diff mbox series

[for-linus,10/12] ftrace: Fix updating FTRACE_FL_TRAMP

Message ID 20201201160006.488267004@goodmis.org
State Accepted
Commit 4c75b0ff4e4bf7a45b5aef9639799719c28d0073
Headers show
Series None | expand

Commit Message

Steven Rostedt Dec. 1, 2020, 3:58 p.m. UTC 
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>

On powerpc, kprobe-direct.tc triggered FTRACE_WARN_ON() in
ftrace_get_addr_new() followed by the below message:
  Bad trampoline accounting at: 000000004222522f (wake_up_process+0xc/0x20) (f0000001)

The set of steps leading to this involved:
- modprobe ftrace-direct-too
- enable_probe
- modprobe ftrace-direct
- rmmod ftrace-direct <-- trigger

The problem turned out to be that we were not updating flags in the
ftrace record properly. From the above message about the trampoline
accounting being bad, it can be seen that the ftrace record still has
FTRACE_FL_TRAMP set though ftrace-direct module is going away. This
happens because we are checking if any ftrace_ops has the
FTRACE_FL_TRAMP flag set _before_ updating the filter hash.

The fix for this is to look for any _other_ ftrace_ops that also needs
FTRACE_FL_TRAMP.

Link: https://lkml.kernel.org/r/56c113aa9c3e10c19144a36d9684c7882bf09af5.1606412433.git.naveen.n.rao@linux.vnet.ibm.com

Cc: stable@vger.kernel.org
Fixes: a124692b698b0 ("ftrace: Enable trampoline when rec count returns back to one")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8185f7240095..9c1bba8cc51b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1629,6 +1629,8 @@  static bool test_rec_ops_needs_regs(struct dyn_ftrace *rec)
 static struct ftrace_ops *
 ftrace_find_tramp_ops_any(struct dyn_ftrace *rec);
 static struct ftrace_ops *
+ftrace_find_tramp_ops_any_other(struct dyn_ftrace *rec, struct ftrace_ops *op_exclude);
+static struct ftrace_ops *
 ftrace_find_tramp_ops_next(struct dyn_ftrace *rec, struct ftrace_ops *ops);
 
 static bool __ftrace_hash_rec_update(struct ftrace_ops *ops,
@@ -1778,7 +1780,7 @@  static bool __ftrace_hash_rec_update(struct ftrace_ops *ops,
 			 * to it.
 			 */
 			if (ftrace_rec_count(rec) == 1 &&
-			    ftrace_find_tramp_ops_any(rec))
+			    ftrace_find_tramp_ops_any_other(rec, ops))
 				rec->flags |= FTRACE_FL_TRAMP;
 			else
 				rec->flags &= ~FTRACE_FL_TRAMP;
@@ -2244,6 +2246,24 @@  ftrace_find_tramp_ops_any(struct dyn_ftrace *rec)
 	return NULL;
 }
 
+static struct ftrace_ops *
+ftrace_find_tramp_ops_any_other(struct dyn_ftrace *rec, struct ftrace_ops *op_exclude)
+{
+	struct ftrace_ops *op;
+	unsigned long ip = rec->ip;
+
+	do_for_each_ftrace_op(op, ftrace_ops_list) {
+
+		if (op == op_exclude || !op->trampoline)
+			continue;
+
+		if (hash_contains_ip(ip, op->func_hash))
+			return op;
+	} while_for_each_ftrace_op(op);
+
+	return NULL;
+}
+
 static struct ftrace_ops *
 ftrace_find_tramp_ops_next(struct dyn_ftrace *rec,
 			   struct ftrace_ops *op)