[mirror_ubuntu-zesty-kernel.git] / kernel / trace / trace_functions_graph.c

/*
 *
 * Function graph tracer.
 * Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
 * Mostly borrowed from function tracer which
 * is Copyright (c) Steven Rostedt <srostedt@redhat.com>
 *
 */
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/slab.h>
#include <linux/fs.h>

#include "trace.h"
#include "trace_output.h"

static bool kill_ftrace_graph;

/**
 * ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called
 *
 * ftrace_graph_stop() is called when a severe error is detected in
 * the function graph tracing. This function is called by the critical
 * paths of function graph to keep those paths from doing any more harm.
 */
bool ftrace_graph_is_dead(void)
{
        return kill_ftrace_graph;
}

/**
 * ftrace_graph_stop - set to permanently disable function graph tracincg
 *
 * In case of an error int function graph tracing, this is called
 * to try to keep function graph tracing from causing any more harm.
 * Usually this is pretty severe and this is called to try to at least
 * get a warning out to the user.
 */
void ftrace_graph_stop(void)
{
        kill_ftrace_graph = true;
}

/* When set, irq functions will be ignored */
static int ftrace_graph_skip_irqs;

struct fgraph_cpu_data {
        pid_t           last_pid;
        int             depth;
        int             depth_irq;
        int             ignore;
        unsigned long   enter_funcs[FTRACE_RETFUNC_DEPTH];
};

struct fgraph_data {
        struct fgraph_cpu_data __percpu *cpu_data;

        /* Place to preserve last processed entry. */
        struct ftrace_graph_ent_entry   ent;
        struct ftrace_graph_ret_entry   ret;
        int                             failed;
        int                             cpu;
};

#define TRACE_GRAPH_INDENT      2

static unsigned int max_depth;

static struct tracer_opt trace_opts[] = {
        /* Display overruns? (for self-debug purpose) */
        { TRACER_OPT(funcgraph-overrun, TRACE_GRAPH_PRINT_OVERRUN) },
        /* Display CPU ? */
        { TRACER_OPT(funcgraph-cpu, TRACE_GRAPH_PRINT_CPU) },
        /* Display Overhead ? */
        { TRACER_OPT(funcgraph-overhead, TRACE_GRAPH_PRINT_OVERHEAD) },
        /* Display proc name/pid */
        { TRACER_OPT(funcgraph-proc, TRACE_GRAPH_PRINT_PROC) },
        /* Display duration of execution */
        { TRACER_OPT(funcgraph-duration, TRACE_GRAPH_PRINT_DURATION) },
        /* Display absolute time of an entry */
        { TRACER_OPT(funcgraph-abstime, TRACE_GRAPH_PRINT_ABS_TIME) },
        /* Display interrupts */
        { TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) },
        /* Display function name after trailing } */
        { TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) },
        { } /* Empty entry */
};

static struct tracer_flags tracer_flags = {
        /* Don't display overruns, proc, or tail by default */
        .val = TRACE_GRAPH_PRINT_CPU | TRACE_GRAPH_PRINT_OVERHEAD |
               TRACE_GRAPH_PRINT_DURATION | TRACE_GRAPH_PRINT_IRQS,
        .opts = trace_opts
};

static struct trace_array *graph_array;

/*
 * DURATION column is being also used to display IRQ signs,
 * following values are used by print_graph_irq and others
 * to fill in space into DURATION column.
 */
enum {
        FLAGS_FILL_FULL  = 1 << TRACE_GRAPH_PRINT_FILL_SHIFT,
        FLAGS_FILL_START = 2 << TRACE_GRAPH_PRINT_FILL_SHIFT,
        FLAGS_FILL_END   = 3 << TRACE_GRAPH_PRINT_FILL_SHIFT,
};

static void
print_graph_duration(unsigned long long duration, struct trace_seq *s,
                     u32 flags);

/* Add a function return address to the trace stack on thread info.*/
int
ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
                         unsigned long frame_pointer)
{
        unsigned long long calltime;
        int index;

        if (unlikely(ftrace_graph_is_dead()))
                return -EBUSY;

        if (!current->ret_stack)
                return -EBUSY;

        /*
         * We must make sure the ret_stack is tested before we read
         * anything else.
         */
        smp_rmb();

        /* The return trace stack is full */
        if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
                atomic_inc(&current->trace_overrun);
                return -EBUSY;
        }

        /*
         * The curr_ret_stack is an index to ftrace return stack of
         * current task.  Its value should be in [0, FTRACE_RETFUNC_
         * DEPTH) when the function graph tracer is used.  To support
         * filtering out specific functions, it makes the index
         * negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
         * so when it sees a negative index the ftrace will ignore
         * the record.  And the index gets recovered when returning
         * from the filtered function by adding the FTRACE_NOTRACE_
         * DEPTH and then it'll continue to record functions normally.
         *
         * The curr_ret_stack is initialized to -1 and get increased
         * in this function.  So it can be less than -1 only if it was
         * filtered out via ftrace_graph_notrace_addr() which can be
         * set from set_graph_notrace file in debugfs by user.
         */
        if (current->curr_ret_stack < -1)
                return -EBUSY;

        calltime = trace_clock_local();

        index = ++current->curr_ret_stack;
        if (ftrace_graph_notrace_addr(func))
                current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
        barrier();
        current->ret_stack[index].ret = ret;
        current->ret_stack[index].func = func;
        current->ret_stack[index].calltime = calltime;
        current->ret_stack[index].subtime = 0;
        current->ret_stack[index].fp = frame_pointer;
        *depth = current->curr_ret_stack;

        return 0;
}

/* Retrieve a function return address to the trace stack on thread info.*/
static void
ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
                        unsigned long frame_pointer)
{
        int index;

        index = current->curr_ret_stack;

