Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!gatech!gitpyr!stat!curci
From: curci@stat.uucp (Ray Curci (scri))
Newsgroups: comp.os.minix
Subject: Re: Passing pointers using callm1() (sendrec())
Message-ID: <7588@pyr.gatech.EDU>
Date: 14 Mar 89 15:41:29 GMT
References: <7575@pyr.gatech.EDU>
Sender: news@pyr.gatech.EDU
Reply-To: curci@stat.fsu.edu (Ray Curci (scri))
Organization: Dept. of Statistics, Florida State Univ.
Lines: 25

In article <7575@pyr.gatech.EDU> curci@stat.fsu.edu (Ray Curci (scri)) writes:
>I have written a minix device driver that sends packets of data between
>minix machines.  The send and receive routines attempt to pass a pointer
>to a buffer using M.m1_p1.  The problem is that when the device driver
>receives the message, the pointer appears to be relative to the caller's
>data or stack segment.  To get at the buffer of data I have tried using
>many combinations of proc_addr(), umap(), and phys_copy() without success.
>Can anyone send me a simple example of how to do this?  For starters, I
>am simply trying to have my task copy the user's buffer into my own
>local buffer.  I will post a summary of responses to the newsgroup.
>ray curci
>curci@stat.fsu.edu

After spending all night until 5am experimenting, I have found the answer
to my own question.  Assuming my process is called TRANSPORT and I have
received the message in msg with a pointer to a 128 byte buffer in m1_p1:

         static unsigned char localbuf[128];
         phys_bytes src, dest, umap();
         src = umap(proc_addr(msg.m_source),D,(vir_bytes)msg.m1_p1,128);
         dest= umap(proc_addr(TRANSPORT),D,(vir_bytes)localbuf,128);
         if (src != (phys_bytes)0)
			phys_copy(src,dest,(phys_bytes)128);

curci@stat.fsu.edu