int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
{
struct mm_struct *mm;
struct vm_area_struct *vma;
struct page *page;
void *old_buf = buf;
/* Worry about races with exit() */
task_lock(tsk);
mm = tsk->mm;
if (mm)
atomic_inc(&mm->mm_users);
task_unlock(tsk);
if (!mm)
return 0;
down_read(&mm->mmap_sem);
/* ignore errors, just check how much was sucessfully transfered */
while (len) {
int bytes, ret, offset;
void *maddr;
ret = get_user_pages(current, mm, addr, 1,
write, 1, &page, &vma);
if (ret <= 0)
break;
bytes = len;
offset = addr & (PAGE_SIZE-1);
if (bytes > PAGE_SIZE-offset)
bytes = PAGE_SIZE-offset;
flush_cache_page(vma, addr);
maddr = kmap(page);
if (write) {
memcpy(maddr + offset, buf, bytes);
flush_page_to_ram(page);
flush_icache_page(vma, page);
} else {
memcpy(buf, maddr + offset, bytes);
flush_page_to_ram(page);
}
kunmap(page);
put_page(page);
len -= bytes;
buf += bytes;
addr += bytes;
}
up_read(&mm->mmap_sem);
mmput(mm);
return buf - old_buf;
}
/*
* do_no_page() tries to create a new page mapping. It aggressively
* tries to share with existing pages, but makes a separate copy if
* the "write_access" parameter is true in order to avoid the next
* page fault.
*
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*
* This is called with the MM semaphore held.
*/
static int do_no_page(struct mm_struct * mm, struct vm_area_struct * vma,
unsigned long address, int write_access, pte_t *page_table)
{
struct page * new_page;
pte_t entry;
if (!vma->vm_ops || !vma->vm_ops->nopage)
return do_anonymous_page(mm, vma, page_table, write_access, address);
/*
* The third argument is "no_share", which tells the low-level code
* to copy, not share the page even if sharing is possible. It's
* essentially an early COW detection.
*/
new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, (vma->vm_flags & VM_SHARED)?0:write_access);
if (new_page == NULL) /* no page was available -- SIGBUS */
return 0;
if (new_page == NOPAGE_OOM)
return -1;
++mm->rss;
/*
* This silly early PAGE_DIRTY setting removes a race
* due to the bad i386 page protection. But it's valid
* for other architectures too.
*
* Note that if write_access is true, we either now have
* an exclusive copy of the page, or this is a shared mapping,
* so we can make it writable and dirty to avoid having to
* handle that later.
*/
flush_page_to_ram(new_page);
flush_icache_page(vma, new_page);
entry = mk_pte(new_page, vma->vm_page_prot);
if (write_access) {
entry = pte_mkwrite(pte_mkdirty(entry));
} else if (page_count(new_page) > 1 &&
!(vma->vm_flags & VM_SHARED))
entry = pte_wrprotect(entry);
set_pte(page_table, entry);
/* no need to invalidate: a not-present page shouldn't be cached */
update_mmu_cache(vma, address, entry);
return 2; /* Major fault */
}
static int do_swap_page(struct mm_struct * mm,
struct vm_area_struct * vma, unsigned long address,
pte_t * page_table, swp_entry_t entry, int write_access)
{
struct page *page = lookup_swap_cache(entry);
pte_t pte;
if (!page) {
lock_kernel();
swapin_readahead(entry);
page = read_swap_cache(entry);
unlock_kernel();
if (!page)
return -1;
flush_page_to_ram(page);
flush_icache_page(vma, page);
}
mm->rss++;
pte = mk_pte(page, vma->vm_page_prot);
/*
* Freeze the "shared"ness of the page, ie page_count + swap_count.
* Must lock page before transferring our swap count to already
* obtained page count.
*/
lock_page(page);
swap_free(entry);
if (write_access && !is_page_shared(page))
pte = pte_mkwrite(pte_mkdirty(pte));
UnlockPage(page);
set_pte(page_table, pte);
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, address, pte);
return 1; /* Minor fault */
}
/*
* do_no_page() tries to create a new page mapping. It aggressively
* tries to share with existing pages, but makes a separate copy if
* the "write_access" parameter is true in order to avoid the next
* page fault.