        /*
         * A negative index here means that it's just returned from a
         * notrace'd function.  Recover index to get an original
         * return address.  See ftrace_push_return_trace().
         *
         * TODO: Need to check whether the stack gets corrupted.
         */
        if (index < 0)
                index += FTRACE_NOTRACE_DEPTH;

        if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
                ftrace_graph_stop();
                WARN_ON(1);
                /* Might as well panic, otherwise we have no where to go */
                *ret = (unsigned long)panic;
                return;
        }

#if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
        /*
         * The arch may choose to record the frame pointer used
         * and check it here to make sure that it is what we expect it
         * to be. If gcc does not set the place holder of the return
         * address in the frame pointer, and does a copy instead, then
         * the function graph trace will fail. This test detects this
         * case.
         *
         * Currently, x86_32 with optimize for size (-Os) makes the latest
         * gcc do the above.
         *
         * Note, -mfentry does not use frame pointers, and this test
         *  is not needed if CC_USING_FENTRY is set.
         */
        if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
                ftrace_graph_stop();
                WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
                     "  from func %ps return to %lx\n",
                     current->ret_stack[index].fp,
                     frame_pointer,
                     (void *)current->ret_stack[index].func,
                     current->ret_stack[index].ret);
                *ret = (unsigned long)panic;
                return;
        }
#endif

        *ret = current->ret_stack[index].ret;
        trace->func = current->ret_stack[index].func;
        trace->calltime = current->ret_stack[index].calltime;
        trace->overrun = atomic_read(&current->trace_overrun);
        trace->depth = index;
}

/*
 * Send the trace to the ring-buffer.
 * @return the original return address.
 */
unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
{
        struct ftrace_graph_ret trace;
        unsigned long ret;

        ftrace_pop_return_trace(&trace, &ret, frame_pointer);
        trace.rettime = trace_clock_local();
        barrier();
        current->curr_ret_stack--;
        /*
         * The curr_ret_stack can be less than -1 only if it was
         * filtered out and it's about to return from the function.
         * Recover the index and continue to trace normal functions.
         */
        if (current->curr_ret_stack < -1) {
                current->curr_ret_stack += FTRACE_NOTRACE_DEPTH;
                return ret;
        }

        /*
         * The trace should run after decrementing the ret counter
         * in case an interrupt were to come in. We don't want to
         * lose the interrupt if max_depth is set.
         */
        ftrace_graph_return(&trace);

        if (unlikely(!ret)) {
                ftrace_graph_stop();
                WARN_ON(1);
                /* Might as well panic. What else to do? */
                ret = (unsigned long)panic;
        }

        return ret;
}

int __trace_graph_entry(struct trace_array *tr,
                                struct ftrace_graph_ent *trace,
                                unsigned long flags,
                                int pc)
{
        struct ftrace_event_call *call = &event_funcgraph_entry;
        struct ring_buffer_event *event;
        struct ring_buffer *buffer = tr->trace_buffer.buffer;
        struct ftrace_graph_ent_entry *entry;

        if (unlikely(__this_cpu_read(ftrace_cpu_disabled)))
                return 0;

        event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT,
                                          sizeof(*entry), flags, pc);
        if (!event)
                return 0;
        entry   = ring_buffer_event_data(event);
        entry->graph_ent                        = *trace;
        if (!call_filter_check_discard(call, entry, buffer, event))
                __buffer_unlock_commit(buffer, event);

        return 1;
}

static inline int ftrace_graph_ignore_irqs(void)
{
        if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
                return 0;

        return in_irq();
}

int trace_graph_entry(struct ftrace_graph_ent *trace)
{
        struct trace_array *tr = graph_array;
        struct trace_array_cpu *data;
        unsigned long flags;
        long disabled;
        int ret;
        int cpu;
        int pc;

        if (!ftrace_trace_task(current))
                return 0;

        /* trace it when it is-nested-in or is a function enabled. */
        if ((!(trace->depth || ftrace_graph_addr(trace->func)) ||
             ftrace_graph_ignore_irqs()) || (trace->depth < 0) ||
            (max_depth && trace->depth >= max_depth))
                return 0;

        /*
         * Do not trace a function if it's filtered by set_graph_notrace.
         * Make the index of ret stack negative to indicate that it should
         * ignore further functions.  But it needs its own ret stack entry
         * to recover the original index in order to continue tracing after
         * returning from the function.
         */
        if (ftrace_graph_notrace_addr(trace->func))
                return 1;

