uaccess: reimplement probe_kernel_address() using probe_kernel_read()

[cascardo/linux.git] / mm / maccess.c

diff --git a/mm/maccess.c b/mm/maccess.c
index 34fe247..1b13638 100644 (file)
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -13,6 +13,11 @@
  *
  * Safely read from address @src to the buffer at @dst.  If a kernel fault
  * happens, handle that and return -EFAULT.
+ *
+ * We ensure that the copy_from_user is executed in atomic context so that
+ * do_page_fault() doesn't attempt to take mmap_sem.  This makes
+ * probe_kernel_read() suitable for use within regions where the caller
+ * already holds mmap_sem, or other locks which nest inside mmap_sem.
  */
 
 long __weak probe_kernel_read(void *dst, const void *src, size_t size)