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/*
* linux/mm/mprotect.c
*
* (C) Copyright 1994 Linus Torvalds
*/
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/shm.h>
#include <linux/errno.h>
#include <linux/mman.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <asm/segment.h>
#include <asm/system.h>
#define CHG_MASK (PAGE_MASK | PAGE_ACCESSED | PAGE_DIRTY | PAGE_PWT | PAGE_PCD)
static void change_protection(unsigned long start, unsigned long end, int prot)
{
unsigned long *page_table, *dir;
unsigned long page, offset;
int nr;
dir = PAGE_DIR_OFFSET(current->tss.cr3, start);
offset = (start >> PAGE_SHIFT) & (PTRS_PER_PAGE-1);
nr = (end - start) >> PAGE_SHIFT;
while (nr > 0) {
page = *dir;
dir++;
if (!(page & PAGE_PRESENT)) {
nr = nr - PTRS_PER_PAGE + offset;
offset = 0;
continue;
}
page_table = offset + (unsigned long *) (page & PAGE_MASK);
offset = PTRS_PER_PAGE - offset;
if (offset > nr)
offset = nr;
nr = nr - offset;
do {
page = *page_table;
if (page & PAGE_PRESENT)
*page_table = (page & CHG_MASK) | prot;
++page_table;
} while (--offset);
}
return;
}
static inline int mprotect_fixup_all(struct vm_area_struct * vma,
int newflags, int prot)
{
vma->vm_flags = newflags;
vma->vm_page_prot = prot;
return 0;
}
static inline int mprotect_fixup_start(struct vm_area_struct * vma,
unsigned long end,
int newflags, int prot)
{
struct vm_area_struct * n;
n = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
if (!n)
return -ENOMEM;
*n = *vma;
vma->vm_start = end;
n->vm_end = end;
vma->vm_offset += vma->vm_start - n->vm_start;
n->vm_flags = newflags;
n->vm_page_prot = prot;
if (n->vm_inode)
n->vm_inode->i_count++;
if (n->vm_ops && n->vm_ops->open)
n->vm_ops->open(n);
insert_vm_struct(current, n);
return 0;
}
static inline int mprotect_fixup_end(struct vm_area_struct * vma,
unsigned long start,
int newflags, int prot)
{
struct vm_area_struct * n;
n = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
if (!n)
return -ENOMEM;
*n = *vma;
vma->vm_end = start;
n->vm_start = start;
n->vm_offset += n->vm_start - vma->vm_start;
n->vm_flags = newflags;
n->vm_page_prot = prot;
if (n->vm_inode)
n->vm_inode->i_count++;
if (n->vm_ops && n->vm_ops->open)
n->vm_ops->open(n);
insert_vm_struct(current, n);
return 0;
}
static inline int mprotect_fixup_middle(struct vm_area_struct * vma,
unsigned long start, unsigned long end,
int newflags, int prot)
{
struct vm_area_struct * left, * right;
left = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
if (!left)
return -ENOMEM;
right = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
if (!right) {
kfree(left);
return -ENOMEM;
}
*left = *vma;
*right = *vma;
left->vm_end = start;
vma->vm_start = start;
vma->vm_end = end;
right->vm_start = end;
vma->vm_offset += vma->vm_start - left->vm_start;
right->vm_offset += right->vm_start - left->vm_start;
vma->vm_flags = newflags;
vma->vm_page_prot = prot;
if (vma->vm_inode)
vma->vm_inode->i_count += 2;
if (vma->vm_ops && vma->vm_ops->open) {
vma->vm_ops->open(left);
vma->vm_ops->open(right);
}
insert_vm_struct(current, left);
insert_vm_struct(current, right);
return 0;
}
static int mprotect_fixup(struct vm_area_struct * vma,
unsigned long start, unsigned long end, unsigned int newflags)
{
int prot, error;
if (newflags == vma->vm_flags)
return 0;
prot = PAGE_PRESENT;
if (newflags & (VM_READ | VM_EXEC))
prot |= PAGE_READONLY;
if (newflags & VM_WRITE)
if (newflags & VM_SHARED)
prot |= PAGE_SHARED;
else
prot |= PAGE_COPY;
if (start == vma->vm_start)
if (end == vma->vm_end)
error = mprotect_fixup_all(vma, newflags, prot);
else
error = mprotect_fixup_start(vma, end, newflags, prot);
else if (end == vma->vm_end)
error = mprotect_fixup_end(vma, start, newflags, prot);
else
error = mprotect_fixup_middle(vma, start, end, newflags, prot);
if (error)
return error;
change_protection(start, end, prot);
return 0;
}
asmlinkage int sys_mprotect(unsigned long start, size_t len, unsigned long prot)
{
unsigned long end, tmp;
struct vm_area_struct * vma, * next;
int error;
if (start & ~PAGE_MASK)
return -EINVAL;
len = (len + ~PAGE_MASK) & PAGE_MASK;
end = start + len;
if (end < start)
return -EINVAL;
if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC))
return -EINVAL;
if (end == start)
return 0;
for (vma = current->mm->mmap ; ; vma = vma->vm_next) {
if (!vma)
return -EFAULT;
if (vma->vm_end > start)
break;
}
if (vma->vm_start > start)
return -EFAULT;
for ( ; ; ) {
unsigned int newflags;
/* Here we know that vma->vm_start <= start < vma->vm_end. */
newflags = prot | (vma->vm_flags & ~(PROT_READ | PROT_WRITE | PROT_EXEC));
if ((newflags & ~(newflags >> 4)) & 0xf) {
error = -EACCES;
break;
}
if (vma->vm_end >= end) {
error = mprotect_fixup(vma, start, end, newflags);
break;
}
tmp = vma->vm_end;
next = vma->vm_next;
error = mprotect_fixup(vma, start, tmp, newflags);
if (error)
break;
start = tmp;
vma = next;
if (!vma || vma->vm_start != start) {
error = -EFAULT;
break;
}
}
merge_segments(current->mm->mmap);
return error;
}
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