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ARCH(7)		   FreeBSD Miscellaneous Information Manual	       ARCH(7)

NAME
     arch -- Architecture-specific details

DESCRIPTION
     Differences between CPU architectures and platforms supported by FreeBSD.

   Introduction
     This document is a	quick reference	of key ABI details of FreeBSD archi-
     tecture ports.  For full details consult the processor-specific ABI sup-
     plement documentation.

     If	not explicitly mentioned, sizes	are in bytes.  The architecture	de-
     tails in this document apply to FreeBSD 11.0 and later, unless otherwise
     noted.

     FreeBSD uses a flat address space.	 Variables of types unsigned long,
     uintptr_t,	and size_t and pointers	all have the same representation.

     In	order to maximize compatibility	with future pointer integrity mecha-
     nisms, manipulations of pointers as integers should be performed via
     uintptr_t or intptr_t and no other	types.	In particular, long and
     ptrdiff_t should be avoided.

     On	some architectures, e.g., powerpc and AIM variants of powerpc64, the
     kernel uses a separate address space.  On other architectures, kernel and
     a user mode process share a single	address	space.	The kernel is located
     at	the highest addresses.

     On	each architecture, the main user mode thread's stack starts near the
     highest user address and grows down.

     FreeBSD architecture support varies by release.  This table shows the
     first FreeBSD release to support each architecture, and, for discontinued
     architectures, the	final release.

	   Architecture	   Initial Release    Final Release
	   aarch64	   11.0
	   alpha	   3.2		      6.4
	   amd64	   5.1
	   arm		   6.0		      12.x
	   armeb	   8.0		      11.4
	   armv6	   10.0
	   armv7	   12.0
	   ia64		   5.0		      10.4
	   i386		   1.0
	   mips		   8.0
	   mipsel	   9.0
	   mipselhf	   12.0
	   mipshf	   12.0
	   mipsn32	   9.0
	   mips64	   9.0
	   mips64el	   9.0
	   mips64elhf	   12.0
	   mips64hf	   12.0
	   pc98		   2.2		      11.4
	   powerpc	   6.0
	   powerpcspe	   12.0
	   powerpc64	   6.0
	   powerpc64le	   13.0
	   riscv64	   12.0
	   riscv64sf	   12.0
	   sparc64	   5.0		      12.x

   Type	sizes
     All FreeBSD architectures use some	variant	of the ELF (see	elf(5))
     Application Binary	Interface (ABI)	for the	machine	processor.  All	sup-
     ported ABIs can be	divided	into two groups:

     ILP32     int, long, void * types machine representations all have	4-byte
	       size.

     LP64      int type	machine	representation uses 4 bytes, while long	and
	       void * are 8 bytes.

     Some machines support more	than one FreeBSD ABI.  Typically these are
     64-bit machines, where the	"native" LP64 execution	environment is accom-
     panied by the "legacy" ILP32 environment, which was the historical	32-bit
     predecessor for 64-bit evolution.	Examples are:

	   LP64		ILP32 counterpart
	   amd64	i386
	   powerpc64	powerpc
	   mips64*	mips*
	   aarch64	armv6/armv7

     aarch64 will support execution of armv6 or	armv7 binaries if the CPU im-
     plements AArch32 execution	state, however armv5 binaries aren't sup-
     ported.

     On	all supported architectures:

	    Type	 Size
	    short	 2
	    int		 4
	    long	 sizeof(void*)
	    long long	 8
	    float	 4
	    double	 8

     Integers are represented in two's complement.  Alignment of integer and
     pointer types is natural, that is,	the address of the variable must be
     congruent to zero modulo the type size.  Most ILP32 ABIs, except arm, re-
     quire only	4-byte alignment for 64-bit integers.

     Machine-dependent type sizes:

	   Architecture	   void	*    long double    time_t
	   aarch64	   8	     16		    8
	   amd64	   8	     16		    8
	   armv6	   4	     8		    8
	   armv7	   4	     8		    8
	   i386		   4	     12		    4
	   mips		   4	     8		    8
	   mipsel	   4	     8		    8
	   mipselhf	   4	     8		    8
	   mipshf	   4	     8		    8
	   mipsn32	   4	     8		    8
	   mips64	   8	     8		    8
	   mips64el	   8	     8		    8
	   mips64elhf	   8	     8		    8
	   mips64hf	   8	     8		    8
	   powerpc	   4	     8		    8
	   powerpcspe	   4	     8		    8
	   powerpc64	   8	     8		    8
	   powerpc64le	   8	     8		    8
	   riscv64	   8	     16		    8
	   riscv64sf	   8	     16		    8

     time_t is 8 bytes on all supported	architectures except i386.

