/*-
 * SPDX-License-Identifier: MIT-CMU
 *
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */
/*
 *      Author: David B. Golub, Carnegie Mellon University
 *      Date:   7/90
 */
/*
 * Command dispatcher.
 */

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/cons.h>
#include <sys/eventhandler.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/linker_set.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/reboot.h>
#include <sys/signalvar.h>
#include <sys/systm.h>
#include <sys/watchdog.h>

#include <ddb/ddb.h>
#include <ddb/db_command.h>
#include <ddb/db_lex.h>
#include <ddb/db_output.h>

#include <machine/cpu.h>
#include <machine/setjmp.h>

#include <security/mac/mac_framework.h>

/*
 * Exported global variables
 */
int             db_cmd_loop_done;
db_addr_t       db_dot;
db_addr_t       db_last_addr;
db_addr_t       db_prev;
db_addr_t       db_next;

static db_cmdfcn_t      db_dump;
static db_cmdfcn_t      db_fncall;
static db_cmdfcn_t      db_gdb;
static db_cmdfcn_t      db_halt;
static db_cmdfcn_t      db_kill;
static db_cmdfcn_t      db_reset;
static db_cmdfcn_t      db_stack_trace;
static db_cmdfcn_t      db_stack_trace_active;
static db_cmdfcn_t      db_stack_trace_all;
static db_cmdfcn_t      db_watchdog;

#define DB_CMD(_name, _func, _flags)    \
{                                       \
        .name = (_name),                \
        .fcn =  (_func),                \
        .flag = (_flags),               \
        .more = NULL,                   \
}
#define DB_TABLE(_name, _more)          \
{                                       \
        .name = (_name),                \
        .fcn =  NULL,                   \
        .more = (_more),                \
}

static struct db_command db_show_active_cmds[] = {
        DB_CMD("trace",         db_stack_trace_active,  DB_CMD_MEMSAFE),
};
struct db_command_table db_show_active_table =
    LIST_HEAD_INITIALIZER(db_show_active_table);

static struct db_command db_show_all_cmds[] = {
        DB_CMD("trace",         db_stack_trace_all,     DB_CMD_MEMSAFE),
};
struct db_command_table db_show_all_table =
    LIST_HEAD_INITIALIZER(db_show_all_table);

static struct db_command db_show_cmds[] = {
        DB_TABLE("active",      &db_show_active_table),
        DB_TABLE("all",         &db_show_all_table),
        DB_CMD("registers",     db_show_regs,           DB_CMD_MEMSAFE),
        DB_CMD("breaks",        db_listbreak_cmd,       DB_CMD_MEMSAFE),
        DB_CMD("threads",       db_show_threads,        DB_CMD_MEMSAFE),
};
struct db_command_table db_show_table = LIST_HEAD_INITIALIZER(db_show_table);

