wrprotect_ptes(9)

💅 wrprotect_ptes — the kernel API manual, but make it make sense

okay bestie, so this is wrprotect_ptes(9) from the Kernel API Manual, and no cap, it's lowkey one of the more chill functions you'll meet. it write-protects PTEs that map consecutive pages of the same folio. tiny job, does it well. let's get into it 🎀

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✨ SYNOPSIS ✨

void wrprotect_ptes (struct mm_struct *mm , unsigned long addr , pte_t
*ptep , unsigned int nr );

that's it. that's the whole vibe. four args, no return value, she just does the thing and leaves. main character energy fr 💅

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🌸 ARGUMENTS 🌸

here's who's who at the function party:

• mm — the address space where the pages are mapped. like, which world are we living in.
• addr — the address where the first page lives. the starting point, the origin story ⭐
• ptep — the page table pointer for the first entry. your little handle onto the action.
• nr — how many entries you want write-protected. the count. the guest list, if you will 🫶

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💖 DESCRIPTION 💖

so the way this works: this function may be overridden by the architecture. so like, your arch could swoop in and do its own special thing (iykyk). otherwise? it's literally just implemented as a simple loop over ptep_set_wrprotect. simple. iconic. efficient. 🧚

and hmm, one thing to clock: the PTE bits in the PTE range besides the PFN can differ. for example — plot twist — some PTEs might already be write-protected. so don't assume they're all identical, bestie. 🙈

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🔥 CONTEXT 🔥

okay so the ground rules for calling this thing:

• the caller holds the page table lock — non-negotiable, periodt 🔒
• the PTEs map consecutive pages that all belong to the same folio
• the PTEs are all in the same PMD

break any of these and you're not just wrong, you're messy about being wrong. and we don't do messy. 💀

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👑 SEE ALSO 👑

the whole friend group, gathered in the kernel file ./include/linux/pgtable.h:

• lazy_mmu_mode_enable(9)
• lazy_mmu_mode_disable(9)
• __task_lazy_mmu_mode_pause(9)
• lazy_mmu_mode_pause(9)
• __task_lazy_mmu_mode_resume(9)
• lazy_mmu_mode_resume(9)
• pte_batch_hint(9)
• set_ptes(9)
• clear_young_dirty_ptes(9)
• get_and_clear_full_ptes(9)
• get_and_clear_ptes(9)
• clear_full_ptes(9)
• clear_ptes(9)
• clear_nonpresent_ptes(9)
• ptep_try_set(9)
• flush_tlb_before_set(9)
• clear_flush_young_ptes(9)
• test_and_clear_young_ptes(9)
• modify_prot_start_ptes(9)
• modify_prot_commit_ptes(9)
• pfnmap_setup_cachemode(9)
• pfnmap_track(9)
• pfnmap_untrack(9)
• pfnmap_setup_cachemode_pfn(9)

like, the entire squad. go read them too, they're all serving 💜

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anyway bestie, that's the page ✨ huge shoutout to ./include/linux for holding it down, and this edition is stamped October 2026 — so like, future-proofed AND cute. go forth and write-protect responsibly, mwah 💋🦋