src/debugger/debugger.c

/*
 *  Copyright (C) 2004-2006  Anders Gavare.  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright  
 *     notice, this list of conditions and the following disclaimer in the 
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 *  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE   
 *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 *  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *  SUCH DAMAGE.
 *
 *
 *  $Id: debugger.c,v 1.10 2006/06/16 18:31:26 debug Exp $
 *
 *  Single-step debugger.
 *
 *
 *  TODO:
 *
 *      This entire module is very much non-reentrant. :-/
 *
 *      Add more functionality that already exists elsewhere in the emulator.
 *
 *      Call stack display (back-trace)?
 *
 *      More generic expression evaluator (for example + - * / between multiple
 *      terms), including _TAB COMPLETION_ of symbols and register names!
 *      Must be possible to reach any emul, any machine in any emul, any
 *      cpu in any machine, other variables in the emulator, and so forth.
 *      Perhaps a "settable variables registry" somewhere?
 *
 *      Nicer looking output of register dumps, floating point registers,
 *      etc. Warn about weird/invalid register contents.
 *
 *      Ctrl-C doesn't enter the debugger on some OSes (HP-UX?)...
 *
 *      Many other TODOs.
 */

#include <ctype.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "console.h"
#include "cpu.h"
#include "device.h"
#include "debugger.h"
#include "debugger_gdb.h"
#include "diskimage.h"
#include "emul.h"
#include "machine.h"
#include "memory.h"
#include "misc.h"
#include "net.h"
#include "settings.h"
#include "x11.h"


extern int extra_argc;
extern char **extra_argv;
extern struct settings *global_settings;
extern int quiet_mode;


/*
 *  Global debugger variables:
 *
 *  TODO: Some of these should be moved to some other place!
 */

volatile int single_step = 0;
volatile int exit_debugger;
int force_debugger_at_exit = 0;
int show_opcode_statistics = 0;

volatile int single_step_breakpoint = 0;
int debugger_n_steps_left_before_interaction = 0;

int old_instruction_trace = 0;
int old_quiet_mode = 0;
int old_show_trace_tree = 0;


/*
 *  Private (global) debugger variables:
 */

static volatile int ctrl_c;

static int debugger_n_emuls;
static struct emul **debugger_emuls;
static struct emul *debugger_emul;
static struct machine *debugger_machine;

#define MAX_CMD_BUFLEN          72
#define N_PREVIOUS_CMDS         150
static char *last_cmd[N_PREVIOUS_CMDS];
static int last_cmd_index;

static char repeat_cmd[MAX_CMD_BUFLEN];

#define MAGIC_UNTOUCHED         0x98ca76c2ffcc0011ULL

static uint64_t last_dump_addr = MAGIC_UNTOUCHED;
static uint64_t last_unasm_addr = MAGIC_UNTOUCHED;


/*
 *  debugger_readchar():
 */
char debugger_readchar(void)
{
        int ch, i, j;

        while ((ch = console_readchar(MAIN_CONSOLE)) < 0 && !exit_debugger) {
                /*  Check for X11 events:  */
                x11_check_event(debugger_emuls, debugger_n_emuls);

                /*  Check for incoming GDB packets:  */
                for (i=0; i<debugger_n_emuls; i++) {
                        struct emul *e = debugger_emuls[i];
                        if (e == NULL)
                                continue;

                        for (j=0; j<e->n_machines; j++) {
                                if (e->machines[j]->gdb.port > 0)
                                        debugger_gdb_check_incoming(
                                            e->machines[j]);
                        }
                }

                /*  TODO: The X11 and GDB checks above should probably
                        be factored out...  */

                /*  Give up some CPU time:  */
                usleep(1);
        }
        return ch;
}


