System Call

[Koushik Chakraborty]

Hi,
  I am trying to build a new system call which needs to perform a 'read'
on a TCP socket. Now when we call read , the system call goes through
sock_read,sock_recvmsg etc .. through to tcp_recvmsg where the data is
actually copied in another function called by tcp_recvmsg ..
memcpy_toiovec. However, in this special case I need the "memcpy_toiovec"
to perform in a slightly different manner. However, all along these calls
no actor is taken as argument so tcp_recvmsg will always call
memcpy_toiovec. I tried to pass a negative "count" paramter during calling
read .. however, this gets mapped to 0 in sock_read and the call returns
0. 

I would like to if there is anyway I can detect when memcpy_iovec is
called that it is coming as a consequence of my system call so that I can
process the data in a different manner ? I don't want to change the
prototype of all the function in between as that would be extremely messy.

Thanks in Advance,
Koushik.

***********************************************************************
 Koushik Chakraborty                                
 Senior Undergraduate,                          
 Dept. of Computer Science and Engineering.   
 Indian Institute of Technology,Kanpur        
 India.    
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