*
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*
* This is called with the MM semaphore held and the page table
* spinlock held. Exit with the spinlock released.
*/
static int do_no_page(struct mm_struct * mm, struct vm_area_struct * vma,
unsigned long address, int write_access, pte_t *page_table)
{
struct page * new_page;
pte_t entry;
if (!vma->vm_ops || !vma->vm_ops->nopage)
return do_anonymous_page(mm, vma, page_table, write_access, address);
spin_unlock(&mm->page_table_lock);
new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0);
if (new_page == NULL) /* no page was available -- SIGBUS */
return 0;
if (new_page == NOPAGE_OOM)
return -1;
/*
* Should we do an early C-O-W break?
*/
if (write_access && !(vma->vm_flags & VM_SHARED)) {
struct page * page = alloc_page(GFP_HIGHUSER);
if (!page) {
page_cache_release(new_page);
return -1;
}
copy_highpage(page, new_page);
page_cache_release(new_page);
lru_cache_add(page);
new_page = page;
}
spin_lock(&mm->page_table_lock);
/*
* This silly early PAGE_DIRTY setting removes a race
* due to the bad i386 page protection. But it's valid
* for other architectures too.
*
* Note that if write_access is true, we either now have
* an exclusive copy of the page, or this is a shared mapping,
* so we can make it writable and dirty to avoid having to
* handle that later.
*/
/* Only go through if we didn't race with anybody else... */
if (pte_none(*page_table)) {
++mm->rss;
flush_page_to_ram(new_page);
flush_icache_page(vma, new_page);
entry = mk_pte(new_page, vma->vm_page_prot);
if (write_access)
entry = pte_mkwrite(pte_mkdirty(entry));
set_pte(page_table, entry);
} else {
/* One of our sibling threads was faster, back out. */
page_cache_release(new_page);
spin_unlock(&mm->page_table_lock);
return 1;
}
/* no need to invalidate: a not-present page shouldn't be cached */
update_mmu_cache(vma, address, entry);
spin_unlock(&mm->page_table_lock);
return 2; /* Major fault */
}
/*
* We hold the mm semaphore and the page_table_lock on entry and
* should release the pagetable lock on exit..
*/
static int do_swap_page(struct mm_struct * mm,
struct vm_area_struct * vma, unsigned long address,
pte_t * page_table, pte_t orig_pte, int write_access)
{
struct page *page;
swp_entry_t entry = pte_to_swp_entry(orig_pte);
pte_t pte;
int ret = 1;
spin_unlock(&mm->page_table_lock);
page = lookup_swap_cache(entry);
if (!page) {
swapin_readahead(entry);
page = read_swap_cache_async(entry);
if (!page) {
/*
* Back out if somebody else faulted in this pte while
* we released the page table lock.
*/
int retval;
spin_lock(&mm->page_table_lock);
retval = pte_same(*page_table, orig_pte) ? -1 : 1;
spin_unlock(&mm->page_table_lock);
return retval;
}
/* Had to read the page from swap area: Major fault */
ret = 2;
}
lock_page(page);
/*
* Back out if somebody else faulted in this pte while we
* released the page table lock.
*/
spin_lock(&mm->page_table_lock);
if (!pte_same(*page_table, orig_pte)) {
spin_unlock(&mm->page_table_lock);
unlock_page(page);
page_cache_release(page);
return 1;
}
/* The page isn't present yet, go ahead with the fault. */
swap_free(entry);
if (vm_swap_full())
remove_exclusive_swap_page(page);
mm->rss++;
pte = mk_pte(page, vma->vm_page_prot);
if (write_access && can_share_swap_page(page))
pte = pte_mkdirty(pte_mkwrite(pte));
unlock_page(page);
flush_page_to_ram(page);
flush_icache_page(vma, page);
set_pte(page_table, pte);
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, address, pte);
spin_unlock(&mm->page_table_lock);
return ret;
}
