diff --git a/include/os/freebsd/spl/sys/atomic.h b/include/os/freebsd/spl/sys/atomic.h
index 8b9cec15c5e1..40a67704fde0 100644
--- a/include/os/freebsd/spl/sys/atomic.h
+++ b/include/os/freebsd/spl/sys/atomic.h
@@ -167,7 +167,7 @@ atomic_dec_64_nv(volatile uint64_t *target)
 	return (atomic_add_64_nv(target, -1));
 }
 
-#if !defined(COMPAT_32BIT) && defined(__LP64__)
+#ifdef __LP64__
 static __inline void *
 atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
 {
@@ -181,7 +181,7 @@ atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
 	return ((void *)atomic_cas_32((volatile uint32_t *)target,
 	    (uint32_t)cmp, (uint32_t)newval));
 }
-#endif	/* !defined(COMPAT_32BIT) && defined(__LP64__) */
+#endif	/* __LP64__ */
 
 #else /* _STANDALONE */
 /*
@@ -190,6 +190,8 @@ atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
  */
 #undef atomic_add_64
 #define	atomic_add_64(ptr, val) *(ptr) += val
+#undef atomic_sub_64
+#define	atomic_sub_64(ptr, val) *(ptr) -= val
 #endif /* !_STANDALONE */
 
 #endif	/* !_OPENSOLARIS_SYS_ATOMIC_H_ */
diff --git a/include/os/freebsd/spl/sys/ccompat.h b/include/os/freebsd/spl/sys/ccompat.h
index eaee9159eabd..e34bab7e896d 100644
--- a/include/os/freebsd/spl/sys/ccompat.h
+++ b/include/os/freebsd/spl/sys/ccompat.h
@@ -1,5 +1,5 @@
 /*
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
diff --git a/include/os/freebsd/spl/sys/ctype.h b/include/os/freebsd/spl/sys/ctype.h
index 53afd8b8bd42..b9ca0f8ef2c4 100644
--- a/include/os/freebsd/spl/sys/ctype.h
+++ b/include/os/freebsd/spl/sys/ctype.h
@@ -39,5 +39,6 @@
 		((C) >= 0x3A && (C) <= 0x40) ||				\
 		((C) >= 0x5B && (C) <= 0x60) ||				\
 		((C) >= 0x7B && (C) <= 0x7E))
+#define	isspace(C)	((C) == 0x20 || ((C) >= 0x9 && (C) <= 0xD))
 
 #endif
diff --git a/include/os/freebsd/spl/sys/spl_condvar.h b/include/os/freebsd/spl/sys/spl_condvar.h
index 7405f647d59a..2835adafd416 100644
--- a/include/os/freebsd/spl/sys/spl_condvar.h
+++ b/include/os/freebsd/spl/sys/spl_condvar.h
@@ -1,5 +1,5 @@
 /*
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2000 Jake Burkholder <jake@freebsd.org>.
  * All rights reserved.
diff --git a/include/os/freebsd/zfs/sys/arc_os.h b/include/os/freebsd/zfs/sys/arc_os.h
index a95618b91fed..ad2aba23b901 100644
--- a/include/os/freebsd/zfs/sys/arc_os.h
+++ b/include/os/freebsd/zfs/sys/arc_os.h
@@ -1,5 +1,5 @@
 /*
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2022 Martin Matuska
  *
diff --git a/include/os/freebsd/zfs/sys/freebsd_event.h b/include/os/freebsd/zfs/sys/freebsd_event.h
index 544ff8b0f81f..a32596d918a1 100644
--- a/include/os/freebsd/zfs/sys/freebsd_event.h
+++ b/include/os/freebsd/zfs/sys/freebsd_event.h
@@ -1,5 +1,5 @@
 /*
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2022 Rob Wing
  *
diff --git a/include/os/freebsd/zfs/sys/zfs_context_os.h b/include/os/freebsd/zfs/sys/zfs_context_os.h
index 1ce72330412c..457fa3af8142 100644
--- a/include/os/freebsd/zfs/sys/zfs_context_os.h
+++ b/include/os/freebsd/zfs/sys/zfs_context_os.h
@@ -78,7 +78,7 @@ extern int hz;
 extern int tick;
 typedef int fstrans_cookie_t;
 #define	spl_fstrans_mark() (0)
-#define	spl_fstrans_unmark(x) (x = 0)
+#define	spl_fstrans_unmark(x) ((void)x)
 #define	signal_pending(x) SIGPENDING(x)
 #define	current curthread
 #define	thread_join(x)
diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index 0d31195447d1..6a337b49edf3 100644
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -695,8 +695,10 @@ extern char *kmem_asprintf(const char *fmt, ...);
 #define	kmem_strfree(str) kmem_free((str), strlen(str) + 1)
 #define	kmem_strdup(s)  strdup(s)
 
+#ifndef __cplusplus
 extern int kmem_scnprintf(char *restrict str, size_t size,
     const char *restrict fmt, ...);
+#endif
 
 /*
  * Hostname information
diff --git a/module/os/freebsd/zfs/event_os.c b/module/os/freebsd/zfs/event_os.c
index 97ac151e4fa1..239d44d0cfe7 100644
--- a/module/os/freebsd/zfs/event_os.c
+++ b/module/os/freebsd/zfs/event_os.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2022 Rob Wing
  *
diff --git a/module/os/freebsd/zfs/kmod_core.c b/module/os/freebsd/zfs/kmod_core.c
index f4c87013dbf0..9a268573528c 100644
--- a/module/os/freebsd/zfs/kmod_core.c
+++ b/module/os/freebsd/zfs/kmod_core.c
@@ -141,7 +141,7 @@ zfsdev_ioctl(struct cdev *dev, ulong_t zcmd, caddr_t arg, int flag,
 	if (len != sizeof (zfs_iocparm_t))
 		return (EINVAL);
 
-	uaddr = (void *)zp->zfs_cmd;
+	uaddr = (void *)(uintptr_t)zp->zfs_cmd;
 	zc = vmem_zalloc(sizeof (zfs_cmd_t), KM_SLEEP);
 #ifdef ZFS_LEGACY_SUPPORT
 	/*
diff --git a/tests/zfs-tests/cmd/dosmode_readonly_write.c b/tests/zfs-tests/cmd/dosmode_readonly_write.c
index 0441d1c7b472..b45602d80651 100644
--- a/tests/zfs-tests/cmd/dosmode_readonly_write.c
+++ b/tests/zfs-tests/cmd/dosmode_readonly_write.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2021 iXsystems, Inc.
  *