue if one of the clients also acted as the server? So for instance if A implemented the three pairs of lock unlock functions instead of the server and then B and C used seL4RPCCall connections to A in order to access them, would there be any synchronization issues? I'm relatively new to this and am trying to build a system with the help of camkes and I want to make sure I understand this before I get too far. I don't want to be working under incorrect assumptions. Thanks for taking the time to read this. Sincerely, Jeff Brandon Associate Staff MIT Lincoln Laboratory Secure Resilient Systems and Technology Ph: +1 781.981.9233

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PPTR address computation on Sel4 Kernel
by Muneeswaran Rajendran 05 Nov '17

05 Nov '17

Hi sel4 development team, I understand from the sel4 kernel the paddr and pptr used in the kernel framework to compute the page table entry. I found from ref manual GICD_PADDR defined as (ARM_PERIPHBASE (0x50040000) + 0x1000) 0x50041000 for that GIC_DISTRIBUTOR_PPTR used as 0xffffffffffff3000. This details was not able to see in the ref manual and other sel4 reference. Can someone help to understand the pptr calculation w.r.t sel4? Thanks in advance Munees

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UART initialisation on seL4 @TX1
by Muneeswaran Rajendran 03 Nov '17

03 Nov '17

Hi sel4 development team, I understand from the seL4 kernel the initial printf message are not routed through sel4 platform uart driver. Because the sel4 UART driver initialisation happened later when seL4 Main kernel initialization is finished. till then sel4 kernel uses u-boot UART driver to route the message. This interpretation is correct as per my understanding. Also mentioned in code as well debug output available via serial interface after kernel init thread started. /* debug output via serial port is only available from here */ printf("Bootstrapping kernel\n"); It means that when sel4 kernel comes up with u-boot uart driver and then later using sel4 uart driver. Please correct me if any thing wrong here and throw some input. Regards, Munees

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Devel November 2017