tracing: Avoid -Warray-bounds warning for __rel_loc macro

Since -Warray-bounds checks the destination size from the type of given
pointer, __assign_rel_str() macro gets warned because it passes the
pointer to the 'u32' field instead of 'trace_event_raw_*' data structure.
Pass the data address calculated from the 'trace_event_raw_*' instead of
'u32' __rel_loc field.

Link: https://lkml.kernel.org/r/20220125233154.dac280ed36944c0c2fe6f3ac@kernel.org
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
[ This did not fix the warning, but is still a nice clean up ]
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index 8c6f7c4..65d927e 100644 (file)
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -318,9 +318,10 @@ TRACE_MAKE_SYSTEM_STR();
 #define __get_str(field) ((char *)__get_dynamic_array(field))
 
 #undef __get_rel_dynamic_array
-#define __get_rel_dynamic_array(field) \
-               ((void *)(&__entry->__rel_loc_##field) +        \
-                sizeof(__entry->__rel_loc_##field) +           \
+#define __get_rel_dynamic_array(field)                                 \
+               ((void *)__entry +                                      \
+                offsetof(typeof(*__entry), __rel_loc_##field) +        \
+                sizeof(__entry->__rel_loc_##field) +                   \
                 (__entry->__rel_loc_##field & 0xffff))
 
 #undef __get_rel_dynamic_array_len