// SPDX-License-Identifier: GPL-2.0
/*
 * trace_events_synth - synthetic trace events
 *
 * Copyright (C) 2015, 2020 Tom Zanussi <tom.zanussi@linux.intel.com>
 */

#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/security.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/rculist.h>
#include <linux/tracefs.h>

/* for gfp flag names */
#include <linux/trace_events.h>
#include <trace/events/mmflags.h>

#include "trace_synth.h"

#undef ERRORS
#define ERRORS  \
        C(BAD_NAME,             "Illegal name"),                \
        C(CMD_INCOMPLETE,       "Incomplete command"),          \
        C(EVENT_EXISTS,         "Event already exists"),        \
        C(TOO_MANY_FIELDS,      "Too many fields"),             \
        C(INCOMPLETE_TYPE,      "Incomplete type"),             \
        C(INVALID_TYPE,         "Invalid type"),                \
        C(INVALID_FIELD,        "Invalid field"),               \
        C(CMD_TOO_LONG,         "Command too long"),

#undef C
#define C(a, b)         SYNTH_ERR_##a

enum { ERRORS };

#undef C
#define C(a, b)         b

static const char *err_text[] = { ERRORS };

static char last_cmd[MAX_FILTER_STR_VAL];

static int errpos(const char *str)
{
        return err_pos(last_cmd, str);
}

static void last_cmd_set(char *str)
{
        if (!str)
                return;

        strncpy(last_cmd, str, MAX_FILTER_STR_VAL - 1);
}

static void synth_err(u8 err_type, u8 err_pos)
{
        tracing_log_err(NULL, "synthetic_events", last_cmd, err_text,
                        err_type, err_pos);
}

static int create_synth_event(int argc, const char **argv);
static int synth_event_show(struct seq_file *m, struct dyn_event *ev);
static int synth_event_release(struct dyn_event *ev);
static bool synth_event_is_busy(struct dyn_event *ev);
static bool synth_event_match(const char *system, const char *event,
                        int argc, const char **argv, struct dyn_event *ev);

static struct dyn_event_operations synth_event_ops = {
        .create = create_synth_event,
        .show = synth_event_show,
        .is_busy = synth_event_is_busy,
        .free = synth_event_release,
        .match = synth_event_match,
};

static bool is_synth_event(struct dyn_event *ev)
{
        return ev->ops == &synth_event_ops;
}

static struct synth_event *to_synth_event(struct dyn_event *ev)
{
        return container_of(ev, struct synth_event, devent);
}

static bool synth_event_is_busy(struct dyn_event *ev)
{
        struct synth_event *event = to_synth_event(ev);

        return event->ref != 0;
}

static bool synth_event_match(const char *system, const char *event,
                        int argc, const char **argv, struct dyn_event *ev)
{
        struct synth_event *sev = to_synth_event(ev);

        return strcmp(sev->name, event) == 0 &&
                (!system || strcmp(system, SYNTH_SYSTEM) == 0);
}

struct synth_trace_event {
        struct trace_entry      ent;
        u64                     fields[];
};

static int synth_event_define_fields(struct trace_event_call *call)
{
        struct synth_trace_event trace;
        int offset = offsetof(typeof(trace), fields);
        struct synth_event *event = call->data;
        unsigned int i, size, n_u64;
        char *name, *type;
        bool is_signed;
        int ret = 0;

        for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
                size = event->fields[i]->size;
                is_signed = event->fields[i]->is_signed;
                type = event->fields[i]->type;
                name = event->fields[i]->name;
                ret = trace_define_field(call, type, name, offset, size,
                                         is_signed, FILTER_OTHER);
                if (ret)
                        break;

                event->fields[i]->offset = n_u64;

                if (event->fields[i]->is_string && !event->fields[i]->is_dynamic) {
                        offset += STR_VAR_LEN_MAX;
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
                        offset += sizeof(u64);
                        n_u64++;
                }
        }

        event->n_u64 = n_u64;

        return ret;
}

static bool synth_field_signed(char *type)
{
        if (str_has_prefix(type, "u"))
                return false;
        if (strcmp(type, "gfp_t") == 0)
                return false;

        return true;
}

static int synth_field_is_string(char *type)
{
        if (strstr(type, "char[") != NULL)
                return true;

        return false;
}

static int synth_field_string_size(char *type)
{
        char buf[4], *end, *start;
        unsigned int len;
        int size, err;

        start = strstr(type, "char[");
        if (start == NULL)
                return -EINVAL;
        start += sizeof("char[") - 1;

        end = strchr(type, ']');
        if (!end || end < start || type + strlen(type) > end + 1)
                return -EINVAL;

        len = end - start;
        if (len > 3)
                return -EINVAL;

        if (len == 0)
                return 0; /* variable-length string */

        strncpy(buf, start, len);
        buf[len] = '\0';

        err = kstrtouint(buf, 0, &size);
        if (err)
                return err;

        if (size > STR_VAR_LEN_MAX)
                return -EINVAL;

        return size;
}

static int synth_field_size(char *type)
{
        int size = 0;

        if (strcmp(type, "s64") == 0)
                size = sizeof(s64);
        else if (strcmp(type, "u64") == 0)
                size = sizeof(u64);
        else if (strcmp(type, "s32") == 0)
                size = sizeof(s32);
        else if (strcmp(type, "u32") == 0)
                size = sizeof(u32);
        else if (strcmp(type, "s16") == 0)
                size = sizeof(s16);
        else if (strcmp(type, "u16") == 0)
                size = sizeof(u16);
        else if (strcmp(type, "s8") == 0)
                size = sizeof(s8);
        else if (strcmp(type, "u8") == 0)
                size = sizeof(u8);
        else if (strcmp(type, "char") == 0)
                size = sizeof(char);
        else if (strcmp(type, "unsigned char") == 0)
                size = sizeof(unsigned char);
        else if (strcmp(type, "int") == 0)
                size = sizeof(int);
        else if (strcmp(type, "unsigned int") == 0)
                size = sizeof(unsigned int);
        else if (strcmp(type, "long") == 0)
                size = sizeof(long);
        else if (strcmp(type, "unsigned long") == 0)
                size = sizeof(unsigned long);
        else if (strcmp(type, "bool") == 0)
                size = sizeof(bool);
        else if (strcmp(type, "pid_t") == 0)
                size = sizeof(pid_t);
        else if (strcmp(type, "gfp_t") == 0)
                size = sizeof(gfp_t);
        else if (synth_field_is_string(type))
                size = synth_field_string_size(type);

        return size;
}

static const char *synth_field_fmt(char *type)
{
        const char *fmt = "%llu";

