ISC Unix 2.2 nlist Help/Where's adb?

[Conor P. Cahill]

In article <49 at sgtech.UUCP> adnan at sgtech.uucp (Adnan Yaqub) writes:
>I am trying to write a program which reads values from /dev/kmem.  The
>program works great except when I try to lseek to the value returned

This should work without any problems.  I have attached a sample program
that can be used to modify a kernel value. (I use this to change the
NFS variable nobody to 0 so that root users on other systems in our
network get root privileges on thier NFS mounted file systems)

>On a related topic, what happened to adb?  It didn't seem to come with
>ISC Unix 2.2.

adb has been gone from AT&T unix since SVR2 although some vendors still
supply it (they do the porting/maintenance themselves).  sdb is the
supported debugger (and 2.2 comes with codewatch, although I don't know
how well that works since I haven't tried it).


X#include <sys/types.h>
X#include <nlist.h>
X#include <fcntl.h>
X#include <stdio.h>
X
Xmain(argc,argv)
X	int		  argc;
X	char		* argv[];
X{
X	int		  err;
X	char		* kernelfile = "/dev/kmem";
X	int		  kfd;
X	struct nlist	  nl;
X	int		  oflags;
X	long		  oldvalue;
X	int		  setval;
X	char		* unixfileptr = "/unix";
X	long		  value;
X
X	if( (argc != 2) && (argc != 3) )
X	{
X		fprintf(stderr,"Usage: %s symbol [value]\n",argv[0]);
X		exit(10);
X	}
X
X	nl.n_name = argv[1];
X	if( argc == 3 )
X	{
X		value = atoi(argv[2]);
X		setval = 1;
X		oflags = O_RDWR;
X	}
X	else
X	{
X		setval = 0;
X		oflags = O_RDONLY;
X	}
X
X	err = nlist(unixfileptr,&nl);
X
X	if( (err == -1) || (nl.n_value == 0) )
X	{
X		fprintf(stderr,"Unable to find symbol '%s' in '%s'\n",
X				nl.n_name, unixfileptr);
X		exit(10);
X	}
X
X	if( (kfd=open(kernelfile,oflags)) == -1)
X	{
X		fprintf(stderr,"Unable to open '%s'\n", kernelfile);
X		exit(40);
X	}
X
X	if( lseek(kfd,nl.n_value,0) != nl.n_value)
X	{
X		fprintf(stderr,"Unable to seek to %s's location\n",nl.n_name);
X		exit(50);
X	}
X
X	if( read(kfd,(char *) &oldvalue,sizeof(long)) != sizeof(long))
X	{
X		fprintf(stderr,"Unable to read %s's data\n",nl.n_name);
X		exit(60);
X	}
X
X	if( ! setval )
X	{
X		fprintf(stdout,"value of %s is %ld\n", nl.n_name, oldvalue);
X		exit(0);
X	}
X
X	/* 
X	 * Now go change the value to be what we want it to be...
X	 */
X
X	if( lseek(kfd,nl.n_value,0) != nl.n_value)
X	{
X		fprintf(stderr,"Unable to seek to %s's location\n",nl.n_name);
X		exit(70);
X	}
X
X	if( write(kfd,(char *) &value,sizeof(long)) != sizeof(long))
X	{
X		fprintf(stderr,"Unable to change %s's data\n",nl.n_name);
X		exit(80);
X	}
X
X	fprintf(stdout,"Value of %s changed from %ld to %ld\n",
X			nl.n_name, oldvalue, value);
X	exit(0);
X}
-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170