/*
 *  debugger_activate():
 *
 *  This is a signal handler for CTRL-C.  It shouldn't be called directly,
 *  but setup code in emul.c sets the CTRL-C signal handler to use this
 *  function.
 */
void debugger_activate(int x)
{
        ctrl_c = 1;

        if (single_step) {
                /*  Already in the debugger. Do nothing.  */
                int i;
                for (i=0; i<MAX_CMD_BUFLEN; i++)
                        console_makeavail(MAIN_CONSOLE, '\b');
                console_makeavail(MAIN_CONSOLE, ' ');
                console_makeavail(MAIN_CONSOLE, '\n');
                printf("^C");
                fflush(stdout);
        } else {
                /*  Enter the single step debugger.  */
                single_step = 1;

                /*  Discard any chars in the input queue:  */
                while (console_charavail(MAIN_CONSOLE))
                        console_readchar(MAIN_CONSOLE);
        }

        /*  Clear the repeat-command buffer:  */
        repeat_cmd[0] = '\0';

        /*  Reactivate the signal handler:  */
        signal(SIGINT, debugger_activate);
}


/*
 *  debugger_parse_name():
 *
 *  This function reads a string, and tries to match it to a register name,
 *  a symbol, or treat it as a decimal numeric value.
 *
 *  Some examples:
 *
 *      "0x7fff1234"            ==> numeric value (hex, in this case)
 *      "pc", "r5", "hi", "t4"  ==> register (CPU dependent)
 *      "memcpy+64"             ==> symbol (plus offset)
 *
 *  Register names can be preceeded by "x:" where x is the CPU number. (CPU
 *  0 is assumed by default.)
 *
 *  To force detection of different types, a character can be added in front of
 *  the name: "$" for numeric values, "%" for registers, and "@" for symbols.
 *
 *  Return value is:
 *
 *      NAME_PARSE_NOMATCH      no match
 *      NAME_PARSE_MULTIPLE     multiple matches
 *
 *  or one of these (and then *valuep is read or written, depending on
 *  the writeflag):
 *
 *      NAME_PARSE_REGISTER     a register
 *      NAME_PARSE_NUMBER       a hex number
 *      NAME_PARSE_SYMBOL       a symbol
 */
#define NAME_PARSE_NOMATCH      0
#define NAME_PARSE_MULTIPLE     1
#define NAME_PARSE_REGISTER     2
#define NAME_PARSE_NUMBER       3
#define NAME_PARSE_SYMBOL       4
static int debugger_parse_name(struct machine *m, char *name, int writeflag,
        uint64_t *valuep)
{
        int match_register = 0, match_symbol = 0, match_numeric = 0;
        int skip_register, skip_numeric, skip_symbol;

        if (m == NULL || name == NULL) {
                fprintf(stderr, "debugger_parse_name(): NULL ptr\n");
                exit(1);
        }

        /*  Warn about non-signextended values:  */
        if (writeflag) {
                if (m->cpus[0]->is_32bit) {
                        /*  Automagically sign-extend.  TODO: Is this good?  */
                        if (((*valuep) >> 32) == 0 && (*valuep) & 0x80000000ULL)
                                (*valuep) |= 0xffffffff00000000ULL;
                } else {
                        if (((*valuep) >> 32) == 0 && (*valuep) & 0x80000000ULL)
                                printf("WARNING: The value is not sign-extende"
                                    "d. Is this what you intended?\n");
                }
        }

        skip_register = name[0] == '$' || name[0] == '@';
        skip_numeric  = name[0] == '%' || name[0] == '@';
        skip_symbol   = name[0] == '$' || name[0] == '%';

        /*  Check for a register match:  */
        if (!skip_register && strlen(name) >= 1)
                cpu_register_match(m, name, writeflag, valuep,
                    &match_register);

        /*  Check for a number match:  */
        if (!skip_numeric && isdigit((int)name[0])) {
                uint64_t x;
                x = strtoull(name, NULL, 0);
                if (writeflag) {
                        printf("You cannot assign like that.\n");
                } else
                        *valuep = x;
                match_numeric = 1;
        }

        /*  Check for a symbol match:  */
        if (!skip_symbol) {
                int res;
                char *p, *sn;
                uint64_t newaddr, ofs = 0;

                sn = malloc(strlen(name) + 1);
                if (sn == NULL) {
                        fprintf(stderr, "out of memory in debugger\n");
                        exit(1);
                }
                strlcpy(sn, name, strlen(name)+1);

