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/*

 *      linux/mm/mprotect.c

 *

 *  (C) Copyright 1994 Linus Torvalds

 */

#include <linux/slab.h>

#include <linux/smp_lock.h>

#include <linux/shm.h>

#include <linux/mman.h>

#include <asm/uaccess.h>

#include <asm/pgalloc.h>

#include <asm/pgtable.h>

static inline void change_pte_range(pmd_t * pmd, unsigned long address,

        unsigned long size, pgprot_t newprot)

{

        pte_t * pte;

        unsigned long end;

        if (pmd_none(*pmd))

                return;

        if (pmd_bad(*pmd)) {

                pmd_ERROR(*pmd);

                pmd_clear(pmd);

                return;

        }

        pte = pte_offset(pmd, address);

        address &= ~PMD_MASK;

        end = address + size;

        if (end > PMD_SIZE)

                end = PMD_SIZE;

        do {

                if (pte_present(*pte)) {

                        pte_t entry;

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

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

                         * into place.

                         */

                        entry = ptep_get_and_clear(pte);

                        set_pte(pte, pte_modify(entry, newprot));

                }

                address += PAGE_SIZE;

                pte++;

        } while (address && (address < end));

}

static inline void change_pmd_range(pgd_t * pgd, unsigned long address,

        unsigned long size, pgprot_t newprot)

{

        pmd_t * pmd;

        unsigned long end;

        if (pgd_none(*pgd))

                return;

        if (pgd_bad(*pgd)) {

                pgd_ERROR(*pgd);

                pgd_clear(pgd);

                return;

        }

        pmd = pmd_offset(pgd, address);

        address &= ~PGDIR_MASK;

        end = address + size;

        if (end > PGDIR_SIZE)

                end = PGDIR_SIZE;

        do {

                change_pte_range(pmd, address, end - address, newprot);

                address = (address + PMD_SIZE) & PMD_MASK;

                pmd++;

        } while (address && (address < end));

}

static void change_protection(unsigned long start, unsigned long end, pgprot_t newprot)

{

        pgd_t *dir;

        unsigned long beg = start;

        dir = pgd_offset(current->mm, start);

        flush_cache_range(current->mm, beg, end);

        if (start >= end)

                BUG();

        spin_lock(&current->mm->page_table_lock);

        do {

                change_pmd_range(dir, start, end - start, newprot);

                start = (start + PGDIR_SIZE) & PGDIR_MASK;

                dir++;

        } while (start && (start < end));

        spin_unlock(&current->mm->page_table_lock);

        flush_tlb_range(current->mm, beg, end);

        return;

}

static inline int mprotect_fixup_all(struct vm_area_struct * vma, struct vm_area_struct ** pprev,

        int newflags, pgprot_t prot)

{

        struct vm_area_struct * prev = *pprev;

        struct mm_struct * mm = vma->vm_mm;

        if (prev && prev->vm_end == vma->vm_start && can_vma_merge(prev, newflags) &&

            !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {

                spin_lock(&mm->page_table_lock);

                prev->vm_end = vma->vm_end;

                __vma_unlink(mm, vma, prev);

                spin_unlock(&mm->page_table_lock);

                kmem_cache_free(vm_area_cachep, vma);

                mm->map_count--;

                return 0;

        }

        spin_lock(&mm->page_table_lock);

        vma->vm_flags = newflags;

        vma->vm_page_prot = prot;

        spin_unlock(&mm->page_table_lock);

        *pprev = vma;

        return 0;

}

static inline int mprotect_fixup_start(struct vm_area_struct * vma, struct vm_area_struct ** pprev,

        unsigned long end,

        int newflags, pgprot_t prot)

{

        struct vm_area_struct * n, * prev = *pprev;

        *pprev = vma;

        if (prev && prev->vm_end == vma->vm_start && can_vma_merge(prev, newflags) &&

            !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {

                spin_lock(&vma->vm_mm->page_table_lock);

                prev->vm_end = end;

                vma->vm_start = end;

                spin_unlock(&vma->vm_mm->page_table_lock);

                return 0;

        }

        n = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);

        if (!n)

                return -ENOMEM;

        *n = *vma;

        n->vm_end = end;

        n->vm_flags = newflags;

        n->vm_raend = 0;

        n->vm_page_prot = prot;

        if (n->vm_file)

                get_file(n->vm_file);

        if (n->vm_ops && n->vm_ops->open)

                n->vm_ops->open(n);

        vma->vm_pgoff += (end - vma->vm_start) >> PAGE_SHIFT;

        lock_vma_mappings(vma);

        spin_lock(&vma->vm_mm->page_table_lock);

        vma->vm_start = end;

        __insert_vm_struct(current->mm, n);

        spin_unlock(&vma->vm_mm->page_table_lock);

        unlock_vma_mappings(vma);

        return 0;

