ftrace.c

/*
 * Infrastructure for profiling code inserted by 'gcc -pg'.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2004-2008 Ingo Molnar <mingo@redhat.com>
 *
 * Originally ported from the -rt patch by:
 *   Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
 *
 * Based on code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */

#include <linux/stop_machine.h>
#include <linux/clocksource.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/suspend.h>
#include <linux/debugfs.h>
#include <linux/hardirq.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
#include <linux/kprobes.h>
#include <linux/ftrace.h>
#include <linux/sysctl.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/hash.h>

#include <asm/ftrace.h>

#include "trace.h"

#define FTRACE_WARN_ON(cond)			\
	do {					\
		if (WARN_ON(cond))		\
			ftrace_kill();		\
	} while (0)

#define FTRACE_WARN_ON_ONCE(cond)		\
	do {					\
		if (WARN_ON_ONCE(cond))		\
			ftrace_kill();		\
	} while (0)

/* hash bits for specific function selection */
#define FTRACE_HASH_BITS 7
#define FTRACE_FUNC_HASHSIZE (1 << FTRACE_HASH_BITS)

/* ftrace_enabled is a method to turn ftrace on or off */
int ftrace_enabled __read_mostly;
static int last_ftrace_enabled;

/* Quick disabling of function tracer. */
int function_trace_stop;

/*
 * ftrace_disabled is set when an anomaly is discovered.
 * ftrace_disabled is much stronger than ftrace_enabled.
 */
static int ftrace_disabled __read_mostly;

static DEFINE_MUTEX(ftrace_lock);

static struct ftrace_ops ftrace_list_end __read_mostly =
{
	.func = ftrace_stub,
};

static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;

static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
{
	struct ftrace_ops *op = ftrace_list;

	/* in case someone actually ports this to alpha! */
	read_barrier_depends();

	while (op != &ftrace_list_end) {
		/* silly alpha */
		read_barrier_depends();
		op->func(ip, parent_ip);
		op = op->next;
	};
}

static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip)
{
	if (!test_tsk_trace_trace(current))
		return;

	ftrace_pid_function(ip, parent_ip);
}

static void set_ftrace_pid_function(ftrace_func_t func)
{
	/* do not set ftrace_pid_function to itself! */
	if (func != ftrace_pid_func)
		ftrace_pid_function = func;
}

/**
 * clear_ftrace_function - reset the ftrace function
 *
 * This NULLs the ftrace function and in essence stops
 * tracing.  There may be lag
 */
void clear_ftrace_function(void)
{
	ftrace_trace_function = ftrace_stub;
	__ftrace_trace_function = ftrace_stub;
	ftrace_pid_function = ftrace_stub;
}

#ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
/*
 * For those archs that do not test ftrace_trace_stop in their
 * mcount call site, we need to do it from C.
 */
static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip)
{
	if (function_trace_stop)
		return;

	__ftrace_trace_function(ip, parent_ip);
}
#endif

static int __register_ftrace_function(struct ftrace_ops *ops)
{
	ops->next = ftrace_list;
	/*
	 * We are entering ops into the ftrace_list but another
	 * CPU might be walking that list. We need to make sure
	 * the ops->next pointer is valid before another CPU sees
	 * the ops pointer included into the ftrace_list.
	 */
	smp_wmb();
	ftrace_list = ops;

	if (ftrace_enabled) {
		ftrace_func_t func;

		if (ops->next == &ftrace_list_end)
			func = ops->func;
		else
			func = ftrace_list_func;

		if (ftrace_pid_trace) {
			set_ftrace_pid_function(func);
			func = ftrace_pid_func;
		}

		/*
		 * For one func, simply call it directly.
		 * For more than one func, call the chain.
		 */
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
		ftrace_trace_function = func;
#else
		__ftrace_trace_function = func;
		ftrace_trace_function = ftrace_test_stop_func;
#endif
	}

	return 0;
}

static int __unregister_ftrace_function(struct ftrace_ops *ops)
{
	struct ftrace_ops **p;

	/*
	 * If we are removing the last function, then simply point
	 * to the ftrace_stub.
	 */
	if (ftrace_list == ops && ops->next == &ftrace_list_end) {
		ftrace_trace_function = ftrace_stub;
		ftrace_list = &ftrace_list_end;
		return 0;
	}

	for (p = &ftrace_list; *p != &ftrace_list_end; p = &(*p)->next)
		if (*p == ops)
			break;

	if (*p != ops)
		return -1;