                /*  Is there a '+' in there? Then treat that as an offset:  */
                p = strchr(sn, '+');
                if (p != NULL) {
                        *p = '\0';
                        ofs = strtoull(p+1, NULL, 0);
                }

                res = get_symbol_addr(&m->symbol_context, sn, &newaddr);
                if (res) {
                        if (writeflag) {
                                printf("You cannot assign like that.\n");
                        } else
                                *valuep = newaddr + ofs;
                        match_symbol = 1;
                }

                free(sn);
        }

        if (match_register + match_symbol + match_numeric > 1)
                return NAME_PARSE_MULTIPLE;

        if (match_register)
                return NAME_PARSE_REGISTER;
        if (match_numeric)
                return NAME_PARSE_NUMBER;
        if (match_symbol)
                return NAME_PARSE_SYMBOL;

        return NAME_PARSE_NOMATCH;
}


/*
 *  show_breakpoint():
 */
static void show_breakpoint(struct machine *m, int i)
{
        printf("%3i: 0x", i);
        if (m->cpus[0]->is_32bit)
                printf("%08"PRIx32, (uint32_t) m->breakpoint_addr[i]);
        else
                printf("%016"PRIx64, (uint64_t) m->breakpoint_addr[i]);
        if (m->breakpoint_string[i] != NULL)
                printf(" (%s)", m->breakpoint_string[i]);
        if (m->breakpoint_flags[i])
                printf(": flags=0x%x", m->breakpoint_flags[i]);
        printf("\n");
}


/****************************************************************************/


#include "debugger_cmds.c"


/****************************************************************************/


/*
 *  debugger_assignment():
 *
 *  cmd contains something like "pc=0x80001000", or "r31=memcpy+0x40".
 */
void debugger_assignment(struct machine *m, char *cmd)
{
        char *left, *right;
        int res_left, res_right;
        uint64_t tmp;
        uint64_t old_pc = m->cpus[0]->pc;       /*  TODO: multiple cpus?  */

        left  = malloc(MAX_CMD_BUFLEN);
        if (left == NULL) {
                fprintf(stderr, "out of memory in debugger_assignment()\n");
                exit(1);
        }
        strlcpy(left, cmd, MAX_CMD_BUFLEN);
        right = strchr(left, '=');
        if (right == NULL) {
                fprintf(stderr, "internal error in the debugger\n");
                exit(1);
        }
        *right = '\0';

        /*  Remove trailing spaces in left:  */
        while (strlen(left) >= 1 && left[strlen(left)-1] == ' ')
                left[strlen(left)-1] = '\0';

        /*  Remove leading spaces in right:  */
        right++;
        while (*right == ' ' && *right != '\0')
                right++;

        /*  printf("left  = '%s'\nright = '%s'\n", left, right);  */

        res_right = debugger_parse_name(m, right, 0, &tmp);
        switch (res_right) {
        case NAME_PARSE_NOMATCH:
                printf("No match for the right-hand side of the assignment.\n");
                break;
        case NAME_PARSE_MULTIPLE:
                printf("Multiple matches for the right-hand side of the "
                    "assignment.\n");
                break;
        default:
                res_left = debugger_parse_name(m, left, 1, &tmp);
                switch (res_left) {
                case NAME_PARSE_NOMATCH:
                        printf("No match for the left-hand side of the "
                            "assignment.\n");
                        break;
                case NAME_PARSE_MULTIPLE:
                        printf("Multiple matches for the left-hand side "
                            "of the assignment.\n");
                        break;
                default:
                        debugger_cmd_print(m, left);
                }
        }

        /*
         *  If the PC has changed, then release any breakpoint we were
         *  currently stopped at.
         *
         *  TODO: multiple cpus?
         */
        if (old_pc != m->cpus[0]->pc)
                single_step_breakpoint = 0;

        free(left);
}


/*
 *  debugger_execute_cmd():
 */
void debugger_execute_cmd(char *cmd, int cmd_len)
{
        int i, n, i_match, matchlen;

