drm_gem_get_unmapped_area(9)

📦 version 7.3.1, in nixpkgs unstable

💅 drm_gem_get_unmapped_area(9) 💅

okay bestie, welcome to the Kernel API Manual — yes we're in kernel-land today, and yes this one's a little niche but it's actually so good once you get it. sit with me 🫶

✨ NAME ✨

drm_gem_get_unmapped_area — the get-memory-mapping-region routine for GEM objects. it literally finds you a place to map your GEM stuff. iconic behavior 💖

🌸 SYNOPSIS 🌸

unsigned long drm_gem_get_unmapped_area (struct file *filp , unsigned
long uaddr , unsigned long len , unsigned long pgoff , unsigned long
flags );

no cap, that's the whole signature. arguments below, keep scrolling 📜

🎀 ARGUMENTS 🎀

  • filp — the DRM file pointer. yeah, the file, we love her 💅
  • uaddr — user address hint. it's a hint, she's not obligated 🫶
  • len — mapping length. how much space we're asking for, be honest about it
  • pgoff — offset, measured in pages (important!! pages not bytes, iykyk) 📏
  • flags — mapping flags. the vibe settings for the mapping ✨

🦋 DESCRIPTION 🦋

so here's the situation. if a driver supports GEM object mapping, then before you ever end up in drm_gem_mmap, mmap calls on the DRM file descriptor will first try to find a free linear address space that's big enough for a mapping. that's the whole errand. literally just finding a spot 🗺️

and because GEM objects are backed by shmem buffers, this should preferably be handled by the shmem virtual memory filesystem — she's the one who can appropriately align addresses to huge page sizes when needed. like, that's her speciality, let her cook 👑🔥

then: look up the GEM object based on the offset you passed in (vma->vm_pgoff will contain the fake offset we created — yes, fake, that's the word, don't come for me 🙈) and call shmem_get_unmapped_area with the right file pointer.

and if a GEM object is not available at the given offset, or if the caller is not granted access to it? no drama, we fall back to mm_get_unmapped_area. plan B is still a plan bestie 💀

⭐ SEE ALSO ⭐

kernel file ./drivers/gpu/drm/drm_gem.c — go read her, she's the main character of this whole directory 🌈

and like the entire extended friend group, all here:

mwah 💋 that's the page. sourced from ./drivers/gpu/drm, dated October 2026, filed under drm_gem_get_unmapped_area(9) — go forth and map responsibly, bestie 🧚‍♀️💜

📦 where this page comes from