[PATCH 5.7 076/204] ftrace: Setup correct FTRACE_FL_REGS flags for module

Greg Kroah-Hartman
2020-08-20T09:38:13Z

From: Chengming Zhou <zhouchengming@bytedance.com>

commit 8a224ffb3f52b0027f6b7279854c71a31c48fc97 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/trace/ftrace.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6198,8 +6198,11 @@ static int referenced_filters(struct dyn
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
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);