// SPDX-License-Identifier: GPL-2.0
/*
 * Generic dynamic event control interface
 *
 * Copyright (C) 2018 Masami Hiramatsu <mhiramat@kernel.org>
 */

#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/tracefs.h>

#include "trace.h"
#include "trace_output.h"       /* for trace_event_sem */
#include "trace_dynevent.h"

static DEFINE_MUTEX(dyn_event_ops_mutex);
static LIST_HEAD(dyn_event_ops_list);

bool trace_event_dyn_try_get_ref(struct trace_event_call *dyn_call)
{
        struct trace_event_call *call;
        bool ret = false;

        if (WARN_ON_ONCE(!(dyn_call->flags & TRACE_EVENT_FL_DYNAMIC)))
                return false;

        down_read(&trace_event_sem);
        list_for_each_entry(call, &ftrace_events, list) {
                if (call == dyn_call) {
                        atomic_inc(&dyn_call->refcnt);
                        ret = true;
                }
        }
        up_read(&trace_event_sem);
        return ret;
}

void trace_event_dyn_put_ref(struct trace_event_call *call)
{
        if (WARN_ON_ONCE(!(call->flags & TRACE_EVENT_FL_DYNAMIC)))
                return;

        if (WARN_ON_ONCE(atomic_read(&call->refcnt) <= 0)) {
                atomic_set(&call->refcnt, 0);
                return;
        }

        atomic_dec(&call->refcnt);
}

bool trace_event_dyn_busy(struct trace_event_call *call)
{
        return atomic_read(&call->refcnt) != 0;
}

int dyn_event_register(struct dyn_event_operations *ops)
{
        if (!ops || !ops->create || !ops->show || !ops->is_busy ||
            !ops->free || !ops->match)
                return -EINVAL;

        INIT_LIST_HEAD(&ops->list);
        mutex_lock(&dyn_event_ops_mutex);
        list_add_tail(&ops->list, &dyn_event_ops_list);
        mutex_unlock(&dyn_event_ops_mutex);
        return 0;
}

int dyn_event_release(const char *raw_command, struct dyn_event_operations *type)
{
        struct dyn_event *pos, *n;
        char *system = NULL, *event, *p;
        int argc, ret = -ENOENT;
        char **argv;

        argv = argv_split(GFP_KERNEL, raw_command, &argc);
        if (!argv)
                return -ENOMEM;

        if (argv[0][0] == '-') {
                if (argv[0][1] != ':') {
                        ret = -EINVAL;
                        goto out;
                }
                event = &argv[0][2];
        } else {
                event = strchr(argv[0], ':');
                if (!event) {
                        ret = -EINVAL;
                        goto out;
                }
                event++;
        }

        p = strchr(event, '/');
        if (p) {
                system = event;
                event = p + 1;
                *p = '\0';
        }
        if (event[0] == '\0') {
                ret = -EINVAL;
                goto out;
        }

        mutex_lock(&event_mutex);
        for_each_dyn_event_safe(pos, n) {
                if (type && type != pos->ops)
                        continue;
                if (!pos->ops->match(system, event,
                                argc - 1, (const char **)argv + 1, pos))
                        continue;

                ret = pos->ops->free(pos);
                if (ret)
                        break;
        }
        mutex_unlock(&event_mutex);
out:
        argv_free(argv);
        return ret;
}

static int create_dyn_event(const char *raw_command)
{
        struct dyn_event_operations *ops;
        int ret = -ENODEV;

        if (raw_command[0] == '-' || raw_command[0] == '!')
                return dyn_event_release(raw_command, NULL);

        mutex_lock(&dyn_event_ops_mutex);
        list_for_each_entry(ops, &dyn_event_ops_list, list) {
                ret = ops->create(raw_command);
                if (!ret || ret != -ECANCELED)
                        break;
        }
        mutex_unlock(&dyn_event_ops_mutex);
        if (ret == -ECANCELED)
                ret = -EINVAL;

        return ret;
}

/* Protected by event_mutex */
LIST_HEAD(dyn_event_list);

void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
{
        mutex_lock(&event_mutex);
        return seq_list_start(&dyn_event_list, *pos);
}

void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
        return seq_list_next(v, &dyn_event_list, pos);
}

void dyn_event_seq_stop(struct seq_file *m, void *v)
{
        mutex_unlock(&event_mutex);
}

