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From: kashtan@sri-iu.UUCP (David L. Kashtan)
Newsgroups: net.eunice
Subject: RE: Reading the IP/TCP routing tables from memory
Message-ID: <14@sri-iu.UUCP>
Date: Wed, 21-Nov-84 03:20:30 EST
Article-I.D.: sri-iu.14
Posted: Wed Nov 21 03:20:30 1984
Date-Received: Fri, 23-Nov-84 03:02:33 EST
Organization: S.R.I. International, Menlo Park, CA
Lines: 90

Under EUNICE, nlist() will indeed read the ETC:INET.STB symbol table.
Since the network data structures in the kernel may contain sensitive
information, they are specifically kept KERNEL-MODE access only.  The
following routines implement klseek()/klread() which act like lseek/read
on /dev/kmem.
David


/*
 *	/dev/kmem seek/read
 */

static char *current_addr = 0;	/* Our current Seek address */

klseek(dummy,addr,whence)
char *addr;
{
	current_addr = addr;	/* Just stash the desired address */
}

static char *klread_buffer;	/* User buffer to read into */
static int   klread_size;	/* User buffer size	    */

klread(dummy,buffer,size)
char *buffer;
{
	extern klread_krnl();

	/*
	 *	Fill in arguments to the kernel mode code
	 */
	klread_buffer = buffer;
	klread_size = size;
	/*
	 *	Fetch the kernel data in kernel mode
	 */
	sys$cmkrnl(klread_krnl,0);
	/*
	 *	Return the given size (just to be consistent with read)
	 */
	return(size);
}

/*
 *	This is executed in kernel mode
 *	(since network data structures are protected from casual user access)
 */
static klread_krnl()
{
	register char *cp,*cp1;
	register int i;

	cp1 = klread_buffer;
	cp  = current_addr;
	i = klread_size;
	while(i > 0) {
		if (kl_prober(cp)) *cp1++ = *cp++;
		current_addr++;
		i--;
	}
	return;
}

static kl_prober(cp)
{

	/*
	 *	Change our previous mode to KERNEL so that the probe
	 *	will check for kernel read access -- construct a new
	 *	PSL/PC on the stack and REI to it
	 */
	asm("	clrl	-(sp)");
	asm("	movab	1f,-(sp)");
	asm("	rei");
	/*
	 *	Now check for read access
	 */
	asm("1:	prober	$0,$4,*4(ap)");
	asm("	bneq	2f");
	asm("	clrl	r0");
	asm("	ret");
	asm("2:	movl	$1,r0");
	asm("	ret");
}


-- 
David Kashtan, Artificial Intelligence Center, SRI International
ARPA: Kashtan@SRI-IU or Kashtan@SRI-AI
UUCP: {lbl-csam, sri-unix, cmcl2} !sri-iu!kashtan