        /*
         *  Is there a '=' on the command line? Then try to do an
         *  assignment.  (Only if there is just one word, followed
         *  by the '=' sign. This makes it possible to use commands
         *  such as "device add name addr=xyz".)
         */
        if (strchr(cmd, '=') != NULL) {
                /*  Count the nr of words:  */
                int nw = 0, inword = 0;
                char *p = cmd;
                while (*p) {
                        if (*p == '=')
                                break;
                        if (*p != ' ') {
                                if (!inword)
                                        nw ++;
                                inword = 1;
                        } else
                                inword = 0;
                        p++;
                }

                if (nw == 1) {
                        debugger_assignment(debugger_machine, cmd);
                        return;
                }
        }

        i = 0;
        while (cmds[i].name != NULL)
                cmds[i++].tmp_flag = 0;

        /*  How many chars in cmd to match against:  */
        matchlen = 0;
        while (isalpha((int)cmd[matchlen]))
                matchlen ++;

        /*  Check for a command name match:  */
        n = i = i_match = 0;
        while (cmds[i].name != NULL) {
                if (strncasecmp(cmds[i].name, cmd, matchlen) == 0
                    && cmds[i].f != NULL) {
                        cmds[i].tmp_flag = 1;
                        i_match = i;
                        n++;
                }
                i++;
        }

        /*  No match?  */
        if (n == 0) {
                printf("Unknown command '%s'. Type 'help' for help.\n", cmd);
                return;
        }

        /*  More than one match?  */
        if (n > 1) {
                printf("Ambiguous command '%s':  ", cmd);
                i = 0;
                while (cmds[i].name != NULL) {
                        if (cmds[i].tmp_flag)
                                printf("  %s", cmds[i].name);
                        i++;
                }
                printf("\n");
                return;
        }

        /*  Exactly one match:  */
        if (cmds[i_match].f != NULL) {
                char *p = cmd + matchlen;
                /*  Remove leading whitespace from the args...  */
                while (*p != '\0' && *p == ' ')
                        p++;

                /*  ... and run the command:  */
                cmds[i_match].f(debugger_machine, p);
        } else
                printf("FATAL ERROR: internal error in debugger.c:"
                    " no handler for this command?\n");
}


/*
 *  debugger_readline():
 *
 *  Read a line from the terminal.
 */
static char *debugger_readline(void)
{
        int ch, i, j, n, i_match, reallen, cmd_len, cursor_pos;
        int read_from_index = last_cmd_index;
        char *cmd = last_cmd[last_cmd_index];

        cmd_len = 0; cmd[0] = '\0';
        printf("GXemul> ");
        fflush(stdout);

        ch = '\0';
        cmd_len = 0;
        cursor_pos = 0;

        while (ch != '\n' && !exit_debugger) {
                ch = debugger_readchar();

