// SPDX-License-Identifier: GPL-2.0
/*
 * in kernel monitor support: allows rv to control in-kernel monitors.
 *
 * Copyright (C) 2022 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
 */
#include <getopt.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <dirent.h>

#include <trace.h>
#include <utils.h>
#include <rv.h>

static int config_has_id;
static int config_is_container;
static int config_my_pid;
static int config_trace;

static char *config_initial_reactor;
static char *config_reactor;

/*
 * __ikm_read_enable - reads monitor's enable status
 *
 * __does not log errors.
 *
 * Returns the current status, or -1 if the monitor does not exist,
 * __hence not logging errors.
 */
static int __ikm_read_enable(char *monitor_name)
{
        char path[MAX_PATH];
        long long enabled;
        int retval;

        snprintf(path, MAX_PATH, "rv/monitors/%s/enable", monitor_name);

        retval = tracefs_instance_file_read_number(NULL, path, &enabled);
        if (retval < 0)
                return -1;

        return enabled;
}

/*
 * __ikm_find_monitor - find the full name of a possibly nested module
 *
 * __does not log errors.
 *
 * Returns 1 if we found the monitor, -1 on error and 0 if it does not exist.
 * The string out_name is populated with the full name, which can be
 * equal to monitor_name or container/monitor_name if nested
 */
static int __ikm_find_monitor_name(char *monitor_name, char *out_name)
{
        char *available_monitors, container[MAX_DA_NAME_LEN+1], *cursor, *end;
        int retval = 1;

        available_monitors = tracefs_instance_file_read(NULL, "rv/available_monitors", NULL);
        if (!available_monitors)
                return -1;

        cursor = strstr(available_monitors, monitor_name);
        if (!cursor) {
                retval = 0;
                goto out_free;
        }

        for (; cursor > available_monitors; cursor--)
                if (*(cursor-1) == '\n')
                        break;
        end = strstr(cursor, "\n");
        memcpy(out_name, cursor, end-cursor);
        out_name[end-cursor] = '\0';

        cursor = strstr(out_name, ":");
        if (cursor)
                *cursor = '/';
        else {
                sprintf(container, "%s:", monitor_name);
                if (strstr(available_monitors, container))
                        config_is_container = 1;
        }

out_free:
        free(available_monitors);
        return retval;
}

/*
 * ikm_read_enable - reads monitor's enable status
 *
 * Returns the current status, or -1 on error.
 */
static int ikm_read_enable(char *monitor_name)
{
        int enabled;

        enabled = __ikm_read_enable(monitor_name);
        if (enabled < 0) {
                err_msg("ikm: fail read enabled: %d\n", enabled);
                return -1;
        }

        debug_msg("ikm: read enabled: %d\n", enabled);

        return enabled;
}

/*
 * ikm_write_enable - write to the monitor's enable file
 *
 * Return the number of bytes written, -1 on error.
 */
static int ikm_write_enable(char *monitor_name, char *enable_disable)
{
        char path[MAX_PATH];
        int retval;

        debug_msg("ikm: writing enabled: %s\n", enable_disable);

        snprintf(path, MAX_PATH, "rv/monitors/%s/enable", monitor_name);
        retval = tracefs_instance_file_write(NULL, path, enable_disable);
        if (retval < strlen(enable_disable)) {
                err_msg("ikm: writing enabled: %s\n", enable_disable);
                return -1;
        }

        return retval;
}

/*
 * ikm_enable - enable a monitor
 *
 * Returns -1 on failure. Success otherwise.
 */
static int ikm_enable(char *monitor_name)
{
        return ikm_write_enable(monitor_name, "1");
}

/*
 * ikm_disable - disable a monitor
 *
 * Returns -1 on failure. Success otherwise.
 */
static int ikm_disable(char *monitor_name)
{
        return ikm_write_enable(monitor_name, "0");
}

/*
 * ikm_read_desc - read monitors' description
 *
 * Return a dynamically allocated string with the monitor's
 * description, NULL otherwise.
 */
static char *ikm_read_desc(char *monitor_name)
{
        char path[MAX_PATH];
        char *desc;

        snprintf(path, MAX_PATH, "rv/monitors/%s/desc", monitor_name);
        desc = tracefs_instance_file_read(NULL, path, NULL);
        if (!desc) {
                err_msg("ikm: error reading monitor %s desc\n", monitor_name);
                return NULL;
        }

