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devel@sel4.systems

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1391 discussions

Clang & LLVM
by da Tyga 08 Nov '14

08 Nov '14

Hi ! There seems to be a general trend towards using Clang / LLVM in the ARM area. AFAIK ARM are going LLVM for V8. Is it viable to do seL4 work with that environment? Cheers!

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Reasoning behind the root cnode's guard value
by Norman Feske 06 Nov '14

06 Nov '14

Hello, the seL4 kernel constructs the root task's CNode (in kernel/boot.c) by using the configurable number CONFIG_ROOT_CNODE_SIZE_BITS as size and a guard value calculated as 32 - CONFIG_ROOT_CNODE_SIZE_BITS. I understand that it makes the capability name space nicely linear. But on the hand, doesn't it impede the number of kernel objects addressable by root task? When using Genode's core as root task on seL4, I will need to maintain a large number of capabilities to kernel objects, in particular one for each page managed by the core process. Naturally. I would like to organize the root task's capability namespace hierarchically, allocating CNodes depending on the dynamic work load. As far as I understand, however, root task would have no way to address slots within such additional CNodes because all address bits are already consumed by the root CNode indices + guard. For example, how is root task supposed to specify capabilities that are not contained in the root CNode as "service" argument to functions like 'seL4_TCB_WriteRegisters'? One way I see would be to move capabilities back and forth between the root CNode and other CNodes using 'seL4_CNode_Copy', effectively using the root CNode as a kind of CNode cache. But this solution seems overly complicated. Another way would be to dimension CONFIG_ROOT_CNODE_SIZE_BITS pessimistically. But introducing such an upper bound a-priory would somehow contradict with seL4's otherwise nicely dynamic resource management. Yet another way would be to let root task use a smaller guard value that leaves enough bits available to be used for second-level or third-level CNodes. But since that would require a change of the kernel code, I suspect that this approach is not in line with right seL4 way. Could you share the reasoning behind the guard-value calculation and help me to get on the right track? Or would you consider a configurable guard value for root task as a reasonable feature request? Cheers Norman -- Dr.-Ing. Norman Feske Genode Labs http://www.genode-labs.com · http://genode.org Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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Make Error : seL4 kernel
by Yashwardhan Singh 29 Oct '14

29 Oct '14

Hi I downloaded the latest repository of seL4 from GitHub. When I am trying to build the kernel using make for ia32 architecture and pc99 platform I am getting this error : *yashward@macaroni-09:~/cs736-proj/seL4$ make ARCH=ia32 PLAT=pc99* * [CC] kernel_final.s* *src/arch/ia32/kernel/boot_sys.c:75:26: error: ‘CONFIG_MAX_NUM_IOAPIC’ undeclared here (not in a function)* * paddr_t ioapic_paddr[CONFIG_MAX_NUM_IOAPIC];* * ^* *src/plat/pc99/machine/hardware.c: In function ‘maskInterrupt’:* *src/plat/pc99/machine/hardware.c:54:9: error: implicit declaration of function ‘pic_mask_irq’ [-Werror=implicit-function-declaration]* * pic_mask_irq(mask, irq);* * ^* *src/plat/pc99/machine/hardware.c:54:9: error: nested extern declaration of ‘pic_mask_irq’ [-Werror=nested-externs]* *cc1: all warnings being treated as errors* *make: *** [kernel_final.s] Error 1* I am trying to compile it on a 64 bit machine with red hat linux machine operating system on it. Please help me with this issue. Regards Yash

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A missing function?
by chengkunck＠gmail.com 29 Oct '14

29 Oct '14

Hello everyone, Currently I'm going through the source code of seL4. I find function in seL4\src\object\Tcb.c that I can't find it's definition. In line 59, tcbSchedEnqueue calls a function 'thread_state_ptr_set_tcbQueued(&tcb->tcbState, true)'. However, even with the help of Source Insight I still can't locate the definition of 'thread_state_ptr_set_tcbQueued' . Does anyone know where it is ? Thanks in advance. Best regards, Kenneth.

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Dynamic number of arguments in interface method
by Lukas Masek 27 Oct '14

27 Oct '14

Hello Everyone, I'm trying to implement interface which will accept similar syntax like printf method in c is accepting. syntax of function in c: void printer(int i,char* format,...){ } However I have problem to create valid syntax in idl4 interface definition for CAmkES. Can somebody help me to create valid syntax for procedure definition used in interface? procedure Test { void printer(in int i,in string format,in ...); }; Or is this approach even supported? Also If there is more complex reference guide for idl4 used by CAmkES which I can use to find answers like this? Thank you for help and if question is stupid please accept my apologize I'm just starting to play with this project. BR, Casper

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sel4 on multi-core
by Yuxin Ren 21 Oct '14

21 Oct '14

Hi All, I think, on IA-32, sel4 supports multi-core machine. But I do not how to use that. Here I have two specfic questions. 1. How to assign a specific core to a process/thread? And can I change this affinity? 2. How to two process/threads communicate via IPC on different cores? I want to know some implementation details in kernel to support cross-core IPC. Could anyone explain its logic or tell me the code for it in the kernel? Thank you very much. Best, Yuxin

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IPC performance for slowpath
by Yuxin Ren 19 Oct '14

19 Oct '14

Hi All, I find there have slow and fast path for IPC. I want to know the performance difference between those two. More accurate, on x86, how many cycles for slow path round-trip ipc between two address space?(on single core) And how many for fast path? Thank you very much. Yuxin

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How to get a capability of a virtual address
by Yuxin Ren 18 Oct '14

18 Oct '14

Hi All, In sel4, how can a process/thread get the capability of its virtual address? I know there is function vspace_get_cap(vspace_t *vspace, void *vaddr) But how can I know the current vspace the process/thread is in? Thank you very much. Yuxin

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Where to begin for Linux on seL4 x86?
by Robert Brewer 16 Oct '14

16 Oct '14

I'm new to seL4 (and L4 generally). I'd like to initially run my application functionality in Linux on top of seL4 (x86) and then over time migrate pieces of its functionality to run directly on seL4 to achieve finer-grained confinement. I'm having trouble finding any instructions on how to run a Linux environment on top of seL4. Either paravirtualized or hardware virtualized would be ok. So far I found pointers to L4Linux but it appears to need L4Re. Can anyone point me in the right direction? Thanks, Rob

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Get a mapping for physical memory
by Yuxin Ren 14 Oct '14

14 Oct '14

Hi All, I am a very beginner for sel4, and I very little about its APIs. Now I have a physical address of memory, I want to know if this address is mapped into my virtual address space. And if so, how can I know what virtual address t is mapped in? Furthermore, how can I share this piece of memory with another process/thread? I find there is a function "simple_get_frame_mapping_f“ in libsel4simple-default library. Its comment is "Request mapped address to a region of physical memory.” It is very similar to what I need, but its implementation just returns NULL.(in sel4\libs\libsel4simple-stable\src\libsel4simple-stable.c) Thank you very much. Yuxin

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