linux-kernel - [PATCH 2/2] ftrace: setup correct flags before replace code of module rec

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Message-Id: <20200728102720.46837-2-zhouchengming@bytedance.com>
Date:   Tue, 28 Jul 2020 18:27:20 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     rostedt@...dmis.org, mingo@...hat.com, linux-kernel@...r.kernel.org
Cc:     songmuchun@...edance.com, zhouchengming@...edance.com
Subject: [PATCH 2/2] ftrace: setup correct flags before replace code of module rec

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.
So setup correct rec->flags when we call referenced_filters to find
ftrace_ops references it.

Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 kernel/trace/ftrace.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index fca01a168ae5..00087dea0174 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6190,8 +6190,17 @@ 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_DIRECT)
+				rec->flags |= FTRACE_FL_DIRECT;
+			if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
+				rec->flags |= FTRACE_FL_REGS;
+			if (cnt == 1 && ops->trampoline)
+				rec->flags |= FTRACE_FL_TRAMP;
+			else
+				rec->flags &= ~FTRACE_FL_TRAMP;
+		}
 	}
 
 	return cnt;
@@ -6373,7 +6382,8 @@ void ftrace_module_enable(struct module *mod)
 			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);
-- 
2.20.1