cpacf_km(9)

💅 cpacf_km — the KM (CIPHER MESSAGE) instruction, but make it make sense

okay so bestie, this is a page from the Kernel API Manual (cpacf_km(9)), and it's literally the kernel-side hook that runs the KM (CIPHER MESSAGE) instruction on s390. sit down, hydrate, and let's get into it 🫶

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✨ SYNOPSIS ✨

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

like… five arguments. that's it. that's the whole vibe check. 💅

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🎀 ARGUMENTS 🎀

• func — the function code that gets passed straight to KM 👑 see the CPACF_KM_xxx defines for your options, bestie.
• param — the address of the parameter block 📦 each func has its own parameter block layout, and the POP has the deets on all of them.
• dest — address of the destination memory area, aka where the good stuff lands 🎯
• src — address of the source memory area, aka the input, the main character 🌸
• src_len — the length of the src operand, in bytes 📏 measured in bytes, no cap.

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🦋 DESCRIPTION 🦋

so here's what it actually returns, and this is highkey the important bit:

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

that's it. that's the description. short, iconic, to the point. periodt. ✨

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🌈 SEE ALSO 🌈

go read these next so you can be that girl who knows the whole CPACF family 💜

• Kernel file ./arch/s390/include/asm/cpacf.h
• cpacf_query(9)
• cpacf_qai(9)
• cpacf_kmc(9)
• cpacf_kimd(9)
• cpacf_klmd(9)
• _cpacf_kmac(9)
• cpacf_kmac(9)
• cpacf_kmctr(9)
• cpacf_prno(9)
• cpacf_trng(9)
• cpacf_pcc(9)
• cpacf_pckmo(9)
• cpacf_kma(9)

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okay that's the whole page, mwah 💋 this lil beauty lives at ./arch/s390/include/asm and it's dated October 2026, page cpacf_km(9) — go forth and cipher, bestie 🧚‍♀️💖