0.3.5/src/useremul.c

/*
 *  Copyright (C) 2004-2005  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: useremul.c,v 1.62 2005/08/16 06:49:26 debug Exp $
 *
 *  Userland (syscall) emulation.
 *
 *  TODO:
 *
 *      NetBSD/pmax:
 *              environment passing
 *              more syscalls
 *
 *      32-bit vs 64-bit problems? MIPS n32, o32, n64?
 *
 *      Dynamic ELFs?
 *
 *      Try to prefix "/emul/mips/" or similar to all filenames,
 *              and only if that fails, try the given filename
 *
 *      Automagic errno translation?
 *
 *      Memory allocation? mmap etc.
 *
 *      File descriptor (0,1,2) assumptions?
 *
 *
 *  This module needs more cleanup.
 *  -------------------------------
 *
 *
 *  NOTE:  This module (useremul.c) is just a quick hack to see if
 *         userland emulation works at all.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/resource.h>
#include <time.h>

#include "cpu.h"
#include "cpu_mips.h"
#include "emul.h"
#include "machine.h"
#include "memory.h"
#include "misc.h"
#include "syscall_linux_ppc.h"
#include "syscall_netbsd.h"
#include "syscall_ultrix.h"
#include "sysctl_netbsd.h"

struct syscall_emul {
        char            *name;
        int             arch;
        char            *cpu_name;
        void            (*f)(struct cpu *, uint32_t);
        void            (*setup)(struct cpu *, int, char **);

        struct syscall_emul *next;
};

static struct syscall_emul *first_syscall_emul;

/*  Max length of strings passed using syscall parameters:  */
#define MAXLEN          8192


/*
 *  useremul_setup():
 *
 *  Set up an emulated environment suitable for running userland code. The
 *  program should already have been loaded into memory when this function
 *  is called.
 */
void useremul_setup(struct cpu *cpu, int argc, char **host_argv)
{
        struct syscall_emul *sep;

        sep = first_syscall_emul;

        while (sep != NULL) {
                if (strcasecmp(cpu->machine->userland_emul, sep->name) == 0) {
                        sep->setup(cpu, argc, host_argv);
                        return;
                }
                sep = sep->next;
        }

        fatal("useremul_setup(): internal error, unimplemented emulation?\n");
        exit(1);
}


/*
 *  useremul__freebsd_setup():
 *
 *  Set up an emulated userland environment suitable for running FreeBSD
 *  binaries.
 */
void useremul__freebsd_setup(struct cpu *cpu, int argc, char **host_argv)
{
        debug("useremul__freebsd_setup(): TODO\n");

        switch (cpu->machine->arch) {
        case ARCH_ALPHA:
                /*  According to FreeBSD's /usr/src/lib/csu/alpha/crt1.c:  */
                /*  a0 = char **ap                                         */
                /*  a1 = void (*cleanup)(void)          from shared loader */
                /*  a2 = struct Struct_Obj_Entry *obj   from shared loader */
                /*  a3 = struct ps_strings *ps_strings                     */
                cpu->cd.alpha.r[ALPHA_A0] = 0;
                cpu->cd.alpha.r[ALPHA_A1] = 0;
                cpu->cd.alpha.r[ALPHA_A2] = 0;
                cpu->cd.alpha.r[ALPHA_A3] = 0;

                /*  What is a good stack pointer? TODO  */
                cpu->cd.alpha.r[ALPHA_SP] = 0x120000000ULL +
                    1048576 * cpu->machine->physical_ram_in_mb - 1024;
                break;
        default:
                fatal("non-Alpha not yet implemented for freebsd emul.\n");
                exit(1);
        }
}


/*
 *  useremul__linux_setup():
 *
 *  Set up an emulated userland environment suitable for running Linux
 *  binaries.
 */
void useremul__linux_setup(struct cpu *cpu, int argc, char **host_argv)
{
        debug("useremul__linux_setup(): TODO\n");

        if (cpu->machine->arch != ARCH_PPC) {
                fatal("non-PPC not yet implemented for linux emul.\n");
                exit(1);
        }