	*p = (*p)->next;

	if (ftrace_enabled) {
		/* If we only have one func left, then call that directly */
		if (ftrace_list->next == &ftrace_list_end) {
			ftrace_func_t func = ftrace_list->func;

			if (ftrace_pid_trace) {
				set_ftrace_pid_function(func);
				func = ftrace_pid_func;
			}
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
			ftrace_trace_function = func;
#else
			__ftrace_trace_function = func;
#endif
		}
	}

	return 0;
}

static void ftrace_update_pid_func(void)
{
	ftrace_func_t func;

	if (ftrace_trace_function == ftrace_stub)
		return;

	func = ftrace_trace_function;

	if (ftrace_pid_trace) {
		set_ftrace_pid_function(func);
		func = ftrace_pid_func;
	} else {
		if (func == ftrace_pid_func)
			func = ftrace_pid_function;
	}

#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
	ftrace_trace_function = func;
#else
	__ftrace_trace_function = func;
#endif
}

/* set when tracing only a pid */
struct pid *ftrace_pid_trace;
static struct pid * const ftrace_swapper_pid = &init_struct_pid;

#ifdef CONFIG_DYNAMIC_FTRACE

#ifndef CONFIG_FTRACE_MCOUNT_RECORD
# error Dynamic ftrace depends on MCOUNT_RECORD
#endif

static struct hlist_head ftrace_func_hash[FTRACE_FUNC_HASHSIZE] __read_mostly;

struct ftrace_func_probe {
	struct hlist_node	node;
	struct ftrace_probe_ops	*ops;
	unsigned long		flags;
	unsigned long		ip;
	void			*data;
	struct rcu_head		rcu;
};


enum {
	FTRACE_ENABLE_CALLS		= (1 << 0),
	FTRACE_DISABLE_CALLS		= (1 << 1),
	FTRACE_UPDATE_TRACE_FUNC	= (1 << 2),
	FTRACE_ENABLE_MCOUNT		= (1 << 3),
	FTRACE_DISABLE_MCOUNT		= (1 << 4),
	FTRACE_START_FUNC_RET		= (1 << 5),
	FTRACE_STOP_FUNC_RET		= (1 << 6),
};

static int ftrace_filtered;

static struct dyn_ftrace *ftrace_new_addrs;

static DEFINE_MUTEX(ftrace_regex_lock);

struct ftrace_page {
	struct ftrace_page	*next;
	int			index;
	struct dyn_ftrace	records[];
};

#define ENTRIES_PER_PAGE \
  ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))

/* estimate from running different kernels */
#define NR_TO_INIT		10000

static struct ftrace_page	*ftrace_pages_start;
static struct ftrace_page	*ftrace_pages;

static struct dyn_ftrace *ftrace_free_records;

/*
 * This is a double for. Do not use 'break' to break out of the loop,
 * you must use a goto.
 */
#define do_for_each_ftrace_rec(pg, rec)					\
	for (pg = ftrace_pages_start; pg; pg = pg->next) {		\
		int _____i;						\
		for (_____i = 0; _____i < pg->index; _____i++) {	\
			rec = &pg->records[_____i];

#define while_for_each_ftrace_rec()		\
		}				\
	}

#ifdef CONFIG_KPROBES

static int frozen_record_count;

static inline void freeze_record(struct dyn_ftrace *rec)
{
	if (!(rec->flags & FTRACE_FL_FROZEN)) {
		rec->flags |= FTRACE_FL_FROZEN;
		frozen_record_count++;
	}
}

static inline void unfreeze_record(struct dyn_ftrace *rec)
{
	if (rec->flags & FTRACE_FL_FROZEN) {
		rec->flags &= ~FTRACE_FL_FROZEN;
		frozen_record_count--;
	}
}

static inline int record_frozen(struct dyn_ftrace *rec)
{
	return rec->flags & FTRACE_FL_FROZEN;
}
#else
# define freeze_record(rec)			({ 0; })
# define unfreeze_record(rec)			({ 0; })
# define record_frozen(rec)			({ 0; })
#endif /* CONFIG_KPROBES */

static void ftrace_free_rec(struct dyn_ftrace *rec)
{
	rec->ip = (unsigned long)ftrace_free_records;
	ftrace_free_records = rec;
	rec->flags |= FTRACE_FL_FREE;
}

