ftrace: Fix updating FTRACE_FL_TRAMP (4c75b0ff) · Commits · 戴 / test

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: ("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

+21 −1

Original line number	Diff line number	Diff line
		@@ -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)

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