[kadet.89]

I'm trying to implement a global hook for TakeDamage:
https://wiki.alliedmods.net/SourceHook_Development

And I can't understand what is player_vtable?
I have the address of this function and the offset. What shall I pass to the SH_ADD_MANUALDVPHOOK macro ?

[donrevan]

You've 2 options as explained in the wiki:

With this understanding in place, there are two separate syntaxes - one for simple hooks and one for manual hooks. Additionally, there are two ways of declaring the virtual interface to use: An instance of the class can be passed. (SH_ADD_VPHOOK) The direct address to the virtual table can be passed. (SH_ADD_DVPHOOK) They are essentially equivalent, although one may be more advantageous than the other (for example, if no instances are known, but the vtable address can be extracted via pattern searching).

a) look for the vtable in the executable(that big table with all the virtual functions), sigscan references to it
--> use SH_ADD_DVPHOOK

b) get vtable from object
-> just use SH_ADD_VPHOOK on the object
-> code for reference(should work for msvc; not sure about gcc):

void *pObject = ...;
void *pVTable = *reinterpret_cast<void**>(pObject);

manual hooks should be straightforward..

[kadet.89]

I don't quite understand what you mean.
There are a lot of vtables in the server_srv.so
If I pass a reference (008CC960) to `vtable for'CCSPlayer, for which I want to hook this function, how then the extension will find out which function it should hook from this table?
Is there a workable example with SH_ADD_DVPHOOK? I can't find any in the sourcemod sdk

[donrevan]

I've never used a global hook but according to the wiki you just need to pass the vtable pointer to SH_ADD_DVPHOOK(same applies for a manual dvphook) ...

SH_ADD_DVPHOOK(Interface, Function, VirtualTable, Handler, Post)

The vtable for CCSPlayer is, as you pointed out, at 008CC960(+8).. the problem is that the binary where the vtable is located will (probably) be rebased to a different address next time you start the server thus 008CC960 will be no longer valid. What to do? sigscan references it!

Example of a (bad) sig for CCSPlayer's vtable for csgo server.so(check attached pic):

2C 8B 5D 08 8B B3 ? ? ? ? C7 03
Offset: 12

pseudocode(using manual hooks):

PHP Code:

SH_DECL_MANUALHOOK1_void(MHook_TakeDamage, ....);
//---------------
SH_MANUALHOOK_RECONFIGURE with the correct offset to the func you want to hook BEFORE SH_ADDing it
//---------------
pGameConf->GetMemSig("CCSPlayerVTable", vtable);
pGameConf->GetOffset("CCSPlayerVTableOffs", offsToVTable);

vtable = *reinterpret_cast<void**>(vtable + offsToVTable);

SH_ADD_MANUALDVPHOOK(MHook_TakeDamage, vtable, SH_STATIC(Hook_TakeDamage), false); 


EDIT:
Instead of using a byte signature on linux(wtf) you should use symbols

[psychonic]

As mentioned a few posts above, it would be easier to use a vphook, rather than dvphook. You would only need a CCSPlayer instance, which you could get upon first player connect.

[kadet.89]

If I use vphook, than when I load my extension, it must find all the players and make hooks for each of them, and when I reload the extension, I have to do it to. When I unload my extension, will it unhook all the hooks automatically, or I will have to find somehow all the hooks and unhook them manually?

I've hooked SetModel, it works, but how can I replace the modelname param:

PHP Code:

SH_DECL_MANUALHOOK1_void(SetModelHook, 0, 0, 0, const char *);

char *modelname = "models/player/ct_gsg9.mdl";
void STools::SetModel( const char *pModelName ) {
    
    g_pSM->LogMessage(myself, "SetModel%s", pModelName);
    RETURN_META_MNEWPARAMS(MRES_SUPERCEDE, SetModelHook, (modelname)); //Doesn't work
}


SH_ADD_MANUALHOOK_MEMFUNC(SetModelHook, Ent, &g_interface, &STools::SetModel, true); 
SH_MANUALHOOK_RECONFIGURE(SetModelHook, Offset, 0, 0); 


[donrevan]

1. Implement IClientListener

PHP Code:

virtual void OnClientPutInServer(int client);
virtual void OnClientDisconnecting(int client); 


2. Add your extension as a IClientListener:

PHP Code:

playerhelpers->AddClientListener(&g_interface); 


3. Reconfigure manual hook to correct offset
4. When a player connects for the first time -> create hook

PHP Code:

void Sample::SetModelHook(const char *model)
{
   g_pSM->LogMessage(..);
   RETURN_META_MNEWPARAMS(..);
}

void Sample::OnClientPutInServer(int client)
{
   if(g_bIsHooked)
     return; // return if already hooked

   CBaseEntity *pEntity = gamehelpers->ReferenceToEntity(client);
   int hook_id = SH_ADD_MANUALVPHOOK(SetModelHook, pEntity, SH_MEMBER(&g_interface, &Sample::SetModelHook), false); //remember hook_id to remove it later
   g_bIsHooked = true;
} 


You only need to unhook on extension unload via SH_REMOVE_HOOK_ID
sdkhooks is using vphooks if you need a working example.

[kadet.89]

Thanks for the explanation.
What shall I use instead of RETURN_META_MNEWPARAMS to replace the modelname value?

[donrevan]

RETURN_META_MNEWPARAMS should work just make sure you use a prehook.

[psychonic]

Originally Posted by kadet.89 If I use vphook, than when I load my extension, it must find all the players and make hooks for each of them

No, the whole point of a (d)vp hook is that the hook fires for any instance. There is only one CCSPlayer vtable shared by all of the players. You only need to hook the vtable once, and can just do it for the first player that you see or that connects.