void ftrace_release(void *start, unsigned long size)
{
	struct dyn_ftrace *rec;
	struct ftrace_page *pg;
	unsigned long s = (unsigned long)start;
	unsigned long e = s + size;

	if (ftrace_disabled || !start)
		return;

	mutex_lock(&ftrace_lock);
	do_for_each_ftrace_rec(pg, rec) {
		if ((rec->ip >= s) && (rec->ip < e) &&
		    !(rec->flags & FTRACE_FL_FREE))
			ftrace_free_rec(rec);
	} while_for_each_ftrace_rec();
	mutex_unlock(&ftrace_lock);
}

static struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
{
	struct dyn_ftrace *rec;

	/* First check for freed records */
	if (ftrace_free_records) {
		rec = ftrace_free_records;

		if (unlikely(!(rec->flags & FTRACE_FL_FREE))) {
			FTRACE_WARN_ON_ONCE(1);
			ftrace_free_records = NULL;
			return NULL;
		}

		ftrace_free_records = (void *)rec->ip;
		memset(rec, 0, sizeof(*rec));
		return rec;
	}

	if (ftrace_pages->index == ENTRIES_PER_PAGE) {
		if (!ftrace_pages->next) {
			/* allocate another page */
			ftrace_pages->next =
				(void *)get_zeroed_page(GFP_KERNEL);
			if (!ftrace_pages->next)
				return NULL;
		}
		ftrace_pages = ftrace_pages->next;
	}

	return &ftrace_pages->records[ftrace_pages->index++];
}

static struct dyn_ftrace *
ftrace_record_ip(unsigned long ip)
{
	struct dyn_ftrace *rec;

	if (ftrace_disabled)
		return NULL;

	rec = ftrace_alloc_dyn_node(ip);
	if (!rec)
		return NULL;

	rec->ip = ip;
	rec->flags = (unsigned long)ftrace_new_addrs;
	ftrace_new_addrs = rec;

	return rec;
}

static void print_ip_ins(const char *fmt, unsigned char *p)
{
	int i;

	printk(KERN_CONT "%s", fmt);

	for (i = 0; i < MCOUNT_INSN_SIZE; i++)
		printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);
}

static void ftrace_bug(int failed, unsigned long ip)
{
	switch (failed) {
	case -EFAULT:
		FTRACE_WARN_ON_ONCE(1);
		pr_info("ftrace faulted on modifying ");
		print_ip_sym(ip);
		break;
	case -EINVAL:
		FTRACE_WARN_ON_ONCE(1);
		pr_info("ftrace failed to modify ");
		print_ip_sym(ip);
		print_ip_ins(" actual: ", (unsigned char *)ip);
		printk(KERN_CONT "\n");
		break;
	case -EPERM:
		FTRACE_WARN_ON_ONCE(1);
		pr_info("ftrace faulted on writing ");
		print_ip_sym(ip);
		break;
	default:
		FTRACE_WARN_ON_ONCE(1);
		pr_info("ftrace faulted on unknown error ");
		print_ip_sym(ip);
	}
}


static int
__ftrace_replace_code(struct dyn_ftrace *rec, int enable)
{
	unsigned long ftrace_addr;
	unsigned long ip, fl;

	ftrace_addr = (unsigned long)FTRACE_ADDR;

	ip = rec->ip;

	/*
	 * If this record is not to be traced and
	 * it is not enabled then do nothing.
	 *
	 * If this record is not to be traced and
	 * it is enabled then disable it.
	 *
	 */
	if (rec->flags & FTRACE_FL_NOTRACE) {
		if (rec->flags & FTRACE_FL_ENABLED)
			rec->flags &= ~FTRACE_FL_ENABLED;
		else
			return 0;

	} else if (ftrace_filtered && enable) {
		/*
		 * Filtering is on:
		 */

		fl = rec->flags & (FTRACE_FL_FILTER | FTRACE_FL_ENABLED);

		/* Record is filtered and enabled, do nothing */
		if (fl == (FTRACE_FL_FILTER | FTRACE_FL_ENABLED))
			return 0;

		/* Record is not filtered or enabled, do nothing */
		if (!fl)
			return 0;

