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seL4 & camkes questions
by Julien Delange 04 Jan '16

04 Jan '16

Hello, First of all, thanks for the help you provided previously. After downloading the virtual machine, everything was fine and I was able to try seL4 and camkes by using the tutorials. Thanks also for making this documentation available publicly, it definitively helps a lot to learn the principles of this operating system. I still do have some questions regarding sel4 and camkes. - About camkes, what are the thread mapping rules. How a component is transformed into one (or several) sel4 threads? Is there a mapping 1 component = 1 thread or is it possible to have multiple threads per component? - How can I find the code generated by camkes? The idl/adl code is ultimately transformed into C code and I was wondering where I could see the code. - How the real-time requirements are handled in camkes? For example, how can I specify that a component is executed periodically every XXX ms. Does the ADL supports that? - How can we specify the scheduling constraints? Can we have an ARINC653-like scheduling where every process has a fixed time slice to be executed? Since the behavior of the system can be deduced from the execution time, allocated a fixed time slice also avoid some attacks - About scheduling, what are the policies actually supported? - How timing is handled? I tried to use nanosleep() from the libc but it seems the syscall/service is not implemented. I also tried the timer example from the sel4 tutorial but when compiling, there is an error (the function timer_handle_irq needs an IRQ as a parameter). Any idea how to fix the example and more information about how time is handled? - is it possible for the OS to load and launch multiple elf at the same time or other processes must be manually started? - How capabilities and services are associated? From the example hello-2 in the sel4 tutorial, I see that a capability is declared (with vka_alloc_endpoint(&vka, &ep_object)) but I do not understand how this is associated with the message being sent between both tasks. In other words, how is it possible to associated a capability with a service. When sending or receiving a message (for example, by using seL4_SetMR(0, MSG_DATA);), there is no use of the capability. So, how the kernel can check that the thread can effectively send a message? - Is there any efforts to support standards such as ARINC653 or MILS? (even experimental) - Is there any significant/big projects that are available online and you would recommend to learn the OS and its associated libraries? Hope you do not mind such a list of questions! I really enjoy digging into the OS and it seems very interesting. Thanks for any help/comment.

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DMA
by Raymond Jennings 04 Jan '16

04 Jan '16

Is it ever possible for seL4 to run on a conventional machine without an IOMMU if any code that manipulates a DMA capable device is included as trusted or does DMA automatically void any assurance? Reason for question: Running seL4 on a system without an IOMMU.

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Determining when would-have-blocked
by Corey Richardson 04 Jan '16

04 Jan '16

Looking at the manual and the C impl, it seems there is no robust way to determine if a non-blocking send failed. How should an application handle this? NBRecv sets the badge register to zero when the recv "failed" - is it expected that most/all endpoints will be badged? I'm still trying to get a feel for what a system designed for this model would look like. -- cmr +16032392210 http://octayn.net/

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Tutorial error
by Julien Delange 23 Dec '15

23 Dec '15

Hello, I am trying to reproduce the tutorial. I followed the steps from the slides on https://github.com/seL4-projects/sel4-tutorials/blob/master/docs/seL4Tutori… When trying to compile, I got the following error in [1]. It seems to be a warning from the compiler, so, I edit the CFLAGS in the .config and tried to compile but then got the error in [2], which then avoid any potential compilation. Is there any special setup for the compiler? I am currently using gcc 5.2.1. Thanks for any suggestion, Julien. [1] /home/julien/tmp/sel4-tutorials/stage/x86/pc99/include/vka/object.h:286:5: warning: 'seL4_AsyncEndpointObject' is deprecated (declared at /home/julien/tmp/sel4-tutorials/stage/x86/pc99/include/sel4/objecttype.h:23): use seL4_NotificationObject [-Wdeprecated-declarations] [2] /home/julien/tmp/sel4-tutorials/kernel/src/plat/pc99/machine/acpi.c:38:13: error: size of array '__assert_failed_acpi_rsdp_packed' is negative

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Camkes dependencies & development environment
by Julien Delange 23 Dec '15