}

static inline int mprotect_fixup_end(struct vm_area_struct * vma, struct vm_area_struct ** pprev,

        unsigned long start,

        int newflags, pgprot_t prot)

{

        struct vm_area_struct * n;

        n = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);

        if (!n)

                return -ENOMEM;

        *n = *vma;

        n->vm_start = start;

        n->vm_pgoff += (n->vm_start - vma->vm_start) >> PAGE_SHIFT;

        n->vm_flags = newflags;

        n->vm_raend = 0;

        n->vm_page_prot = prot;

        if (n->vm_file)

                get_file(n->vm_file);

        if (n->vm_ops && n->vm_ops->open)

                n->vm_ops->open(n);

        lock_vma_mappings(vma);

        spin_lock(&vma->vm_mm->page_table_lock);

        vma->vm_end = start;

        __insert_vm_struct(current->mm, n);

        spin_unlock(&vma->vm_mm->page_table_lock);

        unlock_vma_mappings(vma);

        *pprev = n;

        return 0;

}

static inline int mprotect_fixup_middle(struct vm_area_struct * vma, struct vm_area_struct ** pprev,

        unsigned long start, unsigned long end,

        int newflags, pgprot_t prot)

{

        struct vm_area_struct * left, * right;

        left = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);

        if (!left)

                return -ENOMEM;

        right = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);

        if (!right) {

                kmem_cache_free(vm_area_cachep, left);

                return -ENOMEM;

        }

        *left = *vma;

        *right = *vma;

        left->vm_end = start;

        right->vm_start = end;

        right->vm_pgoff += (right->vm_start - left->vm_start) >> PAGE_SHIFT;

        left->vm_raend = 0;

        right->vm_raend = 0;

        if (vma->vm_file)

                atomic_add(2,&vma->vm_file->f_count);

        if (vma->vm_ops && vma->vm_ops->open) {

                vma->vm_ops->open(left);

                vma->vm_ops->open(right);

        }

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

        vma->vm_raend = 0;

        vma->vm_page_prot = prot;

        lock_vma_mappings(vma);

        spin_lock(&vma->vm_mm->page_table_lock);

        vma->vm_start = start;

        vma->vm_end = end;

        vma->vm_flags = newflags;

        __insert_vm_struct(current->mm, left);

        __insert_vm_struct(current->mm, right);

        spin_unlock(&vma->vm_mm->page_table_lock);

        unlock_vma_mappings(vma);

        *pprev = right;

        return 0;

}

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

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

{

        pgprot_t newprot;

        int error;

        if (newflags == vma->vm_flags) {

                *pprev = vma;

                return 0;

        }

        newprot = protection_map[newflags & 0xf];

        if (start == vma->vm_start) {

                if (end == vma->vm_end)

                        error = mprotect_fixup_all(vma, pprev, newflags, newprot);

                else

                        error = mprotect_fixup_start(vma, pprev, end, newflags, newprot);

        } else if (end == vma->vm_end)

                error = mprotect_fixup_end(vma, pprev, start, newflags, newprot);

        else

                error = mprotect_fixup_middle(vma, pprev, start, end, newflags, newprot);

        if (error)

                return error;

        change_protection(start, end, newprot);

        return 0;

}

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

{

        unsigned long nstart, end, tmp;

        struct vm_area_struct * vma, * next, * prev;

        int error = -EINVAL;

        if (start & ~PAGE_MASK)

                return -EINVAL;

        len = PAGE_ALIGN(len);

        end = start + len;

        if (end < start)

                return -ENOMEM;

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

                return -EINVAL;

        if (end == start)

                return 0;

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

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

        error = -ENOMEM;

        if (!vma || vma->vm_start > start)

                goto out;

        for (nstart = start ; ; ) {

                unsigned int newflags;

                int last = 0;

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

                newflags = prot | (vma->vm_flags & ~(PROT_READ | PROT_WRITE | PROT_EXEC));

                if ((newflags & ~(newflags >> 4)) & 0xf) {

                        error = -EACCES;

                        goto out;

                }

                if (vma->vm_end > end) {

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

                        goto out;

                }

                if (vma->vm_end == end)

                        last = 1;

                tmp = vma->vm_end;

                next = vma->vm_next;

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

                if (error)

                        goto out;

                if (last)

                        break;

                nstart = tmp;

                vma = next;

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

                        error = -ENOMEM;

                        goto out;

                }

        }

        if (next && prev->vm_end == next->vm_start && can_vma_merge(next, prev->vm_flags) &&

            !prev->vm_file && !(prev->vm_flags & VM_SHARED)) {

                spin_lock(&prev->vm_mm->page_table_lock);

                prev->vm_end = next->vm_end;

                __vma_unlink(prev->vm_mm, next, prev);

                spin_unlock(&prev->vm_mm->page_table_lock);

                kmem_cache_free(vm_area_cachep, next);

                prev->vm_mm->map_count--;

        }

out:

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

        return error;

}