static struct db_command db_cmds[] = {
        DB_TABLE("show",        &db_show_table),
        DB_CMD("print",         db_print_cmd,           0),
        DB_CMD("p",             db_print_cmd,           0),
        DB_CMD("examine",       db_examine_cmd,         CS_SET_DOT),
        DB_CMD("x",             db_examine_cmd,         CS_SET_DOT),
        DB_CMD("search",        db_search_cmd,          CS_OWN|CS_SET_DOT),
        DB_CMD("set",           db_set_cmd,             CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("write",         db_write_cmd,           CS_MORE|CS_SET_DOT),
        DB_CMD("w",             db_write_cmd,           CS_MORE|CS_SET_DOT),
        DB_CMD("delete",        db_delete_cmd,          0),
        DB_CMD("d",             db_delete_cmd,          0),
        DB_CMD("dump",          db_dump,                DB_CMD_MEMSAFE),
#ifdef HAS_HW_BREAKPOINT
        DB_CMD("dhbreak",       db_deletehbreak_cmd,    0),
        DB_CMD("hbreak",        db_hbreakpoint_cmd,     0),
#endif
        DB_CMD("break",         db_breakpoint_cmd,      0),
        DB_CMD("b",             db_breakpoint_cmd,      0),
        DB_CMD("dwatch",        db_deletewatch_cmd,     0),
        DB_CMD("watch",         db_watchpoint_cmd,      CS_MORE),
        DB_CMD("dhwatch",       db_deletehwatch_cmd,    0),
        DB_CMD("hwatch",        db_hwatchpoint_cmd,     0),
        DB_CMD("step",          db_single_step_cmd,     DB_CMD_MEMSAFE),
        DB_CMD("s",             db_single_step_cmd,     DB_CMD_MEMSAFE),
        DB_CMD("continue",      db_continue_cmd,        DB_CMD_MEMSAFE),
        DB_CMD("c",             db_continue_cmd,        DB_CMD_MEMSAFE),
        DB_CMD("until",         db_trace_until_call_cmd, DB_CMD_MEMSAFE),
        DB_CMD("next",          db_trace_until_matching_cmd, DB_CMD_MEMSAFE),
        DB_CMD("match",         db_trace_until_matching_cmd, 0),
        DB_CMD("trace",         db_stack_trace,         CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("t",             db_stack_trace,         CS_OWN|DB_CMD_MEMSAFE),
        /* XXX alias for active trace */
        DB_CMD("acttrace",      db_stack_trace_active,  DB_CMD_MEMSAFE),
        /* XXX alias for all trace */
        DB_CMD("alltrace",      db_stack_trace_all,     DB_CMD_MEMSAFE),
        DB_CMD("where",         db_stack_trace,         CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("bt",            db_stack_trace,         CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("call",          db_fncall,              CS_OWN),
        DB_CMD("ps",            db_ps,                  DB_CMD_MEMSAFE),
        DB_CMD("gdb",           db_gdb,                 0),
        DB_CMD("halt",          db_halt,                DB_CMD_MEMSAFE),
        DB_CMD("reboot",        db_reset,               DB_CMD_MEMSAFE),
        DB_CMD("reset",         db_reset,               DB_CMD_MEMSAFE),
        DB_CMD("kill",          db_kill,                CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("watchdog",      db_watchdog,            CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("thread",        db_set_thread,          0),
        DB_CMD("run",           db_run_cmd,             CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("script",        db_script_cmd,          CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("scripts",       db_scripts_cmd,         DB_CMD_MEMSAFE),
        DB_CMD("unscript",      db_unscript_cmd,        CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("capture",       db_capture_cmd,         CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("textdump",      db_textdump_cmd,        CS_OWN|DB_CMD_MEMSAFE),
        DB_CMD("findstack",     db_findstack_cmd,       0),
        DB_CMD("pprint",        db_pprint_cmd,          CS_OWN),
};
struct db_command_table db_cmd_table = LIST_HEAD_INITIALIZER(db_cmd_table);

#undef DB_CMD
#undef DB_TABLE

static struct db_command *db_last_command = NULL;

/*
 * if 'ed' style: 'dot' is set at start of last item printed,
 * and '+' points to next line.
 * Otherwise: 'dot' points to next item, '..' points to last.
 */
static bool     db_ed_style = true;

/*
 * Utility routine - discard tokens through end-of-line.
 */
void
db_skip_to_eol(void)
{
        int t;

        do {
                t = db_read_token();
        } while (t != tEOL);
}

/*
 * Results of command search.
 */
#define CMD_UNIQUE      0
#define CMD_FOUND       1
#define CMD_NONE        2
#define CMD_AMBIGUOUS   3
#define CMD_HELP        4

static void     db_cmd_match(char *name, struct db_command *cmd,
                    struct db_command **cmdp, int *resultp);
static void     db_cmd_list(struct db_command_table *table);
static int      db_cmd_search(char *name, struct db_command_table *table,
                    struct db_command **cmdp);
static void     db_command(struct db_command **last_cmdp,
                    struct db_command_table *cmd_table, bool dopager);

