linux/mm/mlock.c

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/*
* linux/mm/mlock.c
*
* (C) Copyright 1995 Linus Torvalds
* (C) Copyright 2002 Christoph Hellwig
*/
#include <linux/capability.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/mempolicy.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
#include <linux/module.h>
int can_do_mlock(void)
{
if (capable(CAP_IPC_LOCK))
return 1;
if (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 0)
return 1;
return 0;
}
EXPORT_SYMBOL(can_do_mlock);
static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
unsigned long start, unsigned long end, unsigned int newflags)
{
struct mm_struct * mm = vma->vm_mm;
pgoff_t pgoff;
int pages;
int ret = 0;
if (newflags == vma->vm_flags) {
*prev = vma;
goto out;
}
pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
vma->vm_file, pgoff, vma_policy(vma));
if (*prev) {
vma = *prev;
goto success;
}
*prev = vma;
if (start != vma->vm_start) {
ret = split_vma(mm, vma, start, 1);
if (ret)
goto out;
}
if (end != vma->vm_end) {
ret = split_vma(mm, vma, end, 0);
if (ret)
goto out;
}
success:
/*
* vm_flags is protected by the mmap_sem held in write mode.
* It's okay if try_to_unmap_one unmaps a page just after we
* set VM_LOCKED, make_pages_present below will bring it back.
*/
vma->vm_flags = newflags;
/*
* Keep track of amount of locked VM.
*/
pages = (end - start) >> PAGE_SHIFT;
if (newflags & VM_LOCKED) {
pages = -pages;
if (!(newflags & VM_IO))
ret = make_pages_present(start, end);
}
mm->locked_vm -= pages;
out:
return ret;
}
static int do_mlock(unsigned long start, size_t len, int on)
{
unsigned long nstart, end, tmp;
struct vm_area_struct * vma, * prev;
int error;
len = PAGE_ALIGN(len);
end = start + len;
if (end < start)
return -EINVAL;
if (end == start)
return 0;
vma = find_vma_prev(current->mm, start, &prev);
if (!vma || vma->vm_start > start)
return -ENOMEM;
if (start > vma->vm_start)
prev = vma;
for (nstart = start ; ; ) {
unsigned int newflags;
/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
newflags = vma->vm_flags | VM_LOCKED;
if (!on)
newflags &= ~VM_LOCKED;
tmp = vma->vm_end;
if (tmp > end)
tmp = end;
error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
if (error)
break;
nstart = tmp;
if (nstart < prev->vm_end)
nstart = prev->vm_end;
if (nstart >= end)
break;
vma = prev->vm_next;
if (!vma || vma->vm_start != nstart) {
error = -ENOMEM;
break;
}
}
return error;
}
asmlinkage long sys_mlock(unsigned long start, size_t len)
{
unsigned long locked;
unsigned long lock_limit;
int error = -ENOMEM;
if (!can_do_mlock())
return -EPERM;
down_write(&current->mm->mmap_sem);
len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
start &= PAGE_MASK;
locked = len >> PAGE_SHIFT;
locked += current->mm->locked_vm;
lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
lock_limit >>= PAGE_SHIFT;
/* check against resource limits */
if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
error = do_mlock(start, len, 1);
up_write(&current->mm->mmap_sem);
return error;
}
asmlinkage long sys_munlock(unsigned long start, size_t len)
{
int ret;
down_write(&current->mm->mmap_sem);
len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
start &= PAGE_MASK;
ret = do_mlock(start, len, 0);
up_write(&current->mm->mmap_sem);
return ret;
}
static int do_mlockall(int flags)
{
struct vm_area_struct * vma, * prev = NULL;
unsigned int def_flags = 0;
if (flags & MCL_FUTURE)
def_flags = VM_LOCKED;
current->mm->def_flags = def_flags;
if (flags == MCL_FUTURE)
goto out;
for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
unsigned int newflags;
newflags = vma->vm_flags | VM_LOCKED;
if (!(flags & MCL_CURRENT))
newflags &= ~VM_LOCKED;
/* Ignore errors */
mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
}
out:
return 0;
}
asmlinkage long sys_mlockall(int flags)
{
unsigned long lock_limit;
int ret = -EINVAL;
if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
goto out;
ret = -EPERM;
if (!can_do_mlock())
goto out;
down_write(&current->mm->mmap_sem);
lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
lock_limit >>= PAGE_SHIFT;
ret = -ENOMEM;
if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
capable(CAP_IPC_LOCK))
ret = do_mlockall(flags);
up_write(&current->mm->mmap_sem);
out:
return ret;
}
asmlinkage long sys_munlockall(void)
{
int ret;
down_write(&current->mm->mmap_sem);
ret = do_mlockall(0);
up_write(&current->mm->mmap_sem);
return ret;
}
/*
* Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
* shm segments) get accounted against the user_struct instead.
*/
static DEFINE_SPINLOCK(shmlock_user_lock);
int user_shm_lock(size_t size, struct user_struct *user)
{
unsigned long lock_limit, locked;
int allowed = 0;
locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
if (lock_limit == RLIM_INFINITY)
allowed = 1;
lock_limit >>= PAGE_SHIFT;
spin_lock(&shmlock_user_lock);
if (!allowed &&
locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
goto out;
get_uid(user);
user->locked_shm += locked;
allowed = 1;
out:
spin_unlock(&shmlock_user_lock);
return allowed;
}
void user_shm_unlock(size_t size, struct user_struct *user)
{
spin_lock(&shmlock_user_lock);
user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
spin_unlock(&shmlock_user_lock);
free_uid(user);
}