May 2016 - Devel - lists.sel4.systems

IA32 syscall bindings
by Norman Feske 26 Aug '16

26 Aug '16

Dear seL4 developers, first, I'd like to thank you for publishing seL4 under GPL. I am very happy that I can finally get my hands dirty with working with the kernel of your group. :-) Currently, I am taking the first baby steps to bring the Genode OS framework (http://genode.org) to seL4. For reference, I am using the experimental branch. The first smallish issue I stumbled upon stems from the fact that Genode is written in C++. By compiling the seL4 syscall bindings with a C++ compiler, I got the following error: error: inconsistent operand constraints in an ‘asm’ It can be reproduced by putting the following code snippet into a cc file and compiling it with 'g++ -m32 -c' (tested with the Genode tool chain as well as with GCC 4.8.1): typedef enum { seL4_SysDebugPutChar = -9, _enum_pad_seL4_Syscall_ID = (1U << ((sizeof(int)*8) - 1)) } seL4_Syscall_ID; void seL4_DebugPutChar(char c) { asm volatile ( "pushl %%ebp \n" "movl %%esp, %%ecx \n" "leal 1f, %%edx \n" "1: \n" "sysenter \n" "popl %%ebp \n" : : "a" (seL4_SysDebugPutChar), "b" (c) : "%ecx", "%edx", "%esi", "%edi", "memory" ); } When compiling the same code snippet with 'gcc' instead of 'g++', everything is fine. It turns out that the C++ compiler does not like the enum value to be specified as input argument. I found the following ways to circumvent this problem: * Changing the enum value 'SysDebugPutChar' to a positive value, * Removing the definition of '_enum_pad_seL4_Syscall_ID', * Casting 'seL4_SysDebugPutChar' to an integer: : "a" ((int)seL4_SysDebugPutChar), In any case, I seem to have to change the bindings. Do you see a way around it? If not, would you consider one of the solutions above for the seL4 headers? On another note, I noticed that the bindings use the EBX register. Unfortunately, this makes it impossible to compile seL4 userland software as position-independent code (PIC). E.g., when compiling the above code snippet via 'g++ -m32 -fPIC -c', the following error occurs: error: inconsistent operand constraints in an ‘asm’ However, PIC is required in order to use shared libraries. The solution would be to not use EBX to pass arguments to the 'asm' statements, save EBX on the stack prior moving the respective kernel argument to the register, and, of course, restoring it after sysenter returns. Before I start changing the bindings, I'd like to know: is there anyone else working on the same problem? Would you be open to accept a change of the bindings to become PIC compliant on the costs of a few added instructions? Or do you have another suggestion how I should go about it? Best regards 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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Memory allocation & threads
by Доброхотов Ринат 03 Jun '16

03 Jun '16

Hello, I don't understand how static and virtual pool's size related to thread's available working space. I got the example app from the sel4-tutorials project with process creation (app-4). A static pool and a virtual pool are created in this app. I have done experiments with size of this pools and size of arrays in the second thread. For example I set size of virtual pool to zero, as I understand this pool need to create kernel objects. Also I define the test array size of (1 << 23)~8,3Mb. If test array is static, static pool size must be equal to ((1 << seL4_PageBits) * 100) ~0,4Mb. If test array is no static, static pool size not limited. Why is it so? -- Best Regards, Rinat Dobrokhotov

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RT branch questions
by Julien Delange 27 May '16

27 May '16

I am currently trying the RT branch and have some questions: 1. What emulator to use in order to try the examples? I am trying to use x86 with qemu but it seems that it does not work. I got the following trace at execution Starting node #0 APIC: unsupported platform, TSC-deadline mode is not supported seL4 called fail at /home/sel4/camkes-sc-tests/kernel/src/arch/x86/kernel/boot_sys.c:451 in function boot_sys, saying "boot_sys failed for some reason :( So, is there an emulator (for any supported platform) to try it? 2. In the RT-camkes extensions, I have the following new attributes: _period _budget _priority What is the semantics of these attributes? Any information about them? How they are supposed to be isolated from each other then? How to define the scheduling plan for the system then? Also, how these attributes apply to all thread: a thread is created for each interface of the component, so, how can we then define the priority/budget of each thread? Do these attributes apply to all the components of the thread? Thanks for any help/clarification. Julien. assembly { composition { component Client client1; component Client client2; } configuration { client1._priority = 100; client1._period = 10000; client1._budget = 7500; client2._priority = 50; client2._period = 10000; client2._budget = 7500; } }

