uprobes: Change __copy_insn() to use copy_from_page()

Change __copy_insn() to use copy_from_page() and simplify the code.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 850eb9e..ba6acfe 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -500,30 +500,21 @@ __copy_insn(struct address_space *mapping, struct file *filp, char *insn,
                        unsigned long nbytes, loff_t offset)
 {
        struct page *page;
-       void *vaddr;
-       unsigned long off;
-       pgoff_t idx;
 
        if (!filp)
                return -EINVAL;
 
        if (!mapping->a_ops->readpage)
                return -EIO;
-
-       idx = offset >> PAGE_CACHE_SHIFT;
-       off = offset & ~PAGE_MASK;
-
        /*
         * Ensure that the page that has the original instruction is
         * populated and in page-cache.
         */
-       page = read_mapping_page(mapping, idx, filp);
+       page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);
        if (IS_ERR(page))
                return PTR_ERR(page);
 
-       vaddr = kmap_atomic(page);
-       memcpy(insn, vaddr + off, nbytes);
-       kunmap_atomic(vaddr);
+       copy_from_page(page, offset, insn, nbytes);
        page_cache_release(page);
 
        return 0;