Index: sys/kern/subr_kcov.c
===================================================================
RCS file: /cvsroot/src/sys/kern/subr_kcov.c,v
retrieving revision 1.3
diff -u -r1.3 subr_kcov.c
--- sys/kern/subr_kcov.c	23 Feb 2019 12:07:40 -0000	1.3
+++ sys/kern/subr_kcov.c	24 Feb 2019 10:48:48 -0000
@@ -65,10 +65,10 @@
 	kcov_int_t *buf;
 	size_t bufnent;
 	size_t bufsize;
+	bool in_use;
 	TAILQ_ENTRY(kcov_desc) entry;
 } kcov_t;
 
-static specificdata_key_t kcov_proc_key;
 static specificdata_key_t kcov_lwp_key;
 
 static void
@@ -92,7 +92,7 @@
 
 	kd->refcnt++;
 	KASSERT(kd->refcnt == 2);
-	lwp_setspecific(kcov_lwp_key, kd);
+	kd->in_use = true;
 }
 
 static void
@@ -101,7 +101,7 @@
 
 	KASSERT(kd->refcnt == 2);
 	kd->refcnt--;
-	lwp_setspecific(kcov_lwp_key, NULL);
+	kd->in_use = false;
 }
 
 static inline bool
@@ -164,17 +164,16 @@
 static int
 kcov_open(dev_t dev, int flag, int mode, struct lwp *l)
 {
-	struct proc *p = l->l_proc;
 	kcov_t *kd;
 
-	kd = proc_getspecific(p, kcov_proc_key);
+	kd = lwp_getspecific(kcov_lwp_key);
 	if (kd != NULL)
 		return EBUSY;
 
 	kd = kmem_zalloc(sizeof(*kd), KM_SLEEP);
 	mutex_init(&kd->lock, MUTEX_DEFAULT, IPL_NONE);
 	kd->refcnt = 1;
-	proc_setspecific(p, kcov_proc_key, kd);
+	lwp_setspecific(kcov_lwp_key, kd);
 
 	return 0;
 }
@@ -182,6 +181,13 @@
 static int
 kcov_close(dev_t dev, int flag, int mode, struct lwp *l)
 {
+	kcov_t *kd;
+
+	kd = lwp_getspecific(kcov_lwp_key);
+
+	kcov_free(kd);
+
+	lwp_setspecific(kcov_lwp_key, NULL);
 
    	return 0;
 }
@@ -189,11 +195,10 @@
 static int
 kcov_ioctl(dev_t dev, u_long cmd, void *addr, int flag, struct lwp *l)
 {
-	struct proc *p = l->l_proc;
 	int error = 0;
 	kcov_t *kd;
 
-	kd = proc_getspecific(p, kcov_proc_key);
+	kd = lwp_getspecific(kcov_lwp_key);
 	if (kd == NULL)
 		return ENXIO;
 	kcov_lock(kd);
@@ -219,7 +224,7 @@
 		kcov_lwp_take(kd);
 		break;
 	case KCOV_IOC_DISABLE:
-		if (lwp_getspecific(kcov_lwp_key) == NULL) {
+		if (!kd->in_use) {
 			error = ENOENT;
 			break;
 		}
@@ -241,8 +246,10 @@
 	paddr_t pa;
 	vaddr_t va;
 
-	kd = proc_getspecific(curproc, kcov_proc_key);
-	KASSERT(kd != NULL);
+	kd = lwp_getspecific(kcov_lwp_key);
+	if (kd == NULL) {
+		return (paddr_t)-1;
+	}
 
 	if ((offset < 0) || (offset >= kd->bufnent * KCOV_ENTRY_SIZE)) {
 		return (paddr_t)-1;
@@ -289,10 +296,16 @@
 		return;
 	}
 
-	idx = kd->buf[0];
+	if (!kd->in_use) {
+		/* Tracing not enabled */
+		return;
+	}
+
+	idx = KCOV_LOAD(kd->buf[0]);
 	if (idx < kd->bufnent) {
-		kd->buf[idx+1] = (intptr_t)__builtin_return_address(0);
-		kd->buf[0]++;
+		KCOV_STORE(kd->buf[idx+1],
+		    (intptr_t)__builtin_return_address(0));
+		KCOV_STORE(kd->buf[0], idx + 1);
 	}
 }
 
@@ -319,7 +332,6 @@
 kcov_init(void)
 {
 
-	proc_specific_key_create(&kcov_proc_key, kcov_free);
 	lwp_specific_key_create(&kcov_lwp_key, kcov_free);
 }