FreeBSD: make adjustments for the standalone environment

In FreeBSD, there are three compile environments that are supported:
user land, the kernel and the bootloader / standalone. Adjust the
headers to compile in the standalone environment. Limit kernel-only
items from view when _STANDALONE is defined.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Warner Losh <imp@FreeBSD.org>
Closes #10998

include/os/freebsd/spl/sys/ccompile.h

@@ -113,9 +113,9 @@ extern "C" {
 #define	__VPRINTFLIKE(__n)	__sun_attr__((__VPRINTFLIKE__(__n)))
 #define	__KPRINTFLIKE(__n)	__sun_attr__((__KPRINTFLIKE__(__n)))
 #define	__KVPRINTFLIKE(__n)	__sun_attr__((__KVPRINTFLIKE__(__n)))
-#ifdef _KERNEL
+#if	defined(_KERNEL) || defined(_STANDALONE)
 #define	__NORETURN		__sun_attr__((__noreturn__))
-#endif
+#endif /* _KERNEL || _STANDALONE */
 #define	__CONST			__sun_attr__((__const__))
 #define	__PURE			__sun_attr__((__pure__))
 
@@ -174,7 +174,7 @@ typedef int enum_t;
 #define	__exit
 #endif
 
-#ifdef _KERNEL
+#if defined(_KERNEL) || defined(_STANDALONE)
 #define	param_set_charp(a, b) (0)
 #define	ATTR_UID AT_UID
 #define	ATTR_GID AT_GID
@@ -183,9 +183,15 @@ typedef int enum_t;
 #define	ATTR_CTIME	AT_CTIME
 #define	ATTR_MTIME	AT_MTIME
 #define	ATTR_ATIME	AT_ATIME
+#if defined(_STANDALONE)
+#define	vmem_free kmem_free
+#define	vmem_zalloc kmem_zalloc
+#define	vmem_alloc kmem_zalloc
+#else
 #define	vmem_free zfs_kmem_free
 #define	vmem_zalloc(size, flags) zfs_kmem_alloc(size, flags | M_ZERO)
 #define	vmem_alloc zfs_kmem_alloc
+#endif
 #define	MUTEX_NOLOCKDEP 0
 #define	RW_NOLOCKDEP 0