June 2024 - Devel - lists.sel4.systems

Success and Effort in seL4 x86_64 Virtualbox
by thomas.j.hampton＠gmail.com 21 Jun '24

21 Jun '24

Hey; configuration is a pretty big space and I didn't see anything specific, and may have bumped into a bug along the way. Here's some details about getting seL4test working, and using the EGA driver on this platform. Here's the commits I'm on: - sel4test 95522e9 - seL4 ddeb18a01 I managed to get seL4test running in VirtualBox on a Tiger Lake chip some weeks ago, not terribly impressive, things worked pretty well, generally. - I discovered that on the platform I needed to manually set all the '*HAVE_TIMER*' flags in the code to 0 - to get the tests to succeed on VirtualBox; CMake doesn't appear to support this transformation. - a major stumbling block was that these changes were being reverted each time I re-ran CMake, under my feet. So that's pretty cool... Some further exploration I discovered that there's the pc99/ega (ega.c) driver, since I'm curious about the requirements for starting to build a custom OS on top of seL4 for this platform, and seeing it run on the hardware in front of me (again, a Tiger Lake laptop). I spent many weeks trying to massage things into place. Reading and learning along side the bootstrap pathway; multiboot.S -> head.S -> boot_sys -> common -> char_dev ... to no avail. However I came into some time and decided to revisit the problem. - #define MULTIBOOT_GRAPHICS_TEXT 2 is an error; Multiboot1 spec has that this should be 1, instead - When I was trying to boot UEFI, this would manifest as a Protection Fault - Fixing this left the system booting, utilizing high amount of CPU, and then going quiet. - UEFI on this platform has unclear / additional requirements / doesn't actually support EGA/VGA text mode - https://www.reddit.com/r/osdev/comments/st0psl/framebuffer_output_for_multi…

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Assertion failure when booting seL4 image on x86 UEFI via Grub
by fennelfoxxo＠gmail.com 16 Jun '24

16 Jun '24

Hello all! This is my first time posting here, but I'll try to provide all the detail I can, and I'm grateful for any advice others have to fix this issue. I've been trying to boot the seL4 Hello World tutorial in QEMU with UEFI support on the x86 platform, with the help of the Grub bootloader. It seems I can load the kernel okay, but an error occurs when the kernel tries to load the rootserver: > seL4 failed assertion 'mods_end_paddr > boot_state.ki_p_reg.end' at /home/fennel/grubbuild/stacktest/sel4-tutorials/kernel/src/arch/x86/kernel/boot_sys.c:452 in function try_boot_sys From my research, it seems to be happening because grub is loading the rootserver module at a lower address than expected. These two lines from serial output during boot indeed show that the module end address is lower than the kernel end address: > module #0: start=0x751000 end=0x7954c8 size=0x444c8 name='' > Kernel loaded to: start=0x100000 end=0xc12000 size=0xb12000 entry=0x100298 When running the same hello world project using ./simulate in the build directory, the rootserver module is placed at a higher address and boots ok: > module #0: start=0xc13000 end=0xc574c8 size=0x444c8 name='images/hello-world-image-x86_64-pc99' > Kernel loaded to: start=0x100000 end=0xc12000 size=0xb12000 entry=0x100298 Does anyone know if this is a mistake in how I am compiling and building the project, my QEMU settings, or perhaps an issue with how Grub is handling loading the module? Booting from Grub should be possible in theory (https://docs.sel4.systems/Hardware/IA32.html) so any guidance is appreciated. Thank you! - Fennel STEPS TO REPRODUCE: # Contents of grub.cfg - place in current directory menuentry "Load seL4" --class os { insmod efi_gop insmod efi_uga insmod all_video set root='(hd0,gpt1)' multiboot2 /EFI/BOOT/sel4kernel module2 /EFI/BOOT/sel4rootserver } # End of grub.cfg # Compile Grub 2.06 from source to ./grub-2.06 wget https://ftp.gnu.org/gnu/grub/grub-2.06.tar.gz -O grub.tar.gz # Download grub source tar -xvzf grub.tar.gz -C ./ && rm grub.tar.gz # Unzip and remove original file cd grub-2.06 && ./autogen.sh && ./configure --target=x86_64 --with-platform=efi && make # Configure & compile # Install, configure, and compile hello-world seL4 project to ./sel4-tutorials mkdir sel4-tutorials cd sel4-tutorials repo init -u https://github.com/seL4/sel4-tutorials-manifest # Install tutorials repo sync ./init --plat pc99 --tut hello-world cd hello-world_build cmake -DCMAKE_TOOLCHAIN_FILE=../kernel/gcc.cmake -DKernelHugePage=OFF -G Ninja . # Disable huge page requirement ninja # Create final image as disk.img mkdir EFI EFI/BOOT grub-2.06/grub-mkimage -d grub-2.06/grub-core -o EFI/BOOT/BOOTX64.EFI -O x86_64-efi -p "" configfile fat part_gpt gzio multiboot video efi_gop efi_uga normal chain boot multiboot2 all_video cp sel4-tutorials/hello-world_build/images/kernel-x86_64-pc99 EFI/BOOT/sel4kernel cp sel4-tutorials/hello-world_build/images/hello-world-image-x86_64-pc99 EFI/BOOT/sel4rootserver cp grub.cfg EFI/BOOT/grub.cfg dd if=/dev/zero of=disk.img bs=1M count=35 # 35MB is just about the smallest FAT32 partition possible mformat -i disk.img@@2048s -v "EFI SYSTEM" -F # Create fat32 partition 2048 sectors in mcopy -i disk.img@@2048s -s EFI :: parted -s disk.img mklabel gpt mkpart '"EFI SYSTEM"' fat32 2048s 100% set 1 esp on # Create partition entry for ESP # Run in QEMU (most of these arguments are copied from the seL4 ./simulate script - replace OVMF path with your path to OVMF_CODE.fd for UEFI boot) qemu-system-x86_64 -cpu Nehalem,-vme,+pdpe1gb,-xsave,-xsaveopt,-xsavec,-fsgsbase,-invpcid,+syscall,+lm,enforce -serial mon:stdio -m size=512M -drive if=pflash,format=raw,readonly=on,file=PATH_TO_OVMF_CODE.fd -drive file=disk.img

