dt_proc.c

来自「Sun Solaris 10 中的 DTrace 组件的源代码。请参看: htt」· C语言 代码 · 共 1,011 行 · 第 1/3 页

	/*
	 * While we are waiting for the victim to run, clear PR_KLC and PR_RLC
	 * so that if the libdtrace client is killed, the victim stays stopped.
	 * dt_proc_destroy() will also observe this and perform PRELEASE_HANG.
	 */
	(void) Punsetflags(P, krflag);
	Psync(P);

	(void) pthread_mutex_unlock(&dpr->dpr_lock);

	while (!dpr->dpr_quit) {
		if (write(pfd, &wstop, sizeof (wstop)) == -1 && errno == EINTR)
			continue; /* check dpr_quit and continue waiting */

		(void) pthread_mutex_lock(&dpr->dpr_lock);
		(void) Pstopstatus(P, PCNULL, 0);
		psp = &Pstatus(P)->pr_lwp;

		/*
		 * If we've reached a new state, found a new representative, or
		 * the stop timestamp has changed, restore PR_KLC/PR_RLC to its
		 * original setting and then return with dpr_lock held.
		 */
		if (Pstate(P) != PS_STOP || psp->pr_lwpid != lwpid ||
		    bcmp(&psp->pr_tstamp, &tstamp, sizeof (tstamp)) != 0) {
			(void) Psetflags(P, krflag);
			Psync(P);
			return;
		}

		(void) pthread_mutex_unlock(&dpr->dpr_lock);
		(void) poll(NULL, 0, MILLISEC / 2);
	}

	(void) pthread_mutex_lock(&dpr->dpr_lock);
}

/*
 * Main loop for all victim process control threads.  We initialize all the
 * appropriate /proc control mechanisms, and then enter a loop waiting for
 * the process to stop on an event or die.  We process any events by calling
 * appropriate subroutines, and exit when the victim dies or we lose control.
 *
 * The control thread synchronizes the use of dpr_proc with other libdtrace
 * threads using dpr_lock.  We hold the lock for all of our operations except
 * waiting while the process is running: this is accomplished by writing a
 * PCWSTOP directive directly to the underlying /proc/<pid>/ctl file.  If the
 * libdtrace client wishes to exit or abort our wait, SIGCANCEL can be used.
 */
static void *
dt_proc_control(void *arg)
{
	dt_proc_t *dpr = arg;
	dt_proc_hash_t *dph = dpr->dpr_hdl->dt_procs;
	struct ps_prochandle *P = dpr->dpr_proc;

	int pfd = Pctlfd(P);
	int pid = dpr->dpr_pid;

	const long wstop = PCWSTOP;
	int notify = B_FALSE;

	/*
	 * We disable the POSIX thread cancellation mechanism so that the
	 * client program using libdtrace can't accidentally cancel our thread.
	 * dt_proc_destroy() uses SIGCANCEL explicitly to simply poke us out
	 * of PCWSTOP with EINTR, at which point we will see dpr_quit and exit.
	 */
	(void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);

	/*
	 * Set up the corresponding process for tracing by libdtrace.  We want
	 * to be able to catch breakpoints and efficiently single-step over
	 * them, and we need to enable librtld_db to watch libdl activity.
	 */
	(void) pthread_mutex_lock(&dpr->dpr_lock);

	(void) Punsetflags(P, PR_ASYNC);	/* require synchronous mode */
	(void) Psetflags(P, PR_BPTADJ);		/* always adjust eip on x86 */
	(void) Punsetflags(P, PR_FORK);		/* do not inherit on fork */

	(void) Pfault(P, FLTBPT, B_TRUE);	/* always trace breakpoints */
	(void) Pfault(P, FLTTRACE, B_TRUE);	/* always trace single-step */

	/*
	 * We must trace exit from exec() system calls so that if the exec is
	 * successful, we can reset our breakpoints and re-initialize libproc.
	 */
	(void) Psysexit(P, SYS_exec, B_TRUE);
	(void) Psysexit(P, SYS_execve, B_TRUE);

	/*
	 * We must trace entry and exit for fork() system calls in order to
	 * disable our breakpoints temporarily during the fork.  We do not set
	 * the PR_FORK flag, so if fork succeeds the child begins executing and
	 * does not inherit any other tracing behaviors or a control thread.
	 */
	(void) Psysentry(P, SYS_vfork, B_TRUE);
	(void) Psysexit(P, SYS_vfork, B_TRUE);
	(void) Psysentry(P, SYS_fork1, B_TRUE);
	(void) Psysexit(P, SYS_fork1, B_TRUE);
	(void) Psysentry(P, SYS_forkall, B_TRUE);
	(void) Psysexit(P, SYS_forkall, B_TRUE);

