cpacf_trng(9)

💜 cpacf_trng — a little kernel manual moment

okay so this is cpacf_trng from section 9 of the Kernel API Manual, and honestly she's a whole vibe: a tiny function with a big job 🎀

✨ NAME ✨

cpacf_trng — executes the TRNG subfunction of the PRNO instruction

like yes, that's the whole name, and yes, it ate 💅

🌸 SYNOPSIS 🌸

void cpacf_trng (u8 *ucbuf , unsigned long ucbuf_len , u8 *cbuf ,
unsigned long cbuf_len );

that's it, that's the signature — no cap, she takes four args and returns void 🫶

🦋 ARGUMENTS 🦋

okay bestie, here's who's who in the group chat:

• ucbuf — buffer for unconditioned data 🌈
• ucbuf_len — amount of unconditioned data to fetch in bytes
• cbuf — buffer for conditioned data 💖
• cbuf_len — amount of conditioned data to fetch in bytes

so ucbuf + ucbuf_len is one pair, cbuf + cbuf_len is the other, and yes the "u" totally stands for unconditioned, iykyk ✨

🔥 SEE ALSO 🔥

literally the whole cpacf cinematic universe, bestie — the actual kernel file lives at ./arch/s390/include/asm/cpacf.h, and these are her friends:

• cpacf_query(9)
• cpacf_qai(9)
• cpacf_km(9)
• cpacf_kmc(9)
• cpacf_kimd(9)
• cpacf_klmd(9)
• _cpacf_kmac(9)
• cpacf_kmac(9)
• cpacf_kmctr(9)
• cpacf_prno(9)
• cpacf_pcc(9)
• cpacf_pckmo(9)
• cpacf_kma(9)

(note that _cpacf_kmac(9) and cpacf_kmac(9) are two separate entries — they're siblings, not a typo, do not come for me 🙈)

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heads up: I'm only telling you what's in the page, so if you want the deep lore, go read cpacf.h itself, mwah 💋

and that's the whole manual, periodt 👑

— sign-off time 🎀 this cutie lives in ./arch/s390/include/asm, dated October 2026, and she'll always answer to cpacf_trng(9) ⭐