cpacf_kmctr(9)

📦 version 7.3.1, in nixpkgs unstable

💅 cpacf_kmctr(9) — a Kernel API Manual moment ✨

okay so bestie, welcome to the Kernel API Manual entry for cpacf_kmctr and honestly? she's iconic. this is the one that literally runs the KMCTR (CIPHER MESSAGE WITH COUNTER) instruction. no cap, that's her whole thing. 🎀

✨ NAME ✨

cpacf_kmctr — executes the KMCTR (CIPHER MESSAGE WITH COUNTER) instruction 💖

🌸 SYNOPSIS 🌸

int cpacf_kmctr (unsigned long func , void *param , u8 *dest , const u8 *src , long src_len , u8 *counter );

like, that's the whole signature. she's serving function prototype realness 🫶

🦋 ARGUMENTS 🦋

okay so here's the cast of characters, everyone plays a role:

  • func — the function code handed off to KMCTR; go look at the CPACF_KMCTR_xxx defines, they're the ones who actually know things 👀
  • param — address of the parameter block; check the POP for the deets on each func (yes, every single one has its own lore) 📖
  • dest — address of the destination memory area, where the good stuff lands 🌈
  • src — address of the source memory area, where the good stuff comes from ⭐
  • src_len — length of the src operand, counted in bytes (bytes!! not vibes!!) 🔥
  • counter — address of the counter value, she's the main character of the counter, obviously 👑

💜 DESCRIPTION 💜

so what does she return? here's the tea:

  • returns 0 for the query func
  • returns the number of processed bytes for the encryption/decryption funcs

that's it, that's the whole description, and honestly she ate 💅✨

🎀 SEE ALSO 🎀

the whole friend group, fr fr — plus the kernel file they all live in:

Kernel file ./arch/s390/include/asm/cpacf.h

🫶 quick vibe check bestie: _cpacf_kmac(9) and cpacf_kmac(9) are two different entries — one's got the leading underscore, one doesn't. don't get them twisted, that's not the move 😭

and that's the page!! mwah 💋 this lil beauty lives in ./arch/s390/include/asm, dated October 2026, and she answers to cpacf_kmctr(9) — go off, queen 👑🌸🍓

📦 where this page comes from