/*
 * Initialize the command lists from the static tables.
 */
void
db_command_init(void)
{
        int i;

        for (i = 0; i < nitems(db_cmds); i++)
                db_command_register(&db_cmd_table, &db_cmds[i]);
        for (i = 0; i < nitems(db_show_cmds); i++)
                db_command_register(&db_show_table, &db_show_cmds[i]);
        for (i = 0; i < nitems(db_show_active_cmds); i++)
                db_command_register(&db_show_active_table,
                    &db_show_active_cmds[i]);
        for (i = 0; i < nitems(db_show_all_cmds); i++)
                db_command_register(&db_show_all_table, &db_show_all_cmds[i]);
}

/*
 * Register a command.
 */
void
db_command_register(struct db_command_table *list, struct db_command *cmd)
{
        struct db_command *c, *last;

#ifdef MAC
        if (mac_ddb_command_register(list, cmd)) {
                printf("%s: MAC policy refused registration of command %s\n",
                    __func__, cmd->name);
                return;
        }
#endif
        last = NULL;
        LIST_FOREACH(c, list, next) {
                int n = strcmp(cmd->name, c->name);

                /* Check that the command is not already present. */
                if (n == 0) {
                        printf("%s: Warning, the command \"%s\" already exists;"
                             " ignoring request\n", __func__, cmd->name);
                        return;
                }
                if (n < 0) {
                        /* NB: keep list sorted lexicographically */
                        LIST_INSERT_BEFORE(c, cmd, next);
                        return;
                }
                last = c;
        }
        if (last == NULL)
                LIST_INSERT_HEAD(list, cmd, next);
        else
                LIST_INSERT_AFTER(last, cmd, next);
}

/*
 * Remove a command previously registered with db_command_register.
 */
void
db_command_unregister(struct db_command_table *list, struct db_command *cmd)
{
        struct db_command *c;

        LIST_FOREACH(c, list, next) {
                if (cmd == c) {
                        LIST_REMOVE(cmd, next);
                        return;
                }
        }
        /* NB: intentionally quiet */
}

/*
 * Helper function to match a single command.
 */
static void
db_cmd_match(char *name, struct db_command *cmd, struct db_command **cmdp,
    int *resultp)
{
        char *lp, *rp;
        int c;

        lp = name;
        rp = cmd->name;
        while ((c = *lp) == *rp) {
                if (c == 0) {
                        /* complete match */
                        *cmdp = cmd;
                        *resultp = CMD_UNIQUE;
                        return;
                }
                lp++;
                rp++;
        }
        if (c == 0) {
                /* end of name, not end of command -
                   partial match */
                if (*resultp == CMD_FOUND) {
                        *resultp = CMD_AMBIGUOUS;
                        /* but keep looking for a full match -
                           this lets us match single letters */
                } else if (*resultp == CMD_NONE) {
                        *cmdp = cmd;
                        *resultp = CMD_FOUND;
                }
        }
}

/*
 * Search for command prefix.
 */
static int
db_cmd_search(char *name, struct db_command_table *table,
    struct db_command **cmdp)
{
        struct db_command *cmd;
        int result = CMD_NONE;

        LIST_FOREACH(cmd, table, next) {
                db_cmd_match(name,cmd,cmdp,&result);
                if (result == CMD_UNIQUE)
                        break;
        }

        if (result == CMD_NONE) {
                /* check for 'help' */
                if (name[0] == 'h' && name[1] == 'e'
                    && name[2] == 'l' && name[3] == 'p')
                        result = CMD_HELP;
        }
        return (result);
}

static void
db_cmd_list(struct db_command_table *table)
{
        struct db_command *cmd;
        int have_subcommands;

        have_subcommands = 0;
        LIST_FOREACH(cmd, table, next) {
                if (cmd->more != NULL)
                        have_subcommands++;
                db_printf("%-16s", cmd->name);
                db_end_line(16);
        }

        if (have_subcommands > 0) {
                db_printf("\nThe following have subcommands; append \"help\" "
                    "to list (e.g. \"show help\"):\n");
                LIST_FOREACH(cmd, table, next) {
                        if (cmd->more == NULL)
                                continue;
                        db_printf("%-16s", cmd->name);
                        db_end_line(16);
                }
        }
}

