ftrace: prevent ftrace_special from recursion (5aa1ba6a) · Commits · 戴 / test

Impact: stop ftrace_special from recursion The ftrace_special is used to help debug areas of the kernel. Because of this, if it is put in certain locations, the fact that it allows recursion can become a problem if the kernel developer using does not realize that. This patch changes ftrace_special to not allow recursion into itself to make it more robust. It also changes from preempt disable interrupts disable to prevent any loss of trace entries. Signed-off-by:

Steven Rostedt <srostedt@redhat.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -960,6 +960,7 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3)
		{
		struct trace_array *tr = &global_trace;
		struct trace_array_cpu *data;
		unsigned long flags;
		int cpu;
		int pc;

		@@ -967,14 +968,15 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3)
		return;

		pc = preempt_count();
		preempt_disable_notrace();
		local_irq_save(flags);
		cpu = raw_smp_processor_id();
		data = tr->data[cpu];

		if (likely(!atomic_read(&data->disabled)))
		if (likely(atomic_inc_return(&data->disabled) == 1))
		ftrace_trace_special(tr, data, arg1, arg2, arg3, pc);

		preempt_enable_notrace();
		atomic_dec(&data->disabled);
		local_irq_restore(flags);
		}

		#ifdef CONFIG_FUNCTION_TRACER

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