Gdb Multiarch

An MCP (Model Context Protocol) server that gives AI assistants like Claude direct access to gdb-multiarch for debugging Nintendo Switch executables running on Yuzu or a real console with a GDB stub.

Built on top of Ipiano/gdb-mcp, this fork adds Switch-specific debugging tools for offset-based breakpoints, instruction patching (NOP/stub/replace), frame-pointer backtraces, and address localization — all relative to the game's base address ($main).

What It Does

When Claude (or any MCP client) calls switch_start_session, the server:

1. Launches gdb-multiarch inside WSL
2. Loads the Switch debugging commands (.gdbinit.switch)
3. Connects to the GDB stub via target extended-remote
4. Waits for the application to launch, attaches to it
5. Automatically sets $main to the base address of cross2_Release.nss

From there, all standard GDB operations and Switch-specific tools are available through MCP tool calls.

Prerequisites

• Windows with WSL — gdb-multiarch runs inside WSL (tested with Debian)
• gdb-multiarch installed in WSL (sudo apt install gdb-multiarch)
• Python 3.10+ in WSL
• A GDB stub — either Yuzu's built-in GDB stub or a Switch with sys-gdbstub
• Claude Code (or any MCP-compatible client)

Installation

1. Install gdb-multiarch in WSL

wsl -d Debian
sudo apt install gdb-multiarch

2. Install the MCP server

From Windows, run:

wsl.exe -d Debian -e bash -c 'export PATH=$HOME/.local/bin:$PATH && pip install --break-system-packages -e /mnt/c/path/to/gdb-multiarch-mcp'

Or from inside WSL:

pip install -e /mnt/c/path/to/gdb-multiarch-mcp

3. Add to Claude Code

claude mcp add gdb-multiarch -s user -- wsl.exe -d Debian -e bash -c "export PATH=\$HOME/.local/bin:\$PATH && python3 -m gdb_multiarch_mcp"

Or manually add to your .claude.json:

{
  "mcpServers": {
    "gdb-multiarch": {
      "type": "stdio",
      "command": "wsl.exe",
      "args": [
        "-d", "Debian", "-e", "bash", "-c",
        "export PATH=$HOME/.local/bin:$PATH && python3 -m gdb_multiarch_mcp"
      ]
    }
  }
}

4. Verify

claude mcp list

You should see gdb-multiarch: ... - Connected.

Configuration

Set these environment variables in WSL to customize the connection:

Variable	Default	Description
SWITCH_IP	192.168.1.235	IP address of the Switch/Yuzu GDB stub
SWITCH_PORT	22225	GDB stub port
GDB_PATH	gdb-multiarch	Path to the gdb-multiarch binary
GDB_MCP_LOG_LEVEL	INFO	Logging level (DEBUG, INFO, WARNING, ERROR)

To set these, add env to your MCP config:

{
  "mcpServers": {
    "gdb-multiarch": {
      "type": "stdio",
      "command": "wsl.exe",
      "args": ["..."],
      "env": {
        "SWITCH_IP": "192.168.1.100",
        "SWITCH_PORT": "22225"
      }
    }
  }
}

Available Tools

Session Management

Tool	Description
switch_start_session	Connect to the Switch/Yuzu, attach to the game, set $main. Call this first.
switch_stop_session	Disconnect and clean up

Switch Debugging Tools

Tool	Description
switch_break_at	Set breakpoint at $main+offset
switch_no_op	NOP instruction at offset (writes 0xD503201F)
switch_stub	Stub function at offset (writes RET / 0xD65F03C0)
switch_replace	Replace instruction at offset with arbitrary value
switch_get_pc	Get PC as offset relative to $main
switch_localize	Convert absolute address to offset relative to $main
switch_my_bt	Backtrace as absolute addresses (frame pointer walk)
switch_my_bt2	Backtrace with offsets relative to $main
switch_print_trace	Combined: PC offset + LR offset + full backtrace
switch_xxd	Hex dump of memory
switch_prepare_rehook	Dump 4 original instructions at offset for later restore

Standard GDB Tools

All standard gdb-mcp tools are also available:

Tool	Description
gdb_execute_command	Execute any GDB command (CLI or MI)
gdb_set_breakpoint	Set breakpoint at function/file:line/address
gdb_list_breakpoints	List all breakpoints
gdb_delete_breakpoint	Delete breakpoint by number
gdb_enable_breakpoint	Enable breakpoint
gdb_disable_breakpoint	Disable breakpoint
gdb_continue	Continue execution
gdb_step	Step into
gdb_next	Step over
gdb_interrupt	Pause running program
gdb_get_backtrace	Standard GDB backtrace
gdb_get_threads	List threads
gdb_select_thread	Switch to thread
gdb_select_frame	Select stack frame
gdb_get_frame_info	Current frame info
gdb_evaluate_expression	Evaluate C/C++ expression
gdb_get_variables	Local variables for a frame
gdb_get_registers	CPU register values
gdb_call_function	Call function in target process
gdb_get_status	Session status

Troubleshooting

"No route to host" when connecting

WSL networking can be tricky. Try:

1. Confirm SSH is running in WSL: sudo service ssh start
2. Test connectivity: nc -vz <switch_ip> 22225
3. Add a route if needed: sudo ip route add 192.168.1.0/24 via <gateway_ip>
4. Port proxy from Windows PowerShell:

   netsh interface portproxy add v4tov4 listenport=22225 listenaddress=127.0.0.1 connectport=22225 connectaddress=<switch_ip>
   

GDB stub not responding

• Make sure the game is running on Yuzu/Switch before calling switch_start_session
• Verify Yuzu's GDB stub is enabled in Emulation > Configure > Debug > Enable GDB Stub

Session already running

Call switch_stop_session first, then switch_start_session again.

Credits

• Ipiano/gdb-mcp by Andrew Stelter — the upstream MCP server for GDB that this project is built on
• Coolsonickirby/smash-ultimate-research-setup — the modified .gdbinit.switch and attach.py (auto-attach script) used in this project
• blujay — the original .gdbinit.switch commands
• GradualSyrup — print_addr_setup.py (address-to-offset resolution)
• Gdbinit by mammon_, elaine, pusillus, mong, zhang le, l0kit, truthix, fG!, gln — the extended .gdbinit configuration

License

MIT — see LICENSE.