                if ((ch == '\b' || ch == 127) && cursor_pos > 0) {
                        /*  Backspace.  */
                        cursor_pos --;
                        cmd_len --;
                        memmove(cmd + cursor_pos, cmd + cursor_pos + 1,
                            cmd_len);
                        cmd[cmd_len] = '\0';
                        printf("\b");
                        for (i=cursor_pos; i<cmd_len; i++)
                                printf("%c", cmd[i]);
                        printf(" \b");
                        for (i=cursor_pos; i<cmd_len; i++)
                                printf("\b");
                } else if (ch == 4 && cmd_len > 0 && cursor_pos < cmd_len) {
                        /*  CTRL-D: Delete.  */
                        cmd_len --;
                        memmove(cmd + cursor_pos, cmd + cursor_pos + 1,
                            cmd_len);
                        cmd[cmd_len] = '\0';
                        for (i=cursor_pos; i<cmd_len; i++)
                                printf("%c", cmd[i]);
                        printf(" \b");
                        for (i=cursor_pos; i<cmd_len; i++)
                                printf("\b");
                } else if (ch == 1) {
                        /*  CTRL-A: Start of line.  */
                        while (cursor_pos > 0) {
                                cursor_pos --;
                                printf("\b");
                        }
                } else if (ch == 2) {
                        /*  CTRL-B: Backwards one character.  */
                        if (cursor_pos > 0) {
                                printf("\b");
                                cursor_pos --;
                        }
                } else if (ch == 5) {
                        /*  CTRL-E: End of line.  */
                        while (cursor_pos < cmd_len) {
                                printf("%c", cmd[cursor_pos]);
                                cursor_pos ++;
                        }
                } else if (ch == 6) {
                        /*  CTRL-F: Forward one character.  */
                        if (cursor_pos < cmd_len) {
                                printf("%c",
                                    cmd[cursor_pos]);
                                cursor_pos ++;
                        }
                } else if (ch == 11) {
                        /*  CTRL-K: Kill to end of line.  */
                        for (i=0; i<MAX_CMD_BUFLEN; i++)
                                console_makeavail(MAIN_CONSOLE, 4); /*  :-)  */
                } else if (ch == 14 || ch == 16) {
                        /*  CTRL-P: Previous line in the command history,
                            CTRL-N: next line  */
                        do {
                                if (ch == 14 &&
                                    read_from_index == last_cmd_index)
                                        break;
                                if (ch == 16)
                                        i = read_from_index - 1;
                                else
                                        i = read_from_index + 1;

                                if (i < 0)
                                        i = N_PREVIOUS_CMDS - 1;
                                if (i >= N_PREVIOUS_CMDS)
                                        i = 0;

                                /*  Special case: pressing 'down'
                                    to reach last_cmd_index:  */
                                if (i == last_cmd_index) {
                                        read_from_index = i;
                                        for (i=cursor_pos; i<cmd_len;
                                            i++)
                                                printf(" ");
                                        for (i=cmd_len-1; i>=0; i--)
                                                printf("\b \b");
                                        cmd[0] = '\0';
                                        cmd_len = cursor_pos = 0;
                                } else if (last_cmd[i][0] != '\0') {
                                        /*  Copy from old line:  */
                                        read_from_index = i;
                                        for (i=cursor_pos; i<cmd_len;
                                            i++)
                                                printf(" ");
                                        for (i=cmd_len-1; i>=0; i--)
                                                printf("\b \b");
                                        strlcpy(cmd,
                                            last_cmd[read_from_index],
                                            MAX_CMD_BUFLEN);
                                        cmd_len = strlen(cmd);
                                        printf("%s", cmd);
                                        cursor_pos = cmd_len;
                                }
                        } while (0);
                } else if (ch >= ' ' && cmd_len < MAX_CMD_BUFLEN-1) {
                        /*  Visible character:  */
                        memmove(cmd + cursor_pos + 1, cmd + cursor_pos,
                            cmd_len - cursor_pos);
                        cmd[cursor_pos] = ch;
                        cmd_len ++;
                        cursor_pos ++;
                        cmd[cmd_len] = '\0';
                        printf("%c", ch);
                        for (i=cursor_pos; i<cmd_len; i++)
                                printf("%c", cmd[i]);
                        for (i=cursor_pos; i<cmd_len; i++)
                                printf("\b");
                } else if (ch == '\r' || ch == '\n') {
                        ch = '\n';
                        printf("\n");
                } else if (ch == '\t') {
                        /*  Super-simple tab-completion:  */
                        i = 0;
                        while (cmds[i].name != NULL)
                                cmds[i++].tmp_flag = 0;

                        /*  Check for a (partial) command match:  */
                        n = i = i_match = 0;
                        while (cmds[i].name != NULL) {
                                if (strncasecmp(cmds[i].name, cmd,
                                    cmd_len) == 0) {
                                        cmds[i].tmp_flag = 1;
                                        i_match = i;
                                        n++;
                                }
                                i++;
                        }