        /*  What is a good stack pointer? TODO  */
        cpu->cd.ppc.gpr[1] = 0x7ffff000ULL;
}


/*
 *  useremul__netbsd_setup():
 *
 *  Set up an emulated userland environment suitable for running NetBSD
 *  binaries.
 */
void useremul__netbsd_setup(struct cpu *cpu, int argc, char **host_argv)
{
        uint64_t stack_top = 0x7fff0000;
        uint64_t stacksize = 8 * 1048576;
        uint64_t stack_margin = 16384;
        uint64_t cur_argv;
        int i, i2;
        int envc = 1;

        switch (cpu->machine->arch) {
        case ARCH_MIPS:
                /*  See netbsd/sys/src/arch/mips/mips_machdep.c:setregs()  */
                cpu->cd.mips.gpr[MIPS_GPR_A0] = stack_top - stack_margin;
                cpu->cd.mips.gpr[25] = cpu->pc;         /*  reg. t9  */

                /*  The userland stack:  */
                cpu->cd.mips.gpr[MIPS_GPR_SP] = stack_top - stack_margin;
                add_symbol_name(&cpu->machine->symbol_context,
                    stack_top - stacksize, stacksize, "userstack", 0, 0);

                /*  Stack contents:  (TODO: is this correct?)  */
                store_32bit_word(cpu, stack_top - stack_margin, argc);

                cur_argv = stack_top - stack_margin + 128 + (argc + envc)
                    * sizeof(uint32_t);
                for (i=0; i<argc; i++) {
                        debug("adding argv[%i]: '%s'\n", i, host_argv[i]);

                        store_32bit_word(cpu, stack_top - stack_margin +
                            4 + i*sizeof(uint32_t), cur_argv);
                        store_string(cpu, cur_argv, host_argv[i]);
                        cur_argv += strlen(host_argv[i]) + 1;
                }

                /*  Store a NULL value between the args and the environment
                    strings:  */
                store_32bit_word(cpu, stack_top - stack_margin +
                    4 + i*sizeof(uint32_t), 0);  i++;

                /*  TODO: get environment strings from somewhere  */

                /*  Store all environment strings:  */
                for (i2 = 0; i2 < envc; i2 ++) {
                        store_32bit_word(cpu, stack_top - stack_margin + 4
                            + (i+i2)*sizeof(uint32_t), cur_argv);
                        store_string(cpu, cur_argv, "DISPLAY=localhost:0.0");
                        cur_argv += strlen("DISPLAY=localhost:0.0") + 1;
                }
                break;

        case ARCH_ARM:
                debug("useremul__netbsd_setup(): ARM: TODO\n");
                break;

        case ARCH_PPC:
                debug("useremul__netbsd_setup(): PPC: TODO\n");

                /*  What is a good stack pointer? TODO  */
                cpu->cd.ppc.gpr[1] = 0x7ffff000ULL;

                break;

        case ARCH_X86:
                debug("useremul__netbsd_setup(): X86: TODO\n");

                break;

        default:
                fatal("useremul__netbsd_setup(): unimplemented arch\n");
                exit(1);
        }
}


/*
 *  useremul__ultrix_setup():
 *
 *  Set up an emulated userland environment suitable for running Ultrix
 *  binaries.
 */
void useremul__ultrix_setup(struct cpu *cpu, int argc, char **host_argv)
{
        uint64_t stack_top = 0x7fff0000;
        uint64_t stacksize = 8 * 1048576;
        uint64_t stack_margin = 16384;
        uint64_t cur_argv;
        int i, i2;
        int envc = 1;

        /*  TODO:  is this correct?  */
        cpu->cd.mips.gpr[MIPS_GPR_A0] = stack_top - stack_margin;
        cpu->cd.mips.gpr[25] = cpu->pc;         /*  reg. t9  */

