- Devel - lists.sel4.systems

What happens to the IPC buffer when you make another process within the same Vspace?
by Qiwei Wen 20 Mar '16

20 Mar '16

Hi, I'm trying to write a multithreaded seL4 application. It's to be made up of sel4util processes with different cspaces and sharing the same Vspace. I managed to achieve this, but what confuses me is that since the processes share the same Vspace, wouldn't GetIPCBuffer() return the same result for each of them? I looked at libsel4/arch_include/arm/sel4/arch/functions.h, and GetIPCBuffer() is simply: return *(seL4_IPCBuffer**)seL4_GlobalsFrame; Since seL4_GlobalsFrame is just a fixed memory location (0xffffc000) in the shared address space, why does seL4_GetIPCBuffer() return different results for different processes? Below is the output: ========================== PARENT: IPCBUFFER: 00273000 CHILD: GlobalsFrame: ffffc000, *GlobalsFrame 10076000 CHILD: setting shared to 97 PARENT: CHILD DIED, shared char: 97, MR16: 00000000 ============================= Is it that the frame ffffc000 mapping is changed on every context switch perhaps? Can I absolutely trust that IPC is still working correctly with this set up? Thanks, David

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Isabelle itself proven?
by Steve VanderLeest 20 Mar '16

20 Mar '16

Since the formal verification of functional correctness of seL4 was performed using the Isabelle theorem prover, could someone tell me if Isabelle itself has been formally verified? If so, could you suggest some good references to that work? Regards, Steve Steven H. VanderLeest, Ph.D. Chief Operating Officer DornerWorks, Ltd. 3445 Lake Eastbrook Grand Rapids, MI 49546 www.dornerworks.com

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Booting process
by Daniel Wang 19 Mar '16

19 Mar '16

Hi all, I’m very new to seL4 development. I’m particularly interested in understanding seL4 kernel source code. Could someone points me out how the seL4 is booted and where should I start learning? Thanks -Dan

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seL4 wiki
by Anna Lyons 19 Mar '16

19 Mar '16

Hi all, We've created a public wiki for seL4 development here: https://wiki.sel4.systems/ The kernel team have put some effort into creating the initial content, but there is much more to be done. Contributions encouraged! New accounts are restricted to avoid spam, but if you have posted on this mailing list your account will be approved quickly. Otherwise contact us. Thanks, Anna Lyons seL4 Kernel Engineer | PhD Student DATA61 | CSIRO E <mailto:Brigitte.Biscotto@data61.csiro.au> Anna.Lyons(a)data61.csiro.au<mailto:Anna.Lyons@data61.csiro.au> Level 3, K17 Building, UNSW Gate 14, Barker Street, Kensington, NSW, 2033 l Locked Bag 6016, Sydney NSW 1466 www.data61.csiro.au<http://www.data61.csiro.au/> CSIRO’s Digital Productivity business unit and NICTA have joined forces to create digital powerhouse Data61 [cid:image001.png@01D0EFD9.052ECFC0] ________________________________ The information in this e-mail may be confidential and subject to legal professional privilege and/or copyright. National ICT Australia Limited accepts no liability for any damage caused by this email or its attachments.

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FYI: microkernel.info community site
by Jakub Jermář 14 Mar '16

14 Mar '16

Hello, just FYI, I have set up a simple web page[1] to promote the wider microkernel community and its goals. So far, the page comes with a brief description of the microkernel concept and an incomplete list of microkernel projects with links to each project's web. The description is made out of the first two sentences I found in the "What is XYZ" section or elsewhere on the web of the respective project. I also took the freedom to use the respective project's logo (or what I believed was the project's logo) for promoting it. I hope you will find this small web a good idea. It was inspired by a similar (though a little bit more informative) site set up by the unikernel community [2]. The sources of the [1] web are hosted on Github [3], so feel free to submit issues or PR to make the site better. Please send me a PM if there are any issues pertaining your project's cartouche that cannot be dealt with using Github. Thanks, Jakub [1] http://microkernel.info [2] http://unikernel.org/projects/ [3] https://github.com/jermar/microkernel.info