static void
db_command(struct db_command **last_cmdp, struct db_command_table *cmd_table,
    bool dopager)
{
        char modif[TOK_STRING_SIZE];
        struct db_command *cmd = NULL;
        db_expr_t addr, count;
        int t, result;
        bool have_addr = false;

        t = db_read_token();
        if (t == tEOL) {
                /* empty line repeats last command, at 'next' */
                cmd = *last_cmdp;
                addr = (db_expr_t)db_next;
                have_addr = false;
                count = 1;
                modif[0] = '\0';
        } else if (t == tEXCL) {
                db_fncall((db_expr_t)0, false, (db_expr_t)0, NULL);
                return;
        } else if (t != tIDENT) {
                db_printf("Unrecognized input; use \"help\" "
                    "to list available commands\n");
                db_flush_lex();
                return;
        } else {
                /*
                 * Search for command
                 */
                while (cmd_table != NULL) {
                        result = db_cmd_search(db_tok_string, cmd_table, &cmd);
                        switch (result) {
                        case CMD_NONE:
                                db_printf("No such command; use \"help\" "
                                    "to list available commands\n");
                                db_flush_lex();
                                return;
                        case CMD_AMBIGUOUS:
                                db_printf("Ambiguous\n");
                                db_flush_lex();
                                return;
                        case CMD_HELP:
                                if (cmd_table == &db_cmd_table) {
                                        db_printf("This is ddb(4), the kernel debugger; "
                                            "see https://man.FreeBSD.org/ddb/4 for help.\n");
                                        db_printf("Use \"bt\" for backtrace, \"dump\" for "
                                            "kernel core dump, \"reset\" to reboot.\n");
                                        db_printf("Available commands:\n");
                                }
                                db_cmd_list(cmd_table);
                                db_flush_lex();
                                return;
                        case CMD_UNIQUE:
                        case CMD_FOUND:
                                break;
                        }
                        if ((cmd_table = cmd->more) != NULL) {
                                t = db_read_token();
                                if (t != tIDENT) {
                                        db_printf("Subcommand required; "
                                            "available subcommands:\n");
                                        db_cmd_list(cmd_table);
                                        db_flush_lex();
                                        return;
                                }
                        }
                }

                if ((cmd->flag & CS_OWN) == 0) {
                        /*
                         * Standard syntax:
                         * command [/modifier] [addr] [,count]
                         */
                        t = db_read_token();
                        if (t == tSLASH) {
                                t = db_read_token();
                                if (t != tIDENT) {
                                        db_printf("Bad modifier\n");
                                        db_flush_lex();
                                        return;
                                }
                                db_strcpy(modif, db_tok_string);
                        } else {
                                db_unread_token(t);
                                modif[0] = '\0';
                        }

                        if (db_expression(&addr)) {
                                db_dot = (db_addr_t) addr;
                                db_last_addr = db_dot;
                                have_addr = true;
                        } else {
                                addr = (db_expr_t) db_dot;
                                have_addr = false;
                        }

                        t = db_read_token();
                        if (t == tCOMMA) {
                                if (!db_expression(&count)) {
                                        db_printf("Count missing\n");
                                        db_flush_lex();
                                        return;
                                }
                        } else {
                                db_unread_token(t);
                                count = -1;
                        }

                        if ((cmd->flag & CS_MORE) == 0) {
                                db_skip_to_eol();
                        }
                }
        }

        *last_cmdp = cmd;
        if (cmd != NULL) {
#ifdef MAC
                if (mac_ddb_command_exec(cmd, addr, have_addr, count, modif)) {
                        db_printf("MAC prevented execution of command %s\n",
                            cmd->name);
                        return;
                }
#endif
                /*
                 * Execute the command.
                 */
                if (dopager)
                        db_enable_pager();
                else
                        db_disable_pager();
                (*cmd->fcn)(addr, have_addr, count, modif);
                if (dopager)
                        db_disable_pager();

                if (cmd->flag & CS_SET_DOT) {
                        /*
                         * If command changes dot, set dot to previous address
                         * displayed (if 'ed' style).
                         */
                        db_dot = db_ed_style ? db_prev : db_next;
                } else {
                        /*
                         * If command does not change dot, set 'next' location
                         * to be the same.
                         */
                        db_next = db_dot;
                }
        }
}

