u64_to_user_ptr(9)

💅 u64_to_user_ptr(9) 💅

okay so first things first, this is a page from the Kernel API Manual and honestly? it's a tiny one but it eats. let me put you on.

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🌸 NAME 🌸

u64_to_user_ptr — cast a pointer passed as u64 from user space to void __user *

like literally that's the whole gig. that's the job. 🫶

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✨ SYNOPSIS ✨

u64_to_user_ptr (x );

that's it bestie, one argument, no drama, no cap 🎀

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🦋 ARGUMENTS 🦋

• x — the u64 value from user space, usually via IOCTL 💫

so like, it comes in as a u64, and it's usually because you got it through an IOCTL. that's the vibe. that's where this thing lives. 🔥

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💖 DESCRIPTION 💖

okay so u64_to_user_ptr simply casts a pointer passed as u64 from user space to void __user * correctly.

that's the whole thing. it does it right. and the way that using this lets us get rid of all the tiresome casts?? iconic. genuinely iconic. 😭

no more hand-typing casts everywhere like some kind of feral gremlin — you just call this and it handles the conversion properly for you. lowkey the best little macro in the whole kernel. highkey actually. 👑

ngl it's giving "small function, enormous quality-of-life improvement" and i'm obsessed 💅

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👀 SEE ALSO 👀

• Kernel file ./include/linux/util_macros.h — go read it, it's right there 🍓
• for_each_if(9)
• find_closest(9)
• find_closest_descending(9)
• PTR_IF(9)
• is_insidevar(9)

the whole little macro friend group ✨🌸 they all live together, they all slay together 💜

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and that's the page!! 🧚

sign-off time: this lil beauty lives in source dir ./include/linux and the date on it is October 2026 — so yeah, she's from the future and she's still just casting pointers correctly. main character energy fr fr 🌈⭐

mwah, go convert some pointers 💖