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Unblocking the caller of seL4_Call when the receiver is killed
by Arya Stevinson 13 Jun '24

13 Jun '24

Hello, I'll give a brief introduction since this is my first message here. I'm an undergraduate research assistant at the University of British Columbia, and I'm working with Margo Seltzer (https://www.seltzer.com/margo/) in the Systopia Lab. I'm helping with development of Sid Agrawal's (https://sid-agrawal.ca/) project built on seL4. I'm trying to determine what is the correct way to handle this situation: 1. Process 1 makes an seL4_Call to an endpoint that Process 2 is listening on. 2. Process 2 receives the message, and since we are running in non-MCS kernel, it will get a reply capability in its TCB. 3. Process 2 dies, for whatever reason, before it can reply to Process 1. If we wanted to unblock Process 1, what would be the correct approach? - I can use seL4_CNode_SaveCaller in Process 2 as soon as it receives a message, and store the slot number in some shared memory with the root task. Then when Process 2 dies, the root task is able to move the reply capability into its own cspace and send a reply indicating an error. This is not ideal for our purpose, because we do not want Process 2 to be able to perform any operations on its own cspace, but it needs its own root cnode capability in order to perform seL4_CNode_SaveCaller. - Is seL4_Call the wrong function for this purpose? We also considered using NBRecv and considering the call a failure after some timeout period. This is also not ideal since we would lose the convenience of the Call's reply cap, etc. - Is there some other solution that we are missing? As an aside: I notice that for the MCS kernel, if the reply cap is deleted, Process 1's thread state would be moved from ThreadState_BlockedOnReceive to ThreadState_Inactive. In non-MCS kernel, it seems that the state would remain ThreadState_BlockedOnReceive? Is there a reason for this? Best, Arya

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seL4 developer hangout reminder
by Birgit Brecknell 06 Jun '24

06 Jun '24

Hi all A friendly reminder that the seL4 developer hangout is on again next week. Tue 11 Jun, 22:00 UTC. For your local date and time please see https://sel4.systems/contact/. Zoom link: https://unsw.zoom.us/j/82640784431 Birgit Brecknell seL4 Foundation Project Coordinator Sydney, Australia Mon 9-5 Wed 2-5 Fri 9-5 birgit(a)sel4.systems <mailto:birgit@sel4.systems> bbrcknl(a)gmail.com <mailto:bbrcknl@gmail.com>

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Multikernel in RISCV
by David Martin 06 Jun '24

06 Jun '24

Hello, I'm currently working with seL4 & Polarfire (RISCV) and I'm working with a single core at the moment (doing some testing and understanding how seL4 works). Polarfire has 4 cores and I'd like to start using all of them in a multikernel configuration (every hart running its own sel4 kernel). I've found the following RFC: https://sel4.atlassian.net/browse/RFC-17 where Kent McLeod has done some work (https://github.com/kent-mcleod/camkes-manifest/blob/kent/multicore2/master.…) but only for ARM. Does someone know if the same approach will be taken for RISCV? or even better, if someone has already done it? Thanks, David.

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