        /*  The userland stack:  */
        cpu->cd.mips.gpr[MIPS_GPR_SP] = stack_top - stack_margin;
        add_symbol_name(&cpu->machine->symbol_context,
            stack_top - stacksize, stacksize, "userstack", 0, 0);

        /*  Stack contents:  (TODO: is this correct?)  */
        store_32bit_word(cpu, stack_top - stack_margin, argc);

        cur_argv = stack_top - stack_margin + 128 +
            (argc + envc) * sizeof(uint32_t);
        for (i=0; i<argc; i++) {
                debug("adding argv[%i]: '%s'\n", i, host_argv[i]);

                store_32bit_word(cpu, stack_top - stack_margin +
                    4 + i*sizeof(uint32_t), cur_argv);
                store_string(cpu, cur_argv, host_argv[i]);
                cur_argv += strlen(host_argv[i]) + 1;
        }

        /*  Store a NULL value between the args and the environment strings:  */
        store_32bit_word(cpu, stack_top - stack_margin
            + 4 + i*sizeof(uint32_t), 0);  i++;

        /*  TODO: get environment strings from somewhere  */

        /*  Store all environment strings:  */
        for (i2 = 0; i2 < envc; i2 ++) {
                store_32bit_word(cpu, stack_top - stack_margin + 4 +
                    (i+i2)*sizeof(uint32_t), cur_argv);
                store_string(cpu, cur_argv, "DISPLAY=localhost:0.0");
                cur_argv += strlen("DISPLAY=localhost:0.0") + 1;
        }
}


/*
 *  get_userland_string():
 *
 *  This can be used to retrieve strings, for example filenames,
 *  from the emulated memory.
 *
 *  NOTE: This function returns a pointer to a malloced buffer. It is up to
 *        the caller to use free().
 */
static unsigned char *get_userland_string(struct cpu *cpu, uint64_t baseaddr)
{
        unsigned char *charbuf;
        int i, len = 16384;

        charbuf = malloc(len);
        if (charbuf == NULL) {
                fprintf(stderr, "get_userland_string(): out of memory (trying"
                    " to allocate %i bytes)\n", len);
                exit(1);
        }

        /*  TODO: address validity check  */

        for (i=0; i<len; i++) {
                cpu->memory_rw(cpu, cpu->mem, baseaddr+i, charbuf+i,
                    1, MEM_READ, CACHE_DATA);
                if (charbuf[i] == '\0')
                        break;
        }

        charbuf[MAXLEN-1] = 0;
        return charbuf;
}


/*
 *  get_userland_buf():
 *
 *  This can be used to retrieve buffers, for example inet_addr, from
 *  emulated memory.
 *
 *  NOTE: This function returns a pointer to a malloced buffer. It is up to
 *        the caller to use free().
 *
 *  TODO: combine this with get_userland_string() in some way
 */
static unsigned char *get_userland_buf(struct cpu *cpu,
        uint64_t baseaddr, uint64_t len)
{
        unsigned char *charbuf;
        ssize_t i;

        charbuf = malloc(len);
        if (charbuf == NULL) {
                fprintf(stderr, "get_userland_buf(): out of memory (trying"
                    " to allocate %lli bytes)\n", (long long)len);
                exit(1);
        }

        /*  TODO: address validity check  */
        for (i=0; i<len; i++) {
                cpu->memory_rw(cpu, cpu->mem, baseaddr+i, charbuf+i, 1,
                    MEM_READ, CACHE_DATA);
                /*  debug(" %02x", charbuf[i]);  */
        }
        debug("\n");

        return charbuf;
}


/*
 *  useremul_syscall():
 *
 *  Handle userland syscalls.  This function is called whenever a userland
 *  process runs a 'syscall' instruction.  The code argument is the code
 *  embedded into the syscall instruction, if any.  (This 'code' value is not
 *  necessarily used by specific emulations.)
 */
void useremul_syscall(struct cpu *cpu, uint32_t code)
{
        if (cpu->useremul_syscall == NULL) {
                fatal("useremul_syscall(): cpu->useremul_syscall == NULL\n");
        } else
                cpu->useremul_syscall(cpu, code);
}