	Psync(P);				/* enable all /proc changes */
	dt_proc_attach(dpr, B_FALSE);		/* enable rtld breakpoints */

	/*
	 * If PR_KLC is set, we created the process; otherwise we grabbed it.
	 * Check for an appropriate stop request and wait for dt_proc_continue.
	 */
	if (Pstatus(P)->pr_flags & PR_KLC)
		dt_proc_stop(dpr, DT_PROC_STOP_CREATE);
	else
		dt_proc_stop(dpr, DT_PROC_STOP_GRAB);

	if (Psetrun(P, 0, 0) == -1) {
		dt_dprintf("pid %d: failed to set running: %s\n",
		    (int)dpr->dpr_pid, strerror(errno));
	}

	(void) pthread_mutex_unlock(&dpr->dpr_lock);

	/*
	 * Wait for the process corresponding to this control thread to stop,
	 * process the event, and then set it running again.  We want to sleep
	 * with dpr_lock *unheld* so that other parts of libdtrace can use the
	 * ps_prochandle in the meantime (e.g. ustack()).  To do this, we write
	 * a PCWSTOP directive directly to the underlying /proc/<pid>/ctl file.
	 * Once the process stops, we wake up, grab dpr_lock, and then call
	 * Pwait() (which will return immediately) and do our processing.
	 */
	while (!dpr->dpr_quit) {
		const lwpstatus_t *psp;

		if (write(pfd, &wstop, sizeof (wstop)) == -1 && errno == EINTR)
			continue; /* check dpr_quit and continue waiting */

		(void) pthread_mutex_lock(&dpr->dpr_lock);
pwait_locked:
		if (Pstopstatus(P, PCNULL, 0) == -1 && errno == EINTR) {
			(void) pthread_mutex_unlock(&dpr->dpr_lock);
			continue; /* check dpr_quit and continue waiting */
		}

		switch (Pstate(P)) {
		case PS_STOP:
			psp = &Pstatus(P)->pr_lwp;

			dt_dprintf("pid %d: proc stopped showing %d/%d\n",
			    pid, psp->pr_why, psp->pr_what);

			/*
			 * If the process stops showing PR_REQUESTED, then the
			 * DTrace stop() action was applied to it or another
			 * debugging utility (e.g. pstop(1)) asked it to stop.
			 * In either case, the user's intention is for the
			 * process to remain stopped until another external
			 * mechanism (e.g. prun(1)) is applied.  So instead of
			 * setting the process running ourself, we wait for
			 * someone else to do so.  Once that happens, we return
			 * to our normal loop waiting for an event of interest.
			 */
			if (psp->pr_why == PR_REQUESTED) {
				dt_proc_waitrun(dpr);
				(void) pthread_mutex_unlock(&dpr->dpr_lock);
				continue;
			}

			/*
			 * If the process stops showing one of the events that
			 * we are tracing, perform the appropriate response.
			 * Note that we ignore PR_SUSPENDED, PR_CHECKPOINT, and
			 * PR_JOBCONTROL by design: if one of these conditions
			 * occurs, we will fall through to Psetrun() but the
			 * process will remain stopped in the kernel by the
			 * corresponding mechanism (e.g. job control stop).
			 */
			if (psp->pr_why == PR_FAULTED && psp->pr_what == FLTBPT)
				dt_proc_bpmatch(dpr);
			else if (psp->pr_why == PR_SYSENTRY &&
			    IS_SYS_FORK(psp->pr_what))
				dt_proc_bpdisable(dpr);
			else if (psp->pr_why == PR_SYSEXIT &&
			    IS_SYS_FORK(psp->pr_what))
				dt_proc_bpenable(dpr);
			else if (psp->pr_why == PR_SYSEXIT &&
			    IS_SYS_EXEC(psp->pr_what))
				dt_proc_attach(dpr, B_TRUE);
			break;

		case PS_LOST:
			if (Preopen(P) == 0)
				goto pwait_locked;

			dt_dprintf("pid %d: proc lost: %s\n",
			    pid, strerror(errno));

			dpr->dpr_quit = B_TRUE;
			notify = B_TRUE;
			break;

		case PS_UNDEAD:
			dt_dprintf("pid %d: proc died\n", pid);
			dpr->dpr_quit = B_TRUE;
			notify = B_TRUE;
			break;
		}

		if (Pstate(P) != PS_UNDEAD && Psetrun(P, 0, 0) == -1) {
			dt_dprintf("pid %d: failed to set running: %s\n",
			    (int)dpr->dpr_pid, strerror(errno));
		}