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

        if (ev && ev->ops)
                return ev->ops->show(m, ev);

        return 0;
}

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

/*
 * dyn_events_release_all - Release all specific events
 * @type:       the dyn_event_operations * which filters releasing events
 *
 * This releases all events which ->ops matches @type. If @type is NULL,
 * all events are released.
 * Return -EBUSY if any of them are in use, and return other errors when
 * it failed to free the given event. Except for -EBUSY, event releasing
 * process will be aborted at that point and there may be some other
 * releasable events on the list.
 */
int dyn_events_release_all(struct dyn_event_operations *type)
{
        struct dyn_event *ev, *tmp;
        int ret = 0;

        mutex_lock(&event_mutex);
        for_each_dyn_event(ev) {
                if (type && ev->ops != type)
                        continue;
                if (ev->ops->is_busy(ev)) {
                        ret = -EBUSY;
                        goto out;
                }
        }
        for_each_dyn_event_safe(ev, tmp) {
                if (type && ev->ops != type)
                        continue;
                ret = ev->ops->free(ev);
                if (ret)
                        break;
        }
out:
        mutex_unlock(&event_mutex);

        return ret;
}

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

        ret = tracing_check_open_get_tr(NULL);
        if (ret)
                return ret;

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

        return seq_open(file, &dyn_event_seq_op);
}

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

static const struct file_operations dynamic_events_ops = {
        .owner          = THIS_MODULE,
        .open           = dyn_event_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
        .write          = dyn_event_write,
};

/* Make a tracefs interface for controlling dynamic events */
static __init int init_dynamic_event(void)
{
        struct dentry *entry;
        int ret;

        ret = tracing_init_dentry();
        if (ret)
                return 0;

        entry = tracefs_create_file("dynamic_events", TRACE_MODE_WRITE, NULL,
                                    NULL, &dynamic_events_ops);

        /* Event list interface */
        if (!entry)
                pr_warn("Could not create tracefs 'dynamic_events' entry\n");

        return 0;
}
fs_initcall(init_dynamic_event);

/**
 * dynevent_arg_add - Add an arg to a dynevent_cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
 * @arg: The argument to append to the current cmd
 * @check_arg: An (optional) pointer to a function checking arg sanity
 *
 * Append an argument to a dynevent_cmd.  The argument string will be
 * appended to the current cmd string, followed by a separator, if
 * applicable.  Before the argument is added, the @check_arg function,
 * if present, will be used to check the sanity of the current arg
 * string.
 *
 * The cmd string and separator should be set using the
 * dynevent_arg_init() before any arguments are added using this
 * function.
 *
 * Return: 0 if successful, error otherwise.
 */
int dynevent_arg_add(struct dynevent_cmd *cmd,
                     struct dynevent_arg *arg,
                     dynevent_check_arg_fn_t check_arg)
{
        int ret = 0;

        if (check_arg) {
                ret = check_arg(arg);
                if (ret)
                        return ret;
        }

        ret = seq_buf_printf(&cmd->seq, " %s%c", arg->str, arg->separator);
        if (ret) {
                pr_err("String is too long: %s%c\n", arg->str, arg->separator);
                return -E2BIG;
        }

        return ret;
}

/**
 * dynevent_arg_pair_add - Add an arg pair to a dynevent_cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
 * @arg_pair: The argument pair to append to the current cmd
 * @check_arg: An (optional) pointer to a function checking arg sanity
 *
 * Append an argument pair to a dynevent_cmd.  An argument pair
 * consists of a left-hand-side argument and a right-hand-side
 * argument separated by an operator, which can be whitespace, all
 * followed by a separator, if applicable.  This can be used to add
 * arguments of the form 'type variable_name;' or 'x+y'.
 *
 * The lhs argument string will be appended to the current cmd string,
 * followed by an operator, if applicable, followed by the rhs string,
 * followed finally by a separator, if applicable.  Before the
 * argument is added, the @check_arg function, if present, will be
 * used to check the sanity of the current arg strings.
 *
 * The cmd strings, operator, and separator should be set using the
 * dynevent_arg_pair_init() before any arguments are added using this
 * function.
 *
 * Return: 0 if successful, error otherwise.
 */
int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
                          struct dynevent_arg_pair *arg_pair,
                          dynevent_check_arg_fn_t check_arg)
{
        int ret = 0;

        if (check_arg) {
                ret = check_arg(arg_pair);
                if (ret)
                        return ret;
        }

