do_brk_flags(9)

📦 version 7.3.1, in nixpkgs unstable

✨ do_brk_flags(9) ✨

okay so this is a page straight out of the Kernel API Manual bestie, and it's all about do_brk_flags — the little function that says "hey, can we make the brk vma a bit bigger?" but only if the flags line up. lowkey iconic behaviour tbh 💅

🦋 NAME 🦋

do_brk_flags — Increase the brk vma if the flags match.

like, that's the whole vibe. if the flags don't match? bestie, we're doing something else (spoiler: we make a new one, keep reading 💖).

🌸 SYNOPSIS 🌸

int do_brk_flags (struct vma_iterator *vmi , struct vm_area_struct *vma
, unsigned long addr , unsigned long len , vma_flags_t vma_flags );

five arguments, one int coming back at you. no cap 🫶

🎀 ARGUMENTS 🎀

  • vmi — The vma iterator. it's the little tour guide walking through your vmas 🧚
  • vma — The vma, (yes the original literally has that comma, we love a typo moment, keeping it exactly as-is 💀)
  • addr — The start address. where the party begins ✨
  • len — The length of the increase. how much bigger we're going 📏
  • vma_flags — The VMA Flags. the vibe check of this whole operation, fr fr 🌈

💜 DESCRIPTION 💜

so here's the tea: it extends the brk VMA from addr to addr + len. that's the main character move 👑

but — and this is the important part — if the VMA is NULL or the flags do not match, then it creates a new anonymous VMA. so it's not gonna just force the extension through, it switches lanes and makes something fresh instead. no drama, just facts 🦋

and then there's this lil note: Eventually we may be able to do some brk-specific accounting here. so like, future potential, nothing confirmed, we're just manifesting it ✨ (please don't read that as a promise, it's literally a "maybe someday" 😭)

⭐ RETURN ⭐

0 on success, or otherwise an error. that's it, that's the whole return section — short and slay 💅

🔥 SEE ALSO 🔥

Kernel file ./mm/vma.c and its besties:

go read them, iykyk 📚💖

ok genuine reminder bestie: NULL vma or mismatched flags means a new anonymous VMA gets created — not an error, just a different path. don't @ me, that's literally what the page says 🙈

and that's a wrap on do_brk_flags(9) from the ./mm corner of the world, dated October 2026 🎀 tysm for reading, go touch some vmas (responsibly) 💜🫶✨

📦 where this page comes from