The si_status field of the siginfo_t, provided by the waitid(2) and

SIGCHLD signal, should keep full 32 bits of the status passed to the
_exit(2).

Split the combined p_xstat of the struct proc into the separate exit
status p_xexit for normal process exit, and signalled termination
information p_xsig.  Kernel-visible macro KW_EXITCODE() reconstructs
old p_xstat from p_xexit and p_xsig.  p_xexit contains complete status
and copied out into si_status.

Requested by:	Joerg Schilling
Reviewed by:	jilles (previous version), pho
Tested by:	pho
Sponsored by:	The FreeBSD Foundation

1 files changed, 28 insertions, 24 deletions

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index 8fe968e..3310d1d 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -175,7 +175,7 @@ void
 sys_sys_exit(struct thread *td, struct sys_exit_args *uap)
 {
 
-	exit1(td, W_EXITCODE(uap->rval, 0));
+	exit1(td, uap->rval, 0);
 	/* NOTREACHED */
 }
 
@@ -185,13 +185,14 @@ sys_sys_exit(struct thread *td, struct sys_exit_args *uap)
  * and rusage for wait().  Check for child processes and orphan them.
  */
 void
-exit1(struct thread *td, int rv)
+exit1(struct thread *td, int rval, int signo)
 {
 	struct proc *p, *nq, *q, *t;
 	struct thread *tdt;
 	struct vnode *ttyvp = NULL;
 
 	mtx_assert(&Giant, MA_NOTOWNED);
+	KASSERT(rval == 0 || signo == 0, ("exit1 rv %d sig %d", rval, signo));
 
 	p = td->td_proc;
 	/*
@@ -200,8 +201,7 @@ exit1(struct thread *td, int rv)
 	 * shutdown on sparc64 when the gmirror worker process exists.
 	 */
 	if (p == initproc && rebooting == 0) {
-		printf("init died (signal %d, exit %d)\n",
-		    WTERMSIG(rv), WEXITSTATUS(rv));
+		printf("init died (signal %d, exit %d)\n", signo, rval);
 		panic("Going nowhere without my init!");
 	}
 
@@ -257,6 +257,11 @@ exit1(struct thread *td, int rv)
 	KASSERT(p->p_numthreads == 1,
 	    ("exit1: proc %p exiting with %d threads", p, p->p_numthreads));
 	racct_sub(p, RACCT_NTHR, 1);
+
+	/* Let event handler change exit status */
+	p->p_xexit = rval;
+	p->p_xsig = signo;
+
 	/*
 	 * Wakeup anyone in procfs' PIOCWAIT.  They should have a hold
 	 * on our vmspace, so we should block below until they have
@@ -264,7 +269,7 @@ exit1(struct thread *td, int rv)
 	 * requested S_EXIT stops we will block here until they ack
 	 * via PIOCCONT.
 	 */
-	_STOPEVENT(p, S_EXIT, rv);
+	_STOPEVENT(p, S_EXIT, 0);
 
 	/*
 	 * Ignore any pending request to stop due to a stop signal.
@@ -289,7 +294,6 @@ exit1(struct thread *td, int rv)
 	while (p->p_lock > 0)
 		msleep(&p->p_lock, &p->p_mtx, PWAIT, "exithold", 0);
 
-	p->p_xstat = rv;	/* Let event handler change exit status */
 	PROC_UNLOCK(p);
 	/* Drain the limit callout while we don't have the proc locked */
 	callout_drain(&p->p_limco);
@@ -301,7 +305,7 @@ exit1(struct thread *td, int rv)
 	 * it was.  The exit status is WEXITSTATUS(rv), but it's not clear
 	 * what the return value is.
 	 */
-	AUDIT_ARG_EXIT(WEXITSTATUS(rv), 0);
+	AUDIT_ARG_EXIT(rval, 0);
 	AUDIT_SYSCALL_EXIT(0, td);
 #endif
 
@@ -322,7 +326,8 @@ exit1(struct thread *td, int rv)
 
 	/*
 	 * Check if any loadable modules need anything done at process exit.
-	 * E.g. SYSV IPC stuff
+	 * E.g. SYSV IPC stuff.
+	 * Event handler could change exit status.
 	 * XXX what if one of these generates an error?
 	 */
 	EVENTHANDLER_INVOKE(process_exit, p);
@@ -332,7 +337,6 @@ exit1(struct thread *td, int rv)
 	 * P_PPWAIT is set; we will wakeup the parent below.
 	 */
 	PROC_LOCK(p);
-	rv = p->p_xstat;	/* Event handler could change exit status */
 	stopprofclock(p);
 	p->p_flag &= ~(P_TRACED | P_PPWAIT | P_PPTRACE);
 
