| /* |
| * 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/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/pagemap.h> |
| #include <linux/mempolicy.h> |
| #include <linux/syscalls.h> |
| #include <linux/sched.h> |
| #include <linux/export.h> |
| #include <linux/rmap.h> |
| #include <linux/mmzone.h> |
| #include <linux/hugetlb.h> |
| |
| #include "internal.h" |
| |
| int can_do_mlock(void) |
| { |
| if (capable(CAP_IPC_LOCK)) |
| return 1; |
| if (rlimit(RLIMIT_MEMLOCK) != 0) |
| return 1; |
| return 0; |
| } |
| EXPORT_SYMBOL(can_do_mlock); |
| |
| /* |
| * Mlocked pages are marked with PageMlocked() flag for efficient testing |
| * in vmscan and, possibly, the fault path; and to support semi-accurate |
| * statistics. |
| * |
| * An mlocked page [PageMlocked(page)] is unevictable. As such, it will |
| * be placed on the LRU "unevictable" list, rather than the [in]active lists. |
| * The unevictable list is an LRU sibling list to the [in]active lists. |
| * PageUnevictable is set to indicate the unevictable state. |
| * |
| * When lazy mlocking via vmscan, it is important to ensure that the |
| * vma's VM_LOCKED status is not concurrently being modified, otherwise we |
| * may have mlocked a page that is being munlocked. So lazy mlock must take |
| * the mmap_sem for read, and verify that the vma really is locked |
| * (see mm/rmap.c). |
| */ |
| |
| /* |
| * LRU accounting for clear_page_mlock() |
| */ |
| void clear_page_mlock(struct page *page) |
| { |
| if (!TestClearPageMlocked(page)) |
| return; |
| |
| mod_zone_page_state(page_zone(page), NR_MLOCK, |
| -hpage_nr_pages(page)); |
| count_vm_event(UNEVICTABLE_PGCLEARED); |
| if (!isolate_lru_page(page)) { |
| putback_lru_page(page); |
| } else { |
| /* |
| * We lost the race. the page already moved to evictable list. |
| */ |
| if (PageUnevictable(page)) |
| count_vm_event(UNEVICTABLE_PGSTRANDED); |
| } |
| } |
| |
| /* |
| * Mark page as mlocked if not already. |
| * If page on LRU, isolate and putback to move to unevictable list. |
| */ |
| void mlock_vma_page(struct page *page) |
| { |
| /* Serialize with page migration */ |
| BUG_ON(!PageLocked(page)); |
| |
| if (!TestSetPageMlocked(page)) { |
| mod_zone_page_state(page_zone(page), NR_MLOCK, |
| hpage_nr_pages(page)); |
| count_vm_event(UNEVICTABLE_PGMLOCKED); |
| if (!isolate_lru_page(page)) |
| putback_lru_page(page); |
| } |
| } |
| |
| /** |
| * munlock_vma_page - munlock a vma page |
| * @page - page to be unlocked |
| * |
| * called from munlock()/munmap() path with page supposedly on the LRU. |
| * When we munlock a page, because the vma where we found the page is being |
| * munlock()ed or munmap()ed, we want to check whether other vmas hold the |
| * page locked so that we can leave it on the unevictable lru list and not |
| * bother vmscan with it. However, to walk the page's rmap list in |
| * try_to_munlock() we must isolate the page from the LRU. If some other |
| * task has removed the page from the LRU, we won't be able to do that. |
| * So we clear the PageMlocked as we might not get another chance. If we |
| * can't isolate the page, we leave it for putback_lru_page() and vmscan |
| * [page_referenced()/try_to_unmap()] to deal with. |
| */ |
| unsigned int munlock_vma_page(struct page *page) |
| { |
| unsigned int page_mask = 0; |
| |
| /* For try_to_munlock() and to serialize with page migration */ |
| BUG_ON(!PageLocked(page)); |
| |
| if (TestClearPageMlocked(page)) { |
| unsigned int nr_pages = hpage_nr_pages(page); |
| mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages); |
| page_mask = nr_pages - 1; |
| if (!isolate_lru_page(page)) { |
| int ret = SWAP_AGAIN; |
| |
| /* |
| * Optimization: if the page was mapped just once, |
| * that's our mapping and we don't need to check all the |
| * other vmas. |
| */ |
| if (page_mapcount(page) > 1) |
| ret = try_to_munlock(page); |
| /* |
| * did try_to_unlock() succeed or punt? |
| */ |
| if (ret != SWAP_MLOCK) |
| count_vm_event(UNEVICTABLE_PGMUNLOCKED); |
| |
| putback_lru_page(page); |
| } else { |
| /* |
| * Some other task has removed the page from the LRU. |
| * putback_lru_page() will take care of removing the |
| * page from the unevictable list, if necessary. |
| * vmscan [page_referenced()] will move the page back |
| * to the unevictable list if some other vma has it |
| * mlocked. |
| */ |
| if (PageUnevictable(page)) |
| count_vm_event(UNEVICTABLE_PGSTRANDED); |
| else |
| count_vm_event(UNEVICTABLE_PGMUNLOCKED); |
| } |
| } |
| |
| return page_mask; |
| } |
| |
| /** |
| * __mlock_vma_pages_range() - mlock a range of pages in the vma. |
| * @vma: target vma |
| * @start: start address |
| * @end: end address |
| * |
| * This takes care of making the pages present too. |
| * |
| * return 0 on success, negative error code on error. |
| * |
| * vma->vm_mm->mmap_sem must be held for at least read. |
| */ |
| long __mlock_vma_pages_range(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end, int *nonblocking) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| unsigned long nr_pages = (end - start) / PAGE_SIZE; |
| int gup_flags; |
| |
| VM_BUG_ON(start & ~PAGE_MASK); |
| VM_BUG_ON(end & ~PAGE_MASK); |
| VM_BUG_ON(start < vma->vm_start); |
| VM_BUG_ON(end > vma->vm_end); |
| VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| |
| gup_flags = FOLL_TOUCH | FOLL_MLOCK; |
| /* |
| * We want to touch writable mappings with a write fault in order |
| * to break COW, except for shared mappings because these don't COW |
| * and we would not want to dirty them for nothing. |
| */ |
| if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) |
| gup_flags |= FOLL_WRITE; |
| |
| /* |
| * We want mlock to succeed for regions that have any permissions |
| * other than PROT_NONE. |
| */ |
| if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) |
| gup_flags |= FOLL_FORCE; |
| |
| /* |
| * We made sure addr is within a VMA, so the following will |
| * not result in a stack expansion that recurses back here. |
| */ |
| return __get_user_pages(current, mm, start, nr_pages, gup_flags, |
| NULL, NULL, nonblocking); |
| } |
| |
| /* |
| * convert get_user_pages() return value to posix mlock() error |
| */ |
| static int __mlock_posix_error_return(long retval) |
| { |
| if (retval == -EFAULT) |
| retval = -ENOMEM; |
| else if (retval == -ENOMEM) |
| retval = -EAGAIN; |
| return retval; |
| } |
| |
| /* |
| * munlock_vma_pages_range() - munlock all pages in the vma range.' |
| * @vma - vma containing range to be munlock()ed. |
| * @start - start address in @vma of the range |
| * @end - end of range in @vma. |
| * |
| * For mremap(), munmap() and exit(). |
| * |
| * Called with @vma VM_LOCKED. |
| * |
| * Returns with VM_LOCKED cleared. Callers must be prepared to |
| * deal with this. |
| * |
| * We don't save and restore VM_LOCKED here because pages are |
| * still on lru. In unmap path, pages might be scanned by reclaim |
| * and re-mlocked by try_to_{munlock|unmap} before we unmap and |