        *strstr(desc, "\n") = '\0';

        return desc;
}

/*
 * ikm_fill_monitor_definition - fill monitor's definition
 *
 * Returns -1 on error, 1 if the monitor does not belong in the container, 0 otherwise.
 * container can be NULL
 */
static int ikm_fill_monitor_definition(char *name, struct monitor *ikm, char *container)
{
        int enabled;
        char *desc, *nested_name;

        nested_name = strstr(name, ":");
        if (nested_name) {
                /* it belongs in container if it starts with "container:" */
                if (container && strstr(name, container) != name)
                        return 1;
                *nested_name = '/';
                ++nested_name;
                ikm->nested = 1;
        } else {
                if (container)
                        return 1;
                nested_name = name;
                ikm->nested = 0;
        }

        enabled = ikm_read_enable(name);
        if (enabled < 0) {
                err_msg("ikm: monitor %s fail to read enable file, bug?\n", name);
                return -1;
        }

        desc = ikm_read_desc(name);
        if (!desc) {
                err_msg("ikm: monitor %s does not have desc file, bug?\n", name);
                return -1;
        }

        strncpy(ikm->name, nested_name, MAX_DA_NAME_LEN);
        ikm->enabled = enabled;
        strncpy(ikm->desc, desc, MAX_DESCRIPTION);

        free(desc);

        return 0;
}

/*
 * ikm_write_reactor - switch the reactor to *reactor
 *
 * Return the number or characters written, -1 on error.
 */
static int ikm_write_reactor(char *monitor_name, char *reactor)
{
        char path[MAX_PATH];
        int retval;

        snprintf(path, MAX_PATH, "rv/monitors/%s/reactors", monitor_name);
        retval = tracefs_instance_file_write(NULL, path, reactor);
        debug_msg("ikm: write \"%s\" reactors: %d\n", reactor, retval);

        return retval;
}

/*
 * ikm_read_reactor - read the reactors file
 *
 * Returns a dynamically allocated string with monitor's
 * available reactors, or NULL on error.
 */
static char *ikm_read_reactor(char *monitor_name)
{
        char path[MAX_PATH];
        char *reactors;

        snprintf(path, MAX_PATH, "rv/monitors/%s/reactors", monitor_name);
        reactors = tracefs_instance_file_read(NULL, path, NULL);
        if (!reactors) {
                err_msg("ikm: fail reading monitor's %s reactors file\n", monitor_name);
                return NULL;
        }

        return reactors;
}

/*
 * ikm_get_current_reactor - get the current enabled reactor
 *
 * Reads the reactors file and find the currently enabled
 * [reactor].
 *
 * Returns a dynamically allocated memory with the current
 * reactor. NULL otherwise.
 */
static char *ikm_get_current_reactor(char *monitor_name)
{
        char *reactors = ikm_read_reactor(monitor_name);
        char *curr_reactor = NULL;
        char *start;
        char *end;

        if (!reactors)
                return NULL;

        start = strstr(reactors, "[");
        if (!start)
                goto out_free;

        start++;

        end = strstr(start, "]");
        if (!end)
                goto out_free;

        *end = '\0';

        curr_reactor = calloc(strlen(start) + 1, sizeof(char));
        if (!curr_reactor)
                goto out_free;

        strncpy(curr_reactor, start, strlen(start));
        debug_msg("ikm: read current reactor %s\n", curr_reactor);

out_free:
        free(reactors);

        return curr_reactor;
}

static int ikm_has_id(char *monitor_name)
{
        char path[MAX_PATH];
        char *format;
        int has_id;

        snprintf(path, MAX_PATH, "events/rv/event_%s/format", monitor_name);
        format = tracefs_instance_file_read(NULL, path, NULL);
        if (!format) {
                err_msg("ikm: fail reading monitor's %s format event file\n", monitor_name);
                return -1;
        }

        /* print fmt: "%d: %s x %s -> %s %s", REC->id, ... */
        has_id = !!strstr(format, "REC->id");

        debug_msg("ikm: monitor %s has id: %s\n", monitor_name, has_id ? "yes" : "no");

        free(format);

        return has_id;
}

/**
 * ikm_list_monitors - list all available monitors
 *
 * Returns 0 on success, -1 otherwise.
 */
int ikm_list_monitors(char *container)
{
        char *available_monitors;
        struct monitor ikm = {0};
        char *curr, *next;
        int retval, list_monitor = 0;

        available_monitors = tracefs_instance_file_read(NULL, "rv/available_monitors", NULL);

        if (!available_monitors) {
                err_msg("ikm: available monitors is not available, is CONFIG_RV enabled?\n");
                return -1;
        }

        curr = available_monitors;
        do {
                next = strstr(curr, "\n");
                *next = '\0';

                retval = ikm_fill_monitor_definition(curr, &ikm, container);
                if (retval < 0)
                        err_msg("ikm: error reading %d in kernel monitor, skipping\n", curr);

                if (!retval) {
                        int indent = ikm.nested && !container;

