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Manual Pages  — ARCH

NAME

arch – Architecture-specific details

CONTENTS

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__

SEE ALSO

src.conf(5), build(7)

HISTORY

An arch manual page appeared in FreeBSD 12 .
ARCH (7) May 16, 2017
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Please direct any comments about this manual page service to Ben Bullock.

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