From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>,
Joe Lawrence <joe.lawrence@redhat.com>,
live-patching@vger.kernel.org
Subject: [PATCH 6/9] livepatch/ftrace: Add recursion protection to the ftrace callback
Date: Wed, 28 Oct 2020 07:52:50 -0400 [thread overview]
Message-ID: <20201028115613.291169246@goodmis.org> (raw)
In-Reply-To: 20201028115244.995788961@goodmis.org
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.
The default for ftrace_ops is going to assume recursion protection unless
otherwise specified.
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: live-patching@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/livepatch/patch.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index b552cf2d85f8..6c0164d24bbd 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -45,9 +45,13 @@ static void notrace klp_ftrace_handler(unsigned long ip,
struct klp_ops *ops;
struct klp_func *func;
int patch_state;
+ int bit;
ops = container_of(fops, struct klp_ops, fops);
+ bit = ftrace_test_recursion_trylock();
+ if (bit < 0)
+ return;
/*
* A variant of synchronize_rcu() is used to allow patching functions
* where RCU is not watching, see klp_synchronize_transition().
@@ -117,6 +121,7 @@ static void notrace klp_ftrace_handler(unsigned long ip,
unlock:
preempt_enable_notrace();
+ ftrace_test_recursion_unlock(bit);
}
/*
--
2.28.0
next parent reply other threads:[~2020-10-29 0:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201028115244.995788961@goodmis.org>
2020-10-28 11:52 ` Steven Rostedt [this message]
2020-10-29 13:51 ` [PATCH 6/9] livepatch/ftrace: Add recursion protection to the ftrace callback Miroslav Benes
2020-10-29 14:37 ` Steven Rostedt
2020-10-30 12:28 ` Steven Rostedt
2020-10-29 14:57 ` Petr Mladek
2020-10-29 15:03 ` Miroslav Benes
2020-10-29 18:24 ` Steven Rostedt
2020-10-30 9:48 ` Miroslav Benes
2020-10-30 10:41 ` Petr Mladek
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