Reading the symbol table of the currently running executable

[David Goodenough]

bcn at cs.washington.edu (Clifford Neuman) asks:
> Does anyone know how to read the symbol table of a program from within
> that program itself?  More precisely, from within a procedure in a
> library which was used in linking the executable.  The simplest way is
> to read the symbol table from the executable.  Unfortunately, I might
> not know the name of the executable.  I can solve my problem in any of
> several ways, and I would appreciate suggested solutions to any of
> these problems.

This is fairly grotesque, but it might just work:

	int cpid;
	char pidbuf[10];

	sprintf(pidbuf, "%d", getpid());
	if ((cpid = vfork()) == -1)
	 {
	    bitch and complain - the fork failed
	 }
	else if (cpid == 0)
	 {
	    /* child thread */
	    sleep(1)		/* snooze a while to make sure parent is
				 * in the wait */
	    execl("/usr/ucb/gcore", "gcore", pidbuf, 0);
	    bitch and complain - the execl failed
	 }
	else
	  wait(0);		/* wait for child to do it's bit */

	/* now you have a core image in file core.pidbuf. Take nm to it,
	 * open it and do nlist on it, whatever */

It does assume you have gcore, which living in /usr/ucb may be a beserkley
enhancement. Still, it is possible to achieve the equivalent by opening
/dev/mem (you can set this to run effective uid 0 right :-) ), seeking
and reading, it's just a bit of an art to know where to go, and how much
to grab.
-- 
	dg at lakart.UUCP - David Goodenough		+---+
						IHS	| +-+-+
	....... !harvard!xait!lakart!dg			+-+-+ |
AKA:	dg%lakart.uucp at xait.xerox.com			  +---+