        if (strcmp(type, "s64") == 0)
                fmt = "%lld";
        else if (strcmp(type, "u64") == 0)
                fmt = "%llu";
        else if (strcmp(type, "s32") == 0)
                fmt = "%d";
        else if (strcmp(type, "u32") == 0)
                fmt = "%u";
        else if (strcmp(type, "s16") == 0)
                fmt = "%d";
        else if (strcmp(type, "u16") == 0)
                fmt = "%u";
        else if (strcmp(type, "s8") == 0)
                fmt = "%d";
        else if (strcmp(type, "u8") == 0)
                fmt = "%u";
        else if (strcmp(type, "char") == 0)
                fmt = "%d";
        else if (strcmp(type, "unsigned char") == 0)
                fmt = "%u";
        else if (strcmp(type, "int") == 0)
                fmt = "%d";
        else if (strcmp(type, "unsigned int") == 0)
                fmt = "%u";
        else if (strcmp(type, "long") == 0)
                fmt = "%ld";
        else if (strcmp(type, "unsigned long") == 0)
                fmt = "%lu";
        else if (strcmp(type, "bool") == 0)
                fmt = "%d";
        else if (strcmp(type, "pid_t") == 0)
                fmt = "%d";
        else if (strcmp(type, "gfp_t") == 0)
                fmt = "%x";
        else if (synth_field_is_string(type))
                fmt = "%.*s";

        return fmt;
}

static void print_synth_event_num_val(struct trace_seq *s,
                                      char *print_fmt, char *name,
                                      int size, u64 val, char *space)
{
        switch (size) {
        case 1:
                trace_seq_printf(s, print_fmt, name, (u8)val, space);
                break;

        case 2:
                trace_seq_printf(s, print_fmt, name, (u16)val, space);
                break;

        case 4:
                trace_seq_printf(s, print_fmt, name, (u32)val, space);
                break;

        default:
                trace_seq_printf(s, print_fmt, name, val, space);
                break;
        }
}

static enum print_line_t print_synth_event(struct trace_iterator *iter,
                                           int flags,
                                           struct trace_event *event)
{
        struct trace_array *tr = iter->tr;
        struct trace_seq *s = &iter->seq;
        struct synth_trace_event *entry;
        struct synth_event *se;
        unsigned int i, n_u64;
        char print_fmt[32];
        const char *fmt;

        entry = (struct synth_trace_event *)iter->ent;
        se = container_of(event, struct synth_event, call.event);

        trace_seq_printf(s, "%s: ", se->name);

        for (i = 0, n_u64 = 0; i < se->n_fields; i++) {
                if (trace_seq_has_overflowed(s))
                        goto end;

                fmt = synth_field_fmt(se->fields[i]->type);

                /* parameter types */
                if (tr && tr->trace_flags & TRACE_ITER_VERBOSE)
                        trace_seq_printf(s, "%s ", fmt);

                snprintf(print_fmt, sizeof(print_fmt), "%%s=%s%%s", fmt);

                /* parameter values */
                if (se->fields[i]->is_string) {
                        if (se->fields[i]->is_dynamic) {
                                u32 offset, data_offset;
                                char *str_field;

                                offset = (u32)entry->fields[n_u64];
                                data_offset = offset & 0xffff;

                                str_field = (char *)entry + data_offset;

                                trace_seq_printf(s, print_fmt, se->fields[i]->name,
                                                 STR_VAR_LEN_MAX,
                                                 str_field,
                                                 i == se->n_fields - 1 ? "" : " ");
                                n_u64++;
                        } else {
                                trace_seq_printf(s, print_fmt, se->fields[i]->name,
                                                 STR_VAR_LEN_MAX,
                                                 (char *)&entry->fields[n_u64],
                                                 i == se->n_fields - 1 ? "" : " ");
                                n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                        }
                } else {
                        struct trace_print_flags __flags[] = {
                            __def_gfpflag_names, {-1, NULL} };
                        char *space = (i == se->n_fields - 1 ? "" : " ");

                        print_synth_event_num_val(s, print_fmt,
                                                  se->fields[i]->name,
                                                  se->fields[i]->size,
                                                  entry->fields[n_u64],
                                                  space);

                        if (strcmp(se->fields[i]->type, "gfp_t") == 0) {
                                trace_seq_puts(s, " (");
                                trace_print_flags_seq(s, "|",
                                                      entry->fields[n_u64],
                                                      __flags);
                                trace_seq_putc(s, ')');
                        }
                        n_u64++;
                }
        }
end:
        trace_seq_putc(s, '\n');

        return trace_handle_return(s);
}

static struct trace_event_functions synth_event_funcs = {
        .trace          = print_synth_event
};

static unsigned int trace_string(struct synth_trace_event *entry,
                                 struct synth_event *event,
                                 char *str_val,
                                 bool is_dynamic,
                                 unsigned int data_size,
                                 unsigned int *n_u64)
{
        unsigned int len = 0;
        char *str_field;

        if (is_dynamic) {
                u32 data_offset;

                data_offset = offsetof(typeof(*entry), fields);
                data_offset += event->n_u64 * sizeof(u64);
                data_offset += data_size;

                str_field = (char *)entry + data_offset;

                len = strlen(str_val) + 1;
                strscpy(str_field, str_val, len);

                data_offset |= len << 16;
                *(u32 *)&entry->fields[*n_u64] = data_offset;

                (*n_u64)++;
        } else {
                str_field = (char *)&entry->fields[*n_u64];

                strscpy(str_field, str_val, STR_VAR_LEN_MAX);
                (*n_u64) += STR_VAR_LEN_MAX / sizeof(u64);
        }

        return len;
}

static notrace void trace_event_raw_event_synth(void *__data,
                                                u64 *var_ref_vals,
                                                unsigned int *var_ref_idx)
{
        unsigned int i, n_u64, val_idx, len, data_size = 0;
        struct trace_event_file *trace_file = __data;
        struct synth_trace_event *entry;
        struct trace_event_buffer fbuffer;
        struct trace_buffer *buffer;
        struct synth_event *event;
        int fields_size = 0;

        event = trace_file->event_call->data;

        if (trace_trigger_soft_disabled(trace_file))
                return;

        fields_size = event->n_u64 * sizeof(u64);

        for (i = 0; i < event->n_dynamic_fields; i++) {
                unsigned int field_pos = event->dynamic_fields[i]->field_pos;
                char *str_val;

                val_idx = var_ref_idx[field_pos];
                str_val = (char *)(long)var_ref_vals[val_idx];

                len = strlen(str_val) + 1;

                fields_size += len;
        }

        /*
         * Avoid ring buffer recursion detection, as this event
         * is being performed within another event.
         */
        buffer = trace_file->tr->array_buffer.buffer;
        ring_buffer_nest_start(buffer);

        entry = trace_event_buffer_reserve(&fbuffer, trace_file,
                                           sizeof(*entry) + fields_size);
        if (!entry)
                goto out;

        for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
                val_idx = var_ref_idx[i];
                if (event->fields[i]->is_string) {
                        char *str_val = (char *)(long)var_ref_vals[val_idx];