   Endianness and Char Signedness
	   Architecture	   Endianness	 char Signedness
	   aarch64	   little	 unsigned
	   amd64	   little	 signed
	   armv6	   little	 unsigned
	   armv7	   little	 unsigned
	   i386		   little	 signed
	   mips		   big		 signed
	   mipsel	   little	 signed
	   mipselhf	   little	 signed
	   mipshf	   big		 signed
	   mipsn32	   big		 signed
	   mips64	   big		 signed
	   mips64el	   little	 signed
	   mips64elhf	   little	 signed
	   mips64hf	   big		 signed
	   powerpc	   big		 unsigned
	   powerpcspe	   big		 unsigned
	   powerpc64	   big		 unsigned
	   powerpc64le	   little	 unsigned
	   riscv64	   little	 signed
	   riscv64sf	   little	 signed

   Page	Size
	   Architecture	   Page	Sizes
	   aarch64	   4K, 2M, 1G
	   amd64	   4K, 2M, 1G
	   armv6	   4K, 1M
	   armv7	   4K, 1M
	   i386		   4K, 2M (PAE), 4M
	   mips		   4K
	   mipsel	   4K
	   mipselhf	   4K
	   mipshf	   4K
	   mipsn32	   4K
	   mips64	   4K
	   mips64el	   4K
	   mips64elhf	   4K
	   mips64hf	   4K
	   powerpc	   4K
	   powerpcspe	   4K
	   powerpc64	   4K
	   powerpc64le	   4K
	   riscv64	   4K, 2M, 1G
	   riscv64sf	   4K, 2M, 1G

   Floating Point
	   Architecture	   float, double    long double
	   aarch64	   hard		    soft, quad precision
	   amd64	   hard		    hard, 80 bit
	   armv6	   hard		    hard, double precision
	   armv7	   hard		    hard, double precision
	   i386		   hard		    hard, 80 bit
	   mips		   soft		    identical to double
	   mipsel	   soft		    identical to double
	   mipselhf	   hard		    identical to double
	   mipshf	   hard		    identical to double
	   mipsn32	   soft		    identical to double
	   mips64	   soft		    identical to double
	   mips64el	   soft		    identical to double
	   mips64elhf	   hard		    identical to double
	   mips64hf	   hard		    identical to double
	   powerpc	   hard		    hard, double precision
	   powerpcspe	   hard		    hard, double precision
	   powerpc64	   hard		    hard, double precision
	   powerpc64le	   hard		    hard, double precision
	   riscv64	   hard		    hard, quad precision
	   riscv64sf	   soft		    soft, quad precision

   Default Tool	Chain
     FreeBSD uses clang(1) as the default compiler on all supported CPU	archi-
     tectures, LLVM's ld.lld(1)	as the default linker, and ELF Tool Chain bi-
     nary utilities such as objcopy(1) and readelf(1).

   MACHINE_ARCH	vs MACHINE_CPUARCH vs MACHINE
     MACHINE_CPUARCH should be preferred in Makefiles when the generic archi-
     tecture is	being tested.  MACHINE_ARCH should be preferred	when there is
     something specific	to a particular	type of	architecture where there is a
     choice of many, or	could be a choice of many.  Use	MACHINE	when referring
     to	the kernel, interfaces dependent on a specific type of kernel or simi-
     lar things	like boot sequences.

	   MACHINE	 MACHINE_CPUARCH       MACHINE_ARCH
	   arm64	 aarch64	       aarch64
	   amd64	 amd64		       amd64
	   arm		 arm		       armv6, armv7
	   i386		 i386		       i386
	   mips		 mips		       mips, mipsel, mips64, mips64el,
								  mipshf,
								  mipselhf,
								  mips64elhf,
								  mipsn32
	   powerpc	 powerpc	       powerpc,	powerpcspe, powerpc64,
								  powerpc64le
	   riscv	 riscv		       riscv64,	riscv64sf

   Predefined Macros
     The compiler provides a number of predefined macros.  Some	of these pro-
     vide architecture-specific	details	and are	explained below.  Other
     macros, including those required by the language standard,	are not	in-
     cluded here.

     The full set of predefined	macros can be obtained with this command:

	   cc -x c -dM -E /dev/null

     Common type size and endianness macros:

	   Macro	 Meaning
	   __LP64__	 64-bit	(8-byte) long and pointer, 32-bit (4-byte) int
	   __ILP32__	 32-bit	(4-byte) int, long and pointer
	   BYTE_ORDER	 Either	BIG_ENDIAN or LITTLE_ENDIAN.  PDP11_ENDIAN is
				    not	used on	FreeBSD.

     Architecture-specific macros:

	   Architecture	   Predefined macros
	   aarch64	   __aarch64__
	   amd64	   __amd64__, __x86_64__
	   armv6	   __arm__, __ARM_ARCH >= 6
	   armv7	   __arm__, __ARM_ARCH >= 7
	   i386		   __i386__
	   mips		   __mips__, __MIPSEB__, __mips_o32
	   mipsel	   __mips__, __mips_o32
	   mipselhf	   __mips__, __mips_o32
	   mipshf	   __mips__, __MIPSEB__, __mips_o32
	   mipsn32	   __mips__, __MIPSEB__, __mips_n32
	   mips64	   __mips__, __MIPSEB__, __mips_n64
	   mips64el	   __mips__, __mips_n64
	   mips64elhf	   __mips__, __mips_n64
	   mips64hf	   __mips__, __MIPSEB__, __mips_n64
	   powerpc	   __powerpc__
	   powerpcspe	   __powerpc__,	__SPE__
	   powerpc64	   __powerpc__,	__powerpc64__
	   powerpc64le	   __powerpc__,	__powerpc64__
	   riscv64	   __riscv, __riscv_xlen == 64
	   riscv64sf	   __riscv, __riscv_xlen == 64,	__riscv_float_abi_soft

     Compilers may define additional variants of architecture-specific macros.
     The macros	above are preferred for	use in FreeBSD.

