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diff --git a/libc-top-half/musl/INSTALL b/libc-top-half/musl/INSTALL new file mode 100644 index 0000000..c583691 --- /dev/null +++ b/libc-top-half/musl/INSTALL @@ -0,0 +1,191 @@ + +Quick Installation Guide for musl libc +====================================== + +There are many different ways to install musl depending on your usage +case. This document covers only the build and installation of musl by +itself, which is useful for upgrading an existing musl-based system or +compiler toolchain, or for using the provided musl-gcc wrapper with an +existing non-musl-based compiler. + +Building complete native or cross-compiler toolchains is outside the +scope of this INSTALL file. More information can be found on the musl +website and community wiki. + + +Build Prerequisites +------------------- + +The only build-time prerequisites for musl are GNU Make and a +freestanding C99 compiler toolchain targeting the desired instruction +set architecture and ABI, with support for a minimal subset of "GNU C" +extensions consisting mainly of gcc-style inline assembly, weak +aliases, hidden visibility, and stand-alone assembly source files. + +GCC, LLVM/clang, Firm/cparser, and PCC have all successfully built +musl, but GCC is the most widely used/tested. Recent compiler (and +binutils) versions should be used if possible since some older +versions have bugs which affect musl. + +The system used to build musl does not need to be Linux-based, nor do +the Linux kernel headers need to be available. + + + +Supported Targets +----------------- + +musl can be built for the following CPU instruction set architecture +and ABI combinations: + +* i386 + * Minimum CPU model is actually 80486 unless kernel emulation of + the `cmpxchg` instruction is added + +* x86_64 + * ILP32 ABI (x32) is available as a separate arch but is still + experimental + +* ARM + * EABI, standard or hard-float VFP variant + * Little-endian default; big-endian variants also supported + * Compiler toolchains only support armv4t and later + +* AArch64 + * Little-endian default; big-endian variants also supported + +* MIPS + * ABI is o32, fp32/fpxx (except on r6 which is fp64) + * Big-endian default; little-endian variants also supported + * Default ABI variant uses FPU registers; alternate soft-float ABI + that does not use FPU registers or instructions is available + * MIPS2 or later, or kernel emulation of ll/sc (standard in Linux) + is required + * MIPS32r6, an incompatible ISA, is supported as a variant "mipsr6" + +* MIPS64 + * ABI is n64 (LP64) or n32 (ILP32) + * Big-endian default; little-endian variants also supported + * Default ABI variant uses FPU registers; alternate soft-float ABI + that does not use FPU registers or instructions is available + +* PowerPC + * Compiler toolchain must provide 64-bit long double, not IBM + double-double or IEEE quad + * For dynamic linking, compiler toolchain must be configured for + "secure PLT" variant + +* PowerPC64 + * Both little and big endian variants are supported + * Compiler toolchain must provide 64-bit long double, not IBM + double-double or IEEE quad + * Compiler toolchain must use the new (ELFv2) ABI regardless of + whether it is for little or big endian + +* S390X (64-bit S390) + +* SuperH (SH) + * Standard ELF ABI or FDPIC ABI (shared-text without MMU) + * Little-endian by default; big-endian variant also supported + * Full FPU ABI or soft-float ABI is supported, but the + single-precision-only FPU ABI is not + +* Microblaze + * Big-endian default; little-endian variants also supported + * Soft-float + * Requires support for lwx/swx instructions + +* OpenRISC 1000 (or1k) + +* RISC-V 64 + * Little endian + * Hard, soft, and hard-single/soft-double floating point ABIs + * Standard ELF; no shared-text NOMMU support + + + +Build and Installation Procedure +-------------------------------- + +To build and install musl: + +1. Run the provided configure script from the top-level source + directory, passing on its command line any desired options. + +2. Run "make" to compile. + +3. Run "make install" with appropriate privileges to write to the + target locations. + +The configure script attempts to determine automatically the correct +target architecture based on the compiler being used. For some +compilers, this may not be possible. If detection fails or selects the +wrong architecture, you can provide an explicit selection on the +configure command line. + +By default, configure installs to a prefix of "/usr/local/musl". This +differs from the behavior of most configure scripts, and is chosen +specifically to avoid clashing with libraries already present on the +system. DO NOT set the prefix to "/usr", "/usr/local", or "/" unless +you're upgrading libc on an existing musl-based system. Doing so will +break your existing system when you run "make install" and it may be +difficult to recover. + + + +Notes on Dynamic Linking +------------------------ + +If dynamic linking is enabled, one file needs to be installed outside +of the installation prefix: /lib/ld-musl-$ARCH.so.1. This is the +dynamic linker. Its pathname is hard-coded into all dynamic-linked +programs, so for the sake of being able to share binaries between +systems, a consistent location should be used everywhere. Note that +the same applies to glibc and its dynamic linker, which is named +/lib/ld-linux.so.2 on i386 systems. + +If for some reason it is impossible to install the dynamic linker in +its standard location (for example, if you are installing without root +privileges), the --syslibdir option to configure can be used to +provide a different location + +At runtime, the dynamic linker needs to know the paths to search for +shared libraries. You should create a text file named +/etc/ld-musl-$ARCH.path (where $ARCH matches the architecture name +used in the dynamic linker) containing a list of directories where you +want the dynamic linker to search for shared libraries, separated by +colons or newlines. If the dynamic linker has been installed in a +non-default location, the path file also needs to reside at that +location (../etc relative to the chosen syslibdir). + +If you do not intend to use dynamic linking, you may disable it by +passing --disable-shared to configure; this also cuts the build time +in half. + + + +Checking for Successful Installation +------------------------------------ + +After installing, you should be able to use musl via the musl-gcc +wrapper. For example: + +cat > hello.c <<EOF +#include <stdio.h> +int main() +{ + printf("hello, world!\n"); + return 0; +} +EOF +/usr/local/musl/bin/musl-gcc hello.c +./a.out + +To configure autoconf-based program to compile and link against musl, +set the CC variable to musl-gcc when running configure, as in: + +CC=musl-gcc ./configure ... + +You will probably also want to use --prefix when building libraries to +ensure that they are installed under the musl prefix and not in the +main host system library directories. |