Subversion Repositories test_project

/*

 *  mm/mprotect.c

 *

 *  (C) Copyright 1994 Linus Torvalds

 *  (C) Copyright 2002 Christoph Hellwig

 *

 *  Address space accounting code       <alan@redhat.com>

 *  (C) Copyright 2002 Red Hat Inc, All Rights Reserved

 */

#include <linux/mm.h>

#include <linux/hugetlb.h>

#include <linux/slab.h>

#include <linux/shm.h>

#include <linux/mman.h>

#include <linux/fs.h>

#include <linux/highmem.h>

#include <linux/security.h>

#include <linux/mempolicy.h>

#include <linux/personality.h>

#include <linux/syscalls.h>

#include <linux/swap.h>

#include <linux/swapops.h>

#include <asm/uaccess.h>

#include <asm/pgtable.h>

#include <asm/cacheflush.h>

#include <asm/tlbflush.h>

static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,

                unsigned long addr, unsigned long end, pgprot_t newprot,

                int dirty_accountable)

{

        pte_t *pte, oldpte;

        spinlock_t *ptl;

        pte = pte_offset_map_lock(mm, pmd, addr, &ptl);

        arch_enter_lazy_mmu_mode();

        do {

                oldpte = *pte;

                if (pte_present(oldpte)) {

                        pte_t ptent;

                        /* Avoid an SMP race with hardware updated dirty/clean

                         * bits by wiping the pte and then setting the new pte

                         * into place.

                         */

                        ptent = ptep_get_and_clear(mm, addr, pte);

                        ptent = pte_modify(ptent, newprot);

                        /*

                         * Avoid taking write faults for pages we know to be

                         * dirty.

                         */

                        if (dirty_accountable && pte_dirty(ptent))

                                ptent = pte_mkwrite(ptent);

                        set_pte_at(mm, addr, pte, ptent);

#ifdef CONFIG_MIGRATION

                } else if (!pte_file(oldpte)) {

                        swp_entry_t entry = pte_to_swp_entry(oldpte);

                        if (is_write_migration_entry(entry)) {

                                /*

                                 * A protection check is difficult so

                                 * just be safe and disable write

                                 */

                                make_migration_entry_read(&entry);

                                set_pte_at(mm, addr, pte,

                                        swp_entry_to_pte(entry));

                        }

#endif

                }

        } while (pte++, addr += PAGE_SIZE, addr != end);

        arch_leave_lazy_mmu_mode();

        pte_unmap_unlock(pte - 1, ptl);

}

static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,

                unsigned long addr, unsigned long end, pgprot_t newprot,

                int dirty_accountable)

{

        pmd_t *pmd;

        unsigned long next;

        pmd = pmd_offset(pud, addr);

        do {

                next = pmd_addr_end(addr, end);

                if (pmd_none_or_clear_bad(pmd))

                        continue;

                change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);

        } while (pmd++, addr = next, addr != end);

}

static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,

                unsigned long addr, unsigned long end, pgprot_t newprot,

                int dirty_accountable)

{

        pud_t *pud;

        unsigned long next;

        pud = pud_offset(pgd, addr);

        do {

                next = pud_addr_end(addr, end);

                if (pud_none_or_clear_bad(pud))

                        continue;

                change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);

        } while (pud++, addr = next, addr != end);

}

static void change_protection(struct vm_area_struct *vma,

                unsigned long addr, unsigned long end, pgprot_t newprot,

                int dirty_accountable)

{

        struct mm_struct *mm = vma->vm_mm;

        pgd_t *pgd;

        unsigned long next;

        unsigned long start = addr;

        BUG_ON(addr >= end);

        pgd = pgd_offset(mm, addr);

        flush_cache_range(vma, addr, end);

        do {

                next = pgd_addr_end(addr, end);

                if (pgd_none_or_clear_bad(pgd))

                        continue;

                change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);

        } while (pgd++, addr = next, addr != end);

        flush_tlb_range(vma, start, end);

}

int

mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,

        unsigned long start, unsigned long end, unsigned long newflags)

{

        struct mm_struct *mm = vma->vm_mm;

        unsigned long oldflags = vma->vm_flags;

        long nrpages = (end - start) >> PAGE_SHIFT;

        unsigned long charged = 0;

        pgoff_t pgoff;

        int error;

        int dirty_accountable = 0;

        if (newflags == oldflags) {

                *pprev = vma;

                return 0;

        }

        /*

         * If we make a private mapping writable we increase our commit;

         * but (without finer accounting) cannot reduce our commit if we

         * make it unwritable again.

