Index: include/Makefile
===================================================================
--- include/Makefile
+++ include/Makefile
@@ -11,8 +11,8 @@
 SUBDIR_PARALLEL=
 INCS=	a.out.h ar.h assert.h bitstring.h complex.h cpio.h _ctype.h ctype.h \
 	db.h \
-	dirent.h dlfcn.h elf.h elf-hints.h err.h fmtmsg.h fnmatch.h fstab.h \
-	fts.h ftw.h getopt.h glob.h grp.h \
+	dirent.h dlfcn.h elf.h elf-hints.h endian.h err.h fmtmsg.h fnmatch.h \
+	fstab.h fts.h ftw.h getopt.h glob.h grp.h \
 	ieeefp.h ifaddrs.h \
 	inttypes.h iso646.h kenv.h langinfo.h libgen.h limits.h link.h \
 	locale.h malloc.h malloc_np.h memory.h monetary.h mpool.h mqueue.h \
Index: include/endian.h
===================================================================
--- /dev/null
+++ include/endian.h
@@ -0,0 +1,52 @@
+/*-
+ * Copyright (c) 2021 M Warner Losh <imp@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+/*
+ * A mostly compatible with Linux/glibc endian.h
+ */
+
+#ifndef _ENDIAN_H_
+#define _ENDIAN_H_
+
+/*
+ * FreeBSD's sys/endian.h is very close to the Linux. Linux doesn't define the
+ * hto* [bl]*toh macros when there's a strict name space. We request that the
+ * FreeBSD specific [lb]e{16,32,64}{enc,dec} are omitted as well.
+ */
+#define __OMIT_ENDIAN_ENCODE_DECODE
+#include <sys/endian.h>
+
+/*
+ * The bswap* functions cause problems for some Linux code (like mesa), so
+ * remove them from the name space as well.  You need to include sys/endian.h
+ * directly if you want these to be visible.
+ */
+#undef bswap16
+#undef bswap32
+#undef bswap64
+
+/*
+ * glibc uses double underscore for these symbols. Define these unconditionally.
+ * The compiler defines __BYTE_ORDER__ these days, so we don't do anything
+ * with that.
+ */
+#define __BIG_ENDIAN		_BIG_ENDIAN
+#define __BYTE_ORDER		_BYTE_ORDER
+#define __LITTLE_ENDIAN		_LITTLE_ENDIAN
+#define __PDP_ENDIAN		_PDP_ENDIAN
+
+/*
+ * FreeBSD's sys/endian.h and machine/endian.h doesn't define a separate
+ * byte order for floats. Use the host non-float byte order.
+ */
+#define __FLOAT_WORD_ORDER	_BYTE_ORDER
+
+/*
+ * We don't define BIG_ENDI, LITTLE_ENDI, HIGH_HALF and LOW_HALF
+ * since those appear to be internal to internal to glibc
+ */
+
+#endif /* _ENDIAN_H_ */
Index: sys/sys/endian.h
===================================================================
--- sys/sys/endian.h
+++ sys/sys/endian.h
@@ -55,6 +55,7 @@
 #define	_UINT64_T_DECLARED
 #endif
 
+#if __BSD_VISIBLE
 /*
  * General byte order swapping functions.
  */
@@ -97,7 +98,7 @@
 #endif /* _BYTE_ORDER == _LITTLE_ENDIAN */
 
 /* Alignment-agnostic encode/decode bytestream to/from little/big endian. */
-
+#ifndef __OMIT_ENDIAN_ENCODE_DECODE
 static __inline uint16_t
 be16dec(const void *pp)
 {
@@ -203,5 +204,6 @@
 	le32enc(p, (uint32_t)(u & 0xffffffffU));
 	le32enc(p + 4, (uint32_t)(u >> 32));
 }
-
+#endif	/* __OMIT_ENDIAN_ENCODE_DECODE */
+#endif	/* __BSD_VISIBLE */
 #endif	/* _SYS_ENDIAN_H_ */