                        len = trace_string(entry, event, str_val,
                                           event->fields[i]->is_dynamic,
                                           data_size, &n_u64);
                        data_size += len; /* only dynamic string increments */
                } else {
                        struct synth_field *field = event->fields[i];
                        u64 val = var_ref_vals[val_idx];

                        switch (field->size) {
                        case 1:
                                *(u8 *)&entry->fields[n_u64] = (u8)val;
                                break;

                        case 2:
                                *(u16 *)&entry->fields[n_u64] = (u16)val;
                                break;

                        case 4:
                                *(u32 *)&entry->fields[n_u64] = (u32)val;
                                break;

                        default:
                                entry->fields[n_u64] = val;
                                break;
                        }
                        n_u64++;
                }
        }

        trace_event_buffer_commit(&fbuffer);
out:
        ring_buffer_nest_end(buffer);
}

static void free_synth_event_print_fmt(struct trace_event_call *call)
{
        if (call) {
                kfree(call->print_fmt);
                call->print_fmt = NULL;
        }
}

static int __set_synth_event_print_fmt(struct synth_event *event,
                                       char *buf, int len)
{
        const char *fmt;
        int pos = 0;
        int i;

        /* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)

        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
        for (i = 0; i < event->n_fields; i++) {
                fmt = synth_field_fmt(event->fields[i]->type);
                pos += snprintf(buf + pos, LEN_OR_ZERO, "%s=%s%s",
                                event->fields[i]->name, fmt,
                                i == event->n_fields - 1 ? "" : ", ");
        }
        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");

        for (i = 0; i < event->n_fields; i++) {
                if (event->fields[i]->is_string &&
                    event->fields[i]->is_dynamic)
                        pos += snprintf(buf + pos, LEN_OR_ZERO,
                                ", __get_str(%s)", event->fields[i]->name);
                else
                        pos += snprintf(buf + pos, LEN_OR_ZERO,
                                        ", REC->%s", event->fields[i]->name);
        }

#undef LEN_OR_ZERO

        /* return the length of print_fmt */
        return pos;
}

static int set_synth_event_print_fmt(struct trace_event_call *call)
{
        struct synth_event *event = call->data;
        char *print_fmt;
        int len;

        /* First: called with 0 length to calculate the needed length */
        len = __set_synth_event_print_fmt(event, NULL, 0);

        print_fmt = kmalloc(len + 1, GFP_KERNEL);
        if (!print_fmt)
                return -ENOMEM;

        /* Second: actually write the @print_fmt */
        __set_synth_event_print_fmt(event, print_fmt, len + 1);
        call->print_fmt = print_fmt;

        return 0;
}

static void free_synth_field(struct synth_field *field)
{
        kfree(field->type);
        kfree(field->name);
        kfree(field);
}

static struct synth_field *parse_synth_field(int argc, const char **argv,
                                             int *consumed)
{
        struct synth_field *field;
        const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
        int len, ret = -ENOMEM;
        struct seq_buf s;
        ssize_t size;

        if (field_type[0] == ';')
                field_type++;

        if (!strcmp(field_type, "unsigned")) {
                if (argc < 3) {
                        synth_err(SYNTH_ERR_INCOMPLETE_TYPE, errpos(field_type));
                        return ERR_PTR(-EINVAL);
                }
                prefix = "unsigned ";
                field_type = argv[1];
                field_name = argv[2];
                *consumed = 3;
        } else {
                field_name = argv[1];
                *consumed = 2;
        }

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

        len = strlen(field_name);
        array = strchr(field_name, '[');
        if (array)
                len -= strlen(array);
        else if (field_name[len - 1] == ';')
                len--;

        field->name = kmemdup_nul(field_name, len, GFP_KERNEL);
        if (!field->name)
                goto free;

        if (!is_good_name(field->name)) {
                synth_err(SYNTH_ERR_BAD_NAME, errpos(field_name));
                ret = -EINVAL;
                goto free;
        }

        if (field_type[0] == ';')
                field_type++;
        len = strlen(field_type) + 1;

        if (array)
                len += strlen(array);

        if (prefix)
                len += strlen(prefix);

        field->type = kzalloc(len, GFP_KERNEL);
        if (!field->type)
                goto free;

        seq_buf_init(&s, field->type, len);
        if (prefix)
                seq_buf_puts(&s, prefix);
        seq_buf_puts(&s, field_type);
        if (array) {
                seq_buf_puts(&s, array);
                if (s.buffer[s.len - 1] == ';')
                        s.len--;
        }
        if (WARN_ON_ONCE(!seq_buf_buffer_left(&s)))
                goto free;

        s.buffer[s.len] = '\0';

        size = synth_field_size(field->type);
        if (size < 0) {
                synth_err(SYNTH_ERR_INVALID_TYPE, errpos(field_type));
                ret = -EINVAL;
                goto free;
        } else if (size == 0) {
                if (synth_field_is_string(field->type)) {
                        char *type;

                        len = sizeof("__data_loc ") + strlen(field->type) + 1;
                        type = kzalloc(len, GFP_KERNEL);
                        if (!type)
                                goto free;

                        seq_buf_init(&s, type, len);
                        seq_buf_puts(&s, "__data_loc ");
                        seq_buf_puts(&s, field->type);

                        if (WARN_ON_ONCE(!seq_buf_buffer_left(&s)))
                                goto free;
                        s.buffer[s.len] = '\0';

                        kfree(field->type);
                        field->type = type;

                        field->is_dynamic = true;
                        size = sizeof(u64);
                } else {
                        synth_err(SYNTH_ERR_INVALID_TYPE, errpos(field_type));
                        ret = -EINVAL;
                        goto free;
                }
        }
        field->size = size;

        if (synth_field_is_string(field->type))
                field->is_string = true;

        field->is_signed = synth_field_signed(field->type);
 out:
        return field;
 free:
        free_synth_field(field);
        field = ERR_PTR(ret);
        goto out;
}

static void free_synth_tracepoint(struct tracepoint *tp)
{
        if (!tp)
                return;

        kfree(tp->name);
        kfree(tp);
}

static struct tracepoint *alloc_synth_tracepoint(char *name)
{
        struct tracepoint *tp;

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

        tp->name = kstrdup(name, GFP_KERNEL);
        if (!tp->name) {
                kfree(tp);
                return ERR_PTR(-ENOMEM);
        }

        return tp;
}

struct synth_event *find_synth_event(const char *name)
{
        struct dyn_event *pos;
        struct synth_event *event;

        for_each_dyn_event(pos) {
                if (!is_synth_event(pos))
                        continue;
                event = to_synth_event(pos);
                if (strcmp(event->name, name) == 0)
                        return event;
        }

        return NULL;
}

static struct trace_event_fields synth_event_fields_array[] = {
        { .type = TRACE_FUNCTION_TYPE,
          .define_fields = synth_event_define_fields },
        {}
};

static int register_synth_event(struct synth_event *event)
{
        struct trace_event_call *call = &event->call;
        int ret = 0;

        event->call.class = &event->class;
        event->class.system = kstrdup(SYNTH_SYSTEM, GFP_KERNEL);
        if (!event->class.system) {
                ret = -ENOMEM;
                goto out;
        }

        event->tp = alloc_synth_tracepoint(event->name);
        if (IS_ERR(event->tp)) {
                ret = PTR_ERR(event->tp);
                event->tp = NULL;
                goto out;
        }