         *

         * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting

         * a MAP_NORESERVE private mapping to writable will now reserve.

         */

        if (newflags & VM_WRITE) {

                if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) {

                        charged = nrpages;

                        if (security_vm_enough_memory(charged))

                                return -ENOMEM;

                        newflags |= VM_ACCOUNT;

                }

        }

        /*

         * First try to merge with previous and/or next vma.

         */

        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);

        *pprev = vma_merge(mm, *pprev, start, end, newflags,

                        vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));

        if (*pprev) {

                vma = *pprev;

                goto success;

        }

        *pprev = vma;

        if (start != vma->vm_start) {

                error = split_vma(mm, vma, start, 1);

                if (error)

                        goto fail;

        }

        if (end != vma->vm_end) {

                error = split_vma(mm, vma, end, 0);

                if (error)

                        goto fail;

        }

success:

        /*

         * vm_flags and vm_page_prot are protected by the mmap_sem

         * held in write mode.

         */

        vma->vm_flags = newflags;

        vma->vm_page_prot = vm_get_page_prot(newflags);

        if (vma_wants_writenotify(vma)) {

                vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);

                dirty_accountable = 1;

        }

        if (is_vm_hugetlb_page(vma))

                hugetlb_change_protection(vma, start, end, vma->vm_page_prot);

        else

                change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);

        vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);

        vm_stat_account(mm, newflags, vma->vm_file, nrpages);

        return 0;

fail:

        vm_unacct_memory(charged);

        return error;

}

asmlinkage long

sys_mprotect(unsigned long start, size_t len, unsigned long prot)

{

        unsigned long vm_flags, nstart, end, tmp, reqprot;

        struct vm_area_struct *vma, *prev;

        int error = -EINVAL;

        const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);

        prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);

        if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */

                return -EINVAL;

        if (start & ~PAGE_MASK)

                return -EINVAL;

        if (!len)

                return 0;

        len = PAGE_ALIGN(len);

        end = start + len;

        if (end <= start)

                return -ENOMEM;

        if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM))

                return -EINVAL;

        reqprot = prot;

        /*

         * Does the application expect PROT_READ to imply PROT_EXEC:

         */

        if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))

                prot |= PROT_EXEC;

        vm_flags = calc_vm_prot_bits(prot);

        down_write(&current->mm->mmap_sem);

        vma = find_vma_prev(current->mm, start, &prev);

        error = -ENOMEM;

        if (!vma)

                goto out;

        if (unlikely(grows & PROT_GROWSDOWN)) {

                if (vma->vm_start >= end)

                        goto out;

                start = vma->vm_start;

                error = -EINVAL;

                if (!(vma->vm_flags & VM_GROWSDOWN))

                        goto out;

        }

        else {

                if (vma->vm_start > start)

                        goto out;

                if (unlikely(grows & PROT_GROWSUP)) {

                        end = vma->vm_end;

                        error = -EINVAL;

                        if (!(vma->vm_flags & VM_GROWSUP))

                                goto out;

                }

        }

        if (start > vma->vm_start)

                prev = vma;

        for (nstart = start ; ; ) {

                unsigned long newflags;

                /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */

                newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));

                /* newflags >> 4 shift VM_MAY% in place of VM_% */

                if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {

                        error = -EACCES;

                        goto out;

                }

                error = security_file_mprotect(vma, reqprot, prot);

                if (error)

                        goto out;

                tmp = vma->vm_end;

                if (tmp > end)

                        tmp = end;

                error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);

                if (error)

                        goto out;

                nstart = tmp;

                if (nstart < prev->vm_end)

                        nstart = prev->vm_end;

                if (nstart >= end)

                        goto out;

                vma = prev->vm_next;

                if (!vma || vma->vm_start != nstart) {

                        error = -ENOMEM;

                        goto out;

                }

        }

out:

        up_write(&current->mm->mmap_sem);

        return error;

}