// SPDX-License-Identifier: GPL-2.0/* * ring buffer based function tracer * * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com> * * Based on code from the latency_tracer, that is: * *  Copyright (C) 2004-2006 Ingo Molnar *  Copyright (C) 2004 Nadia Yvette Chambers */#include <linux/ring_buffer.h>#include <linux/debugfs.h>#include <linux/uaccess.h>#include <linux/ftrace.h>#include <linux/slab.h>#include <linux/fs.h> #include "trace.h" static void tracing_start_function_trace(struct trace_array *tr);static void tracing_stop_function_trace(struct trace_array *tr);static voidfunction_trace_call(unsigned long ip, unsigned long parent_ip,		    struct ftrace_ops *op, struct pt_regs *pt_regs);static voidfunction_stack_trace_call(unsigned long ip, unsigned long parent_ip,			  struct ftrace_ops *op, struct pt_regs *pt_regs);static struct tracer_flags func_flags; /* Our option */enum {	TRACE_FUNC_OPT_STACK	= 0x1,}; static int allocate_ftrace_ops(struct trace_array *tr){	struct ftrace_ops *ops; 	ops = kzalloc(sizeof(*ops), GFP_KERNEL);	if (!ops)		return -ENOMEM; 	/* Currently only the non stack verision is supported */	ops->func = function_trace_call;	ops->flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_PID; 	tr->ops = ops;	ops->private = tr;	return 0;}  int ftrace_create_function_files(struct trace_array *tr,				 struct dentry *parent){	int ret; 	/*	 * The top level array uses the "global_ops", and the files are	 * created on boot up.	 */	if (tr->flags & TRACE_ARRAY_FL_GLOBAL)		return 0; 	ret = allocate_ftrace_ops(tr);	if (ret)		return ret; 	ftrace_create_filter_files(tr->ops, parent); 	return 0;} void ftrace_destroy_function_files(struct trace_array *tr){	ftrace_destroy_filter_files(tr->ops);	kfree(tr->ops);	tr->ops = NULL;} static int function_trace_init(struct trace_array *tr){	ftrace_func_t func; 	/*	 * Instance trace_arrays get their ops allocated	 * at instance creation. Unless it failed	 * the allocation.	 */	if (!tr->ops)		return -ENOMEM; 	/* Currently only the global instance can do stack tracing */	if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&	    func_flags.val & TRACE_FUNC_OPT_STACK)		func = function_stack_trace_call;	else		func = function_trace_call; 	ftrace_init_array_ops(tr, func); 	tr->trace_buffer.cpu = get_cpu();	put_cpu(); 	tracing_start_cmdline_record();	tracing_start_function_trace(tr);	return 0;} static void function_trace_reset(struct trace_array *tr){	tracing_stop_function_trace(tr);	tracing_stop_cmdline_record();	ftrace_reset_array_ops(tr);} static void function_trace_start(struct trace_array *tr){	tracing_reset_online_cpus(&tr->trace_buffer);} static voidfunction_trace_call(unsigned long ip, unsigned long parent_ip,		    struct ftrace_ops *op, struct pt_regs *pt_regs){	struct trace_array *tr = op->private;	struct trace_array_cpu *data;	unsigned long flags;	int bit;	int cpu;	int pc; 	if (unlikely(!tr->function_enabled))		return; 	pc = preempt_count();	preempt_disable_notrace(); 	bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);	if (bit < 0)		goto out; 	cpu = smp_processor_id();	data = per_cpu_ptr(tr->trace_buffer.data, cpu);	if (!atomic_read(&data->disabled)) {		local_save_flags(flags);		trace_function(tr, ip, parent_ip, flags, pc);	}	trace_clear_recursion(bit);  out:	preempt_enable_notrace();} #ifdef CONFIG_UNWINDER_ORC/* * Skip 2: * *   function_stack_trace_call() *   ftrace_call() */#define STACK_SKIP 2#else/* * Skip 3: *   __trace_stack() *   function_stack_trace_call() *   ftrace_call() */#define STACK_SKIP 3#endif static voidfunction_stack_trace_call(unsigned long ip, unsigned long parent_ip,			  struct ftrace_ops *op, struct pt_regs *pt_regs){	struct trace_array *tr = op->private;	struct trace_array_cpu *data;	unsigned long flags;	long disabled;	int cpu;	int pc; 	if (unlikely(!tr->function_enabled))		return; 	/*	 * Need to use raw, since this must be called before the	 * recursive protection is performed.	 */	local_irq_save(flags);	cpu = raw_smp_processor_id();	data = per_cpu_ptr(tr->trace_buffer.data, cpu);	disabled = atomic_inc_return(&data->disabled); 	if (likely(disabled == 1)) {		pc = preempt_count();		trace_function(tr, ip, parent_ip, flags, pc);		__trace_stack(tr, flags, STACK_SKIP, pc);	} 	atomic_dec(&data->disabled);	local_irq_restore(flags);} static struct tracer_opt func_opts[] = {#ifdef CONFIG_STACKTRACE	{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },#endif	{ } /* Always set a last empty entry */}; static struct tracer_flags func_flags = {	.val = 0, /* By default: all flags disabled */	.opts = func_opts}; static void tracing_start_function_trace(struct trace_array *tr){	tr->function_enabled = 0;	register_ftrace_function(tr->ops);	tr->function_enabled = 1;} static void tracing_stop_function_trace(struct trace_array *tr){	tr->function_enabled = 0;	unregister_ftrace_function(tr->ops);} static struct tracer function_trace; static intfunc_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set){	switch (bit) {	case TRACE_FUNC_OPT_STACK:		/* do nothing if already set */		if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))			break; 		/* We can change this flag when not running. */		if (tr->current_trace != &function_trace)			break; 		unregister_ftrace_function(tr->ops); 		if (set) {			tr->ops->func = function_stack_trace_call;			register_ftrace_function(tr->ops);		} else {			tr->ops->func = function_trace_call;			register_ftrace_function(tr->ops);		} 		break;	default:		return -EINVAL;	} 	return 0;} static struct tracer function_trace __tracer_data ={	.name		= "function",	.init		= function_trace_init,	.reset		= function_trace_reset,	.start		= function_trace_start,	.flags		= &func_flags,	.set_flag	= func_set_flag,	.allow_instances = true,#ifdef CONFIG_FTRACE_SELFTEST	.selftest	= trace_selftest_startup_function,#endif}; #ifdef CONFIG_DYNAMIC_FTRACEstatic void update_traceon_count(struct ftrace_probe_ops *ops,				 unsigned long ip,				 struct trace_array *tr, bool on,				 void *data){	struct ftrace_func_mapper *mapper = data;	long *count;	long old_count; 	/*	 * Tracing gets disabled (or enabled) once per count.	 * This function can be called at the same time on multiple CPUs.	 * It is fine if both disable (or enable) tracing, as disabling	 * (or enabling) the second time doesn't do anything as the	 * state of the tracer is already disabled (or enabled).	 * What needs to be synchronized in this case is that the count	 * only gets decremented once, even if the tracer is disabled	 * (or enabled) twice, as the second one is really a nop.	 *	 * The memory barriers guarantee that we only decrement the	 * counter once. First the count is read to a local variable	 * and a read barrier is used to make sure that it is loaded	 * before checking if the tracer is in the state we want.	 * If the tracer is not in the state we want, then the count	 * is guaranteed to be the old count.	 *	 * Next the tracer is set to the state we want (disabled or enabled)	 * then a write memory barrier is used to make sure that	 * the new state is visible before changing the counter by	 * one minus the old counter. This guarantees that another CPU	 * executing this code will see the new state before seeing	 * the new counter value, and would not do anything if the new	 * counter is seen.	 *	 * Note, there is no synchronization between this and a user	 * setting the tracing_on file. But we currently don't care	 * about that.	 */	count = (long *)ftrace_func_mapper_find_ip(mapper, ip);	old_count = *count; 	if (old_count <= 0)		return; 	/* Make sure we see count before checking tracing state */	smp_rmb(); 	if (on == !!tracer_tracing_is_on(tr))		return; 	if (on)		tracer_tracing_on(tr);	else		tracer_tracing_off(tr); 	/* Make sure tracing state is visible before updating count */	smp_wmb(); 	*count = old_count - 1;} static voidftrace_traceon_count(unsigned long ip, unsigned long parent_ip,		     struct trace_array *tr, struct ftrace_probe_ops *ops,		     void *data){	update_traceon_count(ops, ip, tr, 1, data);} static voidftrace_traceoff_count(unsigned long ip, unsigned long parent_ip,		      struct trace_array *tr, struct ftrace_probe_ops *ops,		      void *data){	update_traceon_count(ops, ip, tr, 0, data);} static voidftrace_traceon(unsigned long ip, unsigned long parent_ip,	       struct trace_array *tr, struct ftrace_probe_ops *ops,	       void *data){	if (tracer_tracing_is_on(tr))		return; 	tracer_tracing_on(tr);} static voidftrace_traceoff(unsigned long ip, unsigned long parent_ip,		struct trace_array *tr, struct ftrace_probe_ops *ops,		void *data){	if (!tracer_tracing_is_on(tr))		return; 	tracer_tracing_off(tr);} #ifdef CONFIG_UNWINDER_ORC/* * Skip 3: * *   function_trace_probe_call() *   ftrace_ops_assist_func() *   ftrace_call() */#define FTRACE_STACK_SKIP 3#else/* * Skip 5: * *   __trace_stack() *   ftrace_stacktrace() *   function_trace_probe_call() *   ftrace_ops_assist_func() *   ftrace_call() */#define FTRACE_STACK_SKIP 5#endif static __always_inline void trace_stack(struct trace_array *tr){	unsigned long flags;	int pc; 	local_save_flags(flags);	pc = preempt_count(); 	__trace_stack(tr, flags, FTRACE_STACK_SKIP, pc);} static voidftrace_stacktrace(unsigned long ip, unsigned long parent_ip,		  struct trace_array *tr, struct ftrace_probe_ops *ops,		  void *data){	trace_stack(tr);} static voidftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip,			struct trace_array *tr, struct ftrace_probe_ops *ops,			void *data){	struct ftrace_func_mapper *mapper = data;	long *count;	long old_count;	long new_count; 	if (!tracing_is_on())		return; 	/* unlimited? */	if (!mapper) {		trace_stack(tr);		return;	} 	count = (long *)ftrace_func_mapper_find_ip(mapper, ip); 	/*	 * Stack traces should only execute the number of times the	 * user specified in the counter.	 */	do {		old_count = *count; 		if (!old_count)			return; 		new_count = old_count - 1;		new_count = cmpxchg(count, old_count, new_count);		if (new_count == old_count)			trace_stack(tr); 		if (!tracing_is_on())			return; 	} while (new_count != old_count);} static int update_count(struct ftrace_probe_ops *ops, unsigned long ip,			void *data){	struct ftrace_func_mapper *mapper = data;	long *count = NULL; 	if (mapper)		count = (long *)ftrace_func_mapper_find_ip(mapper, ip); 	if (count) {		if (*count <= 0)			return 0;		(*count)--;	} 	return 1;} static voidftrace_dump_probe(unsigned long ip, unsigned long parent_ip,		  struct trace_array *tr, struct ftrace_probe_ops *ops,		  void *data){	if (update_count(ops, ip, data))		ftrace_dump(DUMP_ALL);} /* Only dump the current CPU buffer. */static voidftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip,		     struct trace_array *tr, struct ftrace_probe_ops *ops,		     void *data){	if (update_count(ops, ip, data))		ftrace_dump(DUMP_ORIG);} static int

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