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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2020-11-05 21:32:41 -0500
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2020-11-06 08:36:23 -0500
commit13f3ea9a2c829f28610bb8772a8b9c328412930e (patch)
treeeeb798c609c48492b086454a83e2fe076d861b6e /kernel/livepatch
parentc536aa1c5b17fac1ee395932031ff7d82827f2c5 (diff)
livepatch/ftrace: Add recursion protection to the ftrace callback
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 change. It will expect that handlers provide their own recursion protection, unless its ftrace_ops states otherwise. Link: https://lkml.kernel.org/r/20201028115613.291169246@goodmis.org Link: https://lkml.kernel.org/r/20201106023547.122802424@goodmis.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Joe Lawrence <joe.lawrence@redhat.com> Cc: live-patching@vger.kernel.org Reviewed-by: Petr Mladek <pmladek@suse.com> Acked-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/livepatch')
-rw-r--r--kernel/livepatch/patch.c5
1 files changed, 5 insertions, 0 deletions
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);
}
/*