| * free them. This will result in freeing mlocked pages. |
| */ |
| void munlock_vma_pages_range(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end) |
| { |
| vma->vm_flags &= ~VM_LOCKED; |
| |
| while (start < end) { |
| struct page *page; |
| unsigned int page_mask, page_increm; |
| |
| /* |
| * Although FOLL_DUMP is intended for get_dump_page(), |
| * it just so happens that its special treatment of the |
| * ZERO_PAGE (returning an error instead of doing get_page) |
| * suits munlock very well (and if somehow an abnormal page |
| * has sneaked into the range, we won't oops here: great). |
| */ |
| page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP, |
| &page_mask); |
| if (page && !IS_ERR(page)) { |
| lock_page(page); |
| lru_add_drain(); |
| /* |
| * Any THP page found by follow_page_mask() may have |
| * gotten split before reaching munlock_vma_page(), |
| * so we need to recompute the page_mask here. |
| */ |
| page_mask = munlock_vma_page(page); |
| unlock_page(page); |
| put_page(page); |
| } |
| page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask); |
| start += page_increm * PAGE_SIZE; |
| cond_resched(); |
| } |
| } |
| |
| /* |
| * mlock_fixup - handle mlock[all]/munlock[all] requests. |
| * |
| * Filters out "special" vmas -- VM_LOCKED never gets set for these, and |
| * munlock is a no-op. However, for some special vmas, we go ahead and |
| * populate the ptes. |
| * |
| * For vmas that pass the filters, merge/split as appropriate. |
| */ |
| static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev, |
| unsigned long start, unsigned long end, vm_flags_t newflags) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pgoff_t pgoff; |
| int nr_pages; |
| int ret = 0; |
| int lock = !!(newflags & VM_LOCKED); |
| |
| if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) || |
| is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm)) |
| goto out; /* don't set VM_LOCKED, don't count */ |
| |
| 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; |
| } |
| |
| 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: |
| /* |
| * Keep track of amount of locked VM. |
| */ |
| nr_pages = (end - start) >> PAGE_SHIFT; |
| if (!lock) |
| nr_pages = -nr_pages; |
| mm->locked_vm += nr_pages; |
| |
| /* |
| * 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, __mlock_vma_pages_range will bring it back. |
| */ |
| |
| if (lock) |
| vma->vm_flags = newflags; |
| else |
| munlock_vma_pages_range(vma, start, end); |
| |
| out: |
| *prev = vma; |
| 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; |
| |
| VM_BUG_ON(start & ~PAGE_MASK); |
| VM_BUG_ON(len != PAGE_ALIGN(len)); |
| end = start + len; |
| if (end < start) |
| return -EINVAL; |
| if (end == start) |
| return 0; |
| vma = find_vma(current->mm, start); |
| if (!vma || vma->vm_start > start) |
| return -ENOMEM; |
| |
| prev = vma->vm_prev; |
| if (start > vma->vm_start) |
| prev = vma; |
| |
| for (nstart = start ; ; ) { |
| vm_flags_t 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; |
| } |
| |
| /* |
| * __mm_populate - populate and/or mlock pages within a range of address space. |
| * |
| * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap |
| * flags. VMAs must be already marked with the desired vm_flags, and |
| * mmap_sem must not be held. |
| */ |
| int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) |
| { |
| struct mm_struct *mm = current->mm; |
| unsigned long end, nstart, nend; |
| struct vm_area_struct *vma = NULL; |
| int locked = 0; |
