Viewing file:  mremap.c (8.97 KB) -rw-r--r--
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/*
* linux/mm/remap.c
*
* (C) Copyright 1996 Linus Torvalds
*/
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
extern int vm_enough_memory(long pages);
static inline pte_t *get_one_pte(struct mm_struct *mm, unsigned long addr)
{
pgd_t * pgd;
pmd_t * pmd;
pte_t * pte = NULL;
pgd = pgd_offset(mm, addr);
if (pgd_none(*pgd))
goto end;
if (pgd_bad(*pgd)) {
pgd_ERROR(*pgd);
pgd_clear(pgd);
goto end;
}
pmd = pmd_offset(pgd, addr);
if (pmd_none(*pmd))
goto end;
if (pmd_bad(*pmd)) {
pmd_ERROR(*pmd);
pmd_clear(pmd);
goto end;
}
pte = pte_offset(pmd, addr);
if (pte_none(*pte))
pte = NULL;
end:
return pte;
}
static inline pte_t *alloc_one_pte(struct mm_struct *mm, unsigned long addr)
{
pmd_t * pmd;
pte_t * pte = NULL;
pmd = pmd_alloc(mm, pgd_offset(mm, addr), addr);
if (pmd)
pte = pte_alloc(mm, pmd, addr);
return pte;
}
static inline int copy_one_pte(struct mm_struct *mm, pte_t * src, pte_t * dst)
{
int error = 0;
pte_t pte;
if (!pte_none(*src)) {
pte = ptep_get_and_clear(src);
if (!dst) {
/* No dest? We must put it back. */
dst = src;
error++;
}
set_pte(dst, pte);
}
return error;
}
static int move_one_page(struct mm_struct *mm, unsigned long old_addr, unsigned long new_addr)
{
int error = 0;
pte_t * src;
spin_lock(&mm->page_table_lock);
src = get_one_pte(mm, old_addr);
if (src)
error = copy_one_pte(mm, src, alloc_one_pte(mm, new_addr));
spin_unlock(&mm->page_table_lock);
return error;
}
static int move_page_tables(struct mm_struct * mm,
unsigned long new_addr, unsigned long old_addr, unsigned long len)
{
unsigned long offset = len;
flush_cache_range(mm, old_addr, old_addr + len);
/*
* This is not the clever way to do this, but we're taking the
* easy way out on the assumption that most remappings will be
* only a few pages.. This also makes error recovery easier.
*/
while (offset) {
offset -= PAGE_SIZE;
if (move_one_page(mm, old_addr + offset, new_addr + offset))
goto oops_we_failed;
}
flush_tlb_range(mm, old_addr, old_addr + len);
return 0;
/*
* Ok, the move failed because we didn't have enough pages for
* the new page table tree. This is unlikely, but we have to
* take the possibility into account. In that case we just move
* all the pages back (this will work, because we still have
* the old page tables)
*/
oops_we_failed:
flush_cache_range(mm, new_addr, new_addr + len);
while ((offset += PAGE_SIZE) < len)
move_one_page(mm, new_addr + offset, old_addr + offset);
zap_page_range(mm, new_addr, len);
return -1;
}
static inline unsigned long move_vma(struct vm_area_struct * vma,
unsigned long addr, unsigned long old_len, unsigned long new_len,
unsigned long new_addr)
{
struct mm_struct * mm = vma->vm_mm;
struct vm_area_struct * new_vma, * next, * prev;
int allocated_vma;
new_vma = NULL;
next = find_vma_prev(mm, new_addr, &prev);
if (next) {
if (prev && prev->vm_end == new_addr &&
can_vma_merge(prev, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
spin_lock(&mm->page_table_lock);
prev->vm_end = new_addr + new_len;
spin_unlock(&mm->page_table_lock);
new_vma = prev;
if (next != prev->vm_next)
BUG();
if (prev->vm_end == next->vm_start && can_vma_merge(next, prev->vm_flags)) {
spin_lock(&mm->page_table_lock);
prev->vm_end = next->vm_end;
__vma_unlink(mm, next, prev);
spin_unlock(&mm->page_table_lock);
mm->map_count--;
kmem_cache_free(vm_area_cachep, next);
}
} else if (next->vm_start == new_addr + new_len &&
can_vma_merge(next, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
spin_lock(&mm->page_table_lock);
next->vm_start = new_addr;
spin_unlock(&mm->page_table_lock);
new_vma = next;
}
} else {
prev = find_vma(mm, new_addr-1);
if (prev && prev->vm_end == new_addr &&
can_vma_merge(prev, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
spin_lock(&mm->page_table_lock);
prev->vm_end = new_addr + new_len;
spin_unlock(&mm->page_table_lock);
new_vma = prev;
}
}
allocated_vma = 0;
if (!new_vma) {
new_vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
if (!new_vma)
goto out;
allocated_vma = 1;
}
if (!move_page_tables(current->mm, new_addr, addr, old_len)) {
if (allocated_vma) {
*new_vma = *vma;
new_vma->vm_start = new_addr;
new_vma->vm_end = new_addr+new_len;
new_vma->vm_pgoff += (addr - vma->vm_start) >> PAGE_SHIFT;
new_vma->vm_raend = 0;
if (new_vma->vm_file)
get_file(new_vma->vm_file);
if (new_vma->vm_ops && new_vma->vm_ops->open)
new_vma->vm_ops->open(new_vma);
insert_vm_struct(current->mm, new_vma);
}
do_munmap(current->mm, addr, old_len);
current->mm->total_vm += new_len >> PAGE_SHIFT;
if (new_vma->vm_flags & VM_LOCKED) {
current->mm->locked_vm += new_len >> PAGE_SHIFT;
make_pages_present(new_vma->vm_start,
new_vma->vm_end);
}
return new_addr;
}
if (allocated_vma)
kmem_cache_free(vm_area_cachep, new_vma);
out:
return -ENOMEM;
}
/*
* Expand (or shrink) an existing mapping, potentially moving it at the
* same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
*
* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
* This option implies MREMAP_MAYMOVE.
