// 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, };