/*
 * At least one non-optional command must be implemented using
 * DB_COMMAND() so that db_cmd_set gets created.  Here is one.
 */
DB_COMMAND_FLAGS(panic, db_panic, DB_CMD_MEMSAFE)
{
        db_disable_pager();
        panic("from debugger");
}

void
db_command_loop(void)
{
        /*
         * Initialize 'prev' and 'next' to dot.
         */
        db_prev = db_dot;
        db_next = db_dot;

        db_cmd_loop_done = 0;
        while (!db_cmd_loop_done) {
                if (db_print_position() != 0)
                        db_printf("\n");

                db_printf("db> ");
                (void)db_read_line();

                db_command(&db_last_command, &db_cmd_table, /* dopager */ true);
        }
}

/*
 * Execute a command on behalf of a script.  The caller is responsible for
 * making sure that the command string is < DB_MAXLINE or it will be
 * truncated.
 *
 * XXXRW: Runs by injecting faked input into DDB input stream; it would be
 * nicer to use an alternative approach that didn't mess with the previous
 * command buffer.
 */
void
db_command_script(const char *command)
{
        db_prev = db_next = db_dot;
        db_inject_line(command);
        db_command(&db_last_command, &db_cmd_table, /* dopager */ false);
}

void
db_error(const char *s)
{
        if (s)
            db_printf("%s", s);
        db_flush_lex();
        kdb_reenter_silent();
        panic("%s: did not reenter debugger", __func__);
}

static void
db_dump(db_expr_t dummy, bool dummy2, db_expr_t dummy3, char *dummy4)
{
        int error;

        if (textdump_pending) {
                db_printf("textdump_pending set.\n"
                    "run \"textdump unset\" first or \"textdump dump\" for a textdump.\n");
                return;
        }
        error = doadump(false);
        if (error) {
                db_printf("Cannot dump: ");
                switch (error) {
                case EBUSY:
                        db_printf("debugger got invoked while dumping.\n");
                        break;
                case ENXIO:
                        db_printf("no dump device specified.\n");
                        break;
                default:
                        db_printf("unknown error (error=%d).\n", error);
                        break;
                }
        }
}

/*
 * Call random function:
 * !expr(arg,arg,arg)
 */

/* The generic implementation supports a maximum of 10 arguments. */
typedef db_expr_t __db_f(db_expr_t, db_expr_t, db_expr_t, db_expr_t,
    db_expr_t, db_expr_t, db_expr_t, db_expr_t, db_expr_t, db_expr_t);

static __inline int
db_fncall_generic(db_expr_t addr, db_expr_t *rv, int nargs, db_expr_t args[])
{
        __db_f *f = (__db_f *)addr;

        if (nargs > 10) {
                db_printf("Too many arguments (max 10)\n");
                return (0);
        }
        *rv = (*f)(args[0], args[1], args[2], args[3], args[4], args[5],
            args[6], args[7], args[8], args[9]);
        return (1);
}

static void
db_fncall(db_expr_t dummy1, bool dummy2, db_expr_t dummy3, char *dummy4)
{
        db_expr_t       fn_addr;
        db_expr_t       args[DB_MAXARGS];
        int             nargs = 0;
        db_expr_t       retval;
        int             t;

        if (!db_expression(&fn_addr)) {
            db_printf("Bad function\n");
            db_flush_lex();
            return;
        }

        t = db_read_token();
        if (t == tLPAREN) {
            if (db_expression(&args[0])) {
                nargs++;
                while ((t = db_read_token()) == tCOMMA) {
                    if (nargs == DB_MAXARGS) {
                        db_printf("Too many arguments (max %d)\n", DB_MAXARGS);
                        db_flush_lex();
                        return;
                    }
                    if (!db_expression(&args[nargs])) {
                        db_printf("Argument missing\n");
                        db_flush_lex();
                        return;
                    }
                    nargs++;
                }
                db_unread_token(t);
            }
            if (db_read_token() != tRPAREN) {
                db_printf("Mismatched parens\n");
                db_flush_lex();
                return;
            }
        }
        db_skip_to_eol();
        db_disable_pager();

        if (DB_CALL(fn_addr, &retval, nargs, args))
                db_printf("= %#lr\n", (long)retval);
}

static void
db_halt(db_expr_t dummy, bool dummy2, db_expr_t dummy3, char *dummy4)
{

        cpu_halt();
}

static void
db_kill(db_expr_t dummy1, bool dummy2, db_expr_t dummy3, char *dummy4)
{
        db_expr_t old_radix, pid, sig;
        struct proc *p;