        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();
                ret = __trace_graph_entry(tr, trace, flags, pc);
        } else {
                ret = 0;
        }

        atomic_dec(&data->disabled);
        local_irq_restore(flags);

        return ret;
}

static int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
{
        if (tracing_thresh)
                return 1;
        else
                return trace_graph_entry(trace);
}

static void
__trace_graph_function(struct trace_array *tr,
                unsigned long ip, unsigned long flags, int pc)
{
        u64 time = trace_clock_local();
        struct ftrace_graph_ent ent = {
                .func  = ip,
                .depth = 0,
        };
        struct ftrace_graph_ret ret = {
                .func     = ip,
                .depth    = 0,
                .calltime = time,
                .rettime  = time,
        };

        __trace_graph_entry(tr, &ent, flags, pc);
        __trace_graph_return(tr, &ret, flags, pc);
}

void
trace_graph_function(struct trace_array *tr,
                unsigned long ip, unsigned long parent_ip,
                unsigned long flags, int pc)
{
        __trace_graph_function(tr, ip, flags, pc);
}

void __trace_graph_return(struct trace_array *tr,
                                struct ftrace_graph_ret *trace,
                                unsigned long flags,
                                int pc)
{
        struct ftrace_event_call *call = &event_funcgraph_exit;
        struct ring_buffer_event *event;
        struct ring_buffer *buffer = tr->trace_buffer.buffer;
        struct ftrace_graph_ret_entry *entry;

        if (unlikely(__this_cpu_read(ftrace_cpu_disabled)))
                return;

        event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RET,
                                          sizeof(*entry), flags, pc);
        if (!event)
                return;
        entry   = ring_buffer_event_data(event);
        entry->ret                              = *trace;
        if (!call_filter_check_discard(call, entry, buffer, event))
                __buffer_unlock_commit(buffer, event);
}

void trace_graph_return(struct ftrace_graph_ret *trace)
{
        struct trace_array *tr = graph_array;
        struct trace_array_cpu *data;
        unsigned long flags;
        long disabled;
        int cpu;
        int pc;

        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_graph_return(tr, trace, flags, pc);
        }
        atomic_dec(&data->disabled);
        local_irq_restore(flags);
}

void set_graph_array(struct trace_array *tr)
{
        graph_array = tr;

        /* Make graph_array visible before we start tracing */

        smp_mb();
}

static void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
{
        if (tracing_thresh &&
            (trace->rettime - trace->calltime < tracing_thresh))
                return;
        else
                trace_graph_return(trace);
}

static int graph_trace_init(struct trace_array *tr)
{
        int ret;

        set_graph_array(tr);
        if (tracing_thresh)
                ret = register_ftrace_graph(&trace_graph_thresh_return,
                                            &trace_graph_thresh_entry);
        else
                ret = register_ftrace_graph(&trace_graph_return,
                                            &trace_graph_entry);
        if (ret)
                return ret;
        tracing_start_cmdline_record();

        return 0;
}

static void graph_trace_reset(struct trace_array *tr)
{
        tracing_stop_cmdline_record();
        unregister_ftrace_graph();
}

static int graph_trace_update_thresh(struct trace_array *tr)
{
        graph_trace_reset(tr);
        return graph_trace_init(tr);
}

static int max_bytes_for_cpu;

static void print_graph_cpu(struct trace_seq *s, int cpu)
{
        /*
         * Start with a space character - to make it stand out
         * to the right a bit when trace output is pasted into
         * email:
         */
        trace_seq_printf(s, " %*d) ", max_bytes_for_cpu, cpu);
}

#define TRACE_GRAPH_PROCINFO_LENGTH     14

static void print_graph_proc(struct trace_seq *s, pid_t pid)
{
        char comm[TASK_COMM_LEN];
        /* sign + log10(MAX_INT) + '\0' */
        char pid_str[11];
        int spaces = 0;
        int len;
        int i;

        trace_find_cmdline(pid, comm);
        comm[7] = '\0';
        sprintf(pid_str, "%d", pid);

        /* 1 stands for the "-" character */
        len = strlen(comm) + strlen(pid_str) + 1;

        if (len < TRACE_GRAPH_PROCINFO_LENGTH)
                spaces = TRACE_GRAPH_PROCINFO_LENGTH - len;

        /* First spaces to align center */
        for (i = 0; i < spaces / 2; i++)
                trace_seq_putc(s, ' ');

        trace_seq_printf(s, "%s-%s", comm, pid_str);

        /* Last spaces to align center */
        for (i = 0; i < spaces - (spaces / 2); i++)
                trace_seq_putc(s, ' ');
}


static void print_graph_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
{
        trace_seq_putc(s, ' ');
        trace_print_lat_fmt(s, entry);
}

/* If the pid changed since the last trace, output this event */
static void
verif_pid(struct trace_seq *s, pid_t pid, int cpu, struct fgraph_data *data)
{
        pid_t prev_pid;
        pid_t *last_pid;

        if (!data)
                return;

        last_pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);

        if (*last_pid == pid)
                return;

        prev_pid = *last_pid;
        *last_pid = pid;

        if (prev_pid == -1)
                return;
/*
 * Context-switch trace line:

 ------------------------------------------
 | 1)  migration/0--1  =>  sshd-1755
 ------------------------------------------

