Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * linux/mm/mincore.c |
| 3 | * |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 4 | * Copyright (C) 1994-2006 Linus Torvalds |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5 | */ |
| 6 | |
| 7 | /* |
| 8 | * The mincore() system call. |
| 9 | */ |
| 10 | #include <linux/slab.h> |
| 11 | #include <linux/pagemap.h> |
| 12 | #include <linux/mm.h> |
| 13 | #include <linux/mman.h> |
| 14 | #include <linux/syscalls.h> |
| 15 | |
| 16 | #include <asm/uaccess.h> |
| 17 | #include <asm/pgtable.h> |
| 18 | |
| 19 | /* |
| 20 | * Later we can get more picky about what "in core" means precisely. |
| 21 | * For now, simply check to see if the page is in the page cache, |
| 22 | * and is up to date; i.e. that no page-in operation would be required |
| 23 | * at this time if an application were to map and access this page. |
| 24 | */ |
| 25 | static unsigned char mincore_page(struct vm_area_struct * vma, |
| 26 | unsigned long pgoff) |
| 27 | { |
| 28 | unsigned char present = 0; |
| 29 | struct address_space * as = vma->vm_file->f_mapping; |
| 30 | struct page * page; |
| 31 | |
| 32 | page = find_get_page(as, pgoff); |
| 33 | if (page) { |
| 34 | present = PageUptodate(page); |
| 35 | page_cache_release(page); |
| 36 | } |
| 37 | |
| 38 | return present; |
| 39 | } |
| 40 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 41 | /* |
| 42 | * Do a chunk of "sys_mincore()". We've already checked |
| 43 | * all the arguments, we hold the mmap semaphore: we should |
| 44 | * just return the amount of info we're asked for. |
| 45 | */ |
| 46 | static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 47 | { |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 48 | unsigned long i, nr, pgoff; |
| 49 | struct vm_area_struct *vma = find_vma(current->mm, addr); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 50 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 51 | /* |
Linus Torvalds | 4fb23e4 | 2006-12-16 16:01:50 -0800 | [diff] [blame] | 52 | * find_vma() didn't find anything above us, or we're |
| 53 | * in an unmapped hole in the address space: ENOMEM. |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 54 | */ |
Linus Torvalds | 4fb23e4 | 2006-12-16 16:01:50 -0800 | [diff] [blame] | 55 | if (!vma || addr < vma->vm_start) |
| 56 | return -ENOMEM; |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 57 | |
| 58 | /* |
| 59 | * Ok, got it. But check whether it's a segment we support |
| 60 | * mincore() on. Right now, we don't do any anonymous mappings. |
Linus Torvalds | 4fb23e4 | 2006-12-16 16:01:50 -0800 | [diff] [blame] | 61 | * |
| 62 | * FIXME: This is just stupid. And returning ENOMEM is |
| 63 | * stupid too. We should just look at the page tables. But |
| 64 | * this is what we've traditionally done, so we'll just |
| 65 | * continue doing it. |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 66 | */ |
| 67 | if (!vma->vm_file) |
| 68 | return -ENOMEM; |
| 69 | |
| 70 | /* |
| 71 | * Calculate how many pages there are left in the vma, and |
| 72 | * what the pgoff is for our address. |
| 73 | */ |
| 74 | nr = (vma->vm_end - addr) >> PAGE_SHIFT; |
| 75 | if (nr > pages) |
| 76 | nr = pages; |
| 77 | |
| 78 | pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; |
| 79 | pgoff += vma->vm_pgoff; |
| 80 | |
| 81 | /* And then we just fill the sucker in.. */ |
| 82 | for (i = 0 ; i < nr; i++, pgoff++) |
| 83 | vec[i] = mincore_page(vma, pgoff); |
| 84 | |
| 85 | return nr; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 86 | } |
| 87 | |
| 88 | /* |
| 89 | * The mincore(2) system call. |
| 90 | * |
| 91 | * mincore() returns the memory residency status of the pages in the |
| 92 | * current process's address space specified by [addr, addr + len). |
| 93 | * The status is returned in a vector of bytes. The least significant |
| 94 | * bit of each byte is 1 if the referenced page is in memory, otherwise |
| 95 | * it is zero. |
| 96 | * |
| 97 | * Because the status of a page can change after mincore() checks it |
| 98 | * but before it returns to the application, the returned vector may |
| 99 | * contain stale information. Only locked pages are guaranteed to |
| 100 | * remain in memory. |
| 101 | * |
| 102 | * return values: |
| 103 | * zero - success |
| 104 | * -EFAULT - vec points to an illegal address |
| 105 | * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE |
| 106 | * -ENOMEM - Addresses in the range [addr, addr + len] are |
| 107 | * invalid for the address space of this process, or |
| 108 | * specify one or more pages which are not currently |
| 109 | * mapped |
| 110 | * -EAGAIN - A kernel resource was temporarily unavailable. |
| 111 | */ |
| 112 | asmlinkage long sys_mincore(unsigned long start, size_t len, |
| 113 | unsigned char __user * vec) |
| 114 | { |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 115 | long retval; |
| 116 | unsigned long pages; |
| 117 | unsigned char *tmp; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 118 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 119 | /* Check the start address: needs to be page-aligned.. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 120 | if (start & ~PAGE_CACHE_MASK) |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 121 | return -EINVAL; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 122 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 123 | /* ..and we need to be passed a valid user-space range */ |
| 124 | if (!access_ok(VERIFY_READ, (void __user *) start, len)) |
| 125 | return -ENOMEM; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 126 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 127 | /* This also avoids any overflows on PAGE_CACHE_ALIGN */ |
| 128 | pages = len >> PAGE_SHIFT; |
| 129 | pages += (len & ~PAGE_MASK) != 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 130 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 131 | if (!access_ok(VERIFY_WRITE, vec, pages)) |
| 132 | return -EFAULT; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 133 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 134 | tmp = (void *) __get_free_page(GFP_USER); |
| 135 | if (!tmp) |
Linus Torvalds | 4fb23e4 | 2006-12-16 16:01:50 -0800 | [diff] [blame] | 136 | return -EAGAIN; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 137 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 138 | retval = 0; |
| 139 | while (pages) { |
| 140 | /* |
| 141 | * Do at most PAGE_SIZE entries per iteration, due to |
| 142 | * the temporary buffer size. |
| 143 | */ |
| 144 | down_read(¤t->mm->mmap_sem); |
| 145 | retval = do_mincore(start, tmp, max(pages, PAGE_SIZE)); |
| 146 | up_read(¤t->mm->mmap_sem); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 147 | |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 148 | if (retval <= 0) |
| 149 | break; |
| 150 | if (copy_to_user(vec, tmp, retval)) { |
| 151 | retval = -EFAULT; |
| 152 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 153 | } |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 154 | pages -= retval; |
| 155 | vec += retval; |
| 156 | start += retval << PAGE_SHIFT; |
| 157 | retval = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 158 | } |
Linus Torvalds | 2f77d10 | 2006-12-16 09:44:32 -0800 | [diff] [blame] | 159 | free_page((unsigned long) tmp); |
| 160 | return retval; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 161 | } |