Devel March 2023

devel@sel4.systems

12 participants
9 discussions

Bitfield generator EBNF grammar
by June Tate-Gans (ジューン) 07 Jun '23

07 Jun '23

Hey guys, I've been attempting to put together some rust bindings for the seL4 fault handling mechanisms, and I'm afraid the bitfield generator is driving me a bit up a wall at this point. I'd like to find a concise grammar for the language so I can better understand how bitfield_gen.py works, but there doesn't seem to be any explicit BNF for it anywhere. Is there a paper I should be reading or a reference guide somewhere that would help? Thanks! -- June Tate-Gans Software Engineer Techlead, Kata OS / AmbiML, Google

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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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seL4 summit: deadline extension to 24th of April
by June Andronick (seL4 Foundation) 31 Mar '23

31 Mar '23

The deadline to submit a presentation to the seL4 summit 2023 is extended by 2 weeks. You now have until the 24th of April 2023 to propose a talk, by uploading an abstract of one page or less to: https://sel4.systems/Foundation/Summit/2023/submit The reason for the extension is that we want to let you know the definite dates for the summit before the deadline :) Current tentative (and very likely) dates are 19-20-21 September 2023, to be confirmed very soon. Looking forward to receiving your proposals. We want to hear about your cool seL4 work! And spread the word! If you want to hear about specific seL4 work, ping people around you or let us know at summit(a)sel4.systems <mailto:summit@sel4.systems> June

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Issue for setting up the seL4 IPC tutorial
by zhliao＠iastate.edu 26 Mar '23

26 Mar '23

Hi all, I got the following issue when I followed the IPC tutorial to set up an environment. I can build and run the "Hello world" and "Capabilities" tutorials, so I think I have fulfilled the prerequisites for running the IPC tutorial. However, when I built the ipc tutorial using the command "./init --tut ipc --solution" or "./init --tut ipc", and ran the "ninja" command, the following error messages were given: [54/208] Generating capDL-tool/parse-capDL FAILED: capDL-tool/parse-capDL cd /home/zhliao/sel4_tutorials_manifest/ipc_build/capDL-tool && printf capDL-tool/parse-capDL:\ > /home/zhliao/sel4_tutorials_manifest/ipc_build/capDL-tool/parse-capDL.d && find -L /home/zhliao/sel4_tutorials_manifest/projects/capdl/capDL-tool/ -type f -printf %p\ >> /home/zhliao/sel4_tutorials_manifest/ipc_build/capDL-tool/parse-capDL.d && cp -a /home/zhliao/sel4_tutorials_manifest/projects/capdl/capDL-tool/* . && /usr/bin/cmake -E env make stack build --fast Downloading lts-19.12 build plan ... RedownloadInvalidResponse Request { host = "raw.githubusercontent.com" port = 443 secure = True requestHeaders = [] path = "/fpco/lts-haskell/master//lts-19.12.yaml" queryString = "" method = "GET" proxy = Nothing rawBody = False redirectCount = 10 responseTimeout = ResponseTimeoutDefault requestVersion = HTTP/1.1 } "/home/zhliao/.stack/build-plan/lts-19.12.yaml" (Response {responseStatus = Status {statusCode = 404, statusMessage = "Not Found"}, responseVersion = HTTP/1.1, responseHeaders = [("Connection","keep-alive"),("Content-Length","14"),("Content-Security-Policy","default-src 'none'; style-src 'unsafe-inline'; sandbox"),("Strict-Transport-Security","max-age=31536000"),("X-Content-Type-Options","nosniff"),("X-Frame-Options","deny"),("X-XSS-Protection","1; mode=block"),("Content-Type","text/plain; charset=utf-8"),("X-GitHub-Request-Id","35BE:17FF:128736E:17D5D97:641FC551"),("Accept-Ranges","bytes"),("Date","Sun, 26 Mar 2023 04:08:49 GMT"),("Via","1.1 varnish"),("X-Served-By","cache-lga21983-LGA"),("X-Cache","MISS"),("X-Cache-Hits","0"),("X-Timer","S1679803730.680346,VS0,VE66"),("Vary","Authorization,Accept-Encoding,Origin"),("Access-Control-Allow-Origin","*"),("X-Fastly-Request-ID","87538dc12b06e4fb615de6c1a4159b9af113e3a6"),("Expires","Sun, 26 Mar 2023 04:13:49 GMT"),("Source-Age","0")], responseBody = (), responseCookieJar = CJ {expose = []}, responseClose' = ResponseClose}) make: *** [Makefile:51: parse-capDL] Error 1 [62/208] Invoking muslc build system ninja: build stopped: subcommand failed. I am wondering if you got the similar issues or have any idea for this problem? Thanks, Zhonghao

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KataOS modifications to seL4
by Isaac Beckett 23 Mar '23

