🧠 xv6 RISC-V Expert

A Claude Code Skill for debugging, building, and mastering xv6 on 64-bit RISC-V

Syscalls · Schedulers · Page Tables · Traps · Locks · File System

📖 What Is This?

xv6-riscv-expert is a Claude Code Skill designed for students and developers working with MIT-style xv6-riscv and SNU's xv6-riscv-snu operating system assignments.

✨ Perfect For:

Use Case	Description
🎓 Coursework	CSE321 / OS assignments (xv6-riscv)
🔧 Kernel Dev	System calls, scheduler, virtual memory
🐛 Debugging	Traps, page faults, locks
📚 Learning	OS concepts, RISC-V architecture

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🚀 Quick Install

Option 1: One-Line Install (Recommended)

npx skills add shafin027/xv6-riscv-skill-

Option 2: Manual Install

git clone https://github.com/shafin027/xv6-riscv-skill-.git ~/.claude/skills/xv6-riscv-expert

Option 3: Local Project Install

cd /path/to/your/project
npx skills add shafin027/xv6-riscv-skill- --local

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🎯 Usage

Slash Command

/xv6-riscv-expert

Automatic Triggering

Claude Code will use the skill when you ask questions like:

I need to add a new syscall to xv6-riscv.

How do I implement a lottery scheduler in xv6?

Debug this xv6 page fault: scause=15, stval=0x0.

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🛠️ Supported Assignment Types

Type	Examples	Status
System Calls	settickets, getpid, tracing, custom syscalls	✅
Scheduler	Lottery scheduler, priority scheduler, round-robin	✅
Virtual Memory	Page tables, PTEs, vmprint, COW, USYSCALL	✅
Traps & Interrupts	usertrap, page faults, timer interrupts	✅
Process Management	fork, exit, wait, process states	✅
Locks & Concurrency	Spinlocks, sleeplocks, race conditions	✅
File System	Inodes, logging, buffer cache	✅

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📚 Skill Knowledge Base

Core Files Map

File	Purpose
kernel/proc.h	struct proc, process states, fields
kernel/proc.c	Process lifecycle, scheduler, fork, exit
kernel/syscall.c	Syscall dispatcher and table
kernel/syscall.h	Syscall numbers
kernel/trap.c	Trap handling, interrupts, exceptions
kernel/vm.c	Page tables, virtual memory, mapping
kernel/riscv.h	RISC-V registers, PTE flags
user/user.h	User-space function declarations

🎯 Answer Templates

Implementation Answer:

1. Files to change
2. Patch / code
3. Why this works
4. How to test
5. Common mistakes

Debugging Answer:

1. Likely cause
2. What to inspect
3. Exact command(s)
4. Fix
5. Validation

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🎯 Example Workflows

Example 1: Adding a New Syscall

Prompt:

I need to add a syscall called settickets(int n) to xv6-riscv

Skill Response:

• ✅ Lists all files to change
• ✅ Provides exact code patches
• ✅ Explains why each change works
• ✅ Gives test commands (make qemu)
• ✅ Shows common mistakes to avoid

Example 2: Lottery Scheduler Assignment

Prompt:

Implement a lottery scheduler for xv6-riscv where each process 
has tickets and the scheduler picks a random winner

Skill Response:

• ✅ Step-by-step implementation plan
• ✅ Complete code for proc.h, proc.c, sysproc.c
• ✅ Random number generator implementation
• ✅ Test program (test_scheduler.c)
• ✅ Patch file creation instructions

Example 3: Debugging a Page Fault

Prompt:

My xv6 kernel panics with scause=15 (store page fault). 
The fault happens in sys_write. Here's my code...

Skill Response:

• ✅ Identifies likely cause (PTE permissions, user pointer)
• ✅ Shows what to inspect (copyout, walk(), PTE flags)
• ✅ Provides exact fix
• ✅ Gives validation steps

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🔧 xv6-riscv Setup

Before using this skill, ensure you have xv6-riscv set up:

1. Install Prerequisites

# Ubuntu/Debian
sudo apt update
sudo apt install git build-essential gdb-multiarch qemu-system-misc \
                 gcc-riscv64-linux-gnu binutils-riscv64-linux-gnu

2. Clone xv6-riscv

git clone https://github.com/mit-pdos/xv6-riscv.git
cd xv6-riscv

3. Build and Run

make clean
make qemu

4. Debug with GDB

Terminal 1:

make qemu-gdb

Terminal 2:

riscv64-linux-gnu-gdb kernel/kernel

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📋 Assignment Checklist

When working on xv6 assignments, the skill will help you:

• Identify assignment type
• List all files to modify
• Provide minimal correct patches
• Explain why the solution works
• Include test commands
• Warn about common mistakes
• Help create patch files (git diff --staged > ID.patch)

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🤝 Contributing

Found a bug or want to improve the skill? Contributions welcome!

1. Fork the repo
2. Create your feature branch (git checkout -b feature/amazing-improvement)
3. Commit your changes (git commit -m 'Add some amazing improvement')
4. Push to the branch (git push origin feature/amazing-improvement)
5. Open a Pull Request

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Star History

📄 License

MIT License — feel free to use, modify, and distribute.

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🔗 Resources

• xv6-riscv Official Repository
• xv6 Book (MIT)
• RISC-V Documentation
• SNU xv6-riscv-snu

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💬 Support

Having issues?

1. Open an issue on GitHub
2. Ask in the Claude Code Discord

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Made with ❤️ for OS students, xv6 hackers, and RISC-V enthusiasts

_{Part of the Claude Code Skills ecosystem}