linux/arch/x86/include/asm/ftrace.h

#ifndef _ASM_X86_FTRACE_H
#define _ASM_X86_FTRACE_H

#ifdef CONFIG_FUNCTION_TRACER
#define MCOUNT_ADDR		((long)(mcount))
#define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */

#ifndef __ASSEMBLY__
extern void mcount(void);

static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
	/*
	 * call mcount is "e8 <4 byte offset>"
	 * The addr points to the 4 byte offset and the caller of this
	 * function wants the pointer to e8. Simply subtract one.
	 */
	return addr - 1;
}
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */

#ifdef CONFIG_FUNCTION_RET_TRACER
#define FTRACE_RET_STACK_SIZE 20

#ifndef __ASSEMBLY__

/*
 * Stack of return addresses for functions
 * of a thread.
 * Used in struct thread_info
 */
struct ftrace_ret_stack {
	unsigned long ret;
	unsigned long func;
	unsigned long long calltime;
};

/*
 * Primary handler of a function return.
 * It relays on ftrace_return_to_handler.
 * Defined in entry32.S
 */
extern void return_to_handler(void);

#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_RET_TRACER */

#endif /* _ASM_X86_FTRACE_H */