diff --git a/libc/kernel/arch-x86/asm/pgtable-2level.h b/libc/kernel/arch-x86/asm/pgtable-2level.h
index 7ade4ed..77cdefd 100644
--- a/libc/kernel/arch-x86/asm/pgtable-2level.h
+++ b/libc/kernel/arch-x86/asm/pgtable-2level.h
@@ -7,33 +7,44 @@
  ***   structures, and macros generated from the original header, and thus,
  ***   contains no copyrightable information.
  ***
+ ***   To edit the content of this header, modify the corresponding
+ ***   source file (e.g. under external/kernel-headers/original/) then
+ ***   run bionic/libc/kernel/tools/update_all.py
+ ***
+ ***   Any manual change here will be lost the next time this script will
+ ***   be run. You've been warned!
+ ***
  ****************************************************************************
  ****************************************************************************/
 #ifndef _I386_PGTABLE_2LEVEL_H
 #define _I386_PGTABLE_2LEVEL_H
-
 #define pte_ERROR(e)   printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, (e).pte_low)
 #define pgd_ERROR(e)   printk("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))
-
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define set_pte(pteptr, pteval) native_set_pte(pteptr, pteval)
 #define set_pte_at(mm,addr,ptep,pteval) native_set_pte_at(mm, addr, ptep, pteval)
 #define set_pmd(pmdptr, pmdval) native_set_pmd(pmdptr, pmdval)
 #define set_pte_atomic(pteptr, pteval) set_pte(pteptr,pteval)
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define set_pte_present(mm,addr,ptep,pteval) set_pte_at(mm,addr,ptep,pteval)
 #define pte_clear(mm,addr,xp) do { set_pte_at(mm, addr, xp, __pte(0)); } while (0)
 #define pmd_clear(xp) do { set_pmd(xp, __pmd(0)); } while (0)
 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define pte_page(x) pfn_to_page(pte_pfn(x))
 #define pte_none(x) (!(x).pte_low)
 #define pte_pfn(x) (pte_val(x) >> PAGE_SHIFT)
 #define pfn_pte(pfn, prot) __pte(((pfn) << PAGE_SHIFT) | pgprot_val(prot))
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define pfn_pmd(pfn, prot) __pmd(((pfn) << PAGE_SHIFT) | pgprot_val(prot))
 #define PTE_FILE_MAX_BITS 29
 #define pte_to_pgoff(pte)   ((((pte).pte_low >> 1) & 0x1f ) + (((pte).pte_low >> 8) << 5 ))
 #define pgoff_to_pte(off)   ((pte_t) { (((off) & 0x1f) << 1) + (((off) >> 5) << 8) + _PAGE_FILE })
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define __swp_type(x) (((x).val >> 1) & 0x1f)
 #define __swp_offset(x) ((x).val >> 8)
 #define __swp_entry(type, offset) ((swp_entry_t) { ((type) << 1) | ((offset) << 8) })
 #define __pte_to_swp_entry(pte) ((swp_entry_t) { (pte).pte_low })
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define __swp_entry_to_pte(x) ((pte_t) { (x).val })
 #endif