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devel@sel4.systems

9 participants
1390 discussions

virtual memory abstraction
by Raymond Jennings 31 Aug '15

31 Aug '15

I noticed that unlike mach, L4 does not directly manage virtual memory, but instead farms out address space, page directory, and page table capabilities to userspace and lets userspace decide what pages to map and where. Does this imply that virtual memory abstraction is userspace responsibility?

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Port I/O - Permissions Question
by Josef M. 25 Aug '15

25 Aug '15

Hi, I'm experimenting with some x86 code that involves reading from I/O ports. I noticed--much to my surprise--that I don't have to use seL4_IA32_IOPort_In8() to read from a port; my program works just as fine using the "in" assembly statement directly, without any caps. The TSS segment limit is initialized with 0x67 https://github.com/seL4/seL4/blob/master/src/arch/x86/kernel/vspace.c#L158 and the "I/O Map base address" is initialized with 0 (zero) https://github.com/seL4/seL4/blob/master/src/arch/x86/kernel/vspace.c#L43 I believe the result is that ring 3 programs can access I/O port addresses below 0x388 (0x67 * 8) without triggering a protection violation. So my question is: Shouldn't capabilities be required for all ports? Or what what is the reason or motivation behind this? Thanks, Josef

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Running Linux atop sel4
by Sebastian Lau 24 Aug '15

24 Aug '15

On the sel4.systems website, it says that the site is served by the Apache web server on Linux atop sel4. How does that work and could you operate the Linux middleware just on top of sel4, maybe something like mer?

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Roadmap?
by Raymond Jennings 22 Aug '15

22 Aug '15

I remember awhile ago that someone was going to post the roadmap in response to my accessed/dirty bit suggestion...but I haven't seen it yet.

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Some questions about seL4 operating system
by Qing Wei 22 Aug '15

22 Aug '15

Hi, I am a beginner to seL4 as well as microkernel, and very interested in it. I think it is great in terms of its minimality and formally verified security. However, I have some questions about it, (1) How is its performance compared to other monolithic kernel, say, Linux. Could it make use of multicore, multiprocessor to enjoy the performance scalability? (2) How is its ecosystem, fox example, how to support new hardware, does it need write the driver from scratch or could it make use of Linux driver? And how to write application on it, or, could it run Linux application without modification? (3) How is its virtualization support, could it run Linux vm, and does it need any modification to the guest os? Cheers, Qing Wei

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Some comments.
by Mehdi Amiri 17 Aug '15

17 Aug '15

Hi, Thank you for all your efforts and time. I believe the user community is the main success key for all open source projects. Many users and researchers, do not have enough time to read, download and evaluate all the source code in order to investigate a system to see if it is suitable for their research or usage. Usually they will go for clean systems which are easy to use, simple to understand, well documented and have a strong community beside the commercial support to ask and get help in case they had a problem. Here are some comments which may help to increase the number of users and developers for seL4: A) I suggest to add some howtos to the website. It's better to be a wiki like system so other individuals, researchers and students can help in writing some titles. Some interesting topics (at least for me as a beginner in micro-kernel) could be: 1- Running Linux/Android on top of seL4. 2- Writing a simple user application with a use case (not just the SOC). 3. Examples on real-time application. 4- Writing a service (could be a device driver, file-system, etc) for seL4. 5- Documents on using possible run-times like Genode. 6- Documents or case studies on porting an opensource software from Linux or POSIX based system to directly run om seL4. B) Providing ready to use download binary images for supported platforms can also accelerate growth of community. C) A research areas page which can suggest researchers some ideas to chose a title and do their research to expand seL4 could also be useful. Ideas like rump-kernels, lib-OS, visualization (x86/ARM), etc seems to be possible research titles on seL4. I have seen the https://sel4.systems/GettingStarted/ page and I think other than CAmkES, ports and Qubes there could be many more titles. D) I know the major development platform of seL4 has been the Arm architecture, but optimizing the code to utilize the x86 architecture including virtualization can also bring a lot of attention to this project to use seL4 as a replacement for Linux-KVM and Xen in the cloud, IoT or real time systems when stability and security is a matter. Also please note, the archive of both development ( https://sel4.systems/pipermail/devel/) and announcements ( https://sel4.systems/pipermail/announce/) mailing lists are not accessible trough the website. I'm an OS researcher and a senior system engineer (mostly Linux) with a limited time, but I can help in some parts if you think it may be useful. Thank you again! Best Regards, Mehdi

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other communications
by Raymond Jennings 17 Aug '15

17 Aug '15

Is there a mailinglist or forum anywhere for people interested in using seL4? I realized this is a dev list and may not be the right place to ask technical supportr questions.

