ftrace: Setup correct FTRACE_FL_REGS flags for module

When module loaded and enabled, we will use __ftrace_replace_code
for module if any ftrace_ops referenced it found. But we will get
wrong ftrace_addr for module rec in ftrace_get_addr_new, because
rec->flags has not been setup correctly. It can cause the callback
function of a ftrace_ops has FTRACE_OPS_FL_SAVE_REGS to be called
with pt_regs set to NULL.
So setup correct FTRACE_FL_REGS flags for rec when we call
referenced_filters to find ftrace_ops references it.

Link: https://lkml.kernel.org/r/20200728180554.65203-1-zhouchengming@bytedance.com
Cc: stable@vger.kernel.org
Fixes: 8c4f3c3fa9681 ("ftrace: Check module functions being traced on reload")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c141d34..d052f85 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6198,8 +6198,11 @@ static int referenced_filters(struct dyn_ftrace *rec)
        int cnt = 0;
 
        for (ops = ftrace_ops_list; ops != &ftrace_list_end; ops = ops->next) {
-               if (ops_references_rec(ops, rec))
-                   cnt++;
+               if (ops_references_rec(ops, rec)) {
+                       cnt++;
+                       if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
+                               rec->flags |= FTRACE_FL_REGS;
+               }
        }
 
        return cnt;
@@ -6378,8 +6381,8 @@ void ftrace_module_enable(struct module *mod)
                if (ftrace_start_up)
                        cnt += referenced_filters(rec);
 
-               /* This clears FTRACE_FL_DISABLED */
-               rec->flags = cnt;
+               rec->flags &= ~FTRACE_FL_DISABLED;
+               rec->flags += cnt;
 
                if (ftrace_start_up && cnt) {
                        int failed = __ftrace_replace_code(rec, 1);