Project Description
FizzBuzz OS (or just fbos
) is an idea I've had in order to better grasp the fundamentals of the low level of a RISC-V machine. In practice, I'd like to build a small Operating System kernel that is able to launch three processes: one that simply prints "Fizz", another that prints "Buzz", and the third which prints "FizzBuzz". These processes are unaware of each other and it's up to the kernel to schedule them by using the timer interrupts as given on openSBI (fizz on % 3 seconds, buzz on % 5 seconds, and fizzbuzz on % 15 seconds).
This kernel provides just one system call, write
, which allows any program to pass the string to be written into stdout.
This project is free software and you can find it here.
Goal for this Hackweek
- Better understand the RISC-V SBI interface.
- Better understand RISC-V in privileged mode.
- Have fun.
Resources
Results
The project was a resounding success Lots of learning, and the initial target was met.
This project is part of:
Hack Week 24
Activity
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Project Description
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Wrapping up: being back doing kernel hacking is amazing and I don't want to stop it. My battery pack is completely drained but changing the scope gave me a great twist and I really want to feel this energy not doing a single task for months.
I failed in setting up a fuzzing lab but I was too optimistic for the patch submission process.
The patches
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Description
My studies as well my spare time are dedicated to the Linux Kernel. Currently I'm focusing on interrupts on x86_64, but my interests are not restricted to one specific topic, for now.
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Maybe this will be a good chance to...
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Description
Improve UML handling of segmentation faults in kernel mode. Although such page faults are generally caused by a kernel bug, it is annoying if they cause an infinite loop, or panic the kernel. More importantly, a robust implementation allows to write KUnit tests for various guard pages, preventing potential kernel self-protection regressions.
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Convert the UML page fault handler to use oops_* helpers, go through a few review rounds and finally get my patch series merged in 6.14.
Resources
Wrong initial attempt: https://lore.kernel.org/lkml/20231215121431.680-1-petrtesarik@huaweicloud.com/T/
early stage kdump support by mbrugger
Project Description
When we experience a early boot crash, we are not able to analyze the kernel dump, as user-space wasn't able to load the crash system. The idea is to make the crash system compiled into the host kernel (think of initramfs) so that we can create a kernel dump really early in the boot process.
Goal for the Hackweeks
- Investigate if this is possible and the implications it would have (done in HW21)
- Hack up a PoC (done in HW22 and HW23)
- Prepare RFC series (giving it's only one week, we are entering wishful thinking territory here).
update HW23
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init/main.c:start_kernel()
probably afterkcsan_init()
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systemcall which has two problems:- My initramfs in the porduction kernel does not have a new enough kexec version, that's not a blocker but where the week ended
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kexec_file_load()
from user-space.
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update HW24
- Day1
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- setting up a new compilation and qemu/virtme env
- getting desperate as nothing works that used to work
- Day 2
- getting to call the invocation of loading the early kernel from
__init
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- getting to call the invocation of loading the early kernel from
Day 3
- fix problem of memdup not being able to alloc so much memory... use 64K page sizes for now
- code refactoring
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elfcorehdr_read_notes()
Day 4
- crash systems crashes (no pun intended) in
copy_old_mempage()
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vmcore_init() -> parse_crash_elf_headers() -> elfcorehdr_read() -> read_from_oldmem() -> copy_oldmem_page() -> copy_to_iter()
- crash systems crashes (no pun intended) in
Day 5
- hacking
arch/arm64/kernel/crash_dump.c:copy_old_mempage()
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- hacking
TODOs
- fix elfcorehdr so that we actually can make use of all this...
- test where in the boot
__init()
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Similar to previous hackweeks ( https://hackweek.opensuse.org/projects/improve-qualcomm-soc-msm8994-slash-msm8992-kernel-mainline-support, https://hackweek.opensuse.org/projects/test-mainline-kernel-on-an-older-qualcomm-soc-msm89xx-explore-mainline-kernel-qualcomm-mainlining) try to improve kernel mainline support of various phones.
Result
In the end I concentrated again to msm8994:
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- WIP USB support for msm8994