System Call

From: Koushik Chakraborty (
Date: Sat Jan 29 2000 - 04:06:11 EST

  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

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 Chakraborty
 Senior Undergraduate,
 Dept. of Computer Science and Engineering.
 Indian Institute of Technology,Kanpur
 Contact Address :- E-mail :

  Room no. A111, Hall - 1
  IIT Kanpur,
  Pin 208016.


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