 */
        trace_seq_puts(s, " ------------------------------------------\n");
        print_graph_cpu(s, cpu);
        print_graph_proc(s, prev_pid);
        trace_seq_puts(s, " => ");
        print_graph_proc(s, pid);
        trace_seq_puts(s, "\n ------------------------------------------\n\n");
}

static struct ftrace_graph_ret_entry *
get_return_for_leaf(struct trace_iterator *iter,
                struct ftrace_graph_ent_entry *curr)
{
        struct fgraph_data *data = iter->private;
        struct ring_buffer_iter *ring_iter = NULL;
        struct ring_buffer_event *event;
        struct ftrace_graph_ret_entry *next;

        /*
         * If the previous output failed to write to the seq buffer,
         * then we just reuse the data from before.
         */
        if (data && data->failed) {
                curr = &data->ent;
                next = &data->ret;
        } else {

                ring_iter = trace_buffer_iter(iter, iter->cpu);

                /* First peek to compare current entry and the next one */
                if (ring_iter)
                        event = ring_buffer_iter_peek(ring_iter, NULL);
                else {
                        /*
                         * We need to consume the current entry to see
                         * the next one.
                         */
                        ring_buffer_consume(iter->trace_buffer->buffer, iter->cpu,
                                            NULL, NULL);
                        event = ring_buffer_peek(iter->trace_buffer->buffer, iter->cpu,
                                                 NULL, NULL);
                }

                if (!event)
                        return NULL;

                next = ring_buffer_event_data(event);

                if (data) {
                        /*
                         * Save current and next entries for later reference
                         * if the output fails.
                         */
                        data->ent = *curr;
                        /*
                         * If the next event is not a return type, then
                         * we only care about what type it is. Otherwise we can
                         * safely copy the entire event.
                         */
                        if (next->ent.type == TRACE_GRAPH_RET)
                                data->ret = *next;
                        else
                                data->ret.ent.type = next->ent.type;
                }
        }

        if (next->ent.type != TRACE_GRAPH_RET)
                return NULL;

        if (curr->ent.pid != next->ent.pid ||
                        curr->graph_ent.func != next->ret.func)
                return NULL;

        /* this is a leaf, now advance the iterator */
        if (ring_iter)
                ring_buffer_read(ring_iter, NULL);

        return next;
}

static void print_graph_abs_time(u64 t, struct trace_seq *s)
{
        unsigned long usecs_rem;

        usecs_rem = do_div(t, NSEC_PER_SEC);
        usecs_rem /= 1000;

        trace_seq_printf(s, "%5lu.%06lu |  ",
                         (unsigned long)t, usecs_rem);
}

static void
print_graph_irq(struct trace_iterator *iter, unsigned long addr,
                enum trace_type type, int cpu, pid_t pid, u32 flags)
{
        struct trace_seq *s = &iter->seq;
        struct trace_entry *ent = iter->ent;

        if (addr < (unsigned long)__irqentry_text_start ||
                addr >= (unsigned long)__irqentry_text_end)
                return;

        if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
                /* Absolute time */
                if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
                        print_graph_abs_time(iter->ts, s);

                /* Cpu */
                if (flags & TRACE_GRAPH_PRINT_CPU)
                        print_graph_cpu(s, cpu);

                /* Proc */
                if (flags & TRACE_GRAPH_PRINT_PROC) {
                        print_graph_proc(s, pid);
                        trace_seq_puts(s, " | ");
                }

                /* Latency format */
                if (trace_flags & TRACE_ITER_LATENCY_FMT)
                        print_graph_lat_fmt(s, ent);
        }

        /* No overhead */
        print_graph_duration(0, s, flags | FLAGS_FILL_START);

        if (type == TRACE_GRAPH_ENT)
                trace_seq_puts(s, "==========>");
        else
                trace_seq_puts(s, "<==========");

        print_graph_duration(0, s, flags | FLAGS_FILL_END);
        trace_seq_putc(s, '\n');
}

void
trace_print_graph_duration(unsigned long long duration, struct trace_seq *s)
{
        unsigned long nsecs_rem = do_div(duration, 1000);
        /* log10(ULONG_MAX) + '\0' */
        char usecs_str[21];
        char nsecs_str[5];
        int len;
        int i;

        sprintf(usecs_str, "%lu", (unsigned long) duration);

        /* Print msecs */
        trace_seq_printf(s, "%s", usecs_str);

        len = strlen(usecs_str);

        /* Print nsecs (we don't want to exceed 7 numbers) */
        if (len < 7) {
                size_t slen = min_t(size_t, sizeof(nsecs_str), 8UL - len);

                snprintf(nsecs_str, slen, "%03lu", nsecs_rem);
                trace_seq_printf(s, ".%s", nsecs_str);
                len += strlen(nsecs_str);
        }

        trace_seq_puts(s, " us ");

        /* Print remaining spaces to fit the row's width */
        for (i = len; i < 7; i++)
                trace_seq_putc(s, ' ');
}

static void
print_graph_duration(unsigned long long duration, struct trace_seq *s,
                     u32 flags)
{
        if (!(flags & TRACE_GRAPH_PRINT_DURATION) ||
            !(trace_flags & TRACE_ITER_CONTEXT_INFO))
                return;

