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![Linus Torvalds](/assets/img/avatar_default.png)
Several users of "find_vma_prev()" were not in fact interested in the
previous vma if there was no primary vma to be found either. And in
those cases, we're much better off just using the regular "find_vma()",
and then "prev" can be looked up by just checking vma->vm_prev.
The find_vma_prev() semantics are fairly subtle (see Mikulas' recent
commit 83cd904d27
: "mm: fix find_vma_prev"), and the whole "return
prev by reference" means that it generates worse code too.
Thus this "let's avoid using this inconvenient and clearly too subtle
interface when we don't really have to" patch.
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
330 lines
7.9 KiB
C
330 lines
7.9 KiB
C
/*
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* mm/mprotect.c
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*
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* (C) Copyright 1994 Linus Torvalds
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* (C) Copyright 2002 Christoph Hellwig
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*
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* Address space accounting code <alan@lxorguk.ukuu.org.uk>
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* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
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*/
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#include <linux/mm.h>
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#include <linux/hugetlb.h>
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#include <linux/shm.h>
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#include <linux/mman.h>
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#include <linux/fs.h>
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#include <linux/highmem.h>
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#include <linux/security.h>
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#include <linux/mempolicy.h>
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#include <linux/personality.h>
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#include <linux/syscalls.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/mmu_notifier.h>
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#include <linux/migrate.h>
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#include <linux/perf_event.h>
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#include <asm/uaccess.h>
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#include <asm/pgtable.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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#ifndef pgprot_modify
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static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
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{
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return newprot;
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}
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#endif
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static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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pte_t *pte, oldpte;
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spinlock_t *ptl;
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pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
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arch_enter_lazy_mmu_mode();
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do {
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oldpte = *pte;
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if (pte_present(oldpte)) {
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pte_t ptent;
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ptent = ptep_modify_prot_start(mm, addr, pte);
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ptent = pte_modify(ptent, newprot);
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/*
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* Avoid taking write faults for pages we know to be
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* dirty.
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*/
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if (dirty_accountable && pte_dirty(ptent))
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ptent = pte_mkwrite(ptent);
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ptep_modify_prot_commit(mm, addr, pte, ptent);
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} else if (PAGE_MIGRATION && !pte_file(oldpte)) {
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swp_entry_t entry = pte_to_swp_entry(oldpte);
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if (is_write_migration_entry(entry)) {
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/*
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* A protection check is difficult so
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* just be safe and disable write
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*/
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make_migration_entry_read(&entry);
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set_pte_at(mm, addr, pte,
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swp_entry_to_pte(entry));
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}
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}
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} while (pte++, addr += PAGE_SIZE, addr != end);
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arch_leave_lazy_mmu_mode();
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pte_unmap_unlock(pte - 1, ptl);
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}
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static inline void change_pmd_range(struct vm_area_struct *vma, pud_t *pud,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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pmd_t *pmd;
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unsigned long next;
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pmd = pmd_offset(pud, addr);
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do {
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next = pmd_addr_end(addr, end);
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if (pmd_trans_huge(*pmd)) {
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if (next - addr != HPAGE_PMD_SIZE)
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split_huge_page_pmd(vma->vm_mm, pmd);
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else if (change_huge_pmd(vma, pmd, addr, newprot))
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continue;
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/* fall through */
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}
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if (pmd_none_or_clear_bad(pmd))
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continue;
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change_pte_range(vma->vm_mm, pmd, addr, next, newprot,
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dirty_accountable);
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} while (pmd++, addr = next, addr != end);
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}
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static inline void change_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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pud_t *pud;
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unsigned long next;
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pud = pud_offset(pgd, addr);
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do {
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next = pud_addr_end(addr, end);
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if (pud_none_or_clear_bad(pud))
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continue;
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change_pmd_range(vma, pud, addr, next, newprot,
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dirty_accountable);
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} while (pud++, addr = next, addr != end);
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}
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static void change_protection(struct vm_area_struct *vma,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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struct mm_struct *mm = vma->vm_mm;
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pgd_t *pgd;
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unsigned long next;
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unsigned long start = addr;
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BUG_ON(addr >= end);
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pgd = pgd_offset(mm, addr);
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flush_cache_range(vma, addr, end);
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do {
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next = pgd_addr_end(addr, end);
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if (pgd_none_or_clear_bad(pgd))
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continue;
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change_pud_range(vma, pgd, addr, next, newprot,
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dirty_accountable);
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} while (pgd++, addr = next, addr != end);
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flush_tlb_range(vma, start, end);
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}
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int
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mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
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unsigned long start, unsigned long end, unsigned long newflags)
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{
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struct mm_struct *mm = vma->vm_mm;
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unsigned long oldflags = vma->vm_flags;
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long nrpages = (end - start) >> PAGE_SHIFT;
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unsigned long charged = 0;
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pgoff_t pgoff;
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int error;
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int dirty_accountable = 0;
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if (newflags == oldflags) {
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*pprev = vma;
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return 0;
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}
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/*
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* If we make a private mapping writable we increase our commit;
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* but (without finer accounting) cannot reduce our commit if we
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* make it unwritable again. hugetlb mapping were accounted for
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* even if read-only so there is no need to account for them here
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*/
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if (newflags & VM_WRITE) {
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if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
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VM_SHARED|VM_NORESERVE))) {
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charged = nrpages;
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if (security_vm_enough_memory(charged))
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return -ENOMEM;
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newflags |= VM_ACCOUNT;
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}
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}
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/*
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* First try to merge with previous and/or next vma.