                        list_monitor = 1;
                        printf("%s%-*s %s %s\n", indent ? " - " : "",
                               indent ? MAX_DA_NAME_LEN - 3 : MAX_DA_NAME_LEN,
                               ikm.name, ikm.desc, ikm.enabled ? "[ON]" : "[OFF]");
                }
                curr = ++next;

        } while (strlen(curr));

        if (!list_monitor) {
                if (container)
                        printf("-- No monitor found in container %s --\n", container);
                else
                        printf("-- No monitor found --\n");
        }

        free(available_monitors);

        return 0;
}

static void ikm_print_header(struct trace_seq *s)
{
        trace_seq_printf(s, "%16s-%-8s %5s %5s ", "<TASK>", "PID", "[CPU]", "TYPE");
        if (config_has_id)
                trace_seq_printf(s, "%8s ", "ID");

        trace_seq_printf(s, "%24s x %-24s -> %-24s %s\n",
                         "STATE",
                         "EVENT",
                         "NEXT_STATE",
                         "FINAL");

        trace_seq_printf(s, "%16s %-8s %5s %5s ", " | ", " | ", " | ", " | ");

        if (config_has_id)
                trace_seq_printf(s, "%8s ", " | ");

        trace_seq_printf(s, "%24s   %-24s    %-24s %s\n",
                         " | ",
                         " | ",
                         " | ",
                         "|");

}

/*
 * ikm_event_handler - callback to handle event events
 *
 * Called any time a rv:"monitor"_event events is generated.
 * It parses and prints event.
 */
static int
ikm_event_handler(struct trace_seq *s, struct tep_record *record,
                  struct tep_event *trace_event, void *context)
{
        /* if needed: struct trace_instance *inst = context; */
        char *state, *event, *next_state;
        unsigned long long final_state;
        unsigned long long pid;
        unsigned long long id;
        int val;
        bool missing_id;

        if (config_has_id)
                missing_id = tep_get_field_val(s, trace_event, "id", record, &id, 1);

        tep_get_common_field_val(s, trace_event, "common_pid", record, &pid, 1);

        if (config_has_id && (config_my_pid == id))
                return 0;
        else if (config_my_pid == pid)
                return 0;

        tep_print_event(trace_event->tep, s, record, "%16s-%-8d [%.3d] ",
                        TEP_PRINT_COMM, TEP_PRINT_PID, TEP_PRINT_CPU);

        if (config_is_container)
                tep_print_event(trace_event->tep, s, record, "%s ", TEP_PRINT_NAME);
        else
                trace_seq_printf(s, "event ");

        if (config_has_id) {
                if (missing_id)
                        /* placeholder if we are dealing with a mixed-type container*/
                        trace_seq_printf(s, "        ");
                else
                        trace_seq_printf(s, "%8llu ", id);
        }

        state = tep_get_field_raw(s, trace_event, "state", record, &val, 0);
        event = tep_get_field_raw(s, trace_event, "event", record, &val, 0);
        next_state = tep_get_field_raw(s, trace_event, "next_state", record, &val, 0);
        tep_get_field_val(s, trace_event, "final_state", record, &final_state, 1);

        trace_seq_printf(s, "%24s x %-24s -> %-24s %s\n",
                         state,
                         event,
                         next_state,
                         final_state ? "Y" : "N");

        trace_seq_do_printf(s);
        trace_seq_reset(s);

        return 0;
}

/*
 * ikm_error_handler - callback to handle error events
 *
 * Called any time a rv:"monitor"_errors events is generated.
 * It parses and prints event.
 */
static int
ikm_error_handler(struct trace_seq *s, struct tep_record *record,
                  struct tep_event *trace_event, void *context)
{
        unsigned long long pid, id;
        int cpu = record->cpu;
        char *state, *event;
        int val;
        bool missing_id;

        if (config_has_id)
                missing_id = tep_get_field_val(s, trace_event, "id", record, &id, 1);

        tep_get_common_field_val(s, trace_event, "common_pid", record, &pid, 1);

        if (config_has_id && config_my_pid == id)
                return 0;
        else if (config_my_pid == pid)
                return 0;

        trace_seq_printf(s, "%8lld [%03d] ", pid, cpu);

        if (config_is_container)
                tep_print_event(trace_event->tep, s, record, "%s ", TEP_PRINT_NAME);
        else
                trace_seq_printf(s, "error ");

