/* * linux/mm/mincore.c * * Copyright (C) 1994-1999 Linus Torvalds */ /* * The mincore() system call. */ #include <linux/slab.h> #include <linux/pagemap.h> #include <linux/mm.h> #include <linux/mman.h> #include <linux/syscalls.h> #include <asm/uaccess.h> #include <asm/pgtable.h> /* * 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 vm_area_struct * vma, unsigned long pgoff) { unsigned char present = 0; struct address_space * as = vma->vm_file->f_mapping; struct page * page; page = find_get_page(as, pgoff); if (page) { present = PageUptodate(page); page_cache_release(page); } return present; } static long mincore_vma(struct vm_area_struct * vma, unsigned long start, unsigned long end, unsigned char __user * vec) { long error, i, remaining; unsigned char * tmp; error = -ENOMEM; if (!vma->vm_file) return error; start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (end > vma->vm_end) end = vma->vm_end; end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; error = -EAGAIN; tmp = (unsigned char *) __get_free_page(GFP_KERNEL); if (!tmp) return error; /* (end - start) is # of pages, and also # of bytes in "vec */ remaining = (end - start), error = 0; for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) { int j = 0; long thispiece = (remaining < PAGE_SIZE) ? remaining : PAGE_SIZE; while (j < thispiece) tmp[j++] = mincore_page(vma, start++); if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) { error = -EFAULT; break; } } free_page((unsigned long) tmp); return error; } /* * 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. */ asmlinkage long sys_mincore(unsigned long start, size_t len, unsigned char __user * vec) { int index = 0; unsigned long end, limit; struct vm_area_struct * vma; size_t max; int unmapped_error = 0; long error; /* check the arguments */ if (start & ~PAGE_CACHE_MASK) goto einval; limit = TASK_SIZE; if (start >= limit) goto enomem; if (!len) return 0; max = limit - start; len = PAGE_CACHE_ALIGN(len); if (len > max || !len) goto enomem; end = start + len; /* check the output buffer whilst holding the lock */ error = -EFAULT; down_read(¤t->mm->mmap_sem); if (!access_ok(VERIFY_WRITE, vec, len >> PAGE_SHIFT)) goto out; /* * If the interval [start,end) covers some unmapped address * ranges, just ignore them, but return -ENOMEM at the end. */ error = 0; vma = find_vma(current->mm, start); while (vma) { /* Here start < vma->vm_end. */ if (start < vma->vm_start) { unmapped_error = -ENOMEM; start = vma->vm_start; } /* Here vma->vm_start <= start < vma->vm_end. */ if (end <= vma->vm_end) { if (start < end) { error = mincore_vma(vma, start, end, &vec[index]); if (error) goto out; } error = unmapped_error; goto out; } /* Here vma->vm_start <= start < vma->vm_end < end. */ error = mincore_vma(vma, start, vma->vm_end, &vec[index]); if (error) goto out; index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT; start = vma->vm_end; vma = vma->vm_next; } /* we found a hole in the area queried if we arrive here */ error = -ENOMEM; out: up_read(¤t->mm->mmap_sem); return error; einval: return -EINVAL; enomem: return -ENOMEM; }