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[mirror_ubuntu-focal-kernel.git] / kernel / trace / trace_branch.c

// SPDX-License-Identifier: GPL-2.0
/*
 * unlikely profiler
 *
 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
 */
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/irqflags.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/hash.h>
#include <linux/fs.h>
#include <asm/local.h>

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

#ifdef CONFIG_BRANCH_TRACER

static struct tracer branch_trace;
static int branch_tracing_enabled __read_mostly;
static DEFINE_MUTEX(branch_tracing_mutex);

static struct trace_array *branch_tracer;

static void
probe_likely_condition(struct ftrace_likely_data *f, int val, int expect)
{
        struct trace_event_call *call = &event_branch;
        struct trace_array *tr = branch_tracer;
        struct trace_array_cpu *data;
        struct ring_buffer_event *event;
        struct trace_branch *entry;
        struct ring_buffer *buffer;
        unsigned long flags;
        int pc;
        const char *p;

        if (current->trace_recursion & TRACE_BRANCH_BIT)
                return;

        /*
         * I would love to save just the ftrace_likely_data pointer, but
         * this code can also be used by modules. Ugly things can happen
         * if the module is unloaded, and then we go and read the
         * pointer.  This is slower, but much safer.
         */

        if (unlikely(!tr))
                return;

        raw_local_irq_save(flags);
        current->trace_recursion |= TRACE_BRANCH_BIT;
        data = this_cpu_ptr(tr->trace_buffer.data);
        if (atomic_read(&data->disabled))
                goto out;

        pc = preempt_count();
        buffer = tr->trace_buffer.buffer;
        event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
                                          sizeof(*entry), flags, pc);
        if (!event)
                goto out;

        entry   = ring_buffer_event_data(event);

        /* Strip off the path, only save the file */
        p = f->data.file + strlen(f->data.file);
        while (p >= f->data.file && *p != '/')
                p--;
        p++;

        strncpy(entry->func, f->data.func, TRACE_FUNC_SIZE);
        strncpy(entry->file, p, TRACE_FILE_SIZE);
        entry->func[TRACE_FUNC_SIZE] = 0;
        entry->file[TRACE_FILE_SIZE] = 0;
        entry->constant = f->constant;
        entry->line = f->data.line;
        entry->correct = val == expect;

        if (!call_filter_check_discard(call, entry, buffer, event))
                trace_buffer_unlock_commit_nostack(buffer, event);

 out:
        current->trace_recursion &= ~TRACE_BRANCH_BIT;
        raw_local_irq_restore(flags);
}

static inline
void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
{
        if (!branch_tracing_enabled)
                return;

        probe_likely_condition(f, val, expect);
}

int enable_branch_tracing(struct trace_array *tr)
{
        mutex_lock(&branch_tracing_mutex);
        branch_tracer = tr;
        /*
         * Must be seen before enabling. The reader is a condition
         * where we do not need a matching rmb()
         */
        smp_wmb();
        branch_tracing_enabled++;
        mutex_unlock(&branch_tracing_mutex);

        return 0;
}

void disable_branch_tracing(void)
{
        mutex_lock(&branch_tracing_mutex);

        if (!branch_tracing_enabled)
                goto out_unlock;

        branch_tracing_enabled--;

 out_unlock:
        mutex_unlock(&branch_tracing_mutex);
}

static int branch_trace_init(struct trace_array *tr)
{
        return enable_branch_tracing(tr);
}

static void branch_trace_reset(struct trace_array *tr)
{
        disable_branch_tracing();
}

static enum print_line_t trace_branch_print(struct trace_iterator *iter,
                                            int flags, struct trace_event *event)
{
        struct trace_branch *field;

        trace_assign_type(field, iter->ent);

        trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
                         field->correct ? "  ok  " : " MISS ",
                         field->func,
                         field->file,
                         field->line);

        return trace_handle_return(&iter->seq);
}

static void branch_print_header(struct seq_file *s)
{
        seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
                    "  FUNC:FILE:LINE\n"
                    "#              | |       |          |         |   "
                    "    |\n");
}

static struct trace_event_functions trace_branch_funcs = {
        .trace          = trace_branch_print,
};

static struct trace_event trace_branch_event = {
        .type           = TRACE_BRANCH,
        .funcs          = &trace_branch_funcs,
};

static struct tracer branch_trace __read_mostly =
{
        .name           = "branch",
        .init           = branch_trace_init,
        .reset          = branch_trace_reset,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest       = trace_selftest_startup_branch,
#endif /* CONFIG_FTRACE_SELFTEST */
        .print_header   = branch_print_header,
};

__init static int init_branch_tracer(void)
{
        int ret;

        ret = register_trace_event(&trace_branch_event);
        if (!ret) {
                printk(KERN_WARNING "Warning: could not register "
                                    "branch events\n");
                return 1;
        }
        return register_tracer(&branch_trace);
}
core_initcall(init_branch_tracer);

#else
static inline
void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
{
}
#endif /* CONFIG_BRANCH_TRACER */

void ftrace_likely_update(struct ftrace_likely_data *f, int val,
                          int expect, int is_constant)
{
        /* A constant is always correct */
        if (is_constant) {
                f->constant++;
                val = expect;
        }
        /*
         * I would love to have a trace point here instead, but the
         * trace point code is so inundated with unlikely and likely
         * conditions that the recursive nightmare that exists is too
         * much to try to get working. At least for now.
         */
        trace_likely_condition(f, val, expect);