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Capability faults on seL4_Send and seL4_Call
by Qiwei Wen 12 Mar '16

12 Mar '16

Hi all, I understand that capability faults for seL4_Send and seL4_Call only happen when the look-up fails, and not when illegal operations are attempted, such as calling a null cap or a piece of untyped memory. Is there another way at all, then, that such errors can be handled by user-level code? This is part of a project where the faulting process needs to surrender control to another process whenever it performs a system call on an invalid capability. Is there a way to achieve this given that fault endpoints will not work? Thanks, David

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using camkesvm with qemu
by Julien Delange 10 Mar '16

10 Mar '16

Hi, I am currently trying to use the camkesvm example and run it in qemu. I am currently able to compile the c162_twovm_defconfig application. However, when running, I have the following issue (see below). So, I am wondering what would be the good arguments to start the application in qemu. I noticed that the kernel/initrd image for linux are specific in a header file, I assume this is also included in the image loaded by capdl. Any idea about how to run this example with qemu and/or how to test it? Thanks! Starting node #0 vt-x: not supported <<seL4 [decodeUntypedInvocation/193 T0xe2ff1900 "rootserver" @804afa7]: Untyped Retype: Insufficient memory or offset outside untyped>> Unmasking IOAPIC source 2 on ioapic 0 without ever setting its mode! Unmasking IOAPIC source 3 on ioapic 0 without ever setting its mode! Unmasking IOAPIC source 4 on ioapic 0 without ever setting its mode! Unmasking IOAPIC source 16 on ioapic 0 without ever setting its mode! Unmasking IOAPIC source 17 on ioapic 0 without ever setting its mode! Unmasking IOAPIC source 18 on ioapic 0 without ever setting its mode! Unmasking IOAPIC source 23 on ioapic 0 without ever setting its mode! <<seL4 [decodeCNodeInvocation/107 T0xe2ff1900 "rootserver" @804a4b2]: CNode Copy/Mint/Move/Mutate: Source slot invalid or empty.>> capDL-loader :: << Error: init_cnode_slot:1471: seL4_FailedLookup >> Ignoring call to sys_rt_sigprocmask

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Recovering from cap fault?
by Qiwei Wen 10 Mar '16

10 Mar '16

Hi all, On page 26 of the manual (1.2) there's an instruction on how to restart a thread following a capability fault. The program counter where the faulting thread should pick up execution is said to be message register 0. What I'm trying to do is to restart the execution on the next instruction following the system call instruction so as to skip it. Try as I might, it will not work and the faulting thread is stuck in an endless number of faults. Below is the relevant code: seL4_Word pc = seL4_GetMR(0); printf("cap fault, pc: %08x, on %s\n",pc,seL4_GetMR(2)?"wait":"send"); //assert(!faultnum++); seL4_MessageInfo_t info = seL4_MessageInfo_new (seL4_CapFault,0,0,1); seL4_SetMR(0,pc + 4); seL4_Reply(info); It does restart, but immediately cap-faults again at the very same program counter. Is it supposed to work? What did I do wrong? Cheers, David

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seL4 Tutorial Idea
by da Tyga 09 Mar '16