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Detecting dirty/accessed page tables
by Raymond Jennings 15 Aug '15

15 Aug '15

Hey I'm just curious...how do you detect if a memory page mapped by a page table has been written to or accessed? I imagine if you're writing a filesystem task, such information would help you know when to flush data back to disk or which pages to keep around if things get tight. I hope this isn't a stupid question.

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U-boot help sabrelite
by Andrew Shruhan 12 Aug '15

12 Aug '15

Hi, I am attempting to follow the tutorial booting from SPI for the sabrelite https://sel4.systems/Hardware/sabreLite/ when booting I obtain this output and am not able to run "run bootsel4_mmc" U-Boot 2009.08-dirty (Jun 27 2013 - 16:26:46) CPU: Freescale i.MX6 family TO1.2 at 792 MHz Temperature: 36 C, calibration data 0x56a4bc7d mx6q pll1: 792MHz mx6q pll2: 528MHz mx6q pll3: 480MHz mx6q pll8: 50MHz ipg clock : 66000000Hz ipg per clock : 66000000Hz uart clock : 80000000Hz cspi clock : 60000000Hz ahb clock : 132000000Hz axi clock : 264000000Hz emi_slow clock: 132000000Hz ddr clock : 528000000Hz usdhc1 clock : 198000000Hz usdhc2 clock : 198000000Hz usdhc3 clock : 198000000Hz usdhc4 clock : 198000000Hz nfc clock : 24000000Hz Board: MX6Q-SABRELITE:[ POR] Boot Device: I2C I2C: ready DRAM: 1 GB MMC: FSL_USDHC: 0,FSL_USDHC: 1 JEDEC ID: 0xbf:0x25:0x41 Reading SPI NOR flash 0xc0000 [0x2000 bytes] -> ram 0x276009b8 SUCCESS In: serial Out: serial Err: serial Net: got MAC address from IIM: 00:19:b8:01:fd:6d FEC0 Hit any key to stop autoboot: 0 AHCI 0000.0000 1 slots 1 ports ? Gbps 0x0 impl SATA mode flags: No port device detected! Unknown command 'load' - try 'help' SATA device 1: unknown device Unknown command 'load' - try 'help' Card did not respond to voltage select! mmc0(part 0) is current device Unknown command 'load' - try 'help' mmc1 is current device Unknown command 'load' - try 'help' Unknown command 'usb' - try 'help' Unknown command 'usb' - try 'help' Unknown command 'load' - try 'help' Unknown command 'usb' - try 'help' Unknown command 'load' - try 'help' 6x_bootscript not found serial console at 115200, 8N1 details at http://boundarydevices.com/6q_bootscript AHCI 0000.0000 1 slots 1 ports ? Gbps 0x0 impl SATA mode flags: No port device detected! AHCI 0000.0000 1 slots 1 ports ? Gbps 0x0 impl SATA mode flags: No port device detected! Card did not respond to voltage select! mmc0(part 0) is current device expose mmc drive 0 over USB Unknown command 'ums' - try 'help' Card did not respond to voltage select! no block devices found ERTOS MX6Q SABRELITE U-Boot > -- -Andrew Andrew P. Shruhan Research and Development Engineer III DocBox, Inc. 320 Nevada St Newton MA, 02460 Work: 857-598-2819 ext. 117 www.docboxinc.com

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Upstream seL4/RISC-V work?
by Hesham ALMatary 10 Aug '15

10 Aug '15

Hi, The seL4/RISC-V port is now working on Spike (emulator), Rocket Chip (FPGA), and jor1k (online emulator). I've also written a recent blog post how to build/run the port with SOS project [1] from my repos). The code is pretty much like the ARM port, and following the same bootstrapping procedure (more on this on my blog). MMU code provides 4KiB and 4MiB pages (like IA-32). I'd like to ask if there are special requirements to upstream this work: * All libraries that are target-dependant. * seL4 microkernel. * Tools (elf loader, build system). * SOS project? I understand it won't be an easy process because this work is the first "foreign" code that big, of course apart from formal verification. But it wouldn't hurt to ask. [1] http://heshamelmatary.blogspot.co.uk/2015/07/howto-build-and-run-sel4-on-ri… Best, -- Hesham

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