libc — musl for sic

musl 1.2.5, ported to the sic system call ABI. This is its own project, like a libc on Linux: the kernel (sic) knows nothing about it, and the userland (ZAE) just links against it. The repo is a full musl tree with the sic changes applied; NOTICE lists exactly which files.

How the port works

sic has its own syscall table — sic/abi/syscall.tbl — which is deliberately not Linux's numbering (sic is not a Linux clone; Linux binaries will not run). The names are the POSIX/musl vocabulary, so musl needs almost no code changes:

• arch/<arch>/bits/syscall.h.in — generated from the table (make abi)
• the few .s files with hard-coded numbers (clone, vfork, __set_thread_area, __unmapself, restore) and, on x86_64, the vDSO hooks in syscall_arch.h removed
• x86_64 and aarch64 are built with -fPIE, because sic user programs live at 0x8000000000; powerpc is plain non-PIC code at 0x10000000
• aarch64's long double is binary128, so its printf needs the soft-float builtins clang does not ship for a bare target; make ARCH=aarch64 has Zig bundle its compiler-rt into libcompiler_rt.a, installed beside libc.a for programs to link
• src/sic/builtins.c: the 64-bit division/shift/float-conversion helpers a 32-bit target expects from libgcc, since nothing ships them for a bare powerpc-linux-musl clang

Everything else — struct layouts, calling convention (syscall / sc, -errno or CR0.SO+errno returns), TLS, the initial process stack with auxv — is what musl's own port of that architecture expects and what the kernel implements (sic/include/abi/abi.h, sic/kernel/proc/syscall.c). On 32-bit targets the kernel is time64-only, so make abi for them also defines the *_time64 names musl looks for, as aliases of the plain numbers.

Ports: x86_64 (default), aarch64 (make ARCH=aarch64) and powerpc (32-bit big-endian, make ARCH=powerpc, built with -mcpu=7450 -maltivec).

Building

make            # GNUmakefile: cross-builds a static libc into build/ with clang
make install    # -> $SYSROOT/usr/include, $SYSROOT/usr/lib/{libc.a,crt1.o,crti.o,crtn.o}

All four sic projects meet in a sysroot rather than knowing each other's paths: $SIC_SYSROOT, default ~/.sic/sysroot (or make SYSROOT=...). Install the kernel first (make install in sic) — it provides the syscall table that make abi regenerates arch/<arch>/bits/syscall.h.in from. musl's own Makefile and configure are untouched. Objects go to obj/<arch>/, the result to build/<arch>/.

Compile programs with clang --target=x86_64-linux-musl -nostdinc -isystem $SYSROOT/usr/include -fPIE and link with ld.lld -static --image-base=0x8000000000 crt1.o crti.o <objs> libc.a crtn.o (see the ZAE Makefile); for powerpc --target=powerpc-linux-musl -mcpu=7450 -maltivec and ld.lld -m elf32ppc --image-base=0x10000000.

What's missing on the kernel side

mmap is anonymous or private file-backed only (no shared mappings); no job control (setpgid is a no-op); no SIGSTOP/SIGCONT. Sockets are AF_INET only (TCP, UDP, raw ICMP; no AF_UNIX, no socketpair). Unimplemented syscalls return ENOSYS.

Contributing

Patches need a Signed-off-by: line (DCO 1.1). Read CODE_OF_CONFLICT and CONTRIBUTING.

License

Upstream musl is Copyright (c) 2005-2020 Rich Felker et al., MIT (COPYRIGHT). The sic changes are Copyright (C) 2026 Rigby Foundation under the LGPL-2.1-or-later (LICENSE, NOTICE): a libc must not impose terms on the programs that link it.