09 Mar '16

Hi Andrew Jackman! First of all apologies about my assumptions. In my hasty reading of your question I got the impression you were talking about yourself and not the intended audience for your tutorial material proposal. Like yourself, I too would use a practical, tutorial style guide if it were available. So I would like to give my vote for your idea. Unfortunately, I'm a one-man-show and thus not in a position to make a pledge towards a tutorial effort. Perhaps the good folks who are involved with seL4 could suggest how your proposal could come about. Reading these digests, tit would appear that there are quite a few people who are trying to come to grips with seL4. Yes, I was referring to the material that you linked. Cheers, Tyga >>> thread in reverse chrono-order: Andrew Jackman kd7nyq(a)gmail.com On Sun, Mar 6, 2016 at 11:04 AM, Jackman <kd7nyq(a)gmail.com> wrote: > Is anyone interested in tutoring on the topic of sel4? I have two > objectives: > > First, I'm interested in beginning programming, like getting through the > Hello World process. I would hope this eventually includes things like > basic driver development and practical application development. > > Second, I want to understand how virtualization works with sel4 and the > infrastructure behind it. My objective is to be able to stand up my own > virtualization host and guests. > > I'm not sure how payment would work. I'd be interested in turning our > experience into tutorials for community consumption, which may be more > valuable to some of you than the money. > > Thank you. > > Andrew Roy Jackman Hi Andrew, I don't wish to discourage you, but if you are just starting out programming and have limited knowledge of operating systems, etc ... then seL4 might be a very big undertaking to understand and learn from. There are a lot of topics you would need to come up to speed on. I suggest taking a look Gernot's course material at unsw.edu.au. > da Tyga: Thank you for writing back. I totally agree with your assessment. Permit me to elaborate a bit more on my situation. I am a professional software engineer who is primarily dedicated to writing virtualization automation software for sales demonstrations. Naturally, our department is always interested in ways in which we can improve the efficiency of our virtualization environment(s). After reading 'L4 Virtualization and Beyond' (2008, http://os.inf.tu-dresden.de/papers_ps/haertig08_l4_virtualization_and_beyon… ), I became fascinated with L4. I am here talking to you all because of the amount of press that seL4 has gotten as the proofed L4 kernel and because it appears to have the best, most easily understood documentation. Now, that does not mean that I think seL4 is well documented, just that it's the best documented of the L4 projects. The purpose of my original email was to very gently say that the introductory material to seL4 is so bad, that I'm willing to pay someone to either bring it up to date, assist me with it, or both. For example, there is a thread about RefOS, wherein Kevin wrote, "RefOS was a student project that is now no longer actively maintained." Gapry and HyperNewbie, however, provided at least some fixes, but their fixes don't appear to have gotten any attention from upstream. This was on 11 February. Nevertheless, RefOS appears to be the only seL4 project geared towards newcomers on the 'Getting Started' page ( https://sel4.systems/Info/GettingStarted/) You should note that, on that page, there is no indicator that newcomers should, in fact, stay away from that project because it's no longer maintained. I don't think requesting some attention on documentation is a bad or unjust thing. I would hope that lowering the barriers to entry to the seL4 community would increase the flow of developers, users, and sponsors to the seL4 project. In turn, I hope that would be seen as a good thing. I'm offering part-time, albeit unofficial, company sponsored development in exchange for some paid tutoring. I am not asking for a hand-out. If I didn't have to worry about ramp-up time or coming up with deliverables, I wouldn't be bugging you. Now, if you're worried about my qualifications, I'm a university educated computer scientist. While I've spent most of my career on web programming, I've studied operating systems development both at school and on my own. I began a toy kernel with the help of the osdev.org resources, and I'm happy with my progress. When I take inventory, however, I realize I don't have the desire to (re-)write an L4 kernel, nor do I think I can improve upon it. Finally, I think you're referring to Professor Gernot Heiser's page at https://www.cse.unsw.edu.au/~gernot/, and probably more specifically the CS9242 course at http://www.cse.unsw.edu.au/~cs9242/current/. If you're referring to another course, please be more specific. Thank you. Andrew Jackman kd7nyq(a)gmail.com

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Tutor?
by Jackman 09 Mar '16

09 Mar '16

Is anyone interested in tutoring on the topic of sel4? I have two objectives: First, I'm interested in beginning programming, like getting through the Hello World process. I would hope this eventually includes things like basic driver development and practical application development. Second, I want to understand how virtualization works with sel4 and the infrastructure behind it. My objective is to be able to stand up my own virtualization host and guests. I'm not sure how payment would work. I'd be interested in turning our experience into tutorials for community consumption, which may be more valuable to some of you than the money. Thank you. Andrew Roy Jackman

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