23 Mar '23

> Message: 1 > Date: Tue, 21 Mar 2023 10:52:40 -0500 > From: June Tate-Gans (ジューン) <jtgans(a)google.com> > Subject: [seL4] Bitfield generator EBNF grammar > To: devel <devel(a)sel4.systems> > Message-ID: > <CAOPTAH0q0UABvFhffnmJ6ygDuPmpf8fMjxBawmYbhCjjJT8MTA(a)mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > Hey guys, > > I've been attempting to put together some rust bindings for the seL4 fault > handling mechanisms, and I'm afraid the bitfield generator is driving me a > bit up a wall at this point. I'd like to find a concise grammar for the > language so I can better understand how bitfield_gen.py works, but there > doesn't seem to be any explicit BNF for it anywhere. > > Is there a paper I should be reading or a reference guide somewhere that > would help? > > Thanks! > > -- > June Tate-Gans > Software Engineer > Techlead, Kata OS / AmbiML, Google Hello June, I have a question about something I read on the announcement post for KataOS: > The current GitHub release includes most of the KataOS core pieces, including the frameworks we use for Rust (such as the sel4-sys crate, which provides seL4 syscall APIs), an alternate rootserver written in Rust (needed for dynamic system-wide memory management), and the kernel modifications to seL4 that can reclaim the memory used by the rootserver. And we've collaborated with Antmicro to enable GDB debugging and simulation for our target hardware with Renode. Are these changes being formally verified? I understand it involves a not insignificant amount of labor to do so, but I worry about bugs being introduced that undermine the security properties of seL4 if care isn’t taken here. Thanks, Isaac Beckett PS: I decided to post this to the mailing list because I thought it may be of interest to some folks here.

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Reminder seL4 developer hangout
by Birgit Brecknell 20 Mar '23

20 Mar '23

Hi all A friendly reminder that the seL4 developer hangout is on again this week: Tue, Mar 21, 9pm (UTC), Topics: (open) * Sydney: Wed, Mar 22, 8am * Central Europe: Tue, Mar 21, 10pm * US Pacific Time: Tue, Mar 21, 2pm Calendar link: https://sel4.systems/contact/ 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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shoehorn & fudge factor
by Sam Leffler 14 Mar '23

14 Mar '23

I have a target platform with only 4M of memory. When the system image is generated and the shoehorn helper script is used to find a place in memory to load the build artifacts it tacks on an extra 4M of memory use (aka fudge_factor). The comment in the code <https://github.com/AmbiML/sparrow-seL4_tools/blame/master/cmake-tool/helper…> says this is to accommodate sel4test_driver. Needless to say this breaks on my 4M target platform. So I made the fudge-factor settable from the cmd line with a default of 0 and changed the sel4test build glue to set 4M when building elfloader. Works fine for my target platform. But this change breaks building a bootable image for rpi3 (AARCH64=1 bcm28367)--shoehorn places elfloader s.t. it overlaps the image; e.g. ELF-loader started on CPU: ARM Ltd. Cortex-A53 r0p4 > paddr=[335000..51a0ff] > No DTB passed in from boot loader. > Looking for DTB in CPIO archive...found at 378778. > Loaded DTB from 378778. > paddr=[237000..23afff] > ELF-loading image 'kernel' to 0 > paddr=[0..236fff] > vaddr=[ffffff8000000000..ffffff8000236fff] > virt_entry=ffffff8000000000 > ELF-loading image 'capdl-loader' to 23b000 > paddr=[23b000..33bfff] > vaddr=[400000..500fff] > virt_entry=4009a8 > ERROR: image load address overlaps with ELF-loader! > ERROR: Physical address range invalid > ERROR: Could not load user image ELF Debug output of shoehorn for this case: shoehorn: debug: found CPIO identifying sequence b'070701' at offset 0x40 > in > /usr/local/google/home/sleffler/shodan/out/cantrip/aarch64-unknown-elf/release/elfloader/archive.o > shoehorn: debug: encountered CPIO entry name: kernel.elf > shoehorn: debug: encountered CPIO entry name: kernel.dtb > shoehorn: debug: encountered CPIO entry name: capdl-loader > shoehorn: debug: setting marker to 0x0 (region 0 start) > shoehorn: debug: setting marker to 0x237000 (kernel_end) > shoehorn: debug: setting marker to 0x23b000 (dtb_end) > shoehorn: debug: setting marker to 0x335000 (end of rootserver) So two questions: 1. Where is the 4M under-count of sel4test_driver? (the code indicates this might be explained in JIRA SELFOUR-2335 but I couldn't locate it) 2. Should zero'ing fudge_factor work? If yes, where should I look to remedy the above? I looked upstream for changes that might address this issue but didn't see anything. I suspect I can invert my logic and default fudge_factor to some value and then override as needed (e.g. 0 for my sparrow platform & 4M for sel4test builds). -Sam

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memory zero'ing
by Sam Leffler 12 Mar '23

12 Mar '23

I'm chasing an issue that looks like retype'd memory has nonsense data. If I read the kernel code correctly it looks like the object returned by an seL4_UntypeRetype syscall should be zero'd (looks to happen when an untyped memory object is reset here <https://github.com/seL4/seL4/blob/master/src/object/untyped.c#L254>). Is that correct? I don't see anything called out in the manual. -Sam

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Reminder seL4 developer hangout
by Birgit Brecknell 06 Mar '23

06 Mar '23

Hi all A friendly reminder that the seL4 developer hangout is on again this week: Wed, Mar 8, 6am (UTC), Topics: (open) * Sydney: Wed, Mar 8, 5pm * Central Europe: Wed, Mar 8, 7am * US Pacific Time: Tue, Mar 7, 10pm Calendar: https://sel4.systems/contact/ 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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