Merge tag 'trace-v5.2-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing warning fix from Steven Rostedt:
 "Make the GCC 9 warning for sub struct memset go away.

  GCC 9 now warns about calling memset() on partial structures when it
  goes across multiple fields. This adds a helper for the place in
  tracing that does this type of clearing of a structure"

* tag 'trace-v5.2-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Silence GCC 9 array bounds warning

3 files changed, 20 insertions, 10 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2c92b3d9ea30..1c80521fd436 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8910,12 +8910,8 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
 
                 cnt++;
 
-                /* reset all but tr, trace, and overruns */
-                memset(&iter.seq, 0,
-                       sizeof(struct trace_iterator) -
-                       offsetof(struct trace_iterator, seq));
+                trace_iterator_reset(&iter);
                 iter.iter_flags |= TRACE_FILE_LAT_FMT;
-                iter.pos = -1;
 
                 if (trace_find_next_entry_inc(&iter) != NULL) {
                         int ret;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 82c70b63d375..005f08629b8b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1966,4 +1966,22 @@ static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
 
 extern struct trace_iterator *tracepoint_print_iter;
 
+/*
+ * Reset the state of the trace_iterator so that it can read consumed data.
+ * Normally, the trace_iterator is used for reading the data when it is not
+ * consumed, and must retain state.
+ */
+static __always_inline void trace_iterator_reset(struct trace_iterator *iter)
+{
+        const size_t offset = offsetof(struct trace_iterator, seq);
+
+        /*
+         * Keep gcc from complaining about overwriting more than just one
+         * member in the structure.
+         */
+        memset((char *)iter + offset, 0, sizeof(struct trace_iterator) - offset);
+
+        iter->pos = -1;
+}
+
 #endif /* _LINUX_KERNEL_TRACE_H */
diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 6c1ae6b752d1..cca65044c14c 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -37,12 +37,8 @@ static void ftrace_dump_buf(int skip_entries, long cpu_file)
         if (skip_entries)
                 kdb_printf("(skipping %d entries)\n", skip_entries);
 
-        /* reset all but tr, trace, and overruns */
-        memset(&iter.seq, 0,
-                   sizeof(struct trace_iterator) -
-                   offsetof(struct trace_iterator, seq));
+        trace_iterator_reset(&iter);
         iter.iter_flags |= TRACE_FILE_LAT_FMT;
-        iter.pos = -1;
 
         if (cpu_file == RING_BUFFER_ALL_CPUS) {
                 for_each_tracing_cpu(cpu) {