[PATCH 2/5] uprobes: Change __copy_insn() to use copy_from_page()

[Oleg Nesterov]

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

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
 kernel/events/uprobes.c |   13 ++-----------
 1 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index d6891cb..0a759c6 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -477,30 +477,21 @@ __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;
-- 
1.5.5.1

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