May 2020 - Devel - lists.sel4.systems

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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CAmkES VM rootfs.cpio with Python3 Causes Error
by Turner, Ben 12 Jun '20

12 Jun '20

Hi, I have been attempting to create a VM to run as a CAmkES component, and it is a requirement that it has Python3. I have been using the vm_minimal app as a template to get started, and was successful at getting my own buildroot filesystem image running, however when I attempted to add the Python3 package, the resulting image resulted in the following error when it booted: ... <<seL4(CPU 0) [decodeInvocation/631 T0xfec34400 "rootserver" @106f0]: Attempted to invoke a null cap> create_objects@main.c:805 [Err seL4_InvalidCapability]: Untyped retype failed with unexpected error seL4 root server abort()ed Debug halt syscall from user thread 0xfec34400 "rootserver" halting... Kernel entry via Unknown syscall, word: 1 The only change I made to the image was to add the Python3 package, and that has caused this error. Is there something the vm_minimal app is missing that is required in order to get Python3 working? Kind regards, Ben Turner ________________________________________ Roke Manor Research Limited, Romsey, Hampshire, SO51 0ZN, United Kingdom.Part of the Chemring Group. Registered in England & Wales. Registered No: 00267550 http://www.roke.co.uk _______________________________________ The information contained in this e-mail and any attachments is proprietary to Roke Manor Research Limited and must not be passed to any third party without permission. This communication is for information only and shall not create or change any contractual relationship. ________________________________________

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Threads tutorial fails to initialize
by Weiqi Hu 01 Jun '20

01 Jun '20

Hi, I've tried to start the threads tutorial but it fails to initialize or create a build directory. Any hints for moving forward? weiqi@weiqi-ThinkPad-X250:~/sel4-tutorials-manifest-temp/threads$ sudo ../init --verbose --tut threads --solution Traceback (most recent call last): File "../init", line 96, in <module> sys.exit(main()) File "../init", line 85, in main args.task, initialised, tute_dir, build_dir, sys.stdout) File "/home/weiqi/sel4-tutorials-manifest-temp/projects/sel4-tutorials/common.py", line 100, in init_directories os.chdir(build_directory) FileNotFoundError: [Errno 2] No such file or directory: '/home/weiqi/sel4-tutorials-manifest-temp/threads_build'

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Building picoserver example
by Russel emkil.minor 26 May '20

26 May '20

Dear seL4 developers, I am trying to built picoserver example https://github.com/seL4/camkes/tree/master/apps/picoserver <https://github.com/seL4/camkes/tree/master/apps/picoserver> using the following commands: $ ../init-build.sh -DPLATFORM=x86_64 -DCAMKES_APP=picoserver $ ninja But I am getting the following error: fatal error: pico_stack.h: No such file or directory Looks like I need to install libpicotcp. I found it here https://github.com/seL4/util_libs/tree/master/libpicotcp <https://github.com/seL4/util_libs/tree/master/libpicotcp> but no idea how to build and link to the example. Can you give me a hint how to proceed? Best regards, Ruslan Rezin.

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seL4 Whitepaper Released
by Heiser, Gernot (Data61, Kensington NSW) 25 May '20

25 May '20

Dear seL4 community, I’m pleased to announce the seL4 Foundation whitepaper: The seL4 Microkernel – An Introduction This white paper provides an introduction to and overview of seL4. We explain what seL4 is (and is not) and explore its defining features. We explain what makes seL4 uniquely qualified as the operating-system kernel of choice for security- and safety- critical systems, and generally embedded and cyber-physical systems. In particular, we explain seL4’s assurance story, its security- and safety-relevant features, and its benchmark-setting performance. We also discuss typical usage scenarios, including incremental cyber retrofit of legacy systems. You can download it at https://sel4.systems/About/ Feedback welcome. Gernot PS: Some of you may have seen a pre-release version that was up on the Foundation web site since the Foundation launch. This is the complete version.

