modify_prot_commit_ptes(9)

🎀 modify_prot_commit_ptes — the modify_prot_commit_ptes(9) glow-up 🎀

okay so bestie, this is a page from the Kernel API Manual, and it's literally about committing a pte update to a whole batch of ptes while leaving any hardware-controlled bits in the PTE untouched 💅 (yes, untouched — the hardware keeps its toys, we don't touch them, periodt).

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✨ SYNOPSIS ✨

void modify_prot_commit_ptes (struct vm_area_struct *vma , unsigned long
addr , pte_t *ptep , pte_t old_pte , pte_t pte , unsigned int nr );

like, that's the whole signature, no cap 🫶

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🌸 ARGUMENTS 🌸

• vma — the virtual memory area these pages are mapped into. it's giving "where do these pages even live" energy.
• addr — the address the first page is mapped at. first page gets the honors 👑
• ptep — page table pointer for the first entry. your starting point, iykyk.
• old_pte — the old page table entry (for the first entry) which is now cleared. it's had its moment, now it's gone 💀
• pte — the new page table entry to be set. the main character, fr fr.
• nr — number of entries. how many ptes are we doing this to, bestie.

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🦋 DESCRIPTION 🦋

May be overridden by the architecture — so some arches are out here doing their own thing 🧚. Otherwise, it's implemented as a simple loop over ptep_modify_prot_commit. simple loop, simple life, lowkey iconic.

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🔥 CONTEXT 🔥

okay so the important stuff, listen up:

The caller holds the page table lock 🔒. The PTEs are all in the same PMD. On exit, the set ptes in the batch map the same folio.

and here's the part you cannot miss: the ptes set by ptep_modify_prot_start may additionally have young and/or dirty bits set where previously they were not, so the updated ptes may have these additional changes ✨. not me warning you about extra bits showing up uninvited 🙈

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💜 SEE ALSO 💜

Kernel file ./include/linux/pgtable.h and its whole friend group:

• 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)
• wrprotect_ptes(9)
• clear_flush_young_ptes(9)
• test_and_clear_young_ptes(9)
• modify_prot_start_ptes(9)
• pfnmap_setup_cachemode(9)
• pfnmap_track(9)
• pfnmap_untrack(9)
• pfnmap_setup_cachemode_pfn(9)

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bestie reminder: the commit is the second half of the party — modify_prot_start_ptes(9) is the pregame, this one's the drop 🔥

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omg okay that's the whole thing, you ate that 🍓 this lil gem lives in ./include/linux and the manual says October 2026 — so like, future icons only 👑✨ slay, go commit some ptes, mwah 💖