Index: head/cddl/contrib/opensolaris/lib/libctf/common/ctf_lib.c
===================================================================
--- head/cddl/contrib/opensolaris/lib/libctf/common/ctf_lib.c
+++ head/cddl/contrib/opensolaris/lib/libctf/common/ctf_lib.c
@@ -27,6 +27,7 @@
 #pragma ident	"%Z%%M%	%I%	%E% SMI"
 
 #include <sys/types.h>
+#include <sys/endian.h>
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <sys/zmod.h>
Index: head/cddl/contrib/opensolaris/tools/ctf/cvt/ctftools.h
===================================================================
--- head/cddl/contrib/opensolaris/tools/ctf/cvt/ctftools.h
+++ head/cddl/contrib/opensolaris/tools/ctf/cvt/ctftools.h
@@ -38,6 +38,7 @@
 #include <pthread.h>
 
 #include <sys/ccompile.h>
+#include <sys/endian.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -63,6 +64,15 @@
 
 #ifndef MIN
 #define	MIN(a, b) 		((a) > (b) ? (b) : (a))
+#endif
+
+/* Sanity check for cross-build bootstrap tools */
+#if !defined(BYTE_ORDER)
+#error "Missing BYTE_ORDER defines"
+#elif !defined(_LITTLE_ENDIAN)
+#error "Missing _LITTLE_ENDIAN defines"
+#elif !defined(_BIG_ENDIAN)
+#error "Missing _BIG_ENDIAN defines"
 #endif
 
 #define	TRUE	1
Index: head/sys/cddl/compat/opensolaris/sys/stat.h
===================================================================
--- head/sys/cddl/compat/opensolaris/sys/stat.h
+++ head/sys/cddl/compat/opensolaris/sys/stat.h
@@ -32,11 +32,19 @@
 
 #include_next <sys/stat.h>
 
+/*
+ * When bootstrapping on Linux a stat64/fstat64 functions exists in both
+ * glibc and musl libc. To avoid compilation errors, use those functions instead
+ * of redefining them to stat/fstat.
+ * Similarly, macOS provides (deprecated) stat64 functions that we can use
+ * for now.
+ */
+#if !defined(__linux__) && !defined(__APPLE__)
 #define	stat64	stat
 
 #define	MAXOFFSET_T	OFF_MAX
 
-#ifndef _KERNEL
+#if !defined(_KERNEL)
 #include <sys/disk.h>
 
 static __inline int
@@ -51,6 +59,7 @@
 	}
 	return (ret);
 }
-#endif
+#endif /* !defined(_KERNEL) */
+#endif /* !defined(__linux__) && !defined(__APPLE__) */
 
 #endif	/* !_COMPAT_OPENSOLARIS_SYS_STAT_H_ */
Index: head/sys/cddl/compat/opensolaris/sys/time.h
===================================================================
--- head/sys/cddl/compat/opensolaris/sys/time.h
+++ head/sys/cddl/compat/opensolaris/sys/time.h
@@ -29,6 +29,7 @@
 #ifndef _OPENSOLARIS_SYS_TIME_H_
 #define	_OPENSOLARIS_SYS_TIME_H_
 
+#include <sys/types.h>
 #include_next <sys/time.h>
 
 #define SEC		1
Index: head/sys/cddl/contrib/opensolaris/uts/common/sys/sysmacros.h
===================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/sys/sysmacros.h
+++ head/sys/cddl/contrib/opensolaris/uts/common/sys/sysmacros.h
@@ -46,8 +46,12 @@
 /*
  * Disk blocks (sectors) and bytes.
  */
+#ifndef dtob
 #define	dtob(DD)	((DD) << DEV_BSHIFT)
+#endif
+#ifndef btod
 #define	btod(BB)	(((BB) + DEV_BSIZE - 1) >> DEV_BSHIFT)
+#endif
 #define	btodt(BB)	((BB) >> DEV_BSHIFT)
 #define	lbtod(BB)	(((offset_t)(BB) + DEV_BSIZE - 1) >> DEV_BSHIFT)
 
@@ -220,9 +224,12 @@
 /*
  * Macros for counting and rounding.
  */
+#ifndef howmany
 #define	howmany(x, y)	(((x)+((y)-1))/(y))
+#endif
+#ifndef roundup
 #define	roundup(x, y)	((((x)+((y)-1))/(y))*(y))
-
+#endif
 /*
  * Macro to determine if value is a power of 2
  */