        /* No real adata, just filling the column with spaces */
        switch (flags & TRACE_GRAPH_PRINT_FILL_MASK) {
        case FLAGS_FILL_FULL:
                trace_seq_puts(s, "              |  ");
                return;
        case FLAGS_FILL_START:
                trace_seq_puts(s, "  ");
                return;
        case FLAGS_FILL_END:
                trace_seq_puts(s, " |");
                return;
        }

        /* Signal a overhead of time execution to the output */
        if (flags & TRACE_GRAPH_PRINT_OVERHEAD)
                trace_seq_printf(s, "%c ", trace_find_mark(duration));
        else
                trace_seq_puts(s, "  ");

        trace_print_graph_duration(duration, s);
        trace_seq_puts(s, "|  ");
}

/* Case of a leaf function on its call entry */
static enum print_line_t
print_graph_entry_leaf(struct trace_iterator *iter,
                struct ftrace_graph_ent_entry *entry,
                struct ftrace_graph_ret_entry *ret_entry,
                struct trace_seq *s, u32 flags)
{
        struct fgraph_data *data = iter->private;
        struct ftrace_graph_ret *graph_ret;
        struct ftrace_graph_ent *call;
        unsigned long long duration;
        int i;

        graph_ret = &ret_entry->ret;
        call = &entry->graph_ent;
        duration = graph_ret->rettime - graph_ret->calltime;

        if (data) {
                struct fgraph_cpu_data *cpu_data;
                int cpu = iter->cpu;

                cpu_data = per_cpu_ptr(data->cpu_data, cpu);

                /*
                 * Comments display at + 1 to depth. Since
                 * this is a leaf function, keep the comments
                 * equal to this depth.
                 */
                cpu_data->depth = call->depth - 1;

                /* No need to keep this function around for this depth */
                if (call->depth < FTRACE_RETFUNC_DEPTH)
                        cpu_data->enter_funcs[call->depth] = 0;
        }

        /* Overhead and duration */
        print_graph_duration(duration, s, flags);

        /* Function */
        for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
                trace_seq_putc(s, ' ');

        trace_seq_printf(s, "%ps();\n", (void *)call->func);

        return trace_handle_return(s);
}

static enum print_line_t
print_graph_entry_nested(struct trace_iterator *iter,
                         struct ftrace_graph_ent_entry *entry,
                         struct trace_seq *s, int cpu, u32 flags)
{
        struct ftrace_graph_ent *call = &entry->graph_ent;
        struct fgraph_data *data = iter->private;
        int i;

        if (data) {
                struct fgraph_cpu_data *cpu_data;
                int cpu = iter->cpu;

                cpu_data = per_cpu_ptr(data->cpu_data, cpu);
                cpu_data->depth = call->depth;

                /* Save this function pointer to see if the exit matches */
                if (call->depth < FTRACE_RETFUNC_DEPTH)
                        cpu_data->enter_funcs[call->depth] = call->func;
        }

        /* No time */
        print_graph_duration(0, s, flags | FLAGS_FILL_FULL);

        /* Function */
        for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
                trace_seq_putc(s, ' ');

        trace_seq_printf(s, "%ps() {\n", (void *)call->func);

        if (trace_seq_has_overflowed(s))
                return TRACE_TYPE_PARTIAL_LINE;

        /*
         * we already consumed the current entry to check the next one
         * and see if this is a leaf.
         */
        return TRACE_TYPE_NO_CONSUME;
}

static void
print_graph_prologue(struct trace_iterator *iter, struct trace_seq *s,
                     int type, unsigned long addr, u32 flags)
{
        struct fgraph_data *data = iter->private;
        struct trace_entry *ent = iter->ent;
        int cpu = iter->cpu;

        /* Pid */
        verif_pid(s, ent->pid, cpu, data);

        if (type)
                /* Interrupt */
                print_graph_irq(iter, addr, type, cpu, ent->pid, flags);

        if (!(trace_flags & TRACE_ITER_CONTEXT_INFO))
                return;

        /* Absolute time */
        if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
                print_graph_abs_time(iter->ts, s);

        /* Cpu */
        if (flags & TRACE_GRAPH_PRINT_CPU)
                print_graph_cpu(s, cpu);

        /* Proc */
        if (flags & TRACE_GRAPH_PRINT_PROC) {
                print_graph_proc(s, ent->pid);
                trace_seq_puts(s, " | ");
        }

        /* Latency format */
        if (trace_flags & TRACE_ITER_LATENCY_FMT)
                print_graph_lat_fmt(s, ent);

        return;
}

/*
 * Entry check for irq code
 *
 * returns 1 if
 *  - we are inside irq code
 *  - we just entered irq code
 *
 * retunns 0 if
 *  - funcgraph-interrupts option is set
 *  - we are not inside irq code
 */
static int
check_irq_entry(struct trace_iterator *iter, u32 flags,
                unsigned long addr, int depth)
{
        int cpu = iter->cpu;
        int *depth_irq;
        struct fgraph_data *data = iter->private;

        /*
         * If we are either displaying irqs, or we got called as
         * a graph event and private data does not exist,
         * then we bypass the irq check.
         */
        if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
            (!data))
                return 0;

        depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);

