1 2Quick Installation Guide for musl libc 3====================================== 4 5There are many different ways to install musl depending on your usage 6case. This document covers only the build and installation of musl by 7itself, which is useful for upgrading an existing musl-based system or 8compiler toolchain, or for using the provided musl-gcc wrapper with an 9existing non-musl-based compiler. 10 11Building complete native or cross-compiler toolchains is outside the 12scope of this INSTALL file. More information can be found on the musl 13website and community wiki. 14 15 16Build Prerequisites 17------------------- 18 19The only build-time prerequisites for musl are GNU Make and a 20freestanding C99 compiler toolchain targeting the desired instruction 21set architecture and ABI, with support for a minimal subset of "GNU C" 22extensions consisting mainly of gcc-style inline assembly, weak 23aliases, hidden visibility, and stand-alone assembly source files. 24 25GCC, LLVM/clang, Firm/cparser, and PCC have all successfully built 26musl, but GCC is the most widely used/tested. Recent compiler (and 27binutils) versions should be used if possible since some older 28versions have bugs which affect musl. 29 30The system used to build musl does not need to be Linux-based, nor do 31the Linux kernel headers need to be available. 32 33 34 35Supported Targets 36----------------- 37 38musl can be built for the following CPU instruction set architecture 39and ABI combinations: 40 41* i386 42 * Minimum CPU model is actually 80486 unless kernel emulation of 43 the `cmpxchg` instruction is added 44 45* x86_64 46 * ILP32 ABI (x32) is available as a separate arch but is still 47 experimental 48 49* ARM 50 * EABI, standard or hard-float VFP variant 51 * Little-endian default; big-endian variants also supported 52 * Compiler toolchains only support armv4t and later 53 54* AArch64 55 * Little-endian default; big-endian variants also supported 56 57* MIPS 58 * ABI is o32 59 * Big-endian default; little-endian variants also supported 60 * Default ABI variant uses FPU registers; alternate soft-float ABI 61 that does not use FPU registers or instructions is available 62 * MIPS2 or later, or kernel emulation of ll/sc (standard in Linux) 63 is required 64 65* MIPS64 66 * ABI is n64 (LP64) or n32 (ILP32) 67 * Big-endian default; little-endian variants also supported 68 * Default ABI variant uses FPU registers; alternate soft-float ABI 69 that does not use FPU registers or instructions is available 70 71* PowerPC 72 * Compiler toolchain must provide 64-bit long double, not IBM 73 double-double or IEEE quad 74 * For dynamic linking, compiler toolchain must be configured for 75 "secure PLT" variant 76 77* PowerPC64 78 * Both little and big endian variants are supported 79 * Compiler toolchain must provide 64-bit long double, not IBM 80 double-double or IEEE quad 81 * Compiler toolchain must use the new (ELFv2) ABI regardless of 82 whether it is for little or big endian 83 84* S390X (64-bit S390) 85 86* SuperH (SH) 87 * Standard ELF ABI or FDPIC ABI (shared-text without MMU) 88 * Little-endian by default; big-engian variant also supported 89 * Full FPU ABI or soft-float ABI is supported, but the 90 single-precision-only FPU ABI is not 91 92* Microblaze 93 * Big-endian default; little-endian variants also supported 94 * Soft-float 95 * Requires support for lwx/swx instructions 96 97* OpenRISC 1000 (or1k) 98 99* RISC-V 64 100 * Little endian 101 * Hard, soft, and hard-single/soft-double floating point ABIs 102 * Standard ELF; no shared-text NOMMU support 103 104 105 106Build and Installation Procedure 107-------------------------------- 108 109To build and install musl: 110 1111. Run the provided configure script from the top-level source 112 directory, passing on its command line any desired options. 113 1142. Run "make" to compile. 115 1163. Run "make install" with appropriate privileges to write to the 117 target locations. 118 119The configure script attempts to determine automatically the correct 120target architecture based on the compiler being used. For some 121compilers, this may not be possible. If detection fails or selects the 122wrong architecture, you can provide an explicit selection on the 123configure command line. 124 125By default, configure installs to a prefix of "/usr/local/musl". This 126differs from the behavior of most configure scripts, and is chosen 127specifically to avoid clashing with libraries already present on the 128system. DO NOT set the prefix to "/usr", "/usr/local", or "/" unless 129you're upgrading libc on an existing musl-based system. Doing so will 130break your existing system when you run "make install" and it may be 131difficult to recover. 132 133 134 135Notes on Dynamic Linking 136------------------------ 137 138If dynamic linking is enabled, one file needs to be installed outside 139of the installation prefix: /lib/ld-musl-$ARCH.so.1. This is the 140dynamic linker. Its pathname is hard-coded into all dynamic-linked 141programs, so for the sake of being able to share binaries between 142systems, a consistent location should be used everywhere. Note that 143the same applies to glibc and its dynamic linker, which is named 144/lib/ld-linux.so.2 on i386 systems. 145 146If for some reason it is impossible to install the dynamic linker in 147its standard location (for example, if you are installing without root 148privileges), the --syslibdir option to configure can be used to 149provide a different location 150 151At runtime, the dynamic linker needs to know the paths to search for 152shared libraries. You should create a text file named 153/etc/ld-musl-$ARCH.path (where $ARCH matches the architecture name 154used in the dynamic linker) containing a list of directories where you 155want the dynamic linker to search for shared libraries, separated by 156colons or newlines. If the dynamic linker has been installed in a 157non-default location, the path file also needs to reside at that 158location (../etc relative to the chosen syslibdir). 159 160If you do not intend to use dynamic linking, you may disable it by 161passing --disable-shared to configure; this also cuts the build time 162in half. 163 164 165 166Checking for Successful Installation 167------------------------------------ 168 169After installing, you should be able to use musl via the musl-gcc 170wrapper. For example: 171 172cat > hello.c <<EOF 173#include <stdio.h> 174int main() 175{ 176 printf("hello, world!\n"); 177 return 0; 178} 179EOF 180/usr/local/musl/bin/musl-gcc hello.c 181./a.out 182 183To configure autoconf-based program to compile and link against musl, 184set the CC variable to musl-gcc when running configure, as in: 185 186CC=musl-gcc ./configure ... 187 188You will probably also want to use --prefix when building libraries to 189ensure that they are installed under the musl prefix and not in the 190main host system library directories. 191