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Trouble accessing linux guest through tun/tap
by Travis Wheatley 22 May '20

22 May '20

Greetings, I am working with the camkes-arm-vm qemu-arm-virt configuration. I started with the vm_minimal configuration and have added a tun/tap interface by creating the tap on my host thusly: # ip tuntap add tap0 mode tap # ip addr add 10.0.120.100/24 dev tap0 # ip link set dev tap0 up I have added support for what I beleive to be the appropriate interrupts by modifying my devices.camkes file thusly: vm0.untyped_mmios = [ "0x8040000:12", // Interrupt Controller Virtual CPU interface (Virtual Machine view) "0x10040000:17", // QEMU PCI MMIO "0x3eff0000:16", // QEMU PCI IO ports "0x40000000:29", // Linux kernel memory regions ]; vm0.dtb_irqs = [35, 36, 37, 38]; Additionally, I have modified the settings.camkes thusly: if(${PLATFORM} STREQUAL "qemu-arm-virt") # force cpu set(QEMU_MEMORY "2048") set(KernelArmCPU cortex-a53 CACHE STRING "" FORCE) set(VmInitRdFile ON CACHE BOOL "" FORCE) set(VmPCISupport ON CACHE BOOL "" FORCE) set(VmVirtioNetArping OFF CACHE BOOL "" FORCE) set(VmVirtioNetVirtqueue ON CACHE BOOL "" FORCE) # set(qemu_sim_extra_args "-netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no -device virtio-net,netdev=mynet0,mac=52:55:00:d1:55:01") set(qemu_sim_extra_args "-net nic,model=e1000 -netdev tap,id=mynet0,script=no,ifname=tap0 -device virtio-net,netdev=mynet0,mac=52:55:00:d1:55:01") set(KernelArmExportPCNTUser ON CACHE BOOL "" FORCE) set(KernelArmExportPTMRUser ON CACHE BOOL "" FORCE) endif() This results in a tunl0 interface showing up on my linux guest. However, that interface does not have a mac address associated with it. I can use ifconfig to assign an IP address on the same subnet as the corresponding tap interface on the host. However, I can’t ping between the two. I thought this might be because I have VmVitruoNetArping set to OFF. However, I get compile time errors when I turn it on. Because the tunl0 inteface does not have the mac address specied in the qemu_sim_extra_args I am unsure of how to set up an arp table entry. Exctly what do I need to do to enable network communications between my linux guest and the host?

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Help with creating a new project
by Yates, Tim 22 May '20

22 May '20

Hi, I am attempting to create a new CAmkES project. So far I have used the https://github.com/seL4/camkes-manifest.git repository and the https://github.com/SEL4PROJ/camkes-arm-vm-manifest repository and placed my .camkes file and components into the respective app folders for each. I then attempt to initialise my project as instructed here https://docs.sel4.systems/projects/camkes/ but it fails. It gives me the following error: hardware_gen.py: error: argument --dtb: can't open '/workspaces/microimpexor/seL4_build/build/kernel/kernel.dtb': [Errno 2] No such file or directory: '/workspaces/microimpexor/seL4_build/build/kernel/kernel.dtb' I am initialising my project with the following command: ../init-build.sh -DPLATFORM=qemu-arm-virt -DAARCH32=1 -DCAMKES_APP=appname -DSIMULATION=1 Some assistance on this matter would be greatly appreciated. Regards Tim Yates ________________________________________ Roke Manor Research Limited, Romsey, Hampshire, SO51 0ZN, United Kingdom.Part of the Chemring Group. Registered in England & Wales. Registered No: 00267550 http://www.roke.co.uk _______________________________________ The information contained in this e-mail and any attachments is proprietary to Roke Manor Research Limited and must not be passed to any third party without permission. This communication is for information only and shall not create or change any contractual relationship. ________________________________________

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some confuse about "bootstrap_use_current_simple" of bootstrap.c in libsel4allocman
by yadong.li 20 May '20

20 May '20

allocman_t *bootstrap_use_current_simple(simple_t *simple, size_t pool_size, void *pool) { allocman_t *allocman; int error; /* Initialize inside the current 1 level cspace as defined by simple */ allocman = bootstrap_use_current_1level(simple_get_cnode(simple), simple_get_cnode_size_bits(simple), simple_last_valid_cap(simple) + 1, BIT(simple_get_cnode_size_bits(simple)), pool_size, pool); if (!allocman) { LOG_ERROR("Failed to initialize an allocman"); return allocman; } ....... return allocman; } The params of "bootstrap_use_current_1level" below: cnode_size = simple_get_cnode_size_bits(simple), like 23, it is 8M endslot = BIT(simple_get_cnode_size_bits(simple)), also 8M I think we don't have so many endslot, because per slot is not only one byte Thank you very much

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