Reference

Syscalls

The RISC-V runner implements the Linux RV64 syscall ABI that BusyBox, Node.js and the catalog apps use: 98 syscall numbers have a handler in runners/riscv/src/syscall.rs, a few of them deliberate stubs.

The guest executes ECALL with the syscall number in a7 and arguments in a0–a5; the result goes back in a0. Anything without a handler returns -ENOSYS. Counts on this page come from the dispatch match in nano v0.2.1.

Handling modes

Internal: resolved inside the WebAssembly module (memory, threads, sockets, time, signals).
FS_PENDING: file-system calls are written to a shared request block and completed by the host's in-memory filesystem; see Host API.
Blocking: futex, epoll_pwait, ppoll and timers park the thread; the host resumes it when an event or a virtual-server connection arrives.

Implemented syscalls

Area

Syscalls

Files (FS_PENDING)

openat, close, read, write, readv, writev, pread64, pwrite64, preadv, pwritev, lseek, getdents64, newfstatat, fstat, statx, readlinkat, mkdirat, unlinkat, renameat2, faccessat, utimensat, getcwd, chdir, fcntl, ioctl, dup, dup3, pipe2

Durability (succeed, nothing to flush)

sync, fsync, fdatasync, syncfs

Memory

brk, mmap, mremap, munmap (stub), mprotect (stub), madvise (stub)

Processes and threads

clone, execve, wait4, exit, exit_group, getpid, getppid, gettid, set_tid_address, set_robust_list, futex, sched_yield, sched_getaffinity, prctl, prlimit64, rseq, capget, umask

Identity

getuid, geteuid, getgid, getegid

Signals

rt_sigaction (stub), rt_sigprocmask (stub), rt_sigreturn, sigaltstack, kill, tkill, tgkill

Sockets

socket, socketpair, bind, listen, accept, accept4, connect, sendto, recvfrom, shutdown, getsockname, getpeername, getsockopt, setsockopt

Polling and events

epoll_create1, epoll_ctl, epoll_pwait, ppoll, eventfd2, timerfd_create, timerfd_settime

Time

clock_gettime, clock_getres, nanosleep, times

System

uname, sysinfo, syslog, getrandom, riscv_flush_icache (no-op), io_uring_setup (returns ENOSYS on purpose)

That is 98 numbers. Notable gaps: there is no symlinkat or linkat (so ln -s inside the guest fails), signal handlers are never delivered, and munmap doesn't release memory (the allocators are bump allocators). See Limitations.

See which syscalls an app uses

Every catalog manifest records the syscalls the app used in its conformance run (conformance.syscalls_used). The sample maps them to names.

SDK · JavaScript

Syscalls used by ripgrep

javascript

const names = { 17: "getcwd", 25: "fcntl", 29: "ioctl", 56: "openat", 57: "close", 63: "read", 64: "write", 66: "writev", 73: "ppoll", 79: "newfstatat", 80: "fstat", 94: "exit_group", 96: "set_tid_address", 113: "clock_gettime", 123: "sched_getaffinity", 131: "tgkill", 132: "sigaltstack", 134: "rt_sigaction", 135: "rt_sigprocmask", 160: "uname", 172: "getpid", 174: "getuid", 178: "gettid", 214: "brk", 215: "munmap", 222: "mmap", 226: "mprotect", 233: "madvise", 261: "prlimit64", 278: "getrandom" };
const m = await nano.catalog().manifest("ripgrep");
const used = m.conformance.syscalls_used;
print(`${m.name} ${m.version}: ${used.length} syscalls, tested=${m.conformance.tested}`);
print(used.map((n) => names[n] ?? n).join(" "));

loading…

Expected output

ripgrep 14.1.0: 21 syscalls, tested=true
getcwd fcntl ioctl openat close read ppoll newfstatat fstat exit_group set_tid_address clock_gettime sigaltstack rt_sigaction rt_sigprocmask uname getuid brk munmap mmap getrandom

Each catalog app page lists the app's tier; RISC-V apps use this ABI. The other runners don't: host-engine Node.js calls the kernel bus directly and wasm apps use WASI preview 1 (see Runners & engines).

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