| long ret = 0; |
| |
| VM_BUG_ON(start & ~PAGE_MASK); |
| VM_BUG_ON(len != PAGE_ALIGN(len)); |
| end = start + len; |
| |
| for (nstart = start; nstart < end; nstart = nend) { |
| /* |
| * We want to fault in pages for [nstart; end) address range. |
| * Find first corresponding VMA. |
| */ |
| if (!locked) { |
| locked = 1; |
| down_read(&mm->mmap_sem); |
| vma = find_vma(mm, nstart); |
| } else if (nstart >= vma->vm_end) |
| vma = vma->vm_next; |
| if (!vma || vma->vm_start >= end) |
| break; |
| /* |
| * Set [nstart; nend) to intersection of desired address |
| * range with the first VMA. Also, skip undesirable VMA types. |
| */ |
| nend = min(end, vma->vm_end); |
| if (vma->vm_flags & (VM_IO | VM_PFNMAP)) |
| continue; |
| if (nstart < vma->vm_start) |
| nstart = vma->vm_start; |
| /* |
| * Now fault in a range of pages. __mlock_vma_pages_range() |
| * double checks the vma flags, so that it won't mlock pages |
| * if the vma was already munlocked. |
| */ |
| ret = __mlock_vma_pages_range(vma, nstart, nend, &locked); |
| if (ret < 0) { |
| if (ignore_errors) { |
| ret = 0; |
| continue; /* continue at next VMA */ |
| } |
| ret = __mlock_posix_error_return(ret); |
| break; |
| } |
| nend = nstart + ret * PAGE_SIZE; |
| ret = 0; |
| } |
| if (locked) |
| up_read(&mm->mmap_sem); |
| return ret; /* 0 or negative error code */ |
| } |
| |
| SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len) |
| { |
| unsigned long locked; |
| unsigned long lock_limit; |
| int error = -ENOMEM; |
| |
| if (!can_do_mlock()) |
| return -EPERM; |
| |
| lru_add_drain_all(); /* flush pagevec */ |
| |
| down_write(¤t->mm->mmap_sem); |
| len = PAGE_ALIGN(len + (start & ~PAGE_MASK)); |
| start &= PAGE_MASK; |
| |
| locked = len >> PAGE_SHIFT; |
| locked += current->mm->locked_vm; |
| |
| lock_limit = rlimit(RLIMIT_MEMLOCK); |
| lock_limit >>= PAGE_SHIFT; |
| |
| /* check against resource limits */ |
| if ((locked <= lock_limit) || capable(CAP_IPC_LOCK)) |
| error = do_mlock(start, len, 1); |
| up_write(¤t->mm->mmap_sem); |
| if (!error) |
| error = __mm_populate(start, len, 0); |
| return error; |
| } |
| |
| SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) |
| { |
| int ret; |
| |
| down_write(¤t->mm->mmap_sem); |
| len = PAGE_ALIGN(len + (start & ~PAGE_MASK)); |
| start &= PAGE_MASK; |
| ret = do_mlock(start, len, 0); |
| up_write(¤t->mm->mmap_sem); |
| return ret; |
| } |
| |
| static int do_mlockall(int flags) |
| { |
| struct vm_area_struct * vma, * prev = NULL; |
| |
| if (flags & MCL_FUTURE) |
| current->mm->def_flags |= VM_LOCKED; |
| else |
| current->mm->def_flags &= ~VM_LOCKED; |
| if (flags == MCL_FUTURE) |
| goto out; |
| |
| for (vma = current->mm->mmap; vma ; vma = prev->vm_next) { |
| vm_flags_t 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; |
| } |
| |
| SYSCALL_DEFINE1(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; |
| |
| if (flags & MCL_CURRENT) |
| lru_add_drain_all(); /* flush pagevec */ |
| |
| down_write(¤t->mm->mmap_sem); |
| |
| lock_limit = rlimit(RLIMIT_MEMLOCK); |
| 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(¤t->mm->mmap_sem); |
| if (!ret && (flags & MCL_CURRENT)) |
| mm_populate(0, TASK_SIZE); |
| out: |
| return ret; |
| } |
| |
| SYSCALL_DEFINE0(munlockall) |
| { |
| int ret; |
| |
| down_write(¤t->mm->mmap_sem); |
| ret = do_mlockall(0); |
| up_write(¤t->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 = rlimit(RLIMIT_MEMLOCK); |
| 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); |
| } |