        /*
         * We are inside the irq code
         */
        if (*depth_irq >= 0)
                return 1;

        if ((addr < (unsigned long)__irqentry_text_start) ||
            (addr >= (unsigned long)__irqentry_text_end))
                return 0;

        /*
         * We are entering irq code.
         */
        *depth_irq = depth;
        return 1;
}

/*
 * Return check for irq code
 *
 * returns 1 if
 *  - we are inside irq code
 *  - we just left irq code
 *
 * returns 0 if
 *  - funcgraph-interrupts option is set
 *  - we are not inside irq code
 */
static int
check_irq_return(struct trace_iterator *iter, u32 flags, int depth)
{
        int cpu = iter->cpu;
        int *depth_irq;
        struct fgraph_data *data = iter->private;

        /*
         * If we are either displaying irqs, or we got called as
         * a graph event and private data does not exist,
         * then we bypass the irq check.
         */
        if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
            (!data))
                return 0;

        depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);

        /*
         * We are not inside the irq code.
         */
        if (*depth_irq == -1)
                return 0;

        /*
         * We are inside the irq code, and this is returning entry.
         * Let's not trace it and clear the entry depth, since
         * we are out of irq code.
         *
         * This condition ensures that we 'leave the irq code' once
         * we are out of the entry depth. Thus protecting us from
         * the RETURN entry loss.
         */
        if (*depth_irq >= depth) {
                *depth_irq = -1;
                return 1;
        }

        /*
         * We are inside the irq code, and this is not the entry.
         */
        return 1;
}

static enum print_line_t
print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
                        struct trace_iterator *iter, u32 flags)
{
        struct fgraph_data *data = iter->private;
        struct ftrace_graph_ent *call = &field->graph_ent;
        struct ftrace_graph_ret_entry *leaf_ret;
        static enum print_line_t ret;
        int cpu = iter->cpu;

        if (check_irq_entry(iter, flags, call->func, call->depth))
                return TRACE_TYPE_HANDLED;

        print_graph_prologue(iter, s, TRACE_GRAPH_ENT, call->func, flags);

        leaf_ret = get_return_for_leaf(iter, field);
        if (leaf_ret)
                ret = print_graph_entry_leaf(iter, field, leaf_ret, s, flags);
        else
                ret = print_graph_entry_nested(iter, field, s, cpu, flags);

        if (data) {
                /*
                 * If we failed to write our output, then we need to make
                 * note of it. Because we already consumed our entry.
                 */
                if (s->full) {
                        data->failed = 1;
                        data->cpu = cpu;
                } else
                        data->failed = 0;
        }

        return ret;
}

static enum print_line_t
print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
                   struct trace_entry *ent, struct trace_iterator *iter,
                   u32 flags)
{
        unsigned long long duration = trace->rettime - trace->calltime;
        struct fgraph_data *data = iter->private;
        pid_t pid = ent->pid;
        int cpu = iter->cpu;
        int func_match = 1;
        int i;

        if (check_irq_return(iter, flags, trace->depth))
                return TRACE_TYPE_HANDLED;

        if (data) {
                struct fgraph_cpu_data *cpu_data;
                int cpu = iter->cpu;

                cpu_data = per_cpu_ptr(data->cpu_data, cpu);

                /*
                 * Comments display at + 1 to depth. This is the
                 * return from a function, we now want the comments
                 * to display at the same level of the bracket.
                 */
                cpu_data->depth = trace->depth - 1;

                if (trace->depth < FTRACE_RETFUNC_DEPTH) {
                        if (cpu_data->enter_funcs[trace->depth] != trace->func)
                                func_match = 0;
                        cpu_data->enter_funcs[trace->depth] = 0;
                }
        }

        print_graph_prologue(iter, s, 0, 0, flags);

        /* Overhead and duration */
        print_graph_duration(duration, s, flags);

        /* Closing brace */
        for (i = 0; i < trace->depth * TRACE_GRAPH_INDENT; i++)
                trace_seq_putc(s, ' ');

        /*
         * If the return function does not have a matching entry,
         * then the entry was lost. Instead of just printing
         * the '}' and letting the user guess what function this
         * belongs to, write out the function name. Always do
         * that if the funcgraph-tail option is enabled.
         */
        if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
                trace_seq_puts(s, "}\n");
        else
                trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);

        /* Overrun */
        if (flags & TRACE_GRAPH_PRINT_OVERRUN)
                trace_seq_printf(s, " (Overruns: %lu)\n",
                                 trace->overrun);

        print_graph_irq(iter, trace->func, TRACE_GRAPH_RET,
                        cpu, pid, flags);

        return trace_handle_return(s);
}

static enum print_line_t
print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
                    struct trace_iterator *iter, u32 flags)
{
        unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
        struct fgraph_data *data = iter->private;
        struct trace_event *event;
        int depth = 0;
        int ret;
        int i;

        if (data)
                depth = per_cpu_ptr(data->cpu_data, iter->cpu)->depth;

        print_graph_prologue(iter, s, 0, 0, flags);

        /* No time */
        print_graph_duration(0, s, flags | FLAGS_FILL_FULL);

