[GSoC] Questions about emulating missing linux system calls project
Hello, For the past few days, I have been trying to assess support for Linux system calls on a NetBSD system. I am using Linux Test Project for identifying system calls that are yet to be emulated on NetBSD. I have setup QEMU with GENERIC kernel for testing purpose (Thanks iMil for helping me out!) with COMPAT_LINUX option enabled. I have following particular questions: 1. I wish to emulate support for pidfd_* family of system calls, open_tree, openat2, clone3. I believe they still lack emulation support. Where should I look to identify the possible mappings for these system calls in NetBSD kernel? 2. I found around 40 system calls that currently lack emulation support. Most of them are the system calls that aren't popular or are more relevant to Linux kernel. Only some of the newer system calls seem more likely to be able to be mapped directly to NetBSD system calls. Is it expected to actually implement some of them in NetBSD kernel and then add them to compat layer as part of this project? Also, what's the state of splice and sendfile system calls? I can see that they have been implemented as part of GSoC 2022 but the test cases relating to them still can't find these system calls. 1. With respect to system calls relating to scheduler, I get error relating to not finding some particular files in proc directory. I have set up proc as mentioned in documentation but I still get these errors when I run schedular related system calls. Does proc need to be configured in different way or do schedular related system calls actually lack emulation support? I would also like to thank Theodore for helping me understand the work he did last year. Thanking you, Shivraj
Re: [GSOC][NEWBIE]
Hello iMil,
Thanks a lot for the help. I was able to set up the qemu VM following the
commands you specified.
Once again thanks a lot for your help.
Thanking you,
Shivraj
From: Emile 'iMil' Heitor
Sent: Thursday, March 28, 2024 10:23 PM
To: Jamgadepatil Shivraj Shashikant ; tech-kern@netbsd.org
Subject: Re: [GSOC][NEWBIE]
External Email
On 3/28/24 17:44, Jamgadepatil Shivraj Shashikant wrote:
> I even tried gziped kernel image stored in releasedir directory, so I
> guess it's not only PVH boot that was causing the problem. I suspected I
> might have built the kernel incorrectly, so I also tried booting from
> the daily kernel build provided on the github but the kvm error persists.
> qemu command I am using for booting the system is: qemu-system-x86_64 -m
> 2048 -kernel netbsd-GENERIC.gz -drive
> if=virtio,file=disk.qcow2,format=qcow2 -enable-kvm
Don't gzip the kernel, here's an example session:
$ git branch
* perf
$ ./build.sh -U -u -j4 -T obj/tooldir -m amd64 tools
$ ./build.sh -U -u -j4 -T obj/tooldir -m amd64 kernel=MICROVM
$ KERNEL=sys/arch/amd64/compile/obj/MICROVM/netbsd
$ IMG=NetBSD-10.99.10-amd64-live.img # fetch and gunzip this from
https://nycdn.netbsd.org/pub/NetBSD-daily/HEAD/202403200640Z/images/NetBSD-10.99.
10-amd64-live.img.gz
$ qemu-system-x86_64 \
-M microvm,x-option-roms=off,rtc=on,acpi=off,pic=off \
-enable-kvm -m 512 -cpu host,+invtsc \
-append "root=ld0a console=com rw -v" -display none \
-device virtio-blk-device,drive=hd0 \
-drive file=${IMG},format=raw,id=hd0 \
-netdev user,id=net0,hostfwd=tcp::10022-:22 \
-device virtio-net-device,netdev=net0 \
-kernel ${KERNEL} -serial mon:stdio
FYI I'll be mostly AFK till next Tuesday.
Cheers,
--
Emile `iMil' Heitor | https://imil.net
Re: [GSOC][NEWBIE]
Hello iMil, Thanks for your suggestions. I built the kernel from the sources available on the github link you provided. I am still running into the similar issues
[GSOC][NEWBIE]
Hello, I am Shivraj. I found the project about "adding support for emulation of missing linux syscalls" to NetBSD kernel intriguing. I have previously worked on projects involving the Linux kernel. I have worked on adding system calls to Linux kernel for isolating cores, implementing a different scheduler in the kernel for normal processes and to provide support for anonymous memory checkpointing for a user process by writing a custom page fault handler. I have been exploring NetBSD source tree for a few days. I am trying to set up my development environment with qemu to check out some ideas and understand things more clearly. I tried to boot from the kernel compiled from sources, but I am still unable to do so. I would appreciate all the help people here can provide to guide me to set up the development environment. I am using Linux as my host OS and have cross-compiled the NetBSD kernel but loading the custom kernel results in a KVM emulation error. I am unable to find the path where compressed kernel image is generated. Images generated in releasedir results in errors or a frozen qemu screen. Thanking you, Shivraj Jamgade MTech CSA Indian Institute of Science, Bangalore