        /* FIXME: Make this atomic! */
        if (val == expect)
                f->data.correct++;
        else
                f->data.incorrect++;
}
EXPORT_SYMBOL(ftrace_likely_update);

extern unsigned long __start_annotated_branch_profile[];
extern unsigned long __stop_annotated_branch_profile[];

static int annotated_branch_stat_headers(struct seq_file *m)
{
        seq_puts(m, " correct incorrect  % "
                    "       Function                "
                    "  File              Line\n"
                    " ------- ---------  - "
                    "       --------                "
                    "  ----              ----\n");
        return 0;
}

static inline long get_incorrect_percent(struct ftrace_branch_data *p)
{
        long percent;

        if (p->correct) {
                percent = p->incorrect * 100;
                percent /= p->correct + p->incorrect;
        } else
                percent = p->incorrect ? 100 : -1;

        return percent;
}

static const char *branch_stat_process_file(struct ftrace_branch_data *p)
{
        const char *f;

        /* Only print the file, not the path */
        f = p->file + strlen(p->file);
        while (f >= p->file && *f != '/')
                f--;
        return ++f;
}

static void branch_stat_show(struct seq_file *m,
                             struct ftrace_branch_data *p, const char *f)
{
        long percent;

        /*
         * The miss is overlayed on correct, and hit on incorrect.
         */
        percent = get_incorrect_percent(p);

        if (percent < 0)
                seq_puts(m, "  X ");
        else
                seq_printf(m, "%3ld ", percent);

        seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
}

static int branch_stat_show_normal(struct seq_file *m,
                                   struct ftrace_branch_data *p, const char *f)
{
        seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
        branch_stat_show(m, p, f);
        return 0;
}

static int annotate_branch_stat_show(struct seq_file *m, void *v)
{
        struct ftrace_likely_data *p = v;
        const char *f;
        int l;

        f = branch_stat_process_file(&p->data);

        if (!p->constant)
                return branch_stat_show_normal(m, &p->data, f);

        l = snprintf(NULL, 0, "/%lu", p->constant);
        l = l > 8 ? 0 : 8 - l;

        seq_printf(m, "%8lu/%lu %*lu ",
                   p->data.correct, p->constant, l, p->data.incorrect);
        branch_stat_show(m, &p->data, f);
        return 0;
}

static void *annotated_branch_stat_start(struct tracer_stat *trace)
{
        return __start_annotated_branch_profile;
}

static void *
annotated_branch_stat_next(void *v, int idx)
{
        struct ftrace_likely_data *p = v;

        ++p;

        if ((void *)p >= (void *)__stop_annotated_branch_profile)
                return NULL;

        return p;
}

static int annotated_branch_stat_cmp(void *p1, void *p2)
{
        struct ftrace_branch_data *a = p1;
        struct ftrace_branch_data *b = p2;

        long percent_a, percent_b;

        percent_a = get_incorrect_percent(a);
        percent_b = get_incorrect_percent(b);

        if (percent_a < percent_b)
                return -1;
        if (percent_a > percent_b)
                return 1;

        if (a->incorrect < b->incorrect)
                return -1;
        if (a->incorrect > b->incorrect)
                return 1;

        /*
         * Since the above shows worse (incorrect) cases
         * first, we continue that by showing best (correct)
         * cases last.
         */
        if (a->correct > b->correct)
                return -1;
        if (a->correct < b->correct)
                return 1;

        return 0;
}

static struct tracer_stat annotated_branch_stats = {
        .name = "branch_annotated",
        .stat_start = annotated_branch_stat_start,
        .stat_next = annotated_branch_stat_next,
        .stat_cmp = annotated_branch_stat_cmp,
        .stat_headers = annotated_branch_stat_headers,
        .stat_show = annotate_branch_stat_show
};

__init static int init_annotated_branch_stats(void)
{
        int ret;

        ret = register_stat_tracer(&annotated_branch_stats);
        if (!ret) {
                printk(KERN_WARNING "Warning: could not register "
                                    "annotated branches stats\n");
                return 1;
        }
        return 0;
}
fs_initcall(init_annotated_branch_stats);

#ifdef CONFIG_PROFILE_ALL_BRANCHES

extern unsigned long __start_branch_profile[];
extern unsigned long __stop_branch_profile[];

static int all_branch_stat_headers(struct seq_file *m)
{
        seq_puts(m, "   miss      hit    % "
                    "       Function                "
                    "  File              Line\n"
                    " ------- ---------  - "
                    "       --------                "
                    "  ----              ----\n");
        return 0;
}

static void *all_branch_stat_start(struct tracer_stat *trace)
{
        return __start_branch_profile;
}

static void *
all_branch_stat_next(void *v, int idx)
{
        struct ftrace_branch_data *p = v;

        ++p;

        if ((void *)p >= (void *)__stop_branch_profile)
                return NULL;

        return p;
}

static int all_branch_stat_show(struct seq_file *m, void *v)
{
        struct ftrace_branch_data *p = v;
        const char *f;

        f = branch_stat_process_file(p);
        return branch_stat_show_normal(m, p, f);
}

static struct tracer_stat all_branch_stats = {
        .name = "branch_all",
        .stat_start = all_branch_stat_start,
        .stat_next = all_branch_stat_next,
        .stat_headers = all_branch_stat_headers,
        .stat_show = all_branch_stat_show
};

__init static int all_annotated_branch_stats(void)
{
        int ret;

        ret = register_stat_tracer(&all_branch_stats);
        if (!ret) {
                printk(KERN_WARNING "Warning: could not register "
                                    "all branches stats\n");
                return 1;
        }
        return 0;
}
fs_initcall(all_annotated_branch_stats);
#endif /* CONFIG_PROFILE_ALL_BRANCHES */