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Advice on camkes and regular seL4 for driver components
by Norrathep Rattanavipanon 27 May '16

27 May '16

Hello, I currently had codes, implemented as regular seL4, since camkes does not support some features (i.e. transferring capabilities or accessing address space outside the process), Everything is fine up to this point but now I want to create several drivers. And I found that the best and easiest way to do that is to use camkes. So is it possible to use existing regular codes in conjunction with camkes? Or would the best way be to implement drivers as regular seL4 codes? Thanks, Oak -- Norrathep (Oak) Rattanavipanon M.S. in Computer Science University of California - Irvine

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building VMM on Jetson TK1 board
by PX 26 May '16

26 May '16

Hi, all we want to build the seL4-based VMM from https://github.com/smaccm/sel4arm-vmm.git on Jetson TK1 board. However, the seL4 kernel in that project does not support TK1 board. We want to use the new version seL4 version (arm_hyp) at https://github.com/seL4/seL4.git. My questions are: 1) It is feasible to do that? 2) If so, what are the correct steps to do that? 3) we try to compile these source code, but failed. We do the following modifications: A) we add TK1 source codes (i.e. TK1 folders from https://github.com/seL4/seL4.git) to the corresponding libraries in the VMM source code from https://github.com/smaccm/sel4arm-vmm.git; and B) we add relevant config definitions to the VMM code. Currently, we can successfully compile the seL4 kernel code, but have trouble to compile the VMM libraries. Do we miss something here? thanks Peng

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Availability of RT branch?
by Julien Delange 25 May '16

25 May '16

Hi all, Follow-up on our recent discussions on the RT branch: is the RT branch now available? How could I get it and access the related documentation? If not available, is there any idea of when it will be available? Thanks. Julien.

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Getting timer info from seL4 kernel
by Will Klieber 19 May '16

19 May '16

Hi, Is there any way of obtaining the number of elapsed timer ticks from the seL4 kernel (using ARM / BeagleBoard platform)? I know the kernel uses this information internally for the scheduler, but I couldn't find any way of accessing it from userland. Specifically, my usage scenario is as follows. Two mutually distrustful programs are running, and each wants to run an action periodically. We want to temporally isolate the two programs using seL4 time domains. In this case, interacting with the hardware timer in userland seems difficult, since we want to get the updated time whenever a new timer tick arrives, but the userland device driver for the timer can only operate in exactly one of the seL4 time domains. Please let me know if I am misunderstanding something or if there might be a better way to approach this situation. Thanks, Will

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Hello. I'm Kihyun-seo in South Korea.
by 서기현 17 May '16

17 May '16

Hello, I am a student of the Hanseo University in Korea. I want to create a UAV(drone) that uses Odroid XU4 Odroid XU4's Detailed Specifications = http://www.hardkernel.com/main/products/prdt_info.php?g_code=G143452239825 I want to install seL4 on the board for the security of the drones. The board has “ubuntu-15.04-robotics-odroid-xu4-201” 32bit linux version. I have two questions. First, I understood that after installing the seL4 first, and installing the linux later after seeing the 1.jpg. However, in the “https://wiki.sel4.systems/Getting%20started”. “Setting up your machine - These instructions are for Ubuntu. They assume you already know the basics of using the command line, compilers and GNU Make.” So then, Should I install the Linux(ubuntu) first, and install the seL4 later? I wonder what is correct. and I need more detailed explanation. Second, An error occurred during install the seL4 like 2.jpg. (command = "make menuconfig" in "Build ia32" part.) I need a solution about the error. Please answer my two questions.

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multi-core support
by PX 17 May '16

17 May '16

Hi, Just want to double check if the seL4 under link https://github.com/seL4/sel4test supports multi-core? If so, the multi-core support is configured by default? If the sel4 does not support multi core, where can we get the experimental version supporting multi core? thanks Peng

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Trusted Execution Environment on seL4
by rahul mahadev 11 May '16

11 May '16

Hi, I am Rahul Mahadev, I'm currently working on a Google Summer Of Code project with the organization lowRISC. My project is to implement a Trusted Execution Environment for the RISC-V platform. Last year's gsoc had a port of sel4 for RISC-V platform by Hesham Almatery. I plan on using seL4 for the port by either of the two methods. 1. paravirtualize OPTEE(Linaro's TEE) on top of seL4 2. implement an API similar to OPTEE for seL4 I have written a blog post explaining this, I wanted your opinion + ideas regarding this. link: http://mahadevrahul.blogspot.in/2016/05/gsoc-2016-implementing-trusted.html Thank You, Rahul Mahadev

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