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


/*
 *  useremul_exit():
 */
int useremul_exit(struct cpu *cpu, uint64_t arg0)
{
        debug("[ exit(%i) ]\n", (int)arg0);
        cpu->running = 0;
        cpu->machine->exit_without_entering_debugger = 1;
        return 0;
}


/*
 *  useremul_write():
 */
int64_t useremul_write(struct cpu *cpu, int64_t *errnop,
        uint64_t arg0, uint64_t arg1, uint64_t arg2)
{
        int64_t res = 0;
        *errnop = 0;
        debug("[ write(%i,0x%llx,%lli) ]\n",
            (int)arg0, (long long)arg1, (long long)arg2);
        if (arg2 != 0) {
                unsigned char *cp = get_userland_buf(cpu, arg1, arg2);
                res = write(arg0, cp, arg2);
                if (res < 0)
                        *errnop = errno;
                free(cp);
        }
        return res;
}


/*
 *  useremul_break():
 */
int64_t useremul_break(struct cpu *cpu, uint64_t arg0)
{
        debug("[ break(0x%llx): TODO ]\n", (long long)arg0);

        /*  TODO  */
        return 0;
}


/*
 *  useremul_getpid():
 */
int64_t useremul_getpid(struct cpu *cpu)
{
        int64_t pid = getpid();
        debug("[ getpid(): %lli ]\n", (long long)pid);
        return pid;
}


/*
 *  useremul_getuid():
 */
int64_t useremul_getuid(struct cpu *cpu)
{
        int64_t uid = getuid();
        debug("[ getuid(): %lli ]\n", (long long)uid);
        return uid;
}


/*
 *  useremul_getegid():
 */
int64_t useremul_getegid(struct cpu *cpu)
{
        int64_t egid = getegid();
        debug("[ getegid(): %lli ]\n", (long long)egid);
        return egid;
}


/*
 *  useremul_getgid():
 */
int64_t useremul_getgid(struct cpu *cpu)
{
        int64_t gid = getgid();
        debug("[ getgid(): %lli ]\n", (long long)gid);
        return gid;
}


/*
 *  useremul_sync():
 */
int useremul_sync(struct cpu *cpu)
{
        debug("[ sync() ]\n");
        sync();
        return 0;
}


/*
 *  useremul_readlink():
 */
int64_t useremul_readlink(struct cpu *cpu, int64_t *errnop,
        uint64_t arg0, uint64_t arg1, int64_t arg2)
{
        int64_t res = 0;
        unsigned char *charbuf = get_userland_string(cpu, arg0);
        unsigned char *buf2;

        debug("[ readlink(\"%s\",0x%llx,%lli) ]\n",
            charbuf, (long long)arg1, (long long)arg2);
        if (arg2 == 0 || arg2 > 150000) {
                fprintf(stderr, "[ useremul_readlink(): TODO ]\n");
                exit(1);
        }

        buf2 = malloc(arg2);
        if (buf2 == NULL) {
                fprintf(stderr, "[ useremul_readlink(): out of memory ]\n");
                exit(1);
        }
        res = readlink((char *)charbuf, (char *)buf2, arg2);
        buf2[arg2-1] = '\0';
        if (res < 0)
                *errnop = errno;
        else
                store_string(cpu, arg1, (char *)buf2);
        free(buf2);
        free(charbuf);
        return res;
}