		/* Record is not filtered but enabled, disable it */
		if (fl == FTRACE_FL_ENABLED)
			rec->flags &= ~FTRACE_FL_ENABLED;
		else
		/* Otherwise record is filtered but not enabled, enable it */
			rec->flags |= FTRACE_FL_ENABLED;
	} else {
		/* Disable or not filtered */

		if (enable) {
			/* if record is enabled, do nothing */
			if (rec->flags & FTRACE_FL_ENABLED)
				return 0;

			rec->flags |= FTRACE_FL_ENABLED;

		} else {

			/* if record is not enabled, do nothing */
			if (!(rec->flags & FTRACE_FL_ENABLED))
				return 0;

			rec->flags &= ~FTRACE_FL_ENABLED;
		}
	}

	if (rec->flags & FTRACE_FL_ENABLED)
		return ftrace_make_call(rec, ftrace_addr);
	else
		return ftrace_make_nop(NULL, rec, ftrace_addr);
}

static void ftrace_replace_code(int enable)
{
	struct dyn_ftrace *rec;
	struct ftrace_page *pg;
	int failed;

	do_for_each_ftrace_rec(pg, rec) {
		/*
		 * Skip over free records, records that have
		 * failed and not converted.
		 */
		if (rec->flags & FTRACE_FL_FREE ||
		    rec->flags & FTRACE_FL_FAILED ||
		    !(rec->flags & FTRACE_FL_CONVERTED))
			continue;

		/* ignore updates to this record's mcount site */
		if (get_kprobe((void *)rec->ip)) {
			freeze_record(rec);
			continue;
		} else {
			unfreeze_record(rec);
		}

		failed = __ftrace_replace_code(rec, enable);
		if (failed) {
			rec->flags |= FTRACE_FL_FAILED;
			if ((system_state == SYSTEM_BOOTING) ||
			    !core_kernel_text(rec->ip)) {
				ftrace_free_rec(rec);
				} else {
				ftrace_bug(failed, rec->ip);
					/* Stop processing */
					return;
				}
		}
	} while_for_each_ftrace_rec();
}

static int
ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
{
	unsigned long ip;
	int ret;

	ip = rec->ip;

	ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
	if (ret) {
		ftrace_bug(ret, ip);
		rec->flags |= FTRACE_FL_FAILED;
		return 0;
	}
	return 1;
}

/*
 * archs can override this function if they must do something
 * before the modifying code is performed.
 */
int __weak ftrace_arch_code_modify_prepare(void)
{
	return 0;
}

/*
 * archs can override this function if they must do something
 * after the modifying code is performed.
 */
int __weak ftrace_arch_code_modify_post_process(void)
{
	return 0;
}

static int __ftrace_modify_code(void *data)
{
	int *command = data;

	if (*command & FTRACE_ENABLE_CALLS)
		ftrace_replace_code(1);
	else if (*command & FTRACE_DISABLE_CALLS)
		ftrace_replace_code(0);

	if (*command & FTRACE_UPDATE_TRACE_FUNC)
		ftrace_update_ftrace_func(ftrace_trace_function);

	if (*command & FTRACE_START_FUNC_RET)
		ftrace_enable_ftrace_graph_caller();
	else if (*command & FTRACE_STOP_FUNC_RET)
		ftrace_disable_ftrace_graph_caller();

	return 0;
}

static void ftrace_run_update_code(int command)
{
	int ret;

	ret = ftrace_arch_code_modify_prepare();
	FTRACE_WARN_ON(ret);
	if (ret)
		return;

	stop_machine(__ftrace_modify_code, &command, NULL);

	ret = ftrace_arch_code_modify_post_process();
	FTRACE_WARN_ON(ret);
}

static ftrace_func_t saved_ftrace_func;
static int ftrace_start_up;

static void ftrace_startup_enable(int command)
{
	if (saved_ftrace_func != ftrace_trace_function) {
		saved_ftrace_func = ftrace_trace_function;
		command |= FTRACE_UPDATE_TRACE_FUNC;
	}

	if (!command || !ftrace_enabled)
		return;

	ftrace_run_update_code(command);
}

static void ftrace_startup(int command)
{
	if (unlikely(ftrace_disabled))
		return;

	ftrace_start_up++;
	command |= FTRACE_ENABLE_CALLS;

	ftrace_startup_enable(command);
}

static void ftrace_shutdown(int command)
{
	if (unlikely(ftrace_disabled))
		return;

	ftrace_start_up--;
	if (!ftrace_start_up)
		command |= FTRACE_DISABLE_CALLS;

	if (saved_ftrace_func != ftrace_trace_function) {
		saved_ftrace_func = ftrace_trace_function;
		command |= FTRACE_UPDATE_TRACE_FUNC;
	}

	if (!command || !ftrace_enabled)
		return;

	ftrace_run_update_code(command);
}

static void ftrace_startup_sysctl(void)
{
	int command = FTRACE_ENABLE_MCOUNT;

	if (unlikely(ftrace_disabled))
		return;

