// SPDX-License-Identifier: GPL-2.0/* * nop tracer * * Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net> * */ #include <linux/module.h>#include <linux/ftrace.h> #include "trace.h" /* Our two options */enum {	TRACE_NOP_OPT_ACCEPT = 0x1,	TRACE_NOP_OPT_REFUSE = 0x2}; /* Options for the tracer (see trace_options file) */static struct tracer_opt nop_opts[] = {	/* Option that will be accepted by set_flag callback */	{ TRACER_OPT(test_nop_accept, TRACE_NOP_OPT_ACCEPT) },	/* Option that will be refused by set_flag callback */	{ TRACER_OPT(test_nop_refuse, TRACE_NOP_OPT_REFUSE) },	{ } /* Always set a last empty entry */}; static struct tracer_flags nop_flags = {	/* You can check your flags value here when you want. */	.val = 0, /* By default: all flags disabled */	.opts = nop_opts}; static struct trace_array	*ctx_trace; static void start_nop_trace(struct trace_array *tr){	/* Nothing to do! */} static void stop_nop_trace(struct trace_array *tr){	/* Nothing to do! */} static int nop_trace_init(struct trace_array *tr){	ctx_trace = tr;	start_nop_trace(tr);	return 0;} static void nop_trace_reset(struct trace_array *tr){	stop_nop_trace(tr);} /* It only serves as a signal handler and a callback to * accept or refuse the setting of a flag. * If you don't implement it, then the flag setting will be * automatically accepted. */static int nop_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set){	/*	 * Note that you don't need to update nop_flags.val yourself.	 * The tracing Api will do it automatically if you return 0	 */	if (bit == TRACE_NOP_OPT_ACCEPT) {		printk(KERN_DEBUG "nop_test_accept flag set to %d: we accept."			" Now cat trace_options to see the result\n",			set);		return 0;	} 	if (bit == TRACE_NOP_OPT_REFUSE) {		printk(KERN_DEBUG "nop_test_refuse flag set to %d: we refuse."			" Now cat trace_options to see the result\n",			set);		return -EINVAL;	} 	return 0;}  struct tracer nop_trace __read_mostly ={	.name		= "nop",	.init		= nop_trace_init,	.reset		= nop_trace_reset,#ifdef CONFIG_FTRACE_SELFTEST	.selftest	= trace_selftest_startup_nop,#endif	.flags		= &nop_flags,	.set_flag	= nop_set_flag,	.allow_instances = true,};