        INIT_LIST_HEAD(&call->class->fields);
        call->event.funcs = &synth_event_funcs;
        call->class->fields_array = synth_event_fields_array;

        ret = register_trace_event(&call->event);
        if (!ret) {
                ret = -ENODEV;
                goto out;
        }
        call->flags = TRACE_EVENT_FL_TRACEPOINT;
        call->class->reg = trace_event_reg;
        call->class->probe = trace_event_raw_event_synth;
        call->data = event;
        call->tp = event->tp;

        ret = trace_add_event_call(call);
        if (ret) {
                pr_warn("Failed to register synthetic event: %s\n",
                        trace_event_name(call));
                goto err;
        }

        ret = set_synth_event_print_fmt(call);
        if (ret < 0) {
                trace_remove_event_call(call);
                goto err;
        }
 out:
        return ret;
 err:
        unregister_trace_event(&call->event);
        goto out;
}

static int unregister_synth_event(struct synth_event *event)
{
        struct trace_event_call *call = &event->call;
        int ret;

        ret = trace_remove_event_call(call);

        return ret;
}

static void free_synth_event(struct synth_event *event)
{
        unsigned int i;

        if (!event)
                return;

        for (i = 0; i < event->n_fields; i++)
                free_synth_field(event->fields[i]);

        kfree(event->fields);
        kfree(event->dynamic_fields);
        kfree(event->name);
        kfree(event->class.system);
        free_synth_tracepoint(event->tp);
        free_synth_event_print_fmt(&event->call);
        kfree(event);
}

static struct synth_event *alloc_synth_event(const char *name, int n_fields,
                                             struct synth_field **fields)
{
        unsigned int i, j, n_dynamic_fields = 0;
        struct synth_event *event;

        event = kzalloc(sizeof(*event), GFP_KERNEL);
        if (!event) {
                event = ERR_PTR(-ENOMEM);
                goto out;
        }

        event->name = kstrdup(name, GFP_KERNEL);
        if (!event->name) {
                kfree(event);
                event = ERR_PTR(-ENOMEM);
                goto out;
        }

        event->fields = kcalloc(n_fields, sizeof(*event->fields), GFP_KERNEL);
        if (!event->fields) {
                free_synth_event(event);
                event = ERR_PTR(-ENOMEM);
                goto out;
        }

        for (i = 0; i < n_fields; i++)
                if (fields[i]->is_dynamic)
                        n_dynamic_fields++;

        if (n_dynamic_fields) {
                event->dynamic_fields = kcalloc(n_dynamic_fields,
                                                sizeof(*event->dynamic_fields),
                                                GFP_KERNEL);
                if (!event->dynamic_fields) {
                        free_synth_event(event);
                        event = ERR_PTR(-ENOMEM);
                        goto out;
                }
        }

        dyn_event_init(&event->devent, &synth_event_ops);

        for (i = 0, j = 0; i < n_fields; i++) {
                event->fields[i] = fields[i];

                if (fields[i]->is_dynamic) {
                        event->dynamic_fields[j] = fields[i];
                        event->dynamic_fields[j]->field_pos = i;
                        event->dynamic_fields[j++] = fields[i];
                        event->n_dynamic_fields++;
                }
        }
        event->n_fields = n_fields;
 out:
        return event;
}

static int synth_event_check_arg_fn(void *data)
{
        struct dynevent_arg_pair *arg_pair = data;
        int size;

        size = synth_field_size((char *)arg_pair->lhs);
        if (size == 0) {
                if (strstr((char *)arg_pair->lhs, "["))
                        return 0;
        }

        return size ? 0 : -EINVAL;
}

/**
 * synth_event_add_field - Add a new field to a synthetic event cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @type: The type of the new field to add
 * @name: The name of the new field to add
 *
 * Add a new field to a synthetic event cmd object.  Field ordering is in
 * the same order the fields are added.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_add_field(struct dynevent_cmd *cmd, const char *type,
                          const char *name)
{
        struct dynevent_arg_pair arg_pair;
        int ret;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        if (!type || !name)
                return -EINVAL;

        dynevent_arg_pair_init(&arg_pair, 0, ';');

        arg_pair.lhs = type;
        arg_pair.rhs = name;

        ret = dynevent_arg_pair_add(cmd, &arg_pair, synth_event_check_arg_fn);
        if (ret)
                return ret;

        if (++cmd->n_fields > SYNTH_FIELDS_MAX)
                ret = -EINVAL;

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_field);

/**
 * synth_event_add_field_str - Add a new field to a synthetic event cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @type_name: The type and name of the new field to add, as a single string
 *
 * Add a new field to a synthetic event cmd object, as a single
 * string.  The @type_name string is expected to be of the form 'type
 * name', which will be appended by ';'.  No sanity checking is done -
 * what's passed in is assumed to already be well-formed.  Field
 * ordering is in the same order the fields are added.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_add_field_str(struct dynevent_cmd *cmd, const char *type_name)
{
        struct dynevent_arg arg;
        int ret;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        if (!type_name)
                return -EINVAL;

        dynevent_arg_init(&arg, ';');

        arg.str = type_name;

        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        if (++cmd->n_fields > SYNTH_FIELDS_MAX)
                ret = -EINVAL;

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_field_str);

/**
 * synth_event_add_fields - Add multiple fields to a synthetic event cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @fields: An array of type/name field descriptions
 * @n_fields: The number of field descriptions contained in the fields array
 *
 * Add a new set of fields to a synthetic event cmd object.  The event
 * fields that will be defined for the event should be passed in as an
 * array of struct synth_field_desc, and the number of elements in the
 * array passed in as n_fields.  Field ordering will retain the
 * ordering given in the fields array.

