fault_in_writeable(9)

📦 version 7.3.1, in nixpkgs unstable

💅 fault_in_writeable — a.k.a. the "bestie, pls make this memory writable" function

okay so this one's from the Kernel API Manual, and honestly? it's a little sleeper hit. no cap, it's short, it's sweet, it does exactly one thing and it does it well. let's get into it 🎀

✨ NAME ✨

fault_in_writeable — fault in userspace address range for writing

like... the whole personality is right there in the name, bestie. it goes and touches your userspace range so it's ready for writing. that's it. that's the vibe. 💖

🌸 SYNOPSIS 🌸

size_t fault_in_writeable (char __user *uaddr , size_t size );

look at that signature. clean. iconic. no notes. 👑

🦋 ARGUMENTS 🦋

  • uaddr — start of address range 🌈 (where the range begins, literally the starting point, main character energy)
  • size — size of address range 🌸 (how much of it we're talking about, in bytes)

that's the whole cast. two args. two icons. 🫶

💜 DESCRIPTION 💜

so here's the tea ☕ — it returns the number of bytes not faulted in (like copy_to_user and copy_from_user).

that's it. that's the description. it's giving "short and devastating." 🔥 read that return value carefully though, bestie — it's the bytes not faulted in, iykyk. don't @ me, just read it twice. 💀

👑 SEE ALSO 👑

the squad. the whole friend group. the ./mm crew (kernel file ./mm/gup.c) 🧚 — and yes, every single one of them showed up to the group chat:

literally the entire pinning-and-page-fetching friend group in one list. a whole roster. ate. 💅

quick vibe check 🎀: fault_in_writeable(9) is a writers-only situation — if you're here for reading, go say hi to fault_in_readable(9) up there in the SEE ALSO. it's right there. slay.

okay that's the page!! short, sweet, and fr fr useful 🍓

sign-off time, bestie: this lil masterpiece lives in the kernel source at ./mm, and it's dated October 2026. put it in your notes. screenshot it. frame it. 🌈✨💖

fault_in_writeable(9) — 💀 fault in userspace address range for writing 💀

📦 where this page comes from