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>

1 files changed, 2 insertions, 11 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 850eb9eb179b..ba6acfe7c0de 100644
--- 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;