        /* Indentation */
        if (depth > 0)
                for (i = 0; i < (depth + 1) * TRACE_GRAPH_INDENT; i++)
                        trace_seq_putc(s, ' ');

        /* The comment */
        trace_seq_puts(s, "/* ");

        switch (iter->ent->type) {
        case TRACE_BPRINT:
                ret = trace_print_bprintk_msg_only(iter);
                if (ret != TRACE_TYPE_HANDLED)
                        return ret;
                break;
        case TRACE_PRINT:
                ret = trace_print_printk_msg_only(iter);
                if (ret != TRACE_TYPE_HANDLED)
                        return ret;
                break;
        default:
                event = ftrace_find_event(ent->type);
                if (!event)
                        return TRACE_TYPE_UNHANDLED;

                ret = event->funcs->trace(iter, sym_flags, event);
                if (ret != TRACE_TYPE_HANDLED)
                        return ret;
        }

        if (trace_seq_has_overflowed(s))
                goto out;

        /* Strip ending newline */
        if (s->buffer[s->seq.len - 1] == '\n') {
                s->buffer[s->seq.len - 1] = '\0';
                s->seq.len--;
        }

        trace_seq_puts(s, " */\n");
 out:
        return trace_handle_return(s);
}


enum print_line_t
print_graph_function_flags(struct trace_iterator *iter, u32 flags)
{
        struct ftrace_graph_ent_entry *field;
        struct fgraph_data *data = iter->private;
        struct trace_entry *entry = iter->ent;
        struct trace_seq *s = &iter->seq;
        int cpu = iter->cpu;
        int ret;

        if (data && per_cpu_ptr(data->cpu_data, cpu)->ignore) {
                per_cpu_ptr(data->cpu_data, cpu)->ignore = 0;
                return TRACE_TYPE_HANDLED;
        }

        /*
         * If the last output failed, there's a possibility we need
         * to print out the missing entry which would never go out.
         */
        if (data && data->failed) {
                field = &data->ent;
                iter->cpu = data->cpu;
                ret = print_graph_entry(field, s, iter, flags);
                if (ret == TRACE_TYPE_HANDLED && iter->cpu != cpu) {
                        per_cpu_ptr(data->cpu_data, iter->cpu)->ignore = 1;
                        ret = TRACE_TYPE_NO_CONSUME;
                }
                iter->cpu = cpu;
                return ret;
        }

        switch (entry->type) {
        case TRACE_GRAPH_ENT: {
                /*
                 * print_graph_entry() may consume the current event,
                 * thus @field may become invalid, so we need to save it.
                 * sizeof(struct ftrace_graph_ent_entry) is very small,
                 * it can be safely saved at the stack.
                 */
                struct ftrace_graph_ent_entry saved;
                trace_assign_type(field, entry);
                saved = *field;
                return print_graph_entry(&saved, s, iter, flags);
        }
        case TRACE_GRAPH_RET: {
                struct ftrace_graph_ret_entry *field;
                trace_assign_type(field, entry);
                return print_graph_return(&field->ret, s, entry, iter, flags);
        }
        case TRACE_STACK:
        case TRACE_FN:
                /* dont trace stack and functions as comments */
                return TRACE_TYPE_UNHANDLED;

        default:
                return print_graph_comment(s, entry, iter, flags);
        }

        return TRACE_TYPE_HANDLED;
}

static enum print_line_t
print_graph_function(struct trace_iterator *iter)
{
        return print_graph_function_flags(iter, tracer_flags.val);
}

static enum print_line_t
print_graph_function_event(struct trace_iterator *iter, int flags,
                           struct trace_event *event)
{
        return print_graph_function(iter);
}

static void print_lat_header(struct seq_file *s, u32 flags)
{
        static const char spaces[] = "                " /* 16 spaces */
                "    "                                  /* 4 spaces */
                "                 ";                    /* 17 spaces */
        int size = 0;

        if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
                size += 16;
        if (flags & TRACE_GRAPH_PRINT_CPU)
                size += 4;
        if (flags & TRACE_GRAPH_PRINT_PROC)
                size += 17;

        seq_printf(s, "#%.*s  _-----=> irqs-off        \n", size, spaces);
        seq_printf(s, "#%.*s / _----=> need-resched    \n", size, spaces);
        seq_printf(s, "#%.*s| / _---=> hardirq/softirq \n", size, spaces);
        seq_printf(s, "#%.*s|| / _--=> preempt-depth   \n", size, spaces);
        seq_printf(s, "#%.*s||| /                      \n", size, spaces);
}

static void __print_graph_headers_flags(struct seq_file *s, u32 flags)
{
        int lat = trace_flags & TRACE_ITER_LATENCY_FMT;

        if (lat)
                print_lat_header(s, flags);

        /* 1st line */
        seq_putc(s, '#');
        if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
                seq_puts(s, "     TIME       ");
        if (flags & TRACE_GRAPH_PRINT_CPU)
                seq_puts(s, " CPU");
        if (flags & TRACE_GRAPH_PRINT_PROC)
                seq_puts(s, "  TASK/PID       ");
        if (lat)
                seq_puts(s, "||||");
        if (flags & TRACE_GRAPH_PRINT_DURATION)
                seq_puts(s, "  DURATION   ");
        seq_puts(s, "               FUNCTION CALLS\n");

