Add simplefs as new Linux image artifact

[ChinYikMing]

Description

To enhance the guest OS functionality, this commit integrates the simplefs kernel module to support an additional filesystem. It appends simplefs as a new Linux image artifact and automatically builds the latest simplefs.ko when make build-linux-image is executed.

Testing

1. Clone the repo:

$ git clone https://github.com/ChinYikMing/rv32emu.git -b mount-simplefs --depth 1 && cd rv32emu

2. Build emulator

$ make ENABLE_SYSTEM=1 INITRD_SIZE=32 -j8

3. Fetch artifacts

$ make artifact ENABLE_SYSTEM=1

4. Create ext4 disk image and store simple.ko

$ dd if=/dev/zero of=disk.img bs=4M count=32
$ mkfs.ext4 disk.img
$ mkdir mnt
$ sudo mount disk.img mnt
$ sudo cp build/linux-image/simplefs.ko mnt
$ sudo umount mnt

5. Clone simplefs to create simplefs disk image

$ git clone https://github.com/sysprog21/simplefs.git --depth 1
$ make test.img -C simplefs

6. Boot guestOS

$ build/rv32emu -k build/linux-image/Image -i build/linux-image/rootfs.cpio -x vblk:disk.img -x vblk:simplefs/test.img

7. insmod simplefs.ko

# mkdir -p mnt && mount /dev/vdb mnt && insmod mnt/simplefs.ko

8. Mount simplefs disk image

# mkdir -p simplefs && mount -t simplefs /dev/vda simplefs

9. Manipulate the disk image typed simplefs

# cd simplefs
# touch apple
# ls
apple
# mkdir banana
# ls 
apple banana

Expectation

• Filesystem commands like cd, touch, ls, mkdir, etc should be operational.

• Run mount and the /dev/vda has filesystem typed simplefs will be shown.

Sample output:

# mount
rootfs on / type rootfs (rw,size=241136k,nr_inodes=60284)
devtmpfs on /dev type devtmpfs (rw,relatime,size=241136k,nr_inodes=60284,mode=755)
proc on /proc type proc (rw,relatime)
devpts on /dev/pts type devpts (rw,relatime,gid=5,mode=620,ptmxmode=666)
tmpfs on /dev/shm type tmpfs (rw,relatime)
tmpfs on /tmp type tmpfs (rw,relatime)
tmpfs on /run type tmpfs (rw,nosuid,nodev,relatime,mode=755)
sysfs on /sys type sysfs (rw,relatime)
/dev/vdb on /root/mnt type ext4 (rw,relatime)
/dev/vda on /root/simplefs type simplefs (rw,relatime)

---

Summary by cubic

Add simplefs support by auto-building and packaging simplefs.ko as a Linux image artifact, so the guest OS can mount and use simplefs volumes. README includes brief usage steps.

• New Features

  • Build simplefs.ko in tools/build-linux-image.sh and output to build/linux-image/.
  • Include simplefs.ko in artifact checksums (mk/artifact.mk).
  • Add SIMPLEFS as external data and a build prerequisite (mk/external.mk, mk/tools.mk).
  • Document how to attach the module and mount a simplefs disk in the README.

• Dependencies

  • Clone sysprog21/simplefs (master) during build and verify via SHA1.

[cubic-dev-ai]

2 issues found across 5 files

Prompt for AI agents (all 2 issues)

Understand the root cause of the following 2 issues and fix them.


<file name="README.md">

<violation number="1" location="README.md:114">
The sentence uses the singular verb &quot;is&quot; with the plural subject &quot;other filesystems&quot;; please change it to &quot;are&quot; for correct subject–verb agreement.</violation>
</file>

<file name="mk/external.mk">

<violation number="1" location="mk/external.mk:141">
Pin SIMPLEFS to an immutable tag or commit. Using `master` with a fixed SHA causes the verification step to fail as soon as upstream updates, breaking the build.</violation>
</file>

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[jserv]

I like the idea of “eating your own dog food,” and simplefs can be a great demonstration of a minimalist software stack.

[cubic-dev-ai]

No issues found across 9 files

[jserv]

You should track this issue.

[ChinYikMing]

You should track this issue.

Describe the issue in the aaa9c44 commit message and create a issue in simplefs.

[jserv]

Thank @ChinYikMing for contributing!