find-cbaseentity-collisionruleschanged

name	find-CBaseEntity_CollisionRulesChanged
description	Find and identify the CBaseEntity_CollisionRulesChanged virtual function in CS2 binary using IDA Pro MCP. Use this skill when reverse engineering CS2 server.dll or server.so to locate the CollisionRulesChanged function by first finding CBaseEntity_SetOwner and extracting the very last virtual call offset from its decompiled code.

Find CBaseEntity_CollisionRulesChanged

Locate CBaseEntity_CollisionRulesChanged in CS2 server.dll or server.so using IDA Pro MCP tools.

Method

1. Get CBaseEntity_SetOwner Function Info

ALWAYS Use SKILL /get-func-from-yaml with func_name=CBaseEntity_SetOwner.

If the skill returns an error, stop and report to user.

Otherwise, extract func_va for the next step.

2. Decompile CBaseEntity_SetOwner and Extract VTable Offset

Decompile CBaseEntity_SetOwner using func_va from step 1:

mcp__ida-pro-mcp__decompile addr="<func_va>"

Look for the very last virtual call in the decompiled code:

__int64 __fastcall CBaseEntity_SetOwner(__int64 a1, _QWORD *a2)
{

//at the end of the function body, there is a very last virtual call - CBaseEntity_CollisionRulesChanged
  (*(void (__fastcall **)(_DWORD *))(*(_QWORD *)a1 + 1480LL))(a1);

Extract the vtable offset from this last virtual call (e.g., 1480). This is the CBaseEntity_CollisionRulesChanged vtable offset.

Calculate:

• VTable Offset: The value from the pattern (e.g., 1480 = 0x5C8)
• VTable Index: offset / 8 (e.g., 1480 / 8 = 185)

Also note the inst_addr — the address of this virtual call instruction (shown as a comment like /*0x180c0c3b4*/ in the decompiled output).

3. Generate vfunc offset signature for CBaseEntity_CollisionRulesChanged

ALWAYS Use SKILL /generate-signature-for-vfuncoffset to generate a robust and unique signature for CBaseEntity_CollisionRulesChanged, with inst_addr and vfunc_offset from step 2.

4. Write Analysis Results as YAML

ALWAYS Use SKILL /write-vfunc-as-yaml to write the analysis results for CBaseEntity_CollisionRulesChanged.

Required parameters:

• func_name: CBaseEntity_CollisionRulesChanged
• func_addr: None (this is a virtual call target, not a directly resolved function)
• func_sig: None
• vfunc_sig: <vfunc_sig> from step 3

VTable parameters:

• vtable_name: CBaseEntity
• vfunc_index: The vtable index from step 2 (e.g., 185)
• vfunc_offset: The vtable offset from step 2 (e.g., 0x5C8)

VTable Information

• VTable Name: CBaseEntity::vftable'`
• VTable Mangled Name (Windows): ??_7CBaseEntity@@6B@
• VTable Mangled Name (Linux): _ZTV11CBaseEntity
• VTable Index: 185 - This can change when game updates.
• VTable Offset: 0x5C8 (185 * 8 = 1480) - This can change when game updates.

• Note that for server.so, the first 16 bytes of "vftable" are for RTTI. The real vftable = _ZTV11CBaseEntity + 0x10.

Output YAML Format

The output YAML filename depends on the platform:

• server.dll → CBaseEntity_CollisionRulesChanged.windows.yaml
• server.so → CBaseEntity_CollisionRulesChanged.linux.yaml

func_name: CBaseEntity_CollisionRulesChanged
vfunc_sig: FF 90 C8 05 00 00 48 8B 5C 24 ?? 48 8B 74 24 ?? 48 8B 7C 24 ?? 48 83 C4 ?? 41 5E C3 48 89 5C 24 ??
vtable_name: CBaseEntity
vfunc_offset: 0x5c8
vfunc_index: 185

DLL Information

• DLL: server.dll (Windows) / server.so (Linux)

Notes

• CBaseEntity_CollisionRulesChanged is a virtual function called as the very last operation inside CBaseEntity_SetOwner. When the owner entity changes, this function is invoked to notify the collision system that collision rules need to be re-evaluated.
• The function is identified indirectly through the virtual call in CBaseEntity_SetOwner, so func_va, func_rva, func_size, and func_sig are not included in the YAML output.
• The vfunc_sig captures the virtual call instruction pattern including the displacement bytes for the vtable offset.