users October 2016

users@lists.genode.org

14 participants
13 discussions

Reading thread registers
by Denis Huber 07 Mar '17

07 Mar '17

Hello Genode community, in my checkpoint component I intercepted the Cpu session of a child, through which I get all Thread_capabilities created for and by the child. To store the state of a component I need to store the registers of the threads used by the child. I tried reading the registers through the "Thread_state Cpu_thread::state()" method, but it did not contain any information about (just zeros). I'm using Genode 16.05, kernel Fiasco.OC (pbax9 build). By inspecting the kernel API of foc, I found out that the function l4_thread_ex_regs_ret can read the sp and ip register. By changing the state method in platform_thread.cc (in base-foc) I could get the registers: Thread_state Platform_thread::state() { Thread_state s; if (_pager_obj) s = _pager_obj->state; _pager_obj->state.ip = ~0UL; _pager_obj->state.sp = ~0UL; l4_umword_t flags = 0; l4_thread_ex_regs_ret(_thread.local.dst(), &_pager_obj->state.ip, &_pager_obj->state.sp, &flags); s.sp = _pager_obj->state.sp; s.ip = _pager_obj->state.ip; s.kcap = _gate.remote; s.id = _gate.local.local_name(); s.utcb = _utcb; return s; } But other registers like r0 - r12 are missing. Is there a simple way in Genode to get them? Can I utilize the utcb memory location to find the missing registers? Kind regards Denis

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Assembly at 33C3?
by Johannes Schlatow 25 Nov '16

25 Nov '16

Hi Genode hackers, recently, the call for participation for the 33th Chaos Communication Congress [1] has been released, an amazing event I very much enjoy attending for quite a few years now. This year, I'm thinking about organising an assembly at which I can focus on some side projects of mine that are partly Genode related. For those of you who are not familiar with the concept: An assembly is a self-organised get-together and typically targeted at a certain topic. I.e. it can be a place for exchanging ideas, lively discussion and even collaborative hacking, and all of this for the entire congress. ;-) As the Genode community seems to be growing, I'd like to ask whether someone here is 1) considering attending the 33C3 and 2) interested in an assembly about Genode-related projects? @GenodeLabs: I reckon that the date of the congress might not be very convenient for some of you. Nevertheless, I think it'd be great having one or more Genode experts at the congress to represent the project properly. I also see the opportunity for you to do some tutorials, e.g. for the Turmvilla/Heeselicht scenario. [1] https://events.ccc.de/2016/09/01/call-for-participation-33rd-chaos-communic…

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Several sessions of the same type between server and client
by Igor 04 Nov '16

04 Nov '16

Hi list! I need to create several block sessions between ahci_drv (or part_blk) and my client. How it could be done? As far as I can understand, both aforementioned services can't work on a such manner. Did I miss something? Thanks in advance.

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[tz_vmm demo]- execution time
by John David 03 Nov '16

03 Nov '16

Hello, I want to measure execution time of a function in the secure world of tz_vmm demo. I was wondering if I could use elapsed_ms( ) method in timer_session to measure t1 and t2 so that I can take the difference (t2 -t1). Is there any other way? Best regards, John

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Supported ARM devices
by Yevgeny Lavrov 01 Nov '16

01 Nov '16

Hello. My current task is to bring Genode, preferably with seL4 on ARM. Can you please provide me a list of supported ARM devices, or recommend an ARM device that would be the best suited for this task. Thank you.

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Unnecessary default-constructibility requirements for RPC types?
by Edgard Schmidt 26 Oct '16