23 Dec '15

Dear all, First of all, sorry if this question has been asked several times already. I am currently trying to use sel4 & camkes on a debian stable. I installed all the dependencies but I am facing an error message when trying to build the tool (see below). My version of cabal is 1.20, so, version should not be an issue. After searching, it seemed that the version of ghc might be the root cause so I upgraded to testing and/or unstable but faced other issues then. My question is then what is the best development environment to use sel4 and camkes? Any special recommendation? I would like to keep my existing debian/stable as much as possible. Thanks for any help or suggestion, Julien. [parse-capDL] building... export CONFIG_CAPDL_LOADER_MAX_IRQS=256 && cabal configure && cabal build && cp dist/build/parse-capDL/parse-capDL . Resolving dependencies... cabal: The package 'capDL-tool' requires Cabal library version -any && >=1.18 but no suitable version is installed. Makefile:45: recipe for target 'parse-capDL' failed make[1]: *** [parse-capDL] Error 1 Makefile:49: recipe for target '/home/julien/tmp/camkes/stage/arm/imx31/parse-capDL/parse-capDL' failed make: *** [/home/julien/tmp/camkes/stage/arm/imx31/parse-capDL/parse-capDL] Error 2

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domain problems
by ぷ风过无痕?? 23 Dec '15

23 Dec '15

Hi everyone, I'm running the RefOS project on arm kzm board. The config file is kzm_debug_defconfig. I am tring to set two domains in the RefOS by changing the CONFIG_NUM_DOMAIN parameter from 1 to 2 in this file and rebuilt RefOS. When running RefOS it gets stucked and some servers cannot be initialized.How to resolve this bug?

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domain problems
by ぷ风过无痕?? 23 Dec '15

23 Dec '15

Hi everyone, I'm running the RefOS project on arm kzm board. The config file is kzm_debug_defconfig. I am tring to set two domains in the RefOS by changing the CONFIG_NUM_DOMAIN parameter from 1 to 2 in this file and rebuilt RefOS. When running RefOS it gets stucked and some servers cannot be initialized.How to resolve this bug? The full output information is in the adjunct file.

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RTEMS working with seL4
by Hesham Almatary 15 Dec '15

15 Dec '15

Hi all, I got an RTEMS port working for RISC-V architecture along with seL4. This depends on my earlier seL4 port for RISC-V. RTEMS runs with support of seL4 microkernel, and it runs in Supervisor mode (on another core). seL4 application would allocate and map memory for it from its untyped memory (userspace), before off-loading it to another core. seL4 application that loads/runs RTEMS is pretty much the same as SOS. For more details (and instructions) about how to build/run the project, see the github repo of the port [1], and/or this blog post [2] [1] https://github.com/heshamelmatary/rtems-riscv [2] http://heshamelmatary.blogspot.co.uk/2015/12/rtems-port-for-risc-v-withwith… Cheers, -- Hesham

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VSpace translation?
by Ben Karel 14 Dec '15

14 Dec '15

Would any of seL4's guarantees be compromised if a Translate method were added to page directory objects (for mapping a virtual address to the underlying physical address, without exposing the intermediate page capabilities)?

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Capability resolution depth mismatches
by Ben Karel 14 Dec '15

14 Dec '15

Hi all, Some capability resolution, such as for fault handling, winds up calling resolveAddressBits with n_bits = wordBits, and any remaining bits are ignored. In other cases, such as the destination slot for seL4_CNode_Copy, the user provides a resolution depth parameter, and the call to resolveAddressBits is mediated by lookupSlotForCNodeOp, which fails with a depth mismatch if there are any bits remaining. Individually these seem like reasonable choices, but it leads to code like this: seL4_CNode cspace_root = ...; // freshly allocated 256-slot CNode with no guard seL4_CPtr slot_for_copy = 0x23; // arbitrary slot we know is available seL4_CPtr slot_for_tcb = slot_for_copy << 24; seL4_CNode_Copy(cspace_root , endpoint_for_copy, 8, ...); seL4_TCB_Configure(..., endpoint_for_tcb, ...); I found it surprising that two different CPtrs are needed to describe the same slot! Is there a conceptual-model-explanation that doesn't involve appeal to the underlying implementation? Also: my current understanding is that the depth parameter is only needed to disambiguate indirections through CNode-containing slots. What goes wrong if the depth mismatch checks are relaxed?

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