                        switch (n) {
                        case 0: /*  Beep.  */
                                printf("\a");
                                break;
                        case 1: /*  Add the rest of the command:  */
                                reallen = strlen(cmds[i_match].name);
                                for (i=cmd_len; i<reallen; i++)
                                        console_makeavail(MAIN_CONSOLE,
                                            cmds[i_match].name[i]);
                                /*  ... and a space, if the command takes
                                    any arguments:  */
                                if (cmds[i_match].args != NULL &&
                                    cmds[i_match].args[0] != '\0')
                                        console_makeavail(MAIN_CONSOLE, ' ');
                                break;
                        default:
                                /*  Show all possible commands:  */
                                printf("\a\n"); /*  Beep. :-)  */
                                i = 0;          /*  i = cmds index  */
                                j = 0;          /*  j = # of cmds printed  */
                                while (cmds[i].name != NULL) {
                                        if (cmds[i].tmp_flag) {
                                                size_t q;
                                                if (j == 0)
                                                        printf("  ");
                                                printf("%s",
                                                    cmds[i].name);
                                                j++;
                                                if (j != 6)
                                                        for (q=0; q<13-strlen(
                                                            cmds[i].name); q++)
                                                                printf(" ");
                                                if (j == 6) {
                                                        printf("\n");
                                                        j = 0;
                                                }
                                        }
                                        i++;
                                }
                                if (j != 0)
                                        printf("\n");
                                printf("GXemul> ");
                                for (i=0; i<cmd_len; i++)
                                        printf("%c", cmd[i]);
                        }
                } else if (ch == 27) {
                        /*  Escape codes: (cursor keys etc)  */
                        while ((ch = console_readchar(MAIN_CONSOLE)) < 0)
                                usleep(1);
                        if (ch == '[' || ch == 'O') {
                                while ((ch = console_readchar(MAIN_CONSOLE))
                                    < 0)
                                        usleep(1);
                                switch (ch) {
                                case '2':       /*  2~ = ins  */
                                case '5':       /*  5~ = pgup  */
                                case '6':       /*  6~ = pgdn  */
                                        /*  TODO: Ugly hack, but might work.  */
                                        while ((ch = console_readchar(
                                            MAIN_CONSOLE)) < 0)
                                                usleep(1);
                                        /*  Do nothing for these keys.  */
                                        break;
                                case '3':       /*  3~ = delete  */
                                        /*  TODO: Ugly hack, but might work.  */
                                        while ((ch = console_readchar(
                                            MAIN_CONSOLE)) < 0)
                                                usleep(1);
                                        console_makeavail(MAIN_CONSOLE, '\b');
                                        break;
                                case 'A':       /*  Up.  */
                                        /*  Up cursor ==> CTRL-P  */
                                        console_makeavail(MAIN_CONSOLE, 16);
                                        break;
                                case 'B':       /*  Down.  */
                                        /*  Down cursor ==> CTRL-N  */
                                        console_makeavail(MAIN_CONSOLE, 14);
                                        break;
                                case 'C':
                                        /*  Right cursor ==> CTRL-F  */
                                        console_makeavail(MAIN_CONSOLE, 6);
                                        break;
                                case 'D':       /*  Left  */
                                        /*  Left cursor ==> CTRL-B  */
                                        console_makeavail(MAIN_CONSOLE, 2);
                                        break;
                                case 'F':
                                        /*  End ==> CTRL-E  */
                                        console_makeavail(MAIN_CONSOLE, 5);
                                        break;
                                case 'H':
                                        /*  Home ==> CTRL-A  */
                                        console_makeavail(MAIN_CONSOLE, 1);
                                        break;
                                }
                        }
                }

                fflush(stdout);
        }

        if (exit_debugger)
                cmd[0] = '\0';

        return cmd;
}


/*
 *  debugger():
 *
 *  This is a loop, which reads a command from the terminal, and executes it.
 */
void debugger(void)
{
        int i, cmd_len;
        char *cmd;

        if (debugger_n_steps_left_before_interaction > 0) {
                debugger_n_steps_left_before_interaction --;
                return;
        }