26 Oct '16

Hi, as described in "Genode Foundations", all types which are used as argument or return types in RPC functions must have a default constructor. I do not think that such a limitation is really necessary. So I tried to write a proof of concept [1]. These modifications should allow RPC functions to pass most of the non-default-constructible objects which satisfy the rest of the requirements for RPC argument and return types. I extended the "hello_tutorial" with a little test code to show that it works [2]. Software patterns like RAII [3] are a possible reason for removing that limitation. Quite often classes cannot provide a useful default-constructor which does more than merely setting the object state to "invalid". Because often there are no useful default values. So if a class provides a default-constructor which just sets the object to "invalid", the code complexity increases since care has to be taken that the object is fed with data up to a specific point of time. Unfortunately, my implementation does not remove default-constructor calls completely: 1. Capabilities still need default-constructors. Msgbuf stores them directly in an array and I did not find the time to check changes of this storage behavior for possible side effects. 2. Output-only _arguments_ have to be default-constructible too. Please note, that non-default-constructible _return_ types are allowed. So this affects only RPC arguments which are explicitly declared as Output-only, for example by adding custom specializations of Rpc_direction. The reason for this limitation is that my Pod_tuple version still stores the RPC arguments directly. While input arguments are copy-constructed, it is hard to copy from an object that does not yet exist. For the second point, I see no simple solutions: we could create a simple byte buffer instead of a default-constructed output-only argument. Since "normal" RPC arguments have to be trivially copyable [4], a RPC function could easily write to this buffer, which would be accessible by the correctly type-casted reference or pointer. A minimalist version of boost::optional [5] or the like as member of Server_args could make sense. However, it would require more template specializations and case differentiations because the special RPC types Capability and Native_capability are not trivially copyable. I successfully tested the code with the repositories "hello_tutorial" and "demo" on base-linux. But if you decide to use my code contribution, please note that it is rather a proof of concept. There is room for improvements: * I tried to minimize the code modifications. So some refactoring may be useful: I expanded Meta::Empty by constructors and a typedef, I inserted possibly confusing forward declarations, and Meta::Pod_tuples and Meta::Pod_args could be renamed because they do not only accept POD types [6]. * I completely ignored the trace-related code. I do not know if there is a need of modifications. Thanks to Johannes Schlatow who gave me the idea of grappling with this topic. [1] https://github.com/3dik/genode/tree/nodef [2] https://github.com/3dik/genode/commit/c35a8d4a3166da74c46423f5e0b4a35933174… [3] https://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization [4] http://en.cppreference.com/w/cpp/concept/TriviallyCopyable [5] http://www.boost.org/doc/libs/1_62_0/libs/optional/doc/html/boost_optional/… [6] http://en.cppreference.com/w/cpp/concept/PODType

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Checkpoint/restore of capabilities
by Denis Huber 24 Oct '16

24 Oct '16

Dear Genode community, as some of you already know, I want to create a checkpoint/restore mechanism for components on Genode 16.05 and Fiasco.OC. I want to create a component which monitors the PD and CPU sessions of its children (= targets for checkpoint/restore) to have access to their memory and thread states. For a complete checkpoint and restore of a child I also need to store the capabilities used by a child. How can I acquire and also restore all these capabilities? After a restore of a component the capability space shall be the "same" as before the checkpoint: 1) The capabilities after the restore shall point to corresponding object identities. 2) Also the capabilities after the restore shall be on the same slot (have the same address) in the capability space as before the checkpoint. The capability space resides in the kernel and Genode does not offer an API to manipulate it. Is there a way to accomplish my goal with Genode's API anyway? Kind regards, Denis

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Linking genode processes at different address space
by Parfait Tokponnon 24 Oct '16

24 Oct '16

Dear Genode community, I would like to know if there is a way to link Genode process (or components) at different address spaces especially when building Heeselicht scenario. When playing with the kernel (Nova), I encounter some weird values from a userland process, but which component exactly it is, i don't really know since almost all of them are linked to the same virtual adress. According to me, one way to deal with it would be to name each PD (protection domain) in the kernel according to the Genode component they belong to, but I think this would be a bit tedious. So what I am projecting to do is to guess the component name from the adress space they are executing in (if they have different address space, right?). Any other idea is welcome. Thanks -- Parfait T.