 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_add_fields(struct dynevent_cmd *cmd,
                           struct synth_field_desc *fields,
                           unsigned int n_fields)
{
        unsigned int i;
        int ret = 0;

        for (i = 0; i < n_fields; i++) {
                if (fields[i].type == NULL || fields[i].name == NULL) {
                        ret = -EINVAL;
                        break;
                }

                ret = synth_event_add_field(cmd, fields[i].type, fields[i].name);
                if (ret)
                        break;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_fields);

/**
 * __synth_event_gen_cmd_start - Start a synthetic event command from arg list
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @name: The name of the synthetic event
 * @mod: The module creating the event, NULL if not created from a module
 * @args: Variable number of arg (pairs), one pair for each field
 *
 * NOTE: Users normally won't want to call this function directly, but
 * rather use the synth_event_gen_cmd_start() wrapper, which
 * automatically adds a NULL to the end of the arg list.  If this
 * function is used directly, make sure the last arg in the variable
 * arg list is NULL.
 *
 * Generate a synthetic event command to be executed by
 * synth_event_gen_cmd_end().  This function can be used to generate
 * the complete command or only the first part of it; in the latter
 * case, synth_event_add_field(), synth_event_add_field_str(), or
 * synth_event_add_fields() can be used to add more fields following
 * this.
 *
 * There should be an even number variable args, each pair consisting
 * of a type followed by a field name.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int __synth_event_gen_cmd_start(struct dynevent_cmd *cmd, const char *name,
                                struct module *mod, ...)
{
        struct dynevent_arg arg;
        va_list args;
        int ret;

        cmd->event_name = name;
        cmd->private_data = mod;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        dynevent_arg_init(&arg, 0);
        arg.str = name;
        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        va_start(args, mod);
        for (;;) {
                const char *type, *name;

                type = va_arg(args, const char *);
                if (!type)
                        break;
                name = va_arg(args, const char *);
                if (!name)
                        break;

                if (++cmd->n_fields > SYNTH_FIELDS_MAX) {
                        ret = -EINVAL;
                        break;
                }

                ret = synth_event_add_field(cmd, type, name);
                if (ret)
                        break;
        }
        va_end(args);

        return ret;
}
EXPORT_SYMBOL_GPL(__synth_event_gen_cmd_start);

/**
 * synth_event_gen_cmd_array_start - Start synthetic event command from an array
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @name: The name of the synthetic event
 * @fields: An array of type/name field descriptions
 * @n_fields: The number of field descriptions contained in the fields array
 *
 * Generate a synthetic event command to be executed by
 * synth_event_gen_cmd_end().  This function can be used to generate
 * the complete command or only the first part of it; in the latter
 * case, synth_event_add_field(), synth_event_add_field_str(), or
 * synth_event_add_fields() can be used to add more fields following
 * this.
 *
 * The event fields that will be defined for the event should be
 * passed in as an array of struct synth_field_desc, and the number of
 * elements in the array passed in as n_fields.  Field ordering will
 * retain the ordering given in the fields array.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_gen_cmd_array_start(struct dynevent_cmd *cmd, const char *name,
                                    struct module *mod,
                                    struct synth_field_desc *fields,
                                    unsigned int n_fields)
{
        struct dynevent_arg arg;
        unsigned int i;
        int ret = 0;

        cmd->event_name = name;
        cmd->private_data = mod;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        if (n_fields > SYNTH_FIELDS_MAX)
                return -EINVAL;

        dynevent_arg_init(&arg, 0);
        arg.str = name;
        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        for (i = 0; i < n_fields; i++) {
                if (fields[i].type == NULL || fields[i].name == NULL)
                        return -EINVAL;

                ret = synth_event_add_field(cmd, fields[i].type, fields[i].name);
                if (ret)
                        break;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_gen_cmd_array_start);

static int save_cmdstr(int argc, const char *name, const char **argv)
{
        struct seq_buf s;
        char *buf;
        int i;

        buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        seq_buf_init(&s, buf, MAX_DYNEVENT_CMD_LEN);

        seq_buf_puts(&s, name);

        for (i = 0; i < argc; i++) {
                seq_buf_putc(&s, ' ');
                seq_buf_puts(&s, argv[i]);
        }

        if (!seq_buf_buffer_left(&s)) {
                synth_err(SYNTH_ERR_CMD_TOO_LONG, 0);
                kfree(buf);
                return -EINVAL;
        }
        buf[s.len] = 0;
        last_cmd_set(buf);

        kfree(buf);
        return 0;
}

static int __create_synth_event(int argc, const char *name, const char **argv)
{
        struct synth_field *field, *fields[SYNTH_FIELDS_MAX];
        struct synth_event *event = NULL;
        int i, consumed = 0, n_fields = 0, ret = 0;

        ret = save_cmdstr(argc, name, argv);
        if (ret)
                return ret;

        /*
         * Argument syntax:
         *  - Add synthetic event: <event_name> field[;field] ...
         *  - Remove synthetic event: !<event_name> field[;field] ...
         *      where 'field' = type field_name
         */

        if (name[0] == '\0' || argc < 1) {
                synth_err(SYNTH_ERR_CMD_INCOMPLETE, 0);
                return -EINVAL;
        }

        mutex_lock(&event_mutex);

        if (!is_good_name(name)) {
                synth_err(SYNTH_ERR_BAD_NAME, errpos(name));
                ret = -EINVAL;
                goto out;
        }

        event = find_synth_event(name);
        if (event) {
                synth_err(SYNTH_ERR_EVENT_EXISTS, errpos(name));
                ret = -EEXIST;
                goto out;
        }

        for (i = 0; i < argc - 1; i++) {
                if (strcmp(argv[i], ";") == 0)
                        continue;
                if (n_fields == SYNTH_FIELDS_MAX) {
                        synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
                        ret = -EINVAL;
                        goto err;
                }

                field = parse_synth_field(argc - i, &argv[i], &consumed);
                if (IS_ERR(field)) {
                        ret = PTR_ERR(field);
                        goto err;
                }
                fields[n_fields++] = field;
                i += consumed - 1;
        }

        if (i < argc && strcmp(argv[i], ";") != 0) {
                synth_err(SYNTH_ERR_INVALID_FIELD, errpos(argv[i]));
                ret = -EINVAL;
                goto err;
        }

        event = alloc_synth_event(name, n_fields, fields);
        if (IS_ERR(event)) {
                ret = PTR_ERR(event);
                event = NULL;
                goto err;
        }
        ret = register_synth_event(event);
        if (!ret)
                dyn_event_add(&event->devent);
        else
                free_synth_event(event);
 out:
        mutex_unlock(&event_mutex);

        return ret;
 err:
        for (i = 0; i < n_fields; i++)
                free_synth_field(fields[i]);

        goto out;
}

/**
 * synth_event_create - Create a new synthetic event
 * @name: The name of the new synthetic event
 * @fields: An array of type/name field descriptions
 * @n_fields: The number of field descriptions contained in the fields array
 * @mod: The module creating the event, NULL if not created from a module
 *
 * Create a new synthetic event with the given name under the
 * trace/events/synthetic/ directory.  The event fields that will be
 * defined for the event should be passed in as an array of struct
 * synth_field_desc, and the number elements in the array passed in as
 * n_fields. Field ordering will retain the ordering given in the
 * fields array.
 *
 * If the new synthetic event is being created from a module, the mod
 * param must be non-NULL.  This will ensure that the trace buffer
 * won't contain unreadable events.
 *
 * The new synth event should be deleted using synth_event_delete()
 * function.  The new synthetic event can be generated from modules or
 * other kernel code using trace_synth_event() and related functions.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_create(const char *name, struct synth_field_desc *fields,
                       unsigned int n_fields, struct module *mod)
{
        struct dynevent_cmd cmd;
        char *buf;
        int ret;

        buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        synth_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);

        ret = synth_event_gen_cmd_array_start(&cmd, name, mod,
                                              fields, n_fields);
        if (ret)
                goto out;

        ret = synth_event_gen_cmd_end(&cmd);
 out:
        kfree(buf);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_create);

static int destroy_synth_event(struct synth_event *se)
{
        int ret;

        if (se->ref)
                ret = -EBUSY;
        else {
                ret = unregister_synth_event(se);
                if (!ret) {
                        dyn_event_remove(&se->devent);
                        free_synth_event(se);
                }
        }

        return ret;
}

/**
 * synth_event_delete - Delete a synthetic event
 * @event_name: The name of the new sythetic event
 *
 * Delete a synthetic event that was created with synth_event_create().
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_delete(const char *event_name)
{
        struct synth_event *se = NULL;
        struct module *mod = NULL;
        int ret = -ENOENT;

        mutex_lock(&event_mutex);
        se = find_synth_event(event_name);
        if (se) {
                mod = se->mod;
                ret = destroy_synth_event(se);
        }
        mutex_unlock(&event_mutex);

        if (mod) {
                mutex_lock(&trace_types_lock);
                /*
                 * It is safest to reset the ring buffer if the module
                 * being unloaded registered any events that were
                 * used. The only worry is if a new module gets
                 * loaded, and takes on the same id as the events of
                 * this module. When printing out the buffer, traced
                 * events left over from this module may be passed to
                 * the new module events and unexpected results may
                 * occur.
                 */
                tracing_reset_all_online_cpus();
                mutex_unlock(&trace_types_lock);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_delete);

static int create_or_delete_synth_event(int argc, char **argv)
{
        const char *name = argv[0];
        int ret;

        /* trace_run_command() ensures argc != 0 */
        if (name[0] == '!') {
                ret = synth_event_delete(name + 1);
                return ret;
        }

        ret = __create_synth_event(argc - 1, name, (const char **)argv + 1);
        return ret == -ECANCELED ? -EINVAL : ret;
}

static int synth_event_run_command(struct dynevent_cmd *cmd)
{
        struct synth_event *se;
        int ret;

        ret = trace_run_command(cmd->seq.buffer, create_or_delete_synth_event);
        if (ret)
                return ret;

        se = find_synth_event(cmd->event_name);
        if (WARN_ON(!se))
                return -ENOENT;

        se->mod = cmd->private_data;

        return ret;
}

/**
 * synth_event_cmd_init - Initialize a synthetic event command object
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @buf: A pointer to the buffer used to build the command
 * @maxlen: The length of the buffer passed in @buf
 *
 * Initialize a synthetic event command object.  Use this before
 * calling any of the other dyenvent_cmd functions.
 */
void synth_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
{
        dynevent_cmd_init(cmd, buf, maxlen, DYNEVENT_TYPE_SYNTH,
                          synth_event_run_command);
}
EXPORT_SYMBOL_GPL(synth_event_cmd_init);

static inline int
__synth_event_trace_init(struct trace_event_file *file,
                         struct synth_event_trace_state *trace_state)
{
        int ret = 0;

        memset(trace_state, '\0', sizeof(*trace_state));

        /*
         * Normal event tracing doesn't get called at all unless the
         * ENABLED bit is set (which attaches the probe thus allowing
         * this code to be called, etc).  Because this is called
         * directly by the user, we don't have that but we still need
         * to honor not logging when disabled.  For the iterated
         * trace case, we save the enabled state upon start and just
         * ignore the following data calls.
         */
        if (!(file->flags & EVENT_FILE_FL_ENABLED) ||
            trace_trigger_soft_disabled(file)) {
                trace_state->disabled = true;
                ret = -ENOENT;
                goto out;
        }

        trace_state->event = file->event_call->data;
out:
        return ret;
}

static inline int
__synth_event_trace_start(struct trace_event_file *file,
                          struct synth_event_trace_state *trace_state,
                          int dynamic_fields_size)
{
        int entry_size, fields_size = 0;
        int ret = 0;

        fields_size = trace_state->event->n_u64 * sizeof(u64);
        fields_size += dynamic_fields_size;

        /*
         * Avoid ring buffer recursion detection, as this event
         * is being performed within another event.
         */
        trace_state->buffer = file->tr->array_buffer.buffer;
        ring_buffer_nest_start(trace_state->buffer);

        entry_size = sizeof(*trace_state->entry) + fields_size;
        trace_state->entry = trace_event_buffer_reserve(&trace_state->fbuffer,
                                                        file,
                                                        entry_size);
        if (!trace_state->entry) {
                ring_buffer_nest_end(trace_state->buffer);
                ret = -EINVAL;
        }

        return ret;
}

static inline void
__synth_event_trace_end(struct synth_event_trace_state *trace_state)
{
        trace_event_buffer_commit(&trace_state->fbuffer);

        ring_buffer_nest_end(trace_state->buffer);
}

/**
 * synth_event_trace - Trace a synthetic event
 * @file: The trace_event_file representing the synthetic event
 * @n_vals: The number of values in vals
 * @args: Variable number of args containing the event values
 *
 * Trace a synthetic event using the values passed in the variable
 * argument list.
 *
 * The argument list should be a list 'n_vals' u64 values.  The number
 * of vals must match the number of field in the synthetic event, and
 * must be in the same order as the synthetic event fields.
 *
 * All vals should be cast to u64, and string vals are just pointers
 * to strings, cast to u64.  Strings will be copied into space
 * reserved in the event for the string, using these pointers.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
{
        unsigned int i, n_u64, len, data_size = 0;
        struct synth_event_trace_state state;
        va_list args;
        int ret;

        ret = __synth_event_trace_init(file, &state);
        if (ret) {
                if (ret == -ENOENT)
                        ret = 0; /* just disabled, not really an error */
                return ret;
        }

        if (state.event->n_dynamic_fields) {
                va_start(args, n_vals);

                for (i = 0; i < state.event->n_fields; i++) {
                        u64 val = va_arg(args, u64);

                        if (state.event->fields[i]->is_string &&
                            state.event->fields[i]->is_dynamic) {
                                char *str_val = (char *)(long)val;

                                data_size += strlen(str_val) + 1;
                        }
                }

                va_end(args);
        }

        ret = __synth_event_trace_start(file, &state, data_size);
        if (ret)
                return ret;

        if (n_vals != state.event->n_fields) {
                ret = -EINVAL;
                goto out;
        }

        data_size = 0;

        va_start(args, n_vals);
        for (i = 0, n_u64 = 0; i < state.event->n_fields; i++) {
                u64 val;

                val = va_arg(args, u64);

                if (state.event->fields[i]->is_string) {
                        char *str_val = (char *)(long)val;