	/* Force update next time */
	saved_ftrace_func = NULL;
	/* ftrace_start_up is true if we want ftrace running */
	if (ftrace_start_up)
		command |= FTRACE_ENABLE_CALLS;

	ftrace_run_update_code(command);
}

static void ftrace_shutdown_sysctl(void)
{
	int command = FTRACE_DISABLE_MCOUNT;

	if (unlikely(ftrace_disabled))
		return;

	/* ftrace_start_up is true if ftrace is running */
	if (ftrace_start_up)
		command |= FTRACE_DISABLE_CALLS;

	ftrace_run_update_code(command);
}

static cycle_t		ftrace_update_time;
static unsigned long	ftrace_update_cnt;
unsigned long		ftrace_update_tot_cnt;

static int ftrace_update_code(struct module *mod)
{
	struct dyn_ftrace *p;
	cycle_t start, stop;

	start = ftrace_now(raw_smp_processor_id());
	ftrace_update_cnt = 0;

	while (ftrace_new_addrs) {

		/* If something went wrong, bail without enabling anything */
		if (unlikely(ftrace_disabled))
			return -1;

		p = ftrace_new_addrs;
		ftrace_new_addrs = (struct dyn_ftrace *)p->flags;
		p->flags = 0L;

		/* convert record (i.e, patch mcount-call with NOP) */
		if (ftrace_code_disable(mod, p)) {
			p->flags |= FTRACE_FL_CONVERTED;
			ftrace_update_cnt++;
		} else
			ftrace_free_rec(p);
	}

	stop = ftrace_now(raw_smp_processor_id());
	ftrace_update_time = stop - start;
	ftrace_update_tot_cnt += ftrace_update_cnt;

	return 0;
}

static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
{
	struct ftrace_page *pg;
	int cnt;
	int i;

	/* allocate a few pages */
	ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
	if (!ftrace_pages_start)
		return -1;

	/*
	 * Allocate a few more pages.
	 *
	 * TODO: have some parser search vmlinux before
	 *   final linking to find all calls to ftrace.
	 *   Then we can:
	 *    a) know how many pages to allocate.
	 *     and/or
	 *    b) set up the table then.
	 *
	 *  The dynamic code is still necessary for
	 *  modules.
	 */

	pg = ftrace_pages = ftrace_pages_start;

	cnt = num_to_init / ENTRIES_PER_PAGE;
	pr_info("ftrace: allocating %ld entries in %d pages\n",
		num_to_init, cnt + 1);

	for (i = 0; i < cnt; i++) {
		pg->next = (void *)get_zeroed_page(GFP_KERNEL);

		/* If we fail, we'll try later anyway */
		if (!pg->next)
			break;

		pg = pg->next;
	}

	return 0;
}

enum {
	FTRACE_ITER_FILTER	= (1 << 0),
	FTRACE_ITER_CONT	= (1 << 1),
	FTRACE_ITER_NOTRACE	= (1 << 2),
	FTRACE_ITER_FAILURES	= (1 << 3),
	FTRACE_ITER_PRINTALL	= (1 << 4),
	FTRACE_ITER_HASH	= (1 << 5),
};

#define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */

struct ftrace_iterator {
	struct ftrace_page	*pg;
	int			hidx;
	int			idx;
	unsigned		flags;
	unsigned char		buffer[FTRACE_BUFF_MAX+1];
	unsigned		buffer_idx;
	unsigned		filtered;
};

static void *
t_hash_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct ftrace_iterator *iter = m->private;
	struct hlist_node *hnd = v;
	struct hlist_head *hhd;

	WARN_ON(!(iter->flags & FTRACE_ITER_HASH));

