X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=lib%2Fringbuffer%2Fbackend.h;fp=lib%2Fringbuffer%2Fbackend.h;h=8f6d7d04d8a8ed76d86ed694c44e1864cc05d509;hb=3c8ebbc8658330fcd7794aecccdec16c46193da1;hp=b908ed06e92665e127bac42e19d57ffbb7ec9670;hpb=d87a9f0376535ea0ab125f2f0cfc6ce6e325c0c1;p=lttng-modules.git

diff --git a/lib/ringbuffer/backend.h b/lib/ringbuffer/backend.h
index b908ed06..8f6d7d04 100644
--- a/lib/ringbuffer/backend.h
+++ b/lib/ringbuffer/backend.h
@@ -478,4 +478,29 @@ unsigned long lib_ring_buffer_get_records_unread(
 	return records_unread;
 }
 
+/*
+ * We use __copy_from_user_inatomic to copy userspace data after
+ * checking with access_ok() and disabling page faults.
+ *
+ * Return 0 if OK, nonzero on error.
+ */
+static inline
+unsigned long lib_ring_buffer_copy_from_user_check_nofault(void *dest,
+						const void __user *src,
+						unsigned long len)
+{
+	unsigned long ret;
+	mm_segment_t old_fs;
+
+	if (!access_ok(VERIFY_READ, src, len))
+		return 1;
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+	ret = __copy_from_user_inatomic(dest, src, len);
+	pagefault_enable();
+	set_fs(old_fs);
+	return ret;
+}
+
 #endif /* _LIB_RING_BUFFER_BACKEND_H */