/*
 *  useremul_getrusage():
 */
int64_t useremul_getrusage(struct cpu *cpu, int64_t *errnop,
        uint64_t arg0, uint64_t arg1)
{
        int64_t res;
        struct rusage rusage;
        debug("[ getrusage(%i,0x%llx) ]\n", (int)arg0, (long long)arg1);
        res = getrusage(arg0, &rusage);

        fatal("TODO: convert rusage into emulated memory!\n");
        store_64bit_word(cpu, arg1 +  0, rusage.ru_utime.tv_sec);
        store_64bit_word(cpu, arg1 +  8, rusage.ru_utime.tv_usec);
        store_64bit_word(cpu, arg1 + 16, rusage.ru_stime.tv_sec);
        store_64bit_word(cpu, arg1 + 24, rusage.ru_stime.tv_usec);

        return res;
}


/*
 *  useremul_fstat():
 */
int64_t useremul_fstat(struct cpu *cpu, int64_t *errnop,
        int64_t arg0, uint64_t arg1)
{
        int64_t res;
        struct stat sb;
        debug("[ fstat(%i,0x%llx) ]\n", (int)arg0, (long long)arg1);
        res = fstat(arg0, &sb);
        if (res < 0)
                *errnop = errno;
        else {
                fatal("TODO: convert sb into emulated memory!\n");

/*  NOTE: FreeBSD/alpha only  */

                store_32bit_word(cpu, arg1 + 0, sb.st_dev);
                store_32bit_word(cpu, arg1 + 4, sb.st_ino);
/*              store_16bit_word(cpu, arg1 + 8, sb.st_mode);
*/              store_16bit_word(cpu, arg1 + 10, sb.st_nlink);
                store_32bit_word(cpu, arg1 + 12, sb.st_uid);
                store_32bit_word(cpu, arg1 + 16, sb.st_gid);
                store_32bit_word(cpu, arg1 + 20, sb.st_rdev);
#if 0
                store_64bit_word(cpu, arg1 + 24, sb.st_atimespec.tv_sec);
                store_64bit_word(cpu, arg1 + 32, sb.st_atimespec.tv_nsec);
                store_64bit_word(cpu, arg1 + 40, sb.st_mtimespec.tv_sec);
                store_64bit_word(cpu, arg1 + 48, sb.st_mtimespec.tv_nsec);
                store_64bit_word(cpu, arg1 + 56, sb.st_ctimespec.tv_sec);
                store_64bit_word(cpu, arg1 + 64, sb.st_ctimespec.tv_nsec);

                store_64bit_word(cpu, arg1 + 72, sb.st_size);
                store_64bit_word(cpu, arg1 + 80, sb.st_blocks);
                store_64bit_word(cpu, arg1 + 88, sb.st_blksize);
                store_64bit_word(cpu, arg1 + 92, sb.st_flags);
                store_64bit_word(cpu, arg1 + 96, sb.st_gen);
#endif
        }
        return res;
}


/*
 *  useremul_mmap():
 */
int64_t useremul_mmap(struct cpu *cpu, int64_t *errnop,
        uint64_t arg0, int64_t arg1, int64_t arg2,
        int64_t arg3, int64_t arg4, uint64_t arg5)
{
        int64_t res = 0;

        /*  arg0..5: addr, len, prot, flags, fd, offset  */
        debug("[ mmap(0x%llx,%lli,%i,%i,%i,%lli) ]\n",
            (long long)arg0, (long long)arg1,
            (int)arg2, (int)arg3, (int)arg4, (long long)arg5);

        if (arg4 != -1) {
                fatal("[ useremul_mmap(): fd != -1: TODO ]\n");
                cpu->running = 0;
                return 0;
        }

