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Add tool to break into a live debugger session. #40

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24 changes: 23 additions & 1 deletion src/mcp_windbg/cdb_session.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import re
import os
import platform
import signal
from typing import List, Optional

# Regular expression to detect CDB prompts
Expand Down Expand Up @@ -97,13 +98,19 @@ def __init__(
cmd_args.extend(additional_args)

try:
# Only create a new process group for remote sessions where CTRL+BREAK is needed
creationflags = 0
if os.name == 'nt' and self.remote_connection:
creationflags = subprocess.CREATE_NEW_PROCESS_GROUP

self.process = subprocess.Popen(
cmd_args,
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
text=True,
bufsize=1
bufsize=1,
creationflags=creationflags,
)
except Exception as e:
raise CDBError(f"Failed to start CDB process: {str(e)}")
Expand Down Expand Up @@ -239,6 +246,21 @@ def shutdown(self):
finally:
self.process = None

def send_ctrl_break(self) -> None:
"""Send a CTRL+BREAK event to the CDB process to break in.

Raises:
CDBError: If the signal cannot be delivered or the process is not running.
"""
if not self.process or self.process.poll() is not None:
raise CDBError("CDB process is not running")

try:
# On Windows, deliver CTRL+BREAK to the new process group we created
self.process.send_signal(signal.CTRL_BREAK_EVENT)
except Exception as e:
raise CDBError(f"Failed to send CTRL+BREAK: {str(e)}")

def get_session_id(self) -> str:
"""Get a unique identifier for this CDB session."""
if self.dump_path:
Expand Down
35 changes: 35 additions & 0 deletions src/mcp_windbg/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,20 @@ class ListWindbgDumpsParams(BaseModel):
)


class SendCtrlBreakParams(BaseModel):
"""Parameters for sending CTRL+BREAK to a CDB/WinDbg session."""
dump_path: Optional[str] = Field(default=None, description="Path to the Windows crash dump file")
connection_string: Optional[str] = Field(default=None, description="Remote connection string (e.g., 'tcp:Port=5005,Server=192.168.0.100')")

@model_validator(mode='after')
def validate_connection_params(self):
if not self.dump_path and not self.connection_string:
raise ValueError("Either dump_path or connection_string must be provided")
if self.dump_path and self.connection_string:
raise ValueError("dump_path and connection_string are mutually exclusive")
return self


def get_or_create_session(
dump_path: Optional[str] = None,
connection_string: Optional[str] = None,
Expand Down Expand Up @@ -315,6 +329,14 @@ async def list_tools() -> list[Tool]:
""",
inputSchema=RunWindbgCmdParams.model_json_schema(),
),
Tool(
name="send_ctrl_break",
description="""
Send a CTRL+BREAK event to the active CDB/WinDbg session, causing it to break in.
Useful for interrupting a running target or breaking into a remote session.
""",
inputSchema=SendCtrlBreakParams.model_json_schema(),
),
Tool(
name="close_windbg_dump",
description="""
Expand Down Expand Up @@ -452,6 +474,19 @@ async def call_tool(name, arguments: dict) -> list[TextContent]:
text=f"Command: {args.command}\n\nOutput:\n```\n" + "\n".join(output) + "\n```"
)]

elif name == "send_ctrl_break":
args = SendCtrlBreakParams(**arguments)
session = get_or_create_session(
dump_path=args.dump_path, connection_string=args.connection_string,
cdb_path=cdb_path, symbols_path=symbols_path, timeout=timeout, verbose=verbose
)
session.send_ctrl_break()
target = args.dump_path if args.dump_path else f"remote: {args.connection_string}"
return [TextContent(
type="text",
text=f"Sent CTRL+BREAK to CDB session ({target})."
)]

elif name == "close_windbg_dump":
args = CloseWindbgDumpParams(**arguments)
success = unload_session(dump_path=args.dump_path)
Expand Down