@@ -561,9 +565,9 @@ exit1(struct thread *td, int rv)
 
 #ifdef KDTRACE_HOOKS
 	int reason = CLD_EXITED;
-	if (WCOREDUMP(rv))
+	if (WCOREDUMP(signo))
 		reason = CLD_DUMPED;
-	else if (WIFSIGNALED(rv))
+	else if (WIFSIGNALED(signo))
 		reason = CLD_KILLED;
 	SDT_PROBE(proc, kernel, , exit, reason, 0, 0, 0, 0);
 #endif
@@ -742,7 +746,7 @@ out:
 	sbuf_finish(sb);
 	log(LOG_INFO, "%s", sbuf_data(sb));
 	sbuf_delete(sb);
-	exit1(td, W_EXITCODE(0, sig));
+	exit1(td, 0, sig);
 	return (0);
 }
 
@@ -841,7 +845,7 @@ proc_reap(struct thread *td, struct proc *p, int *status, int options)
 
 	PROC_SUNLOCK(p);
 	if (status)
-		*status = p->p_xstat;	/* convert to int */
+		*status = KW_EXITCODE(p->p_xexit, p->p_xsig);
 	if (options & WNOWAIT) {
 		/*
 		 *  Only poll, returning the status.  Caller does not wish to
@@ -905,7 +909,7 @@ proc_reap(struct thread *td, struct proc *p, int *status, int options)
 	 * nothing can reach this process anymore. As such further locking
 	 * is unnecessary.
 	 */
-	p->p_xstat = 0;		/* XXX: why? */
+	p->p_xexit = p->p_xsig = 0;		/* XXX: why? */
 
 	PROC_LOCK(q);
 	ruadd(&q->p_stats->p_cru, &q->p_crux, &p->p_ru, &p->p_rux);
@@ -1064,15 +1068,15 @@ proc_to_reap(struct thread *td, struct proc *p, idtype_t idtype, id_t id,
 		 *  This is still a rough estimate.  We will fix the
 		 *  cases TRAPPED, STOPPED, and CONTINUED later.
 		 */
-		if (WCOREDUMP(p->p_xstat)) {
+		if (WCOREDUMP(p->p_xsig)) {
 			siginfo->si_code = CLD_DUMPED;
-			siginfo->si_status = WTERMSIG(p->p_xstat);
-		} else if (WIFSIGNALED(p->p_xstat)) {
+			siginfo->si_status = WTERMSIG(p->p_xsig);
+		} else if (WIFSIGNALED(p->p_xsig)) {
 			siginfo->si_code = CLD_KILLED;
-			siginfo->si_status = WTERMSIG(p->p_xstat);
+			siginfo->si_status = WTERMSIG(p->p_xsig);
 		} else {
 			siginfo->si_code = CLD_EXITED;
-			siginfo->si_status = WEXITSTATUS(p->p_xstat);
+			siginfo->si_status = p->p_xexit;
 		}
 
 		siginfo->si_pid = p->p_pid;
@@ -1223,9 +1227,9 @@ loop:
 			sx_xunlock(&proctree_lock);
 
 			if (status != NULL)
-				*status = W_STOPCODE(p->p_xstat);
+				*status = W_STOPCODE(p->p_xsig);
 			if (siginfo != NULL) {
-				siginfo->si_status = p->p_xstat;
+				siginfo->si_status = p->p_xsig;
 				siginfo->si_code = CLD_TRAPPED;
 			}
 			if ((options & WNOWAIT) == 0) {
@@ -1236,7 +1240,7 @@ loop:
 
 			CTR4(KTR_PTRACE,
 	    "wait: returning trapped pid %d status %#x (xstat %d) xthread %d",
-			    p->p_pid, W_STOPCODE(p->p_xstat), p->p_xstat,
+			    p->p_pid, W_STOPCODE(p->p_xsig), p->p_xsig,
 			    p->p_xthread != NULL ? p->p_xthread->td_tid : -1);
 			PROC_UNLOCK(p);
 			td->td_retval[0] = pid;
@@ -1252,9 +1256,9 @@ loop:
 			sx_xunlock(&proctree_lock);
 
 			if (status != NULL)
-				*status = W_STOPCODE(p->p_xstat);
+				*status = W_STOPCODE(p->p_xsig);
 			if (siginfo != NULL) {
-				siginfo->si_status = p->p_xstat;
+				siginfo->si_status = p->p_xsig;
 				siginfo->si_code = CLD_STOPPED;
 			}
 			if ((options & WNOWAIT) == 0) {