cond_install_uffd_wp_ptes(9)

💅 cond_install_uffd_wp_ptes(9) — kernel API manual energy ✨

okay so bestie, today's main character is cond_install_uffd_wp_ptes, straight out of the Kernel API Manual. she's a little niche, she's a little spicy, but she's doing very important page-table work and we're gonna stan 🫶

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🌸 NAME 🌸

cond_install_uffd_wp_ptes — installs uffd-wp markers after the PTEs have already been cleared. no cap, that ordering is the whole point 💅

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🎀 SYNOPSIS 🎀

bool cond_install_uffd_wp_ptes (struct vm_area_struct *vma , unsigned
       long addr , pte_t *ptep , pte_t pte , unsigned long nr_ptes );

that's the whole signature, copy it exactly, don't be weird about it 💖

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✨ ARGUMENTS ✨

• vma — the VMA that the pages are mapped into. it's giving "the neighborhood these pages live in" 🏡
• addr — the address where the first page of this batch is mapped. like the street number for entry one 🗺️
• ptep — the page table pointer for the first entry of this batch. your starting point fr fr 📍
• pte — the old value of the entry that ptep points at. vintage, pre-loved, previous owner energy 🍓
• nr_ptes — how many entries we're installing. the batch size, the headcount, the "how many of these are we doing" number 🔢

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💖 DESCRIPTION 💖

so here's the vibe: if the PTEs got write-protected by uffd-wp in any form, we arm special PTEs to replace none PTEs. it's giving glow-up, but make it page tables ✨

⚠️ NOTE! this should only be called when the PTEs are already cleared, so we never accidentally replace something valuable. like, ever. we do not touch the precious cargo 🙈

meanwhile, none PTEs also mean we are not demoting the PTEs, so a TLB flush is not needed. e.g., when the PTEs were cleared, the caller should have already taken care of the TLB flush. that's the caller's job bestie, not ours 💅

it must be called with the page table lock held, so that no thread will see the none PTEs — and if they do see them, they'll fault and serialize at the page table lock. everyone gets in line, single file, no cutting 🚦

returns true if uffd-wp PTEs were installed, and false otherwise. simple as that, slay 🎀

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🦋 SEE ALSO 🦋

kernel file ./mm/memory.c — and the whole friend group:

free_pgd_range(9), free_pgtables(9), __vm_normal_page(9), vm_normal_page(9), vm_normal_folio(9), vm_normal_page_pmd(9), vm_normal_folio_pmd(9), vm_normal_page_pud(9), restore_exclusive_pte(9), zap_vma_for_reaping(9), unmap_vmas(9), zap_vma_range_batched(9), zap_vma_range(9), zap_special_vma_range(9), vm_insert_pages(9), vm_insert_page(9), vm_map_pages(9), vm_map_pages_zero(9), vmf_insert_pfn_prot(9), vmf_insert_pfn(9), remap_pfn_range(9), vm_iomap_memory(9), __vmf_anon_prepare(9), finish_mkwrite_fault(9), unmap_mapping_folio(9), unmap_mapping_pages(9), unmap_mapping_range(9), set_pte_range(9), finish_fault(9), mm_account_fault(9), follow_pfnmap_start(9), follow_pfnmap_end(9), generic_access_phys(9), access_remote_vm(9), copy_remote_vm_str(9), folio_zero_user(9)

like, that's the entire group chat, all tagged, no one left on read 💜

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and that's the page!! 🫶 this one lives in ./mm, dated October 2026, and it's cond_install_uffd_wp_ptes(9) — go forth and install those markers responsibly, bestie 👑