        /* 2nd line */
        seq_putc(s, '#');
        if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
                seq_puts(s, "      |         ");
        if (flags & TRACE_GRAPH_PRINT_CPU)
                seq_puts(s, " |  ");
        if (flags & TRACE_GRAPH_PRINT_PROC)
                seq_puts(s, "   |    |        ");
        if (lat)
                seq_puts(s, "||||");
        if (flags & TRACE_GRAPH_PRINT_DURATION)
                seq_puts(s, "   |   |      ");
        seq_puts(s, "               |   |   |   |\n");
}

static void print_graph_headers(struct seq_file *s)
{
        print_graph_headers_flags(s, tracer_flags.val);
}

void print_graph_headers_flags(struct seq_file *s, u32 flags)
{
        struct trace_iterator *iter = s->private;

        if (!(trace_flags & TRACE_ITER_CONTEXT_INFO))
                return;

        if (trace_flags & TRACE_ITER_LATENCY_FMT) {
                /* print nothing if the buffers are empty */
                if (trace_empty(iter))
                        return;

                print_trace_header(s, iter);
        }

        __print_graph_headers_flags(s, flags);
}

void graph_trace_open(struct trace_iterator *iter)
{
        /* pid and depth on the last trace processed */
        struct fgraph_data *data;
        int cpu;

        iter->private = NULL;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                goto out_err;

        data->cpu_data = alloc_percpu(struct fgraph_cpu_data);
        if (!data->cpu_data)
                goto out_err_free;

        for_each_possible_cpu(cpu) {
                pid_t *pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
                int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
                int *ignore = &(per_cpu_ptr(data->cpu_data, cpu)->ignore);
                int *depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);

                *pid = -1;
                *depth = 0;
                *ignore = 0;
                *depth_irq = -1;
        }

        iter->private = data;

        return;

 out_err_free:
        kfree(data);
 out_err:
        pr_warning("function graph tracer: not enough memory\n");
}

void graph_trace_close(struct trace_iterator *iter)
{
        struct fgraph_data *data = iter->private;

        if (data) {
                free_percpu(data->cpu_data);
                kfree(data);
        }
}

static int
func_graph_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
{
        if (bit == TRACE_GRAPH_PRINT_IRQS)
                ftrace_graph_skip_irqs = !set;

        return 0;
}

static struct trace_event_functions graph_functions = {
        .trace          = print_graph_function_event,
};

static struct trace_event graph_trace_entry_event = {
        .type           = TRACE_GRAPH_ENT,
        .funcs          = &graph_functions,
};

static struct trace_event graph_trace_ret_event = {
        .type           = TRACE_GRAPH_RET,
        .funcs          = &graph_functions
};

static struct tracer graph_trace __tracer_data = {
        .name           = "function_graph",
        .update_thresh  = graph_trace_update_thresh,
        .open           = graph_trace_open,
        .pipe_open      = graph_trace_open,
        .close          = graph_trace_close,
        .pipe_close     = graph_trace_close,
        .init           = graph_trace_init,
        .reset          = graph_trace_reset,
        .print_line     = print_graph_function,
        .print_header   = print_graph_headers,
        .flags          = &tracer_flags,
        .set_flag       = func_graph_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest       = trace_selftest_startup_function_graph,
#endif
};


static ssize_t
graph_depth_write(struct file *filp, const char __user *ubuf, size_t cnt,
                  loff_t *ppos)
{
        unsigned long val;
        int ret;

        ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
        if (ret)
                return ret;

        max_depth = val;

        *ppos += cnt;

        return cnt;
}

static ssize_t
graph_depth_read(struct file *filp, char __user *ubuf, size_t cnt,
                 loff_t *ppos)
{
        char buf[15]; /* More than enough to hold UINT_MAX + "\n"*/
        int n;

        n = sprintf(buf, "%d\n", max_depth);

        return simple_read_from_buffer(ubuf, cnt, ppos, buf, n);
}

static const struct file_operations graph_depth_fops = {
        .open           = tracing_open_generic,
        .write          = graph_depth_write,
        .read           = graph_depth_read,
        .llseek         = generic_file_llseek,
};

static __init int init_graph_debugfs(void)
{
        struct dentry *d_tracer;

        d_tracer = tracing_init_dentry();
        if (!d_tracer)
                return 0;

        trace_create_file("max_graph_depth", 0644, d_tracer,
                          NULL, &graph_depth_fops);

        return 0;
}
fs_initcall(init_graph_debugfs);

static __init int init_graph_trace(void)
{
        max_bytes_for_cpu = snprintf(NULL, 0, "%d", nr_cpu_ids - 1);

        if (!register_ftrace_event(&graph_trace_entry_event)) {
                pr_warning("Warning: could not register graph trace events\n");
                return 1;
        }

        if (!register_ftrace_event(&graph_trace_ret_event)) {
                pr_warning("Warning: could not register graph trace events\n");
                return 1;
        }

        return register_tracer(&graph_trace);
}

core_initcall(init_graph_trace);