*/
unsigned long do_mremap(unsigned long addr,
unsigned long old_len, unsigned long new_len,
unsigned long flags, unsigned long new_addr)
{
struct vm_area_struct *vma;
unsigned long ret = -EINVAL;
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
goto out;
if (addr & ~PAGE_MASK)
goto out;
old_len = PAGE_ALIGN(old_len);
new_len = PAGE_ALIGN(new_len);
/* new_addr is only valid if MREMAP_FIXED is specified */
if (flags & MREMAP_FIXED) {
if (new_addr & ~PAGE_MASK)
goto out;
if (!(flags & MREMAP_MAYMOVE))
goto out;
if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
goto out;
/* Check if the location we're moving into overlaps the
* old location at all, and fail if it does.
*/
if ((new_addr <= addr) && (new_addr+new_len) > addr)
goto out;
if ((addr <= new_addr) && (addr+old_len) > new_addr)
goto out;
do_munmap(current->mm, new_addr, new_len);
}
/*
* Always allow a shrinking remap: that just unmaps
* the unnecessary pages..
*/
ret = addr;
if (old_len >= new_len) {
do_munmap(current->mm, addr+new_len, old_len - new_len);
if (!(flags & MREMAP_FIXED) || (new_addr == addr))
goto out;
}
/*
* Ok, we need to grow.. or relocate.
*/
ret = -EFAULT;
vma = find_vma(current->mm, addr);
if (!vma || vma->vm_start > addr)
goto out;
/* We can't remap across vm area boundaries */
if (old_len > vma->vm_end - addr)
goto out;
if (vma->vm_flags & VM_DONTEXPAND) {
if (new_len > old_len)
goto out;
}
if (vma->vm_flags & VM_LOCKED) {
unsigned long locked = current->mm->locked_vm << PAGE_SHIFT;
locked += new_len - old_len;
ret = -EAGAIN;
if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
goto out;
}
ret = -ENOMEM;
if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len)
> current->rlim[RLIMIT_AS].rlim_cur)
goto out;
/* Private writable mapping? Check memory availability.. */
if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) == VM_WRITE &&
!(flags & MAP_NORESERVE) &&
!vm_enough_memory((new_len - old_len) >> PAGE_SHIFT))
goto out;
/* old_len exactly to the end of the area..
* And we're not relocating the area.
*/
if (old_len == vma->vm_end - addr &&
!((flags & MREMAP_FIXED) && (addr != new_addr)) &&
(old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
unsigned long max_addr = TASK_SIZE;
if (vma->vm_next)
max_addr = vma->vm_next->vm_start;
/* can we just expand the current mapping? */
if (max_addr - addr >= new_len) {
int pages = (new_len - old_len) >> PAGE_SHIFT;
spin_lock(&vma->vm_mm->page_table_lock);
vma->vm_end = addr + new_len;
spin_unlock(&vma->vm_mm->page_table_lock);
current->mm->total_vm += pages;
if (vma->vm_flags & VM_LOCKED) {
current->mm->locked_vm += pages;
make_pages_present(addr + old_len,
addr + new_len);
}
ret = addr;
goto out;
}
}
/*
* We weren't able to just expand or shrink the area,
* we need to create a new one and move it..
*/
ret = -ENOMEM;
if (flags & MREMAP_MAYMOVE) {
if (!(flags & MREMAP_FIXED)) {
unsigned long map_flags = 0;
if (vma->vm_flags & VM_SHARED)
map_flags |= MAP_SHARED;
new_addr = get_unmapped_area(vma->vm_file, 0, new_len, vma->vm_pgoff, map_flags);
ret = new_addr;
if (new_addr & ~PAGE_MASK)
goto out;
}
ret = move_vma(vma, addr, old_len, new_len, new_addr);
}
out:
return ret;
}
asmlinkage unsigned long sys_mremap(unsigned long addr,
unsigned long old_len, unsigned long new_len,
unsigned long flags, unsigned long new_addr)
{
unsigned long ret;
down_write(¤t->mm->mmap_sem);
ret = do_mremap(addr, old_len, new_len, flags, new_addr);
up_write(¤t->mm->mmap_sem);
return ret;
}
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