                        len = trace_string(state.entry, state.event, str_val,
                                           state.event->fields[i]->is_dynamic,
                                           data_size, &n_u64);
                        data_size += len; /* only dynamic string increments */
                } else {
                        struct synth_field *field = state.event->fields[i];

                        switch (field->size) {
                        case 1:
                                *(u8 *)&state.entry->fields[n_u64] = (u8)val;
                                break;

                        case 2:
                                *(u16 *)&state.entry->fields[n_u64] = (u16)val;
                                break;

                        case 4:
                                *(u32 *)&state.entry->fields[n_u64] = (u32)val;
                                break;

                        default:
                                state.entry->fields[n_u64] = val;
                                break;
                        }
                        n_u64++;
                }
        }
        va_end(args);
out:
        __synth_event_trace_end(&state);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace);

/**
 * synth_event_trace_array - Trace a synthetic event from an array
 * @file: The trace_event_file representing the synthetic event
 * @vals: Array of values
 * @n_vals: The number of values in vals
 *
 * Trace a synthetic event using the values passed in as 'vals'.
 *
 * The 'vals' array is just an array of 'n_vals' u64.  The number of
 * vals must match the number of field in the synthetic event, and
 * must be in the same order as the synthetic event fields.
 *
 * All vals should be cast to u64, and string vals are just pointers
 * to strings, cast to u64.  Strings will be copied into space
 * reserved in the event for the string, using these pointers.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
                            unsigned int n_vals)
{
        unsigned int i, n_u64, field_pos, len, data_size = 0;
        struct synth_event_trace_state state;
        char *str_val;
        int ret;

        ret = __synth_event_trace_init(file, &state);
        if (ret) {
                if (ret == -ENOENT)
                        ret = 0; /* just disabled, not really an error */
                return ret;
        }

        if (state.event->n_dynamic_fields) {
                for (i = 0; i < state.event->n_dynamic_fields; i++) {
                        field_pos = state.event->dynamic_fields[i]->field_pos;
                        str_val = (char *)(long)vals[field_pos];
                        len = strlen(str_val) + 1;
                        data_size += len;
                }
        }

        ret = __synth_event_trace_start(file, &state, data_size);
        if (ret)
                return ret;

        if (n_vals != state.event->n_fields) {
                ret = -EINVAL;
                goto out;
        }

        data_size = 0;

        for (i = 0, n_u64 = 0; i < state.event->n_fields; i++) {
                if (state.event->fields[i]->is_string) {
                        char *str_val = (char *)(long)vals[i];

                        len = trace_string(state.entry, state.event, str_val,
                                           state.event->fields[i]->is_dynamic,
                                           data_size, &n_u64);
                        data_size += len; /* only dynamic string increments */
                } else {
                        struct synth_field *field = state.event->fields[i];
                        u64 val = vals[i];

                        switch (field->size) {
                        case 1:
                                *(u8 *)&state.entry->fields[n_u64] = (u8)val;
                                break;

                        case 2:
                                *(u16 *)&state.entry->fields[n_u64] = (u16)val;
                                break;

                        case 4:
                                *(u32 *)&state.entry->fields[n_u64] = (u32)val;
                                break;

                        default:
                                state.entry->fields[n_u64] = val;
                                break;
                        }
                        n_u64++;
                }
        }
out:
        __synth_event_trace_end(&state);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace_array);

/**
 * synth_event_trace_start - Start piecewise synthetic event trace
 * @file: The trace_event_file representing the synthetic event
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * Start the trace of a synthetic event field-by-field rather than all
 * at once.
 *
 * This function 'opens' an event trace, which means space is reserved
 * for the event in the trace buffer, after which the event's
 * individual field values can be set through either
 * synth_event_add_next_val() or synth_event_add_val().
 *
 * A pointer to a trace_state object is passed in, which will keep
 * track of the current event trace state until the event trace is
 * closed (and the event finally traced) using
 * synth_event_trace_end().
 *
 * Note that synth_event_trace_end() must be called after all values
 * have been added for each event trace, regardless of whether adding
 * all field values succeeded or not.
 *
 * Note also that for a given event trace, all fields must be added
 * using either synth_event_add_next_val() or synth_event_add_val()
 * but not both together or interleaved.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace_start(struct trace_event_file *file,
                            struct synth_event_trace_state *trace_state)
{
        int ret;

        if (!trace_state)
                return -EINVAL;

        ret = __synth_event_trace_init(file, trace_state);
        if (ret) {
                if (ret == -ENOENT)
                        ret = 0; /* just disabled, not really an error */
                return ret;
        }

        if (trace_state->event->n_dynamic_fields)
                return -ENOTSUPP;

        ret = __synth_event_trace_start(file, trace_state, 0);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace_start);

static int __synth_event_add_val(const char *field_name, u64 val,
                                 struct synth_event_trace_state *trace_state)
{
        struct synth_field *field = NULL;
        struct synth_trace_event *entry;
        struct synth_event *event;
        int i, ret = 0;

        if (!trace_state) {
                ret = -EINVAL;
                goto out;
        }

        /* can't mix add_next_synth_val() with add_synth_val() */
        if (field_name) {
                if (trace_state->add_next) {
                        ret = -EINVAL;
                        goto out;
                }
                trace_state->add_name = true;
        } else {
                if (trace_state->add_name) {
                        ret = -EINVAL;
                        goto out;
                }
                trace_state->add_next = true;
        }

        if (trace_state->disabled)
                goto out;

        event = trace_state->event;
        if (trace_state->add_name) {
                for (i = 0; i < event->n_fields; i++) {
                        field = event->fields[i];
                        if (strcmp(field->name, field_name) == 0)
                                break;
                }
                if (!field) {
                        ret = -EINVAL;
                        goto out;
                }
        } else {
                if (trace_state->cur_field >= event->n_fields) {
                        ret = -EINVAL;
                        goto out;
                }
                field = event->fields[trace_state->cur_field++];
        }

        entry = trace_state->entry;
        if (field->is_string) {
                char *str_val = (char *)(long)val;
                char *str_field;

                if (field->is_dynamic) { /* add_val can't do dynamic strings */
                        ret = -EINVAL;
                        goto out;
                }

                if (!str_val) {
                        ret = -EINVAL;
                        goto out;
                }

                str_field = (char *)&entry->fields[field->offset];
                strscpy(str_field, str_val, STR_VAR_LEN_MAX);
        } else {
                switch (field->size) {
                case 1:
                        *(u8 *)&trace_state->entry->fields[field->offset] = (u8)val;
                        break;

                case 2:
                        *(u16 *)&trace_state->entry->fields[field->offset] = (u16)val;
                        break;

                case 4:
                        *(u32 *)&trace_state->entry->fields[field->offset] = (u32)val;
                        break;

                default:
                        trace_state->entry->fields[field->offset] = val;
                        break;
                }
        }
 out:
        return ret;
}

