fault_in_readable(9)

🎀 NAME 🎀

okay so bestie, welcome to fault_in_readable(9) from the Kernel API Manual — yes, section 9, kernel API edition, we are seated. 💖 The official one-liner is: fault_in_readable - fault in userspace address range for reading. that's the whole name-and-game, and it's iconic.

✨ SYNOPSIS ✨

the signature is literally:

size_t fault_in_readable (const char __user *uaddr , size_t size );

No cap, that's exactly how it's written. 🫶

🫶 ARGUMENTS 🫶

• uaddr — start of user address range
• size — size of user address range

💅 DESCRIPTION 💅

okay so the description is short and sweet: Returns the number of bytes not faulted in (like copy_to_user and copy_from_user). that's the tea. 💅

🌈 SEE ALSO 🌈

bestie, the cross-refs go OFF. here's every single one, no skipping:

• Kernel file: ./mm/gup.c
• try_grab_folio(9)
• unpin_user_page(9)
• unpin_folio(9)
• folio_add_pin(9)
• unpin_user_pages_dirty_lock(9)
• unpin_user_page_range_dirty_lock(9)
• unpin_user_pages(9)
• unpin_user_folio(9)
• unpin_folios(9)
• try_grab_folio_fast(9)
• follow_page_mask(9)
• __get_user_pages(9)
• fixup_user_fault(9)
• populate_vma_page_range(9)
• fault_in_writeable(9)
• fault_in_subpage_writeable(9)
• get_dump_page(9)
• get_user_pages_remote(9)
• get_user_pages(9)
• get_user_pages_fast_only(9)
• get_user_pages_fast(9)
• pin_user_pages_fast(9)
• pin_user_pages_remote(9)
• pin_user_pages(9)
• memfd_pin_folios(9)
• folio_add_pins(9)

mwah 💋 — footer tea: source/version path ./mm, date October 2026, page fault_in_readable(9). that's the cute sign-off, bestie, we're done. go forth and fault in those readable ranges. 🌸