1 files changed, 191 insertions, 0 deletions

diff --git a/mm/mincore.c b/mm/mincore.c
new file mode 100644
index 000000000000..07833dc5829d
--- /dev/null
+++ b/mm/mincore.c
@@ -0,0 +1,191 @@
+/*
+ *      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;
+
+        if (start < FIRST_USER_PGD_NR * PGDIR_SIZE)
+                goto enomem;
+
+        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(&current->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(&current->mm->mmap_sem);
+        return error;
+
+einval:
+        return -EINVAL;
+enomem:
+        return -ENOMEM;
+}