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