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ARCH(7) BSD 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.x 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.x 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. BSD September 22, 2020 BSD
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