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/*
* 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,
};
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