arch(7) manual page

Manual Pages — ARCH

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 architecture ports. For full details consult the processor-specific ABI supplement documentation.

If not explicitly mentioned, sizes are in bytes. The architecture details in this document apply to FreeBSD 10.0 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 mechanisms, 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. sparc64, 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

alpha 3.2 6.4

amd64 5.1

arm 6.0

armeb 8.0

armv6 10.0

arm64 11.0

ia64 5.0 10.x

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.x

powerpc 6.0

powerpcspe 12.0

powerpc64 6.0

riscv64 12.0

riscv64sf 12.0

sparc64 5.0

Type sizes

All FreeBSD architectures use some variant of the ELF (see elf(5)) Application Binary Interface (ABI) for the machine processor. All supported 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.

Compilers define the _LP64 symbol when compiling for an LP64 ABI.

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

LP64 ILP32 counterpart
amd64 i386
powerpc64 powerpc
mips64* mips*
arm64 currently does not support execution of armv6 binaries, even if the CPU implements AArch32 execution state.

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, require only 4-byte alignment for 64-bit integers.

Machine-dependent type sizes:

Architecture void * long double time_t

amd64 8 16 8

arm 4 8 8

armeb 4 8 8

armv6 4 8 8

arm64 8 16 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 4

powerpcspe 4 8 4

powerpc64 8 8 8

riscv64 8 16 8

riscv64sf 8 16 8

sparc64 8 16 8

time_t is 8 bytes on all supported architectures except i386 and 32-bit variants of powerpc.

Endianness and Char Signedness

Architecture	Endianness	char Signedness
amd64	little	signed
arm	little	unsigned
armeb	big	unsigned
armv6	little	unsigned
arm64	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
riscv64	little	signed
riscv64sf	little	signed
sparc64	big	signed

Page Size

Architecture	Page Sizes
amd64	4K, 2M, 1G
arm	4K
armeb	4K
armv6	4K, 1M
arm64	4K, 2M, 1G
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
riscv64	4K
riscv64sf	4K
sparc64	8K

Floating Point

Architecture	float, double	long double
amd64	hard	hard, 80 bit
arm	soft	soft, double precision
armeb	soft	soft, double precision
armv6	hard(1)	hard, double precision
arm64	hard	soft, quad 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
riscv64	hard	hard, double precision
riscv64sf	soft	soft, double precision
sparc64	hard	hard, quad precision

(1) Prior to FreeBSD 11.0, armv6 used the softfp ABI even though it supported only processors with a floating point unit.

Predefined Macros

The compiler provides a number of predefined macros. Some of these provide architecture-specific details and are explained below. Other macros, including those required by the language standard, are not included 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

amd64 __amd64__, __x86_64__

arm __arm__

armeb __arm__

armv6 __arm__, __ARM_ARCH >= 6

arm64 __aarch64__

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__

riscv64 __riscv__, __riscv64

riscv64sf __riscv__, __riscv64

sparc64 __sparc64__

HISTORY

An arch manual page appeared in FreeBSD 12 .

ARCH (7)

May 16, 2017

Please direct any comments about this manual page service to Ben Bullock. Privacy policy.

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