Devel July 2022

devel@sel4.systems

20 participants
16 discussions

Questions about Memory Management in seL4
by Daniel Wang 19 May '23

19 May '23

Hi all, Sorry to bother, I have some basic questions about seL4 memory management. Can someone help me? 1. where is the kernel’s address space? I know there are basically three methods: a) separate virtual address space, e.g. through changing page tables on entry into privileged mode to access b) physical space, e.g. through disable automatic hardware translation of virtual addresses on entry into privilege mode c) privilege region in each process’s virtual address space, e.g. through page table to map kernel address into use-mode process. My question is which of this is being used by seL4 microkernel? 2. Objects like CSpace, VSpace, CNode, TCB, Endpoint, etc. are called kernel objects, but it seems all dynamically allocated in thread running/creating time. Are those objects (e.g. Figure 3.3 in seL4 manual) in kernel space or in user space? 3. I read that after the kernel boot up, it passes all resources, untyped memory to the first thread. Are those untyped memory physical memory or virtual memory in a single page? The reason I ask is I’m learning the code of the UNSW AOS project (two of the assignment projects are implementing frame and papers). I’m confused that before the implementation of frames and pages what kind of memory is passed to the the first thread? I saw int AOS project, it uses ut_table_init(), ut_steal_mem(), I wonder what kind of memory it operates on? Thanks -Dan

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Proper seL4 APi/ABI design
by Eric Jacobs 17 Sep '22

17 Sep '22

Jumping off from the recent thread, I was curious if anyone had any thoughts about how to optimally design API's for seL4. I noticed we had a bit of info about what not to do (don't do long IPC, don't implement Posix, don't use messaging as synchronization, etc.) Are there any shining examples of what _to_ do with an API? Thanks, -Eric

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Thread Scheduling Domains
by June Tate-Gans (ジューン) 02 Aug '22

02 Aug '22

Hey folks, So Sam and I are at the point now where we're attempting to get our untrusted user threads running in a different scheduling domain, and it's not exactly clear how this is supposed to work in terms of enabling more than one domain in the kernel. So far, I've set KernelNumDomains to 2 in the easy-settings.cmake for our project, but unless I provide a separate implementation of kernel/config/default_domain.c by overriding KernelDomainSchedule, the resulting kernel will only think it has one domain and only ever schedule domain 0 for execution. Are we expected to override the default_domain.c file with our own in the project, like sel4test seems to do? Thanks! -- June Tate-Gans Software Engineer

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Reminder seL4 developer hangout
by Birgit Brecknell 25 Jul '22

25 Jul '22

Hi all A friendly reminder that the seL4 developer hangout is on again next week: Wed, Jul 27, 7am (UTC), Topics: (open) * Sydney: Wed, Jul 27, 5pm * Central Europe: Wed, Jul 27, 9am * US Pacific Time: Wed, Jul 27, 12 midnight * Zoom link: https://unsw.zoom.us/j/82640784431 cheers Birg --- Dr. Birgit Brecknell Project Officer Trustworthy Systems, UNSW, birgit.brecknell(a)unsw.edu.au<mailto:birgit.brecknell@unsw.edu.au> seL4 Foundation, birgit(a)sel4.systems<mailto:birgit@sel4.systems> 0433 880 571 Mon 9am-5pm Wed 9am-12pm Fri 9am-5pm

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Sydney get-together on seL4 Day?
by Gernot Heiser 20 Jul '22

20 Jul '22

This is only of interest for those physically in Sydney. We have seL4 Day coming up (29 July, the 13th anniversary of completion of the seL4 verification and 8th anniversary of its open-sourcing). It would be great to use the occasion to get together. The continuing abnormal (i.e. very wet) weather in Sydney makes planning such an event difficult (and I’ll be on leave and out of town until the evening of the 28th), so things may have to happen on short notice. But weather permitting, a BYO BBQ in Maroubra would be great, and I would really love to catch up with the rest of the Sydney-based seL4 community. So I suggest people interested save the date (and let us know if you’re interested). Gernot

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suggestion; update faq reference to ODROID-C2
by Van Ly 18 Jul '22

18 Jul '22

Hello, The faq section on "How can I build a system with seL4?" [1] has an obsoleted/discountinued product pointing to ODROID-C2 [2] a current product such as the one from OnLogic can replace, perhaps. [3] ``` If you have access to an Odroid-C2, you should be able to do the project work yourself as a way of familiarising yourself with seL4. ``` [1] https://docs.sel4.systems/projects/sel4/frequently-asked-questions.html [2] https://www.hardkernel.com/shop/odroid-c2/ [3] https://www.onlogic.com/industrial-raspberry-pi/ -- vl