        /*
         *  Clear all dyntrans translations, because otherwise things would
         *  become to complex to keep in sync.
         */
        /*  TODO: In all machines  */
        for (i=0; i<debugger_machine->ncpus; i++)
                if (debugger_machine->cpus[i]->translation_cache != NULL)
                        cpu_create_or_reset_tc(debugger_machine->cpus[i]);

        /*
         *  Ugly GDB hack: After single stepping, we need to send back
         *  status to GDB:
         */
        if (exit_debugger == -1) {
                int i, j;
                for (i=0; i<debugger_n_emuls; i++) {
                        struct emul *e = debugger_emuls[i];
                        if (e == NULL)
                                continue;

                        for (j=0; j<e->n_machines; j++) {
                                if (e->machines[j]->gdb.port > 0)
                                        debugger_gdb_after_singlestep(
                                            e->machines[j]);
                        }
                }
        }


        exit_debugger = 0;

        while (!exit_debugger) {
                /*  Read a line from the terminal:  */
                cmd = debugger_readline();

                /*  Special hack for the "step" _GDB_ command:  */
                if (exit_debugger == -1)
                        return;

                cmd_len = strlen(cmd);

                /*  Remove spaces:  */
                while (cmd_len > 0 && cmd[0]==' ')
                        memmove(cmd, cmd+1, cmd_len --);
                while (cmd_len > 0 && cmd[cmd_len-1] == ' ')
                        cmd[(cmd_len--)-1] = '\0';

                /*  No command? Then try reading another line.  */
                if (cmd_len == 0) {
                        /*  Special case for repeated commands:  */
                        if (repeat_cmd[0] != '\0')
                                strlcpy(cmd, repeat_cmd, MAX_CMD_BUFLEN);
                        else
                                continue;
                } else {
                        last_cmd_index ++;
                        if (last_cmd_index >= N_PREVIOUS_CMDS)
                                last_cmd_index = 0;

                        repeat_cmd[0] = '\0';
                }

                debugger_execute_cmd(cmd, cmd_len);

                /*  Special hack for the "step" command:  */
                if (exit_debugger == -1)
                        return;
        }

        gettimeofday(&debugger_machine->starttime, NULL);
        debugger_machine->ncycles_since_gettimeofday = 0;

        single_step = 0;
        debugger_machine->instruction_trace = old_instruction_trace;
        debugger_machine->show_trace_tree = old_show_trace_tree;
        quiet_mode = old_quiet_mode;
}


/*
 *  debugger_reset():
 *
 *  This function should be called before calling debugger(), when it is
 *  absolutely necessary that debugger() is interactive. Otherwise, it might
 *  return without doing anything, such as when single-stepping multiple
 *  instructions at a time.
 */
void debugger_reset(void)
{
        debugger_n_steps_left_before_interaction = 0;
}


/*
 *  debugger_init():
 *
 *  Must be called before any other debugger function is used.
 */
void debugger_init(struct emul **emuls, int n_emuls)
{
        int i, j;

        debugger_n_emuls = n_emuls;
        debugger_emuls = emuls;

        if (n_emuls < 1) {
                fprintf(stderr, "\nERROR: No emuls (?)\n");
                exit(1);
        }

        debugger_emul = emuls[0];
        if (emuls[0]->n_machines < 1) {
                fprintf(stderr, "\nERROR: No machines in emuls[0], "
                    "cannot handle this situation yet.\n\n");
                exit(1);
        }

        for (i=0; i<n_emuls; i++)
                for (j=0; j<emuls[i]->n_machines; j++)
                        debugger_gdb_init(emuls[i]->machines[j]);

        debugger_machine = emuls[0]->machines[0];

        for (i=0; i<N_PREVIOUS_CMDS; i++) {
                last_cmd[i] = malloc(MAX_CMD_BUFLEN);
                if (last_cmd[i] == NULL) {
                        fprintf(stderr, "debugger_init(): out of memory\n");
                        exit(1);
                }
                last_cmd[i][0] = '\0';
        }

        last_cmd_index = 0;
        repeat_cmd[0] = '\0';
}