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*/
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pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
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*pprev = vma_merge(mm, *pprev, start, end, newflags,
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vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
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if (*pprev) {
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vma = *pprev;
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goto success;
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}
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*pprev = vma;
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if (start != vma->vm_start) {
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error = split_vma(mm, vma, start, 1);
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if (error)
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goto fail;
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}
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if (end != vma->vm_end) {
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error = split_vma(mm, vma, end, 0);
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if (error)
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goto fail;
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}
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success:
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/*
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* vm_flags and vm_page_prot are protected by the mmap_sem
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* held in write mode.
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*/
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vma->vm_flags = newflags;
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vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
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vm_get_page_prot(newflags));
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if (vma_wants_writenotify(vma)) {
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vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
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dirty_accountable = 1;
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}
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mmu_notifier_invalidate_range_start(mm, start, end);
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if (is_vm_hugetlb_page(vma))
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hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
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else
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change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
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mmu_notifier_invalidate_range_end(mm, start, end);
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vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
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vm_stat_account(mm, newflags, vma->vm_file, nrpages);
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perf_event_mmap(vma);
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return 0;
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fail:
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vm_unacct_memory(charged);
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return error;
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}
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SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
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unsigned long, prot)
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{
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unsigned long vm_flags, nstart, end, tmp, reqprot;
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struct vm_area_struct *vma, *prev;
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int error = -EINVAL;
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const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
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prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
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if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
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return -EINVAL;
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if (start & ~PAGE_MASK)
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return -EINVAL;
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if (!len)
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return 0;
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len = PAGE_ALIGN(len);
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end = start + len;
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if (end <= start)
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return -ENOMEM;
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if (!arch_validate_prot(prot))
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return -EINVAL;
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reqprot = prot;
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/*
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* Does the application expect PROT_READ to imply PROT_EXEC:
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*/
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if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
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prot |= PROT_EXEC;
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vm_flags = calc_vm_prot_bits(prot);
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down_write(¤t->mm->mmap_sem);
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vma = find_vma(current->mm, start);
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error = -ENOMEM;
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if (!vma)
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goto out;
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prev = vma->vm_prev;
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if (unlikely(grows & PROT_GROWSDOWN)) {
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if (vma->vm_start >= end)
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goto out;
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start = vma->vm_start;
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error = -EINVAL;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto out;
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}
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else {
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if (vma->vm_start > start)
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goto out;
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if (unlikely(grows & PROT_GROWSUP)) {
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end = vma->vm_end;
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error = -EINVAL;
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if (!(vma->vm_flags & VM_GROWSUP))
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goto out;
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}
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}
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if (start > vma->vm_start)
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prev = vma;
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for (nstart = start ; ; ) {
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unsigned long newflags;
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/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
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newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
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/* newflags >> 4 shift VM_MAY% in place of VM_% */
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if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
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error = -EACCES;
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goto out;
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}
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error = security_file_mprotect(vma, reqprot, prot);
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if (error)
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goto out;
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tmp = vma->vm_end;
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if (tmp > end)
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tmp = end;
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error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
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if (error)
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goto out;
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nstart = tmp;
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if (nstart < prev->vm_end)
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nstart = prev->vm_end;
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if (nstart >= end)
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goto out;
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vma = prev->vm_next;
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if (!vma || vma->vm_start != nstart) {
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error = -ENOMEM;
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goto out;
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}
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}
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out:
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up_write(¤t->mm->mmap_sem);
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return error;
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}
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