write-structoffset-as-yaml

Write Struct Offset as YAML

Persist a single struct member offset analysis result to a YAML file beside the binary using IDA Pro MCP.

Prerequisites

Before using this skill, you should have:

1. Identified the struct name and member name
2. Determined the member offset (and optionally size)
3. Generated a unique signature using /generate-signature-for-structoffset
4. An IDA Pro MCP session, resolved per mcp-ida-session.md: idb_list → idb_open (script fallback only if the endpoint is unreachable). Honor its IDB save discipline — an idle-TTL self-exit does not save.

Required Parameters

Parameter	Description	Example
struct_name	Name of the struct/class	CBaseEntity
member_name	Name of the struct member	m_skeletonInstance
offset	Hex offset of the member from struct start	0x278

Optional Parameters

Parameter	Description	Example
size	Size of the member in bytes (use None to omit)	8
artifact_name	Stable caller-provided filename stem; defaults to <struct_name>_<member_name>. Honor the finder's OUTPUT_NAME_MAP key even when the member name was corrected.	CEntitySystem_m_bEnableAutoDeletionExecution
offset_sig	Unique byte signature locating an instruction that contains the offset (use None to omit)	8B 93 E0 04 00 00
offset_sig_disp	Byte displacement from signature start to the target instruction. 0 or None means signature starts at the target instruction. Non-zero means backward expansion was used by /generate-signature-for-structoffset. (use None to omit)	8

Method

mcp__ida-pro-mcp__py_eval code="""
import idaapi
import os
import yaml

# === REQUIRED: Replace these values ===
struct_name = "<struct_name>"           # e.g., "CBaseEntity"
member_name = "<member_name>"           # e.g., "m_skeletonInstance"
artifact_name = f"{struct_name}_{member_name}"  # Override with the expected legacy artifact stem if different.
offset = <offset>                       # e.g., 0x278
# ======================================

# === OPTIONAL: Set to None to omit from output ===
size = <size>                           # e.g., 8 or None
offset_sig = <offset_sig>              # e.g., "8B 93 E0 04 00 00" or None
offset_sig_disp = <offset_sig_disp>    # e.g., 8 or None (0 also omitted)
# =================================================

# Get binary path and determine platform
input_file = idaapi.get_input_file_path()
dir_path = os.environ.get('CS2VIBE_ARTIFACT_DIR') or os.path.dirname(input_file)

if input_file.endswith('.dll'):
    platform = 'windows'
else:
    platform = 'linux'

# Build data dictionary conditionally
data = {}

data['struct_name'] = struct_name
data['member_name'] = member_name
data['offset'] = hex(offset)

if size is not None and size > 0:
    data['size'] = size

if offset_sig is not None:
    data['offset_sig'] = offset_sig

if offset_sig_disp is not None and offset_sig_disp > 0:
    data['offset_sig_disp'] = offset_sig_disp

yaml_path = os.path.join(dir_path, f"{artifact_name}.{platform}.yaml")
with open(yaml_path, 'w', encoding='utf-8') as f:
    yaml.dump(data, f, default_flow_style=False, sort_keys=False, allow_unicode=True)
print(f"Written to: {yaml_path}")
"""