diff options
Diffstat (limited to 'kernel/mm/mincore.c')
| -rw-r--r-- | kernel/mm/mincore.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/kernel/mm/mincore.c b/kernel/mm/mincore.c new file mode 100644 index 000000000..be25efde6 --- /dev/null +++ b/kernel/mm/mincore.c @@ -0,0 +1,269 @@ +/* + * linux/mm/mincore.c + * + * Copyright (C) 1994-2006 Linus Torvalds + */ + +/* + * The mincore() system call. + */ +#include <linux/pagemap.h> +#include <linux/gfp.h> +#include <linux/mm.h> +#include <linux/mman.h> +#include <linux/syscalls.h> +#include <linux/swap.h> +#include <linux/swapops.h> +#include <linux/hugetlb.h> + +#include <asm/uaccess.h> +#include <asm/pgtable.h> + +static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, + unsigned long end, struct mm_walk *walk) +{ +#ifdef CONFIG_HUGETLB_PAGE + unsigned char present; + unsigned char *vec = walk->private; + + /* + * Hugepages under user process are always in RAM and never + * swapped out, but theoretically it needs to be checked. + */ + present = pte && !huge_pte_none(huge_ptep_get(pte)); + for (; addr != end; vec++, addr += PAGE_SIZE) + *vec = present; + walk->private = vec; +#else + BUG(); +#endif + return 0; +} + +/* + * Later we can get more picky about what "in core" means precisely. + * For now, simply check to see if the page is in the page cache, + * and is up to date; i.e. that no page-in operation would be required + * at this time if an application were to map and access this page. + */ +static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) +{ + unsigned char present = 0; + struct page *page; + + /* + * When tmpfs swaps out a page from a file, any process mapping that + * file will not get a swp_entry_t in its pte, but rather it is like + * any other file mapping (ie. marked !present and faulted in with + * tmpfs's .fault). So swapped out tmpfs mappings are tested here. + */ +#ifdef CONFIG_SWAP + if (shmem_mapping(mapping)) { + page = find_get_entry(mapping, pgoff); + /* + * shmem/tmpfs may return swap: account for swapcache + * page too. + */ + if (radix_tree_exceptional_entry(page)) { + swp_entry_t swp = radix_to_swp_entry(page); + page = find_get_page(swap_address_space(swp), swp.val); + } + } else + page = find_get_page(mapping, pgoff); +#else + page = find_get_page(mapping, pgoff); +#endif + if (page) { + present = PageUptodate(page); + page_cache_release(page); + } + + return present; +} + +static int __mincore_unmapped_range(unsigned long addr, unsigned long end, + struct vm_area_struct *vma, unsigned char *vec) +{ + unsigned long nr = (end - addr) >> PAGE_SHIFT; + int i; + + if (vma->vm_file) { + pgoff_t pgoff; + + pgoff = linear_page_index(vma, addr); + for (i = 0; i < nr; i++, pgoff++) + vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); + } else { + for (i = 0; i < nr; i++) + vec[i] = 0; + } + return nr; +} + +static int mincore_unmapped_range(unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + walk->private += __mincore_unmapped_range(addr, end, + walk->vma, walk->private); + return 0; +} + +static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + spinlock_t *ptl; + struct vm_area_struct *vma = walk->vma; + pte_t *ptep; + unsigned char *vec = walk->private; + int nr = (end - addr) >> PAGE_SHIFT; + + if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { + memset(vec, 1, nr); + spin_unlock(ptl); + goto out; + } + + if (pmd_trans_unstable(pmd)) { + __mincore_unmapped_range(addr, end, vma, vec); + goto out; + } + + ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + for (; addr != end; ptep++, addr += PAGE_SIZE) { + pte_t pte = *ptep; + + if (pte_none(pte)) + __mincore_unmapped_range(addr, addr + PAGE_SIZE, + vma, vec); + else if (pte_present(pte)) + *vec = 1; + else { /* pte is a swap entry */ + swp_entry_t entry = pte_to_swp_entry(pte); + + if (non_swap_entry(entry)) { + /* + * migration or hwpoison entries are always + * uptodate + */ + *vec = 1; + } else { +#ifdef CONFIG_SWAP + *vec = mincore_page(swap_address_space(entry), + entry.val); +#else + WARN_ON(1); + *vec = 1; +#endif + } + } + vec++; + } + pte_unmap_unlock(ptep - 1, ptl); +out: + walk->private += nr; + cond_resched(); + return 0; +} + +/* + * Do a chunk of "sys_mincore()". We've already checked + * all the arguments, we hold the mmap semaphore: we should + * just return the amount of info we're asked for. + */ +static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) +{ + struct vm_area_struct *vma; + unsigned long end; + int err; + struct mm_walk mincore_walk = { + .pmd_entry = mincore_pte_range, + .pte_hole = mincore_unmapped_range, + .hugetlb_entry = mincore_hugetlb, + .private = vec, + }; + + vma = find_vma(current->mm, addr); + if (!vma || addr < vma->vm_start) + return -ENOMEM; + mincore_walk.mm = vma->vm_mm; + end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); + err = walk_page_range(addr, end, &mincore_walk); + if (err < 0) + return err; + return (end - addr) >> PAGE_SHIFT; +} + +/* + * The mincore(2) system call. + * + * mincore() returns the memory residency status of the pages in the + * current process's address space specified by [addr, addr + len). + * The status is returned in a vector of bytes. The least significant + * bit of each byte is 1 if the referenced page is in memory, otherwise + * it is zero. + * + * Because the status of a page can change after mincore() checks it + * but before it returns to the application, the returned vector may + * contain stale information. Only locked pages are guaranteed to + * remain in memory. + * + * return values: + * zero - success + * -EFAULT - vec points to an illegal address + * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE + * -ENOMEM - Addresses in the range [addr, addr + len] are + * invalid for the address space of this process, or + * specify one or more pages which are not currently + * mapped + * -EAGAIN - A kernel resource was temporarily unavailable. + */ +SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, + unsigned char __user *, vec) +{ + long retval; + unsigned long pages; + unsigned char *tmp; + + /* Check the start address: needs to be page-aligned.. */ + if (start & ~PAGE_CACHE_MASK) + return -EINVAL; + + /* ..and we need to be passed a valid user-space range */ + if (!access_ok(VERIFY_READ, (void __user *) start, len)) + return -ENOMEM; + + /* This also avoids any overflows on PAGE_CACHE_ALIGN */ + pages = len >> PAGE_SHIFT; + pages += (len & ~PAGE_MASK) != 0; + + if (!access_ok(VERIFY_WRITE, vec, pages)) + return -EFAULT; + + tmp = (void *) __get_free_page(GFP_USER); + if (!tmp) + return -EAGAIN; + + retval = 0; + while (pages) { + /* + * Do at most PAGE_SIZE entries per iteration, due to + * the temporary buffer size. + */ + down_read(¤t->mm->mmap_sem); + retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); + up_read(¤t->mm->mmap_sem); + + if (retval <= 0) + break; + if (copy_to_user(vec, tmp, retval)) { + retval = -EFAULT; + break; + } + pages -= retval; + vec += retval; + start += retval << PAGE_SHIFT; + retval = 0; + } + free_page((unsigned long) tmp); + return retval; +} |