getrandom (nr 318)

Linux Signature

ssize_t getrandom(void *buf, size_t buflen, unsigned int flags);

Description

Fills a buffer with random bytes. Used by Rust’s HashMap for hash seed randomisation and by musl for stack canary initialisation.

Current Implementation

Uses a simple xorshift64* PRNG seeded from the x86 TSC (Time Stamp Counter via rdtsc). Fills the user buffer byte-by-byte from the PRNG state. The flags parameter is accepted but ignored.

Note: This is not cryptographically secure. It provides enough entropy for HashMap seeds and similar non-security use cases.

Source: osl/src/syscalls/misc.rs — sys_getrandom

Errors

Future Work

• Seed from a proper entropy source (e.g. RDSEED/RDRAND instructions).
• Distinguish GRND_RANDOM vs GRND_NONBLOCK flags.