/**
 * synth_event_add_next_val - Add the next field's value to an open synth trace
 * @val: The value to set the next field to
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * Set the value of the next field in an event that's been opened by
 * synth_event_trace_start().
 *
 * The val param should be the value cast to u64.  If the value points
 * to a string, the val param should be a char * cast to u64.
 *
 * This function assumes all the fields in an event are to be set one
 * after another - successive calls to this function are made, one for
 * each field, in the order of the fields in the event, until all
 * fields have been set.  If you'd rather set each field individually
 * without regard to ordering, synth_event_add_val() can be used
 * instead.
 *
 * Note however that synth_event_add_next_val() and
 * synth_event_add_val() can't be intermixed for a given event trace -
 * one or the other but not both can be used at the same time.
 *
 * Note also that synth_event_trace_end() must be called after all
 * values have been added for each event trace, regardless of whether
 * adding all field values succeeded or not.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_add_next_val(u64 val,
                             struct synth_event_trace_state *trace_state)
{
        return __synth_event_add_val(NULL, val, trace_state);
}
EXPORT_SYMBOL_GPL(synth_event_add_next_val);

/**
 * synth_event_add_val - Add a named field's value to an open synth trace
 * @field_name: The name of the synthetic event field value to set
 * @val: The value to set the next field to
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * Set the value of the named field in an event that's been opened by
 * synth_event_trace_start().
 *
 * The val param should be the value cast to u64.  If the value points
 * to a string, the val param should be a char * cast to u64.
 *
 * This function looks up the field name, and if found, sets the field
 * to the specified value.  This lookup makes this function more
 * expensive than synth_event_add_next_val(), so use that or the
 * none-piecewise synth_event_trace() instead if efficiency is more
 * important.
 *
 * Note however that synth_event_add_next_val() and
 * synth_event_add_val() can't be intermixed for a given event trace -
 * one or the other but not both can be used at the same time.
 *
 * Note also that synth_event_trace_end() must be called after all
 * values have been added for each event trace, regardless of whether
 * adding all field values succeeded or not.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_add_val(const char *field_name, u64 val,
                        struct synth_event_trace_state *trace_state)
{
        return __synth_event_add_val(field_name, val, trace_state);
}
EXPORT_SYMBOL_GPL(synth_event_add_val);

/**
 * synth_event_trace_end - End piecewise synthetic event trace
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * End the trace of a synthetic event opened by
 * synth_event_trace__start().
 *
 * This function 'closes' an event trace, which basically means that
 * it commits the reserved event and cleans up other loose ends.
 *
 * A pointer to a trace_state object is passed in, which will keep
 * track of the current event trace state opened with
 * synth_event_trace_start().
 *
 * Note that this function must be called after all values have been
 * added for each event trace, regardless of whether adding all field
 * values succeeded or not.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace_end(struct synth_event_trace_state *trace_state)
{
        if (!trace_state)
                return -EINVAL;

        __synth_event_trace_end(trace_state);

        return 0;
}
EXPORT_SYMBOL_GPL(synth_event_trace_end);

static int create_synth_event(int argc, const char **argv)
{
        const char *name = argv[0];
        int len;

        if (name[0] != 's' || name[1] != ':')
                return -ECANCELED;
        name += 2;

        /* This interface accepts group name prefix */
        if (strchr(name, '/')) {
                len = str_has_prefix(name, SYNTH_SYSTEM "/");
                if (len == 0)
                        return -EINVAL;
                name += len;
        }
        return __create_synth_event(argc - 1, name, argv + 1);
}

static int synth_event_release(struct dyn_event *ev)
{
        struct synth_event *event = to_synth_event(ev);
        int ret;

        if (event->ref)
                return -EBUSY;

        ret = unregister_synth_event(event);
        if (ret)
                return ret;

        dyn_event_remove(ev);
        free_synth_event(event);
        return 0;
}

static int __synth_event_show(struct seq_file *m, struct synth_event *event)
{
        struct synth_field *field;
        unsigned int i;
        char *type, *t;

        seq_printf(m, "%s\t", event->name);

        for (i = 0; i < event->n_fields; i++) {
                field = event->fields[i];

                type = field->type;
                t = strstr(type, "__data_loc");
                if (t) { /* __data_loc belongs in format but not event desc */
                        t += sizeof("__data_loc");
                        type = t;
                }

                /* parameter values */
                seq_printf(m, "%s %s%s", type, field->name,
                           i == event->n_fields - 1 ? "" : "; ");
        }

        seq_putc(m, '\n');

        return 0;
}

static int synth_event_show(struct seq_file *m, struct dyn_event *ev)
{
        struct synth_event *event = to_synth_event(ev);

        seq_printf(m, "s:%s/", event->class.system);

        return __synth_event_show(m, event);
}

static int synth_events_seq_show(struct seq_file *m, void *v)
{
        struct dyn_event *ev = v;

        if (!is_synth_event(ev))
                return 0;

        return __synth_event_show(m, to_synth_event(ev));
}

static const struct seq_operations synth_events_seq_op = {
        .start  = dyn_event_seq_start,
        .next   = dyn_event_seq_next,
        .stop   = dyn_event_seq_stop,
        .show   = synth_events_seq_show,
};

static int synth_events_open(struct inode *inode, struct file *file)
{
        int ret;

        ret = security_locked_down(LOCKDOWN_TRACEFS);
        if (ret)
                return ret;

        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
                ret = dyn_events_release_all(&synth_event_ops);
                if (ret < 0)
                        return ret;
        }

        return seq_open(file, &synth_events_seq_op);
}

static ssize_t synth_events_write(struct file *file,
                                  const char __user *buffer,
                                  size_t count, loff_t *ppos)
{
        return trace_parse_run_command(file, buffer, count, ppos,
                                       create_or_delete_synth_event);
}

static const struct file_operations synth_events_fops = {
        .open           = synth_events_open,
        .write          = synth_events_write,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

/*
 * Register dynevent at core_initcall. This allows kernel to setup kprobe
 * events in postcore_initcall without tracefs.
 */
static __init int trace_events_synth_init_early(void)
{
        int err = 0;

        err = dyn_event_register(&synth_event_ops);
        if (err)
                pr_warn("Could not register synth_event_ops\n");

        return err;
}
core_initcall(trace_events_synth_init_early);

static __init int trace_events_synth_init(void)
{
        struct dentry *entry = NULL;
        int err = 0;
        err = tracing_init_dentry();
        if (err)
                goto err;

        entry = tracefs_create_file("synthetic_events", 0644, NULL,
                                    NULL, &synth_events_fops);
        if (!entry) {
                err = -ENODEV;
                goto err;
        }

        return err;
 err:
        pr_warn("Could not create tracefs 'synthetic_events' entry\n");

        return err;
}

fs_initcall(trace_events_synth_init);