        if (config_has_id) {
                if (missing_id)
                        /* placeholder if we are dealing with a mixed-type container*/
                        trace_seq_printf(s, "        ");
                else
                        trace_seq_printf(s, "%8llu ", id);
        }

        state = tep_get_field_raw(s, trace_event, "state", record, &val, 0);
        event = tep_get_field_raw(s, trace_event, "event", record, &val, 0);

        trace_seq_printf(s, "%24s x %s\n", state, event);

        trace_seq_do_printf(s);
        trace_seq_reset(s);

        return 0;
}

static int ikm_enable_trace_events(char *monitor_name, struct trace_instance *inst)
{
        char event[MAX_DA_NAME_LEN + 7]; /* max(error_,event_) + '0' = 7 */
        int retval;

        snprintf(event, sizeof(event), "event_%s", monitor_name);
        retval = tracefs_event_enable(inst->inst, "rv",  event);
        if (retval)
                return -1;

        tep_register_event_handler(inst->tep, -1, "rv", event,
                                   ikm_event_handler, NULL);

        snprintf(event, sizeof(event), "error_%s", monitor_name);
        retval = tracefs_event_enable(inst->inst, "rv", event);
        if (retval)
                return -1;

        tep_register_event_handler(inst->tep, -1, "rv", event,
                                   ikm_error_handler, NULL);

        /* set if at least 1 monitor has id in case of a container */
        config_has_id = ikm_has_id(monitor_name);
        if (config_has_id < 0)
                return -1;


        return 0;
}

static int ikm_enable_trace_container(char *monitor_name,
                                      struct trace_instance *inst)
{
        DIR *dp;
        char *abs_path, rv_path[MAX_PATH];
        struct dirent *ep;
        int retval = 0;

        snprintf(rv_path, MAX_PATH, "rv/monitors/%s", monitor_name);
        abs_path = tracefs_instance_get_file(NULL, rv_path);
        if (!abs_path)
                return -1;
        dp = opendir(abs_path);
        if (!dp)
                goto out_free;

        while (!retval && (ep = readdir(dp))) {
                if (ep->d_type != DT_DIR || ep->d_name[0] == '.')
                        continue;
                retval = ikm_enable_trace_events(ep->d_name, inst);
        }

        closedir(dp);
out_free:
        free(abs_path);
        return retval;
}

/*
 * ikm_setup_trace_instance - set up a tracing instance to collect data
 *
 * Create a trace instance, enable rv: events and enable the trace.
 *
 * Returns the trace_instance * with all set, NULL otherwise.
 */
static struct trace_instance *ikm_setup_trace_instance(char *monitor_name)
{
        struct trace_instance *inst;
        int retval;

        if (!config_trace)
                return NULL;

        /* alloc data */
        inst = calloc(1, sizeof(*inst));
        if (!inst) {
                err_msg("ikm: failed to allocate trace instance");
                goto out_err;
        }

        retval = trace_instance_init(inst, monitor_name);
        if (retval)
                goto out_free;

        if (config_is_container)
                retval = ikm_enable_trace_container(monitor_name, inst);
        else
                retval = ikm_enable_trace_events(monitor_name, inst);
        if (retval)
                goto out_inst;

        /* ready to enable */
        tracefs_trace_on(inst->inst);

        return inst;

out_inst:
        trace_instance_destroy(inst);
out_free:
        free(inst);
out_err:
        return NULL;
}

/**
 * ikm_destroy_trace_instance - destroy a previously created instance
 */
static void ikm_destroy_trace_instance(struct trace_instance *inst)
{
        if (!inst)
                return;

        trace_instance_destroy(inst);
        free(inst);
}

/*
 * ikm_usage_print_reactors - print all available reactors, one per line.
 */
static void ikm_usage_print_reactors(void)
{
        char *reactors = tracefs_instance_file_read(NULL, "rv/available_reactors", NULL);
        char *start, *end;

        if (!reactors)
                return;

        fprintf(stderr, "  available reactors:");

        start = reactors;
        end = strstr(start, "\n");

        while (end) {
                *end = '\0';

                fprintf(stderr, " %s", start);

                start = ++end;
                end = strstr(start, "\n");
        }

        fprintf(stderr, "\n");
}
/*
 * ikm_usage - print usage
 */
static void ikm_usage(int exit_val, char *monitor_name, const char *fmt, ...)
{

        char message[1024];
        va_list ap;
        int i;