		(void) pthread_mutex_unlock(&dpr->dpr_lock);
	}

	/*
	 * If the control thread detected PS_UNDEAD or PS_LOST, then enqueue
	 * the dt_proc_t structure on the dt_proc_hash_t notification list.
	 */
	if (notify) {
		(void) pthread_mutex_lock(&dph->dph_lock);

		dpr->dpr_notify = dph->dph_notify;
		dph->dph_notify = dpr;

		(void) pthread_mutex_unlock(&dph->dph_lock);
		(void) pthread_cond_broadcast(&dph->dph_cv);
	}

	/*
	 * Destroy and remove any remaining breakpoints, set dpr_done and clear
	 * dpr_tid to indicate the control thread has exited, and notify any
	 * waiting thread in dt_proc_destroy() that we have succesfully exited.
	 */
	(void) pthread_mutex_lock(&dpr->dpr_lock);

	dt_proc_bpdestroy(dpr, B_TRUE);
	dpr->dpr_done = B_TRUE;
	dpr->dpr_tid = 0;

	(void) pthread_mutex_unlock(&dpr->dpr_lock);
	(void) pthread_cond_broadcast(&dpr->dpr_cv);

	return (NULL);
}

/*PRINTFLIKE3*/
static struct ps_prochandle *
dt_proc_error(dtrace_hdl_t *dtp, dt_proc_t *dpr, const char *format, ...)
{
	va_list ap;

	va_start(ap, format);
	dt_set_errmsg(dtp, NULL, NULL, NULL, 0, format, ap);
	va_end(ap);

	if (dpr->dpr_proc != NULL)
		Prelease(dpr->dpr_proc, 0);

	dt_free(dtp, dpr);
	(void) dt_set_errno(dtp, EDT_COMPILER);
	return (NULL);
}

dt_proc_t *
dt_proc_lookup(dtrace_hdl_t *dtp, struct ps_prochandle *P, int remove)
{
	dt_proc_hash_t *dph = dtp->dt_procs;
	pid_t pid = Pstatus(P)->pr_pid;
	dt_proc_t *dpr, **dpp = &dph->dph_hash[pid & (dph->dph_hashlen - 1)];

	for (dpr = *dpp; dpr != NULL; dpr = dpr->dpr_hash) {
		if (dpr->dpr_pid == pid)
			break;
		else
			dpp = &dpr->dpr_hash;
	}

	assert(dpr != NULL);
	assert(dpr->dpr_proc == P);

	if (remove)
		*dpp = dpr->dpr_hash; /* remove from pid hash chain */

	return (dpr);
}

static void
dt_proc_destroy(dtrace_hdl_t *dtp, struct ps_prochandle *P)
{
	dt_proc_t *dpr = dt_proc_lookup(dtp, P, B_TRUE);
	dt_proc_hash_t *dph = dtp->dt_procs;
	dt_proc_t *npr, **npp;
	int rflag;

	assert(dpr != NULL);

	/*
	 * If neither PR_KLC nor PR_RLC is set, then the process is stopped by
	 * an external debugger and we were waiting in dt_proc_waitrun().
	 * Leave the process in this condition using PRELEASE_HANG.
	 */
	if (!(Pstatus(dpr->dpr_proc)->pr_flags & (PR_KLC | PR_RLC))) {
		dt_dprintf("abandoning pid %d\n", (int)dpr->dpr_pid);
		rflag = PRELEASE_HANG;
	} else {
		dt_dprintf("releasing pid %d\n", (int)dpr->dpr_pid);
		rflag = 0; /* apply kill or run-on-last-close */
	}

	if (dpr->dpr_tid) {
		/*
		 * Set the dpr_quit flag to tell the daemon thread to exit.  We
		 * send it a SIGCANCEL to poke it out of PCWSTOP or any other
		 * long-term /proc system call.  Our daemon threads have POSIX
		 * cancellation disabled, so EINTR will be the only effect.  We
		 * then wait for dpr_done to indicate the thread has exited.
		 */
		(void) pthread_mutex_lock(&dpr->dpr_lock);
		dpr->dpr_quit = B_TRUE;
		(void) pthread_kill(dpr->dpr_tid, SIGCANCEL);

		while (!dpr->dpr_done)
			(void) pthread_cond_wait(&dpr->dpr_cv, &dpr->dpr_lock);

		(void) pthread_mutex_unlock(&dpr->dpr_lock);
	}

	/*
	 * Before we free the process structure, walk the dt_proc_hash_t's
	 * notification list and remove this dt_proc_t if it is enqueued.
	 */
	(void) pthread_mutex_lock(&dph->dph_lock);
	npp = &dph->dph_notify;