#define DB_ERROR(f)     do { db_printf f; db_flush_lex(); goto out; } while (0)

        /*
         * PIDs and signal numbers are typically represented in base
         * 10, so make that the default here.  It can, of course, be
         * overridden by specifying a prefix.
         */
        old_radix = db_radix;
        db_radix = 10;
        /* Retrieve arguments. */
        if (!db_expression(&sig))
                DB_ERROR(("Missing signal number\n"));
        if (!db_expression(&pid))
                DB_ERROR(("Missing process ID\n"));
        db_skip_to_eol();
        if (!_SIG_VALID(sig))
                DB_ERROR(("Signal number out of range\n"));

        /*
         * Find the process in question.  allproc_lock is not needed
         * since we're in DDB.
         */
        /* sx_slock(&allproc_lock); */
        FOREACH_PROC_IN_SYSTEM(p)
            if (p->p_pid == pid)
                    break;
        /* sx_sunlock(&allproc_lock); */
        if (p == NULL)
                DB_ERROR(("Can't find process with pid %ld\n", (long) pid));

        /* If it's already locked, bail; otherwise, do the deed. */
        if (PROC_TRYLOCK(p) == 0)
                DB_ERROR(("Can't lock process with pid %ld\n", (long) pid));
        else {
                pksignal(p, sig, NULL);
                PROC_UNLOCK(p);
        }

out:
        db_radix = old_radix;
#undef DB_ERROR
}

/*
 * Reboot.  In case there is an additional argument, take it as delay in
 * seconds.  Default to 15s if we cannot parse it and make sure we will
 * never wait longer than 1 week.  Some code is similar to
 * kern_shutdown.c:shutdown_panic().
 */
#ifndef DB_RESET_MAXDELAY
#define DB_RESET_MAXDELAY       (3600 * 24 * 7)
#endif

static void
db_reset(db_expr_t addr, bool have_addr, db_expr_t count __unused,
    char *modif)
{
        int delay, loop;

        if (have_addr) {
                delay = (int)db_hex2dec(addr);

                /* If we parse to fail, use 15s. */
                if (delay == -1)
                        delay = 15;

                /* Cap at one week. */
                if ((uintmax_t)delay > (uintmax_t)DB_RESET_MAXDELAY)
                        delay = DB_RESET_MAXDELAY;

                db_printf("Automatic reboot in %d seconds - "
                    "press a key on the console to abort\n", delay);
                for (loop = delay * 10; loop > 0; --loop) {
                        DELAY(1000 * 100); /* 1/10th second */
                        /* Did user type a key? */
                        if (cncheckc() != -1)
                                return;
                }
        }

        /*
         * Conditionally try the standard reboot path, so any registered
         * shutdown/reset handlers have a chance to run first. Some platforms
         * may not support the machine-dependent mechanism used by cpu_reset()
         * and rely on some other non-standard mechanism to perform the reset.
         * For example, the BCM2835 watchdog driver or gpio-poweroff driver.
         */
        if (modif[0] != 's') {
                kern_reboot(RB_NOSYNC);
                /* NOTREACHED */
        }

        cpu_reset();
}

static void
db_watchdog(db_expr_t dummy1, bool dummy2, db_expr_t dummy3, char *dummy4)
{
        db_expr_t old_radix, tout;
        int err, i;

        old_radix = db_radix;
        db_radix = 10;
        err = db_expression(&tout);
        db_skip_to_eol();
        db_radix = old_radix;