        static const char *const usage[] = {
                "",
                "       -h/--help: print this menu and the reactor list",
                "       -r/--reactor 'reactor': enables the 'reactor'",
                "       -s/--self: when tracing (-t), also trace rv command",
                "       -t/--trace: trace monitor's event",
                "       -v/--verbose: print debug messages",
                "",
                NULL,
        };

        va_start(ap, fmt);
        vsnprintf(message, sizeof(message), fmt, ap);
        va_end(ap);

        fprintf(stderr, "  %s\n", message);

        fprintf(stderr, "\n  usage: rv mon %s [-h] [-q] [-r reactor] [-s] [-v]", monitor_name);

        for (i = 0; usage[i]; i++)
                fprintf(stderr, "%s\n", usage[i]);

        ikm_usage_print_reactors();
        exit(exit_val);
}

/*
 * parse_arguments - parse arguments and set config
 */
static int parse_arguments(char *monitor_name, int argc, char **argv)
{
        int c, retval;

        config_my_pid = getpid();

        while (1) {
                static struct option long_options[] = {
                        {"help",                no_argument,            0, 'h'},
                        {"reactor",             required_argument,      0, 'r'},
                        {"self",                no_argument,            0, 's'},
                        {"trace",               no_argument,            0, 't'},
                        {"verbose",             no_argument,            0, 'v'},
                        {0, 0, 0, 0}
                };

                /* getopt_long stores the option index here. */
                int option_index = 0;

                c = getopt_long(argc, argv, "hr:stv", long_options, &option_index);

                /* detect the end of the options. */
                if (c == -1)
                        break;

                switch (c) {
                case 'h':
                        ikm_usage(0, monitor_name, "help:");
                        break;
                case 'r':
                        config_reactor = optarg;
                        break;
                case 's':
                        config_my_pid = -1;
                        break;
                case 't':
                        config_trace = 1;
                        break;
                case 'v':
                        config_debug = 1;
                        break;
                }
        }

        if (config_reactor) {
                config_initial_reactor = ikm_get_current_reactor(monitor_name);
                if (!config_initial_reactor)
                        ikm_usage(1, monitor_name,
                                  "ikm: failed to read current reactor, are reactors enabled?");

                retval = ikm_write_reactor(monitor_name, config_reactor);
                if (retval <= 0)
                        ikm_usage(1, monitor_name,
                                  "ikm: failed to set %s reactor, is it available?",
                                  config_reactor);
        }

        debug_msg("ikm: my pid is %d\n", config_my_pid);

        return 0;
}

/**
 * ikm_run_monitor - apply configs and run the monitor
 *
 * Returns 1 if a monitor was found an executed, 0 if no
 * monitors were found, or -1 on error.
 */
int ikm_run_monitor(char *monitor_name, int argc, char **argv)
{
        struct trace_instance *inst = NULL;
        char *nested_name, full_name[2*MAX_DA_NAME_LEN];
        int retval;

        nested_name = strstr(monitor_name, ":");
        if (nested_name)
                ++nested_name;
        else
                nested_name = monitor_name;

        retval = __ikm_find_monitor_name(monitor_name, full_name);
        if (!retval)
                return 0;
        if (retval < 0) {
                err_msg("ikm: error finding monitor %s\n", nested_name);
                return -1;
        }

        retval = __ikm_read_enable(full_name);
        if (retval) {
                err_msg("ikm: monitor %s (in-kernel) is already enabled\n", nested_name);
                return -1;
        }

        /* we should be good to go */
        retval = parse_arguments(full_name, argc, argv);
        if (retval)
                ikm_usage(1, nested_name, "ikm: failed parsing arguments");

        if (config_trace) {
                inst = ikm_setup_trace_instance(nested_name);
                if (!inst)
                        return -1;
        }

        retval = ikm_enable(full_name);
        if (retval < 0)
                goto out_free_instance;

        if (config_trace)
                ikm_print_header(inst->seq);

        while (!should_stop()) {
                if (config_trace) {
                        retval = tracefs_iterate_raw_events(inst->tep,
                                                            inst->inst,
                                                            NULL,
                                                            0,
                                                            collect_registered_events,
                                                            inst);
                        if (retval) {
                                err_msg("ikm: error reading trace buffer\n");
                                break;
                        }
                }

                sleep(1);
        }

        ikm_disable(full_name);
        ikm_destroy_trace_instance(inst);

        if (config_reactor && config_initial_reactor)
                ikm_write_reactor(full_name, config_initial_reactor);

        return 1;

out_free_instance:
        ikm_destroy_trace_instance(inst);
        if (config_reactor && config_initial_reactor)
                ikm_write_reactor(full_name, config_initial_reactor);
        return -1;
}