        ret = seq_buf_printf(&cmd->seq, " %s%c%s%c", arg_pair->lhs,
                             arg_pair->operator, arg_pair->rhs,
                             arg_pair->separator);
        if (ret) {
                pr_err("field string is too long: %s%c%s%c\n", arg_pair->lhs,
                       arg_pair->operator, arg_pair->rhs,
                       arg_pair->separator);
                return -E2BIG;
        }

        return ret;
}

/**
 * dynevent_str_add - Add a string to a dynevent_cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
 * @str: The string to append to the current cmd
 *
 * Append a string to a dynevent_cmd.  The string will be appended to
 * the current cmd string as-is, with nothing prepended or appended.
 *
 * Return: 0 if successful, error otherwise.
 */
int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
{
        int ret = 0;

        ret = seq_buf_puts(&cmd->seq, str);
        if (ret) {
                pr_err("String is too long: %s\n", str);
                return -E2BIG;
        }

        return ret;
}

/**
 * dynevent_cmd_init - Initialize a dynevent_cmd object
 * @cmd: A pointer to the dynevent_cmd struct representing the cmd
 * @buf: A pointer to the buffer to generate the command into
 * @maxlen: The length of the buffer the command will be generated into
 * @type: The type of the cmd, checked against further operations
 * @run_command: The type-specific function that will actually run the command
 *
 * Initialize a dynevent_cmd.  A dynevent_cmd is used to build up and
 * run dynamic event creation commands, such as commands for creating
 * synthetic and kprobe events.  Before calling any of the functions
 * used to build the command, a dynevent_cmd object should be
 * instantiated and initialized using this function.
 *
 * The initialization sets things up by saving a pointer to the
 * user-supplied buffer and its length via the @buf and @maxlen
 * params, and by saving the cmd-specific @type and @run_command
 * params which are used to check subsequent dynevent_cmd operations
 * and actually run the command when complete.
 */
void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
                       enum dynevent_type type,
                       dynevent_create_fn_t run_command)
{
        memset(cmd, '\0', sizeof(*cmd));

        seq_buf_init(&cmd->seq, buf, maxlen);
        cmd->type = type;
        cmd->run_command = run_command;
}

/**
 * dynevent_arg_init - Initialize a dynevent_arg object
 * @arg: A pointer to the dynevent_arg struct representing the arg
 * @separator: An (optional) separator, appended after adding the arg
 *
 * Initialize a dynevent_arg object.  A dynevent_arg represents an
 * object used to append single arguments to the current command
 * string.  After the arg string is successfully appended to the
 * command string, the optional @separator is appended.  If no
 * separator was specified when initializing the arg, a space will be
 * appended.
 */
void dynevent_arg_init(struct dynevent_arg *arg,
                       char separator)
{
        memset(arg, '\0', sizeof(*arg));

        if (!separator)
                separator = ' ';
        arg->separator = separator;
}

/**
 * dynevent_arg_pair_init - Initialize a dynevent_arg_pair object
 * @arg_pair: A pointer to the dynevent_arg_pair struct representing the arg
 * @operator: An (optional) operator, appended after adding the first arg
 * @separator: An (optional) separator, appended after adding the second arg
 *
 * Initialize a dynevent_arg_pair object.  A dynevent_arg_pair
 * represents an object used to append argument pairs such as 'type
 * variable_name;' or 'x+y' to the current command string.  An
 * argument pair consists of a left-hand-side argument and a
 * right-hand-side argument separated by an operator, which can be
 * whitespace, all followed by a separator, if applicable.  After the
 * first arg string is successfully appended to the command string,
 * the optional @operator is appended, followed by the second arg and
 * optional @separator.  If no separator was specified when
 * initializing the arg, a space will be appended.
 */
void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
                            char operator, char separator)
{
        memset(arg_pair, '\0', sizeof(*arg_pair));

        if (!operator)
                operator = ' ';
        arg_pair->operator = operator;

        if (!separator)
                separator = ' ';
        arg_pair->separator = separator;
}

/**
 * dynevent_create - Create the dynamic event contained in dynevent_cmd
 * @cmd: The dynevent_cmd object containing the dynamic event creation command
 *
 * Once a dynevent_cmd object has been successfully built up via the
 * dynevent_cmd_init(), dynevent_arg_add() and dynevent_arg_pair_add()
 * functions, this function runs the final command to actually create
 * the event.
 *
 * Return: 0 if the event was successfully created, error otherwise.
 */
int dynevent_create(struct dynevent_cmd *cmd)
{
        return cmd->run_command(cmd);
}
EXPORT_SYMBOL_GPL(dynevent_create);