        /* If no argument is provided the watchdog will just be disabled. */
        if (err == 0) {
                db_printf("No argument provided, disabling watchdog\n");
                tout = 0;
        } else if ((tout & WD_INTERVAL) == WD_TO_NEVER) {
                db_error("Out of range watchdog interval\n");
                return;
        }
        EVENTHANDLER_INVOKE(watchdog_list, tout, &i);
}

static void
db_gdb(db_expr_t dummy1, bool dummy2, db_expr_t dummy3, char *dummy4)
{

        if (kdb_dbbe_select("gdb") != 0) {
                db_printf("The remote GDB backend could not be selected.\n");
                return;
        }
        /*
         * Mark that we are done in the debugger.  kdb_trap()
         * should re-enter with the new backend.
         */
        db_cmd_loop_done = 1;
        db_printf("(ctrl-c will return control to ddb)\n");
}

static void
db_stack_trace(db_expr_t tid, bool hastid, db_expr_t count, char *modif)
{
        struct thread *td;
        db_expr_t radix;
        pid_t pid;
        int t;

        /*
         * We parse our own arguments. We don't like the default radix.
         */
        radix = db_radix;
        db_radix = 10;
        hastid = db_expression(&tid);
        t = db_read_token();
        if (t == tCOMMA) {
                if (!db_expression(&count)) {
                        db_printf("Count missing\n");
                        db_flush_lex();
                        db_radix = radix;
                        return;
                }
        } else {
                db_unread_token(t);
                count = -1;
        }
        db_skip_to_eol();
        db_radix = radix;

        if (hastid) {
                td = kdb_thr_lookup((lwpid_t)tid);
                if (td == NULL)
                        td = kdb_thr_from_pid((pid_t)tid);
                if (td == NULL) {
                        db_printf("Thread %d not found\n", (int)tid);
                        return;
                }
        } else
                td = kdb_thread;
        if (td->td_proc != NULL)
                pid = td->td_proc->p_pid;
        else
                pid = -1;
        db_printf("Tracing pid %d tid %ld td %p\n", pid, (long)td->td_tid, td);
        db_trace_thread(td, count);
}

static void
_db_stack_trace_all(bool active_only)
{
        struct thread *td;
        jmp_buf jb;
        void *prev_jb;

        for (td = kdb_thr_first(); td != NULL; td = kdb_thr_next(td)) {
                prev_jb = kdb_jmpbuf(jb);
                if (setjmp(jb) == 0) {
                        if (TD_IS_RUNNING(td))
                                db_printf("\nTracing command %s pid %d"
                                    " tid %ld td %p (CPU %d)\n",
                                    td->td_proc->p_comm, td->td_proc->p_pid,
                                    (long)td->td_tid, td, td->td_oncpu);
                        else if (active_only)
                                continue;
                        else
                                db_printf("\nTracing command %s pid %d"
                                    " tid %ld td %p\n", td->td_proc->p_comm,
                                    td->td_proc->p_pid, (long)td->td_tid, td);
                        db_trace_thread(td, -1);
                        if (db_pager_quit) {
                                kdb_jmpbuf(prev_jb);
                                return;
                        }
                }
                kdb_jmpbuf(prev_jb);
        }
}

static void
db_stack_trace_active(db_expr_t dummy, bool dummy2, db_expr_t dummy3,
    char *dummy4)
{

        _db_stack_trace_all(true);
}

static void
db_stack_trace_all(db_expr_t dummy, bool dummy2, db_expr_t dummy3,
    char *dummy4)
{

        _db_stack_trace_all(false);
}

/*
 * Take the parsed expression value from the command line that was parsed
 * as a hexadecimal value and convert it as if the expression was parsed
 * as a decimal value.  Returns -1 if the expression was not a valid
 * decimal value.
 */
db_expr_t
db_hex2dec(db_expr_t expr)
{
        uintptr_t x, y;
        db_expr_t val;

        y = 1;
        val = 0;
        x = expr;
        while (x != 0) {
                if (x % 16 > 9)
                        return (-1);
                val += (x % 16) * (y);
                x >>= 4;
                y *= 10;
        }
        return (val);
}