	(*pos)++;

 retry:
	if (iter->hidx >= FTRACE_FUNC_HASHSIZE)
		return NULL;

	hhd = &ftrace_func_hash[iter->hidx];

	if (hlist_empty(hhd)) {
		iter->hidx++;
		hnd = NULL;
		goto retry;
	}

	if (!hnd)
		hnd = hhd->first;
	else {
		hnd = hnd->next;
		if (!hnd) {
			iter->hidx++;
			goto retry;
		}
	}

	return hnd;
}

static void *t_hash_start(struct seq_file *m, loff_t *pos)
{
	struct ftrace_iterator *iter = m->private;
	void *p = NULL;

	iter->flags |= FTRACE_ITER_HASH;

	return t_hash_next(m, p, pos);
}

static int t_hash_show(struct seq_file *m, void *v)
{
	struct ftrace_func_probe *rec;
	struct hlist_node *hnd = v;
	char str[KSYM_SYMBOL_LEN];

	rec = hlist_entry(hnd, struct ftrace_func_probe, node);

	if (rec->ops->print)
		return rec->ops->print(m, rec->ip, rec->ops, rec->data);

	kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
	seq_printf(m, "%s:", str);

	kallsyms_lookup((unsigned long)rec->ops->func, NULL, NULL, NULL, str);
	seq_printf(m, "%s", str);

	if (rec->data)
		seq_printf(m, ":%p", rec->data);
	seq_putc(m, '\n');

	return 0;
}

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct ftrace_iterator *iter = m->private;
	struct dyn_ftrace *rec = NULL;

	if (iter->flags & FTRACE_ITER_HASH)
		return t_hash_next(m, v, pos);

	(*pos)++;

	if (iter->flags & FTRACE_ITER_PRINTALL)
		return NULL;

 retry:
	if (iter->idx >= iter->pg->index) {
		if (iter->pg->next) {
			iter->pg = iter->pg->next;
			iter->idx = 0;
			goto retry;
		} else {
			iter->idx = -1;
		}
	} else {
		rec = &iter->pg->records[iter->idx++];
		if ((rec->flags & FTRACE_FL_FREE) ||

		    (!(iter->flags & FTRACE_ITER_FAILURES) &&
		     (rec->flags & FTRACE_FL_FAILED)) ||

		    ((iter->flags & FTRACE_ITER_FAILURES) &&
		     !(rec->flags & FTRACE_FL_FAILED)) ||

		    ((iter->flags & FTRACE_ITER_FILTER) &&
		     !(rec->flags & FTRACE_FL_FILTER)) ||

		    ((iter->flags & FTRACE_ITER_NOTRACE) &&
		     !(rec->flags & FTRACE_FL_NOTRACE))) {
			rec = NULL;
			goto retry;
		}
	}

	return rec;
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
	struct ftrace_iterator *iter = m->private;
	void *p = NULL;

	mutex_lock(&ftrace_lock);
	/*
	 * For set_ftrace_filter reading, if we have the filter
	 * off, we can short cut and just print out that all
	 * functions are enabled.
	 */
	if (iter->flags & FTRACE_ITER_FILTER && !ftrace_filtered) {
		if (*pos > 0)
			return t_hash_start(m, pos);
		iter->flags |= FTRACE_ITER_PRINTALL;
		(*pos)++;
		return iter;
	}

	if (iter->flags & FTRACE_ITER_HASH)
		return t_hash_start(m, pos);

	if (*pos > 0) {
		if (iter->idx < 0)
			return p;
		(*pos)--;
		iter->idx--;
	}

	p = t_next(m, p, pos);

	if (!p)
		return t_hash_start(m, pos);

	return p;
}

static void t_stop(struct seq_file *m, void *p)
{
	mutex_unlock(&ftrace_lock);
}

static int t_show(struct seq_file *m, void *v)
{
	struct ftrace_iterator *iter = m->private;
	struct dyn_ftrace *rec = v;
	char str[KSYM_SYMBOL_LEN];

	if (iter->flags & FTRACE_ITER_HASH)
		return t_hash_show(m, v);

	if (iter->flags & FTRACE_ITER_PRINTALL) {
		seq_printf(m, "#### all functions enabled ####\n");
		return 0;
	}

	if (!rec)
		return 0;

	kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);

	seq_printf(m, "%s\n", str);

	return 0;
}

static struct seq_operations show_ftrace_seq_ops = {
	.start = t_start,
	.next = t_next,
	.stop = t_stop,