cpacf_kmc(9)

💜 cpacf_kmc — the one that runs KMC

okay so this is a page from the Kernel API Manual (yes, the cpacf_kmc(9) one, section 9, we're in kernel-land bestie) and it's literally about the KMC instruction — that's CIPHER MESSAGE WITH CHAINING for those of us keeping score 🎀

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✨ NAME ✨

cpacf_kmc — runs the KMC instruction, aka CIPHER MESSAGE WITH CHAINING. That's the whole vibe. 💅

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🌸 SYNOPSIS 🌸

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

no cap, that's the signature. five things go in, an int comes out. 🦋

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🧚 ARGUMENTS 🧚

• func — the function code you hand over to KM; peep the CPACF_KMC_xxx defines for what's on the menu 🔥
• param — address of the parameter block; the POP has the deets on what each func actually wants in there 👑
• 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, in bytes. bytes!! that's the unit!! ⭐

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🦋 DESCRIPTION 🦋

so here's the tea: it returns 0 for the query func, and the number of processed bytes for the encryption/decryption funcs. that's it, that's the whole return situation. slay. ✨

iykyk: query func ➡️ 0. encrypt/decrypt func ➡️ processed byte count. don't mix them up bestie 😭

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🌈 SEE ALSO 🌈

• Kernel file ./arch/s390/include/asm/cpacf.h 💀 (yes, that's the file, that's the whole path)
• cpacf_query(9)
• cpacf_qai(9)
• cpacf_km(9)
• cpacf_kimd(9)
• cpacf_klmd(9)
• _cpacf_kmac(9) (yes the underscore is real, don't come for me 🙈)
• cpacf_kmac(9)
• cpacf_kmctr(9)
• cpacf_prno(9)
• cpacf_trng(9)
• cpacf_pcc(9)
• cpacf_pckmo(9)
• cpacf_kma(9)

like a whole friend group of cpacf functions. the whole squad fr fr 🫶

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and that's the page!! this cutie lives in ./arch/s390/include/asm, dated October 2026, and it goes by cpacf_kmc(9) — go read the whole fam, mwah 💋🍓