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linux: For better compatibility, provide compatible endian.h

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Add endian.h. This includes sys/endian.h and then adds extra defines
that glibc defines with double underscores for our
_{BIG,BYTE,LITTLE,PDP}_ENDIAN macros. We also define __FLOAT_WORD_ORDER
to be the same as _BYTE_ENDIAN since FreeBSD doesn't currently define
this, and the default with glibc is exactly this for our platforms.
Move common parts of endian.h and sys/endian.h into sys/_endian.h
to limit namespace pollution from endian.h

All this gives us good compatibility with Linux. There may be one or two
upstreams that haven't integrated the patches I tried to send up.

There are some minor differences:
	o The extra glibc macros are not defined. These are all
	  controlled with either __ at the start, or only defined
	  when glibc is being built. We also don't define macros
	  that are used internally in glibc that would pollute
	  the namespace.
	o For complete compatibility, this change must also be
	  paired with providing a glibc-compatible byteswap.h.

Sponsored by:		Netflix
Reviewed by:		mhorne, markj, jhb
Differential Revision:	https://reviews.freebsd.org/D31962
This commit is contained in:
Warner Losh 2023-01-20 16:32:45 -07:00
parent e8c1bd7257
commit 30e0d2a510
4 changed files with 86 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/Makefile
View File

@ -14,8 +14,8 @@ SUBDIR+= i386
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 \

43
include/endian.h Normal file
View File

@ -0,0 +1,43 @@
/*-
* Copyright (c) 2021 M. Warner Losh <imp@FreeBSD.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
/*
* A mostly Linux/glibc-compatible endian.h
*/
#ifndef _ENDIAN_H_
#define _ENDIAN_H_
/*
* FreeBSD's sys/_endian.h is very close to the interface provided on Linux by
* glibc's endian.h.
*/
#include <sys/_endian.h>
/*
* 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 since sys/endian.h defines _BYTE_ORDER based on it.
*/
#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 macros that
* glibc's endian.h defines since those appear to be internal to internal to
* glibc. We also don't try to emulate the various helper macros that glibc
* uses to limit namespace visibility.
*/
#endif /* _ENDIAN_H_ */

36
sys/sys/_endian.h
View File

@ -32,7 +32,7 @@
#ifndef _SYS__ENDIAN_H_
#define _SYS__ENDIAN_H_
#ifndef _MACHINE_ENDIAN_H_
#if !defined(_MACHINE_ENDIAN_H_) && !defined(_ENDIAN_H_)
#error "sys/_endian.h should not be included directly"
#endif
@ -89,4 +89,38 @@
#define __ntohs(x) ((__uint16_t)(x))
#endif
/*
* Host to big endian, host to little endian, big endian to host, and little
* endian to host byte order functions as detailed in byteorder(9).
*/
#if _BYTE_ORDER == _LITTLE_ENDIAN
#define htobe16(x) __bswap16((x))
#define htobe32(x) __bswap32((x))
#define htobe64(x) __bswap64((x))
#define htole16(x) ((uint16_t)(x))
#define htole32(x) ((uint32_t)(x))
#define htole64(x) ((uint64_t)(x))
#define be16toh(x) __bswap16((x))
#define be32toh(x) __bswap32((x))
#define be64toh(x) __bswap64((x))
#define le16toh(x) ((uint16_t)(x))
#define le32toh(x) ((uint32_t)(x))
#define le64toh(x) ((uint64_t)(x))
#else /* _BYTE_ORDER != _LITTLE_ENDIAN */
#define htobe16(x) ((uint16_t)(x))
#define htobe32(x) ((uint32_t)(x))
#define htobe64(x) ((uint64_t)(x))
#define htole16(x) __bswap16((x))
#define htole32(x) __bswap32((x))
#define htole64(x) __bswap64((x))
#define be16toh(x) ((uint16_t)(x))
#define be32toh(x) ((uint32_t)(x))
#define be64toh(x) ((uint64_t)(x))
#define le16toh(x) __bswap16((x))
#define le32toh(x) __bswap32((x))
#define le64toh(x) __bswap64((x))
#endif /* _BYTE_ORDER == _LITTLE_ENDIAN */
#endif /* _SYS__ENDIAN_H_ */

42
sys/sys/endian.h
View File

@ -55,6 +55,12 @@ typedef __uint64_t uint64_t;
#define _UINT64_T_DECLARED
#endif
/*
* Note: While tempting to try to avoid namespace pollution from this file,
* several software packages assume these marcos are defined, even when it
* defines _POSIX_C_SOURCE to request an unpolluted namespace.
*/
/*
* General byte order swapping functions.
*/
@ -62,42 +68,7 @@ typedef __uint64_t uint64_t;
#define bswap32(x) __bswap32(x)
#define bswap64(x) __bswap64(x)
/*
* Host to big endian, host to little endian, big endian to host, and little
* endian to host byte order functions as detailed in byteorder(9).
*/
#if _BYTE_ORDER == _LITTLE_ENDIAN
#define htobe16(x) __bswap16((x))
#define htobe32(x) __bswap32((x))
#define htobe64(x) __bswap64((x))
#define htole16(x) ((uint16_t)(x))
#define htole32(x) ((uint32_t)(x))
#define htole64(x) ((uint64_t)(x))
#define be16toh(x) __bswap16((x))
#define be32toh(x) __bswap32((x))
#define be64toh(x) __bswap64((x))
#define le16toh(x) ((uint16_t)(x))
#define le32toh(x) ((uint32_t)(x))
#define le64toh(x) ((uint64_t)(x))
#else /* _BYTE_ORDER != _LITTLE_ENDIAN */
#define htobe16(x) ((uint16_t)(x))
#define htobe32(x) ((uint32_t)(x))
#define htobe64(x) ((uint64_t)(x))
#define htole16(x) __bswap16((x))
#define htole32(x) __bswap32((x))
#define htole64(x) __bswap64((x))
#define be16toh(x) ((uint16_t)(x))
#define be32toh(x) ((uint32_t)(x))
#define be64toh(x) ((uint64_t)(x))
#define le16toh(x) __bswap16((x))
#define le32toh(x) __bswap32((x))
#define le64toh(x) __bswap64((x))
#endif /* _BYTE_ORDER == _LITTLE_ENDIAN */
/* Alignment-agnostic encode/decode bytestream to/from little/big endian. */
static __inline uint16_t
be16dec(const void *pp)
{
@ -203,5 +174,4 @@ le64enc(void *pp, uint64_t u)
le32enc(p, (uint32_t)(u & 0xffffffffU));
le32enc(p + 4, (uint32_t)(u >> 32));
}
#endif /* _SYS_ENDIAN_H_ */