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From: bridej@prism.CS.ORST.EDU (Jim Bride)
Newsgroups: comp.unix.internals,comp.unix.wizards
Subject: Help getting pointer to a u structure of a process
Keywords: process, user structure
Message-ID: <1991Mar06.203225.20019@lynx.CS.ORST.EDU>
Date: 6 Mar 91 20:32:25 GMT
Sender: @lynx.CS.ORST.EDU
Reply-To: bridej@prism.CS.ORST.EDU (Jim Bride)
Organization: Oregon State Univ. -- Computer Science
Lines: 27
Nntp-Posting-Host: prism.cs.orst.edu


Hi.  I am working on a program which requires me to be able to access the 
u (user) structure of a process OTHER than the process which is currently 
running.  After reading over several thousand lines of source code I can't
find out how to get a pointer to the other process' user structure.  I think
it involves translating the pointer inside the proc structure (p->p_addr) that
points to the PTEs for the user structure into an address (which I can then
cast to a (struct user *)).  My program is running as a system call and I have
been able to access the proc structure for the process I need to modify (via a
call to pfind()), but I need to change a few things in the user structure of 
the process as well.  Does anyone know of a way (preferably in C, but I would
be willing to resort to assembler if I have to) that I can translate the
p_addr pointer to a usable address that I can use to access the u structure or
another method that I can the the address of the u structure of this other
process?  Any help you could offer would be greatly appreciated.

BTW, I am using a HP 9000 series 300 CPU running 4.3BSD Utah.

Thanks!

Jim


-------------------------------------------------------------------------
Jim Bride - Networking | Internet:   bridej@CS.ORST.EDU                  
Computer Science Dept. | UUCP:       hplabs!hp-pcd!orstcs!bridej         
Oregon State University| Phone:      737-6178