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Systems with multiple PCI root complexes
by Peter Chubb 18 Jul '22

18 Jul '22

Has anyone extended the code in https://github.com/seL4/util_libs libpci to handle multiple root complexes? See bug https://github.com/seL4/util_libs/issues/131 I know genode added code to handle this, but they don't use that library. Peter C -- Dr Peter Chubb https://trustworthy.systems/ Trustworthy Systems Group CSE, UNSW

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seL4 kernel memory footprint
by Sam Leffler 14 Jul '22

14 Jul '22

I'm trying to figure out the physical memory used by the kernel. This is for riscv if it matters. -Sam

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sel4 smmuv2.0 on tx2 related questions
by Tao Heng 陶恒-SW 13 Jul '22

13 Jul '22

Hi sel4-devs, I have been trying to make some understandings of smmuv2.0 features provided by sel4. According to the vmm project for the tx2 platform, such as the vm_minimal apps, after all the compiling, there will be two caps,vm0_sid and vm0_cb,which is supposed to be used for stage2 address translation. My questions are as followed: 1. Which smmu device was the sid cap assigned to ? 2. How were these two caps created in the cdl file? There seems no special configuration for Cmakes that is related to the caps. 3. According to the tx2.dts, there are many sid numbers assigned to the smmu device. Why was there just one sid cap created by sel4? 邮件免责申明 Email Disclaimer 本邮件仅供本邮件指定收件人使用，其所载内容可能因含有保密信息或其它原因而不得披露。除本公司及本邮件指定收件人外，任何人不得公开、传播、分发、复制、印刷或使用本邮件之任何部分或其所载之任何内容。如您误收到本邮件，请立即通知本公司，并将原始邮件、附件及其所有复本从系统中删除，切勿使用。 This email is for the use of the designated receivers only，and the content is not allowed to be disclosed due to the confidential information or other reasons. Except for the Company and the designated receivers of this email, no one shall disclose, disseminate, distribute, copy, print or use any part of this email or any content contained therein. If you receive this email by mistake, please notify the Company immediately, and delete the original email, attachments and all copies from the system. Do not use it. 网络通信可能含有计算机病毒或其它缺陷，可能无法准确和/或及时送达其它系统，亦可能受阻而不为本公司或本邮件指定收件人所知。本公司对此类错误或遗漏以及任何因使用本邮件而引致之任何损失概不承担责任。 Network communication may contain computer viruses or other defects, which may not be delivered to other systems accurately and / or in time, or may be blocked by the Company or the designated receivers of this email. The Company shall not be liable for such errors or omissions and for any loss arising from this email. 本邮件所载任何内容仅作为业务层面交流与参考，除非明确说明，本公司不对邮件所载内容之准确性、完整性或公平性等承担任何法律责任。 Any contents contained in this email are only for the purpose of business communication and reference only. Unless explicitly stated otherwise, the Company shall not assume any legal responsibility for the accuracy, completeness or fairness of the content contained in the email. 本邮件指定收件人应特别注意：本邮件所载任何内容不构成本公司对本邮件指定收件人和/或其所属商业实体的任何要约、要约邀请或承诺，任何权利义务皆以双方签字盖章的书面文件为准。除经本公司以签字盖章的书面文件确认外，收件人和/或其所属商业实体不得以本邮件所载任何内容作为其向本公司主张任何权利或利益的正式依据。 The designated receivers should pay special attention to the fact that nothing contained in this email shall constitute an offer, invitation or acceptance by the Company to the designated receivers of this email and/or its affiliated business entities, and any rights and obligations are subject to the written documents signed and sealed by both parties. Except from the written document signed ,sealed and confirmed by the Company, the receivers and / or its affiliated business entity shall not rely on anything contained in this email as the formal basis for claiming any rights or interests to the Company.

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Anyone using capability transfer in an seL4 project? Looking for examples for research
by sjwebb＠student.unimelb.edu.au 12 Jul '22

12 Jul '22

Hi all, I'm working on a Masters research project looking into mapping an object-capability programming language onto seL4, in a way that includes some kind of mapping from the language object capabilities onto seL4's capabilities (or vice versa). I'm at a stage of the project now where it would be really helpful to have some 'motivating examples' for transferring caps between threads/CSpaces. So I was hoping I could reach out to other seL4 developers to see if they had built any systems that made extensive use of moving capabilities around. Ideally, in an ocap language, these examples would be much easier to program than they currently would be in C... The simplest example I can think of is a memory allocation server, but that wouldn't necessarily involve handing caps on beyond the one (requesting) process, which is the kind of thing I think more interesting examples would comprise of. Cheers, Stewart Webb [Masters Research student at University of Melbourne]

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