fpu_xstate_prctl(9)

🌸 NAME 🌸

okay so this is fpu_xstate_prctl from the Kernel API Manual, and the whole vibe is xstate permission operations ✨ literally the permission desk for xstate, bestie 💅

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✨ SYNOPSIS ✨

long fpu_xstate_prctl (int option , unsigned long arg2 );

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🎀 ARGUMENTS 🎀

• option — a subfunction of arch_prctl 🫶
• arg2 — the option argument, iykyk 💖

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💖 RETURN 💖

0 if successful; otherwise, an error code 😭 that’s the whole deal, no cap.

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🦋 DESCRIPTION 🦋

Option arguments, bestie — here’s the lineup 👑

• ARCH_GET_XCOMP_SUPP — pointer to user space u64 to store the info ✨
• ARCH_GET_XCOMP_PERM — pointer to user space u64 to store the info 💖
• ARCH_REQ_XCOMP_PERM — facility number requested 👑

For facilities which require more than one XSTATE component, the request must be the highest state component number related to that facility, e.g. for AMX which requires XFEATURE_XTILE_CFG(17) and XFEATURE_XTILE_DATA(18) this would be XFEATURE_XTILE_DATA(18) 🔥

fr fr, that “highest component number” part is the main-character rule here — don’t show up with the lower one and expect it to slay 💀

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🌈 SEE ALSO 🌈

• Kernel file ./arch/x86/kernel/fpu/xstate.c 🦋
• check_xtile_data_against_struct(9)
• __copy_xstate_to_uabi_buf(9)
• copy_xstate_to_uabi_buf(9)
• copy_uabi_to_xstate(9)
• xsaves(9)
• xrstors(9)
• fpstate_realloc(9)

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xoxo, your fave kernel bestie 💅 — source/version: ./arch/x86/kernel/fpu, date: October 2026, page: fpu_xstate_prctl(9) 🎀