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Number of components per init
by Roman Iten 18 Oct '16

18 Oct '16

Hi, I wrote a simple run script 'manytimer', based on 'timer': https://github.com/rite/genode/tree/manytimer When the number of components exceeds 19, I get a "Quota exceeded!" warning. It seems that it doesn't matter if I use timer or other components. It also doesn't matter how much RAM quota I configure per timer. - Is this behaviour intended? - Whose quota exceeds (init, core, ...)? - Can I resolve the warning by increasing its quota? - In a scenario with 19 or more components (within one init), is it still possible to "assign all remaining resources to the last child by simply specifying an overly large quantum" as described in "Genode 16.05 Foundations" (see Chapter 6.2.2 "Resource quota saturation"). Or would there be no more slack memory available for init and core respectively? Thanks, Roman

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Microkernels / Component-based OSes devroom - Call for Participation
by Josef Söntgen 17 Oct '16

17 Oct '16

FOSDEM 2017 - Microkernels / Component-based OSes devroom CALL FOR PARTICIPATION The developers of several free and open-source microkernel-based operating systems will meet at FOSDEM 2017 [1] in Brussels, Belgium and will share a developer room on Saturday of February 04, 2017 [2]. The devroom is currently looking for content in the form of talks and activities related to the area of microkernel-based operating systems. Possible topics include, but are not limited to: * Introduction of a specific OS or framework * Design of subsystems and the general architecture of an OS * Enabling support for hardware (architectures, device drivers) * Used languages and tools * Maintainance and testing * Security and robustness * Trends and challenges * Use cases, experiences, lessons learned and demos Please use the Pentabarf [3] system to submit your proposals and file it under the track “Microkernels and Component-based OS”. You do not need to create a new account if you already have one. When in doubt, please use the devroom mailing list [4]. If you do not want to give a talk yourself, you may still send suggestions for what else you would like to see, or do in the devroom. Please send your suggestions to the mailing list. The deadline for your proposal is on December the 4th. Make sure to include the following in your proposal: * Title of your talk (will be printed in the FOSDEM booklet) * Your full name (will be printed in the FOSDEM booklet) * A short abstract (one or two paragraphs) * Duration of your talk (please, at least 25 and no longer than 45 min) The official devroom schedule (along with the accepted talks) will be announced on December the 11th on the devroom's mailing list and the speakers will be notified via e-mail. The schedule will also be published on the FOSDEM website. About FOSDEM FOSDEM is a two-day event organised by volunteers to promote the widespread use of free and open source software. Taking place in the beautiful city of Brussels (Belgium), FOSDEM is widely recognised as the best such conference in Europe. FOSDEM covers a wide spectrum of free and open source software projects, and offers a platform for people to collaborate. To this end, FOSDEM has set up developer rooms (devrooms) with network/internet connectivity and projectors where teams can meet and showcase their projects. Devrooms are a place for teams to discuss, hack and publicly present latest directions, lightning talks, news and discussions. Besides developer rooms, FOSDEM also offers main tracks, lightning talks, certification exams and project stands. Every year, FOSDEM hosts more than 5000 developers at the ULB Solbosch campus. Participation and attendance is totally free, though the organisers gratefully accept donations and sponsorship. No registration necessary. About the devroom Since the first Microkernel devroom in 2012 this devroom has been part of each following FOSDEM. By now it has become a somewhat institutionalized tradition for the micro kernel community to meet there; to this date over a dozen projects have participated in one way or another. Each of the projects face similar challenges but come up with partially differend solutions. Therefore, the goal of the Microkernel devroom is to bring the various projects together, let them exchange ideas, cross-pollinate and socialize. Social events It also has become a habit that the microkernel projects dine together somewhere in downtown Brussels after the devroom closes. The year 2017 will not be any different, so there is going to be a microkernel family dinner on Saturday night. The exact location and time will be specified later. Consult the FOSDEM web and other projects for additional social events such as the famous FOSDEM-organized Friday Beer Event and the FOSDEM-arranged free sightseeing tours for spouses. Important dates recap * 04.12.2016: Deadline for submissions * 11.12.2016: Schedule published and speakers notified of acceptance * 04.02.2017: The devroom takes places Links [1] http://fosdem.org/ [2] https://fosdem.org/2017/practical/transportation/ [3] https://fosdem.org/submit [4] https://lists.fosdem.org/listinfo/microkernel-devroom See you all at FOSDEM!

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users October 2016