path: root/kernel/trace/trace_functions.c

// 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 void
function_trace_call(unsigned long ip, unsigned long parent_ip,
		    struct ftrace_ops *op, struct ftrace_regs *fregs);
static void
function_args_trace_call(unsigned long ip, unsigned long parent_ip,
			 struct ftrace_ops *op, struct ftrace_regs *fregs);
static void
function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
			  struct ftrace_ops *op, struct ftrace_regs *fregs);
static void
function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
			       struct ftrace_ops *op, struct ftrace_regs *fregs);
static void
function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
				     struct ftrace_ops *op,
				     struct ftrace_regs *fregs);
static struct tracer_flags func_flags;

/* Our option */
enum {

	TRACE_FUNC_NO_OPTS		= 0x0, /* No flags set. */
	TRACE_FUNC_OPT_STACK		= 0x1,
	TRACE_FUNC_OPT_NO_REPEATS	= 0x2,
	TRACE_FUNC_OPT_ARGS		= 0x4,

	/* Update this to next highest bit. */
	TRACE_FUNC_OPT_HIGHEST_BIT	= 0x8
};

#define TRACE_FUNC_OPT_MASK	(TRACE_FUNC_OPT_HIGHEST_BIT - 1)

int ftrace_allocate_ftrace_ops(struct trace_array *tr)
{
	struct ftrace_ops *ops;

	/* The top level array uses the "global_ops" */
	if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
		return 0;

	ops = kzalloc(sizeof(*ops), GFP_KERNEL);
	if (!ops)
		return -ENOMEM;

	/* Currently only the non stack version is supported */
	ops->func = function_trace_call;
	ops->flags = FTRACE_OPS_FL_PID;

	tr->ops = ops;
	ops->private = tr;

	return 0;
}

void ftrace_free_ftrace_ops(struct trace_array *tr)
{
	kfree(tr->ops);
	tr->ops = NULL;
}

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;

	if (!tr->ops)
		return -EINVAL;

	ret = allocate_fgraph_ops(tr, tr->ops);
	if (ret) {
		kfree(tr->ops);
		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);
	ftrace_free_ftrace_ops(tr);
	free_fgraph_ops(tr);
}

static ftrace_func_t select_trace_function(u32 flags_val)
{
	switch (flags_val & TRACE_FUNC_OPT_MASK) {
	case TRACE_FUNC_NO_OPTS:
		return function_trace_call;
	case TRACE_FUNC_OPT_ARGS:
		return function_args_trace_call;
	case TRACE_FUNC_OPT_STACK:
		return function_stack_trace_call;
	case TRACE_FUNC_OPT_NO_REPEATS:
		return function_no_repeats_trace_call;
	case TRACE_FUNC_OPT_STACK | TRACE_FUNC_OPT_NO_REPEATS:
		return function_stack_no_repeats_trace_call;
	default:
		return NULL;
	}
}

static bool handle_func_repeats(struct trace_array *tr, u32 flags_val)
{
	if (!tr->last_func_repeats &&
	    (flags_val & TRACE_FUNC_OPT_NO_REPEATS)) {
		tr->last_func_repeats = alloc_percpu(struct trace_func_repeats);
		if (!tr->last_func_repeats)
			return false;
	}

	return true;
}

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;

	func = select_trace_function(func_flags.val);
	if (!func)
		return -EINVAL;

	if (!handle_func_repeats(tr, func_flags.val))
		return -ENOMEM;

	ftrace_init_array_ops(tr, func);

	tr->array_buffer.cpu = raw_smp_processor_id();

	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->array_buffer);
}

/* fregs are guaranteed not to be NULL if HAVE_DYNAMIC_FTRACE_WITH_ARGS is set */
#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS)
static __always_inline unsigned long
function_get_true_parent_ip(unsigned long parent_ip, struct ftrace_regs *fregs)
{
	unsigned long true_parent_ip;
	int idx = 0;

	true_parent_ip = parent_ip;
	if (unlikely(parent_ip == (unsigned long)&return_to_handler) && fregs)
		true_parent_ip = ftrace_graph_ret_addr(current, &idx, parent_ip,
				(unsigned long *)ftrace_regs_get_stack_pointer(fregs));
	return true_parent_ip;
}
#else
static __always_inline unsigned long
function_get_true_parent_ip(