   Important make(1) variables
     Most of the externally settable variables are defined in the build(7) man
     page.  These variables are	not otherwise documented and are used exten-
     sively in the build system.

     MACHINE	      Represents the hardware platform.	 This is the same as
		      the native platform's uname(1) -m	output.	 It defines
		      both the userland	/ kernel interface, as well as the
		      bootloader / kernel interface.  It should	only be	used
		      in these contexts.  Each CPU architecture	may have mul-
		      tiple hardware platforms it supports where MACHINE dif-
		      fers among them.	It is used to collect together all the
		      files from config(8) to build the	kernel.	 It is often
		      the same as MACHINE_ARCH just as one CPU architecture
		      can be implemented by many different hardware platforms,
		      one hardware platform may	support	multiple CPU architec-
		      ture family members, though with different binaries.
		      For example, MACHINE of i386 supported the IBM-AT	hard-
		      ware platform while the MACHINE of pc98 supported	the
		      Japanese company NEC's PC-9801 and PC-9821 hardware
		      platforms.  Both of these	hardware platforms supported
		      only the MACHINE_ARCH of i386 where they shared a	common
		      ABI, except for certain kernel / userland	interfaces re-
		      lating to	underlying hardware platform differences in
		      bus architecture,	device enumeration and boot interface.
		      Generally, MACHINE should	only be	used in	src/sys	and
		      src/stand	or in system imagers or	installers.

     MACHINE_ARCH     Represents the CPU processor architecture.  This is the
		      same as the native platforms uname(1) -p output.	It de-
		      fines the	CPU instruction	family supported.  It may also
		      encode a variation in the	byte ordering of multi-byte
		      integers (endian).  It may also encode a variation in
		      the size of the integer or pointer.  It may also encode
		      a	ISA revision.  It may also encode hard versus soft
		      floating point ABI and usage.  It	may also encode	a
		      variant ABI when the other factors do not	uniquely de-
		      fine the ABI (e.g., MIPS'	n32 ABI).  It, along with
		      MACHINE, defines the ABI used by the system.  For	exam-
		      ple, the MIPS CPU	processor family supports 9 different
		      combinations encoding pointer size, endian and hard ver-
		      sus soft float (for 8 combinations) as well as N32
		      (which only ever had one variation of all	these).	 Gen-
		      erally, the plain	CPU name specifies the most common (or
		      at least first) variant of the CPU.  This	is why mips
		      and mips64 imply 'big endian' while 'armv6' and 'armv7'
		      imply little endian.  If we ever were to support the so-
		      called x32 ABI (using 32-bit pointers on the amd64 ar-
		      chitecture), it would most likely	be encoded as
		      amd64-x32.  It is	unfortunate that amd64 specifies the
		      64-bit evolution of the x86 platform (it matches the
		      'first rule') as everybody else uses x86_64.  There is
		      no standard name for the processor: each OS selects its
		      own conventions.

     MACHINE_CPUARCH  Represents the source location for a given MACHINE_ARCH.
		      It is generally the common prefix	for all	the MA-
		      CHINE_ARCH that share the	same implementation, though
		      'riscv' breaks this rule.	 For example, MACHINE_CPUARCH
		      is defined to be mips for	all the	flavors	of mips	that
		      we support since we support them all with	a shared set
		      of sources.  While amd64 and i386	are closely related,
		      MACHINE_CPUARCH is not x86 for them.  The	FreeBSD	source
		      base supports amd64 and i386 with	two distinct source
		      bases living in subdirectories named amd64 and i386
		      (though behind the scenes	there's	some sharing that fits
		      into this	framework).

     CPUTYPE	      Sets the flavor of MACHINE_ARCH to build.	 It is used to
		      optimize the build for a specific	CPU / core that	the
		      binaries run on.	Generally, this	does not change	the
		      ABI, though it can be a fine line	between	optimization
		      for specific cases.

     TARGET	      Used to set MACHINE in the top level Makefile for	cross
		      building.	 Unused	outside	of that	scope.	It is not
		      passed down to the rest of the build.  Makefiles outside
		      of the top level should not use it at all	(though	some
		      have their own private copy for hysterical raisons).

     TARGET_ARCH      Used to set MACHINE_ARCH by the top level	Makefile for
		      cross building.  Like TARGET, it is unused outside of
		      that scope.

SEE ALSO
     src.conf(5), build(7)

HISTORY
     An	arch manual page appeared in FreeBSD 11.1.

FreeBSD	13.0		      September	22, 2020		  FreeBSD 13.0

NAME | DESCRIPTION | SEE ALSO | HISTORY

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