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ftrace.c

/*
 * ftrace graph code
 *
 * Copyright (C) 2009 Analog Devices Inc.
 * Licensed under the GPL-2 or later.
 */

#include <linux/ftrace.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <asm/atomic.h>

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
{
      struct ftrace_graph_ent trace;
      unsigned long return_hooker = (unsigned long)&return_to_handler;

      if (unlikely(atomic_read(&current->tracing_graph_pause)))
            return;

      if (ftrace_push_return_trace(*parent, self_addr, &trace.depth, 0) == -EBUSY)
            return;

      trace.func = self_addr;

      /* Only trace if the calling function expects to */
      if (!ftrace_graph_entry(&trace)) {
            current->curr_ret_stack--;
            return;
      }

      /* all is well in the world !  hijack RETS ... */
      *parent = return_hooker;
}

#endif

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