        /*  Anonymous allocation.  */
        if (arg0 != 0) {
                fatal("[ useremul_mmap(): addr != 0: TODO ]\n");
                cpu->running = 0;
                return 0;
        }

        fatal("[ useremul_mmap(): TODO ]\n");

res = 0x18000000ULL;

        return res;
}


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


/*
 *  useremul__freebsd():
 *
 *  FreeBSD/Alpha syscall emulation.
 *
 *  TODO: How to make this work nicely with non-Alpha archs.
 */
static void useremul__freebsd(struct cpu *cpu, uint32_t code)
{
        int nr;
        int64_t res = 0, err = 0;
        uint64_t arg0, arg1, arg2, arg3, arg4, arg5;

        nr = cpu->cd.alpha.r[ALPHA_V0];
        arg0 = cpu->cd.alpha.r[ALPHA_A0];
        arg1 = cpu->cd.alpha.r[ALPHA_A1];
        arg2 = cpu->cd.alpha.r[ALPHA_A2];
        arg3 = cpu->cd.alpha.r[ALPHA_A3];
        arg4 = cpu->cd.alpha.r[ALPHA_A4];
        arg5 = cpu->cd.alpha.r[ALPHA_A5];

        if (nr == 198) {
                /*  ___syscall  */
                nr = arg0;
                arg0 = arg1;
                arg1 = arg2;
                arg2 = arg3;
                arg3 = arg4;
                arg4 = arg5;
                /*  TODO: stack arguments  */
        }

        switch (nr) {

        case 1: res = useremul_exit(cpu, arg0);
                break;

        case 4: res = useremul_write(cpu, &err, arg0, arg1, arg2);
                break;

        case 17:res = useremul_break(cpu, arg0);
                break;

        case 20:res = useremul_getpid(cpu);
                break;

        case 24:res = useremul_getuid(cpu);
                break;

        case 43:res = useremul_getegid(cpu);
                break;

        case 47:res = useremul_getgid(cpu);
                break;

        case 58:res = useremul_readlink(cpu, &err, arg0, arg1, arg2);
                break;

        case 117:res = useremul_getrusage(cpu, &err, arg0, arg1);
                break;

        case 189:res = useremul_fstat(cpu, &err, arg0, arg1);
                break;

        case 197:res = useremul_mmap(cpu, &err, arg0, arg1, arg2, arg3,
                    arg4, arg5);
                break;

        default:fatal("useremul__freebsd(): syscall %i not yet "
                    "implemented\n", nr);
                cpu->running = 0;
        }

        if (err) {
                cpu->cd.alpha.r[ALPHA_A3] = 1;
                cpu->cd.alpha.r[ALPHA_V0] = err;
        } else {
                cpu->cd.alpha.r[ALPHA_A3] = 0;
                cpu->cd.alpha.r[ALPHA_V0] = res;
        }
}


/*
 *  useremul__linux():
 *
 *  Linux syscall emulation.
 *
 *  TODO: How to make this work nicely with non-PPC archs.
 */
static void useremul__linux(struct cpu *cpu, uint32_t code)
{
        int nr;
        int64_t res = 0, err = 0;
        uint64_t arg0, arg1, arg2, arg3;

        if (code != 0) {
                fatal("useremul__linux(): code %i: TODO\n", (int)code);
                exit(1);
        }

        nr = cpu->cd.ppc.gpr[0];
        arg0 = cpu->cd.ppc.gpr[3];
        arg1 = cpu->cd.ppc.gpr[4];
        arg2 = cpu->cd.ppc.gpr[5];
        arg3 = cpu->cd.ppc.gpr[6];

        switch (nr) {

        case LINUX_PPC_SYS_exit:
                res = useremul_exit(cpu, arg0);
                break;

        case LINUX_PPC_SYS_write:
                res = useremul_write(cpu, &err, arg0, arg1, arg2);
                break;

        default:
                fatal("useremul__linux(): syscall %i not yet implemented\n",
                    nr);
                cpu->running = 0;
        }

        /*  return res: TODO  */
}


/*
 *  useremul__netbsd():
 *
 *  NetBSD syscall emulation.
 */
static void useremul__netbsd(struct cpu *cpu, uint32_t code)
{
        int error_flag = 0, result_high_set = 0;
        uint64_t arg0=0,arg1=0,arg2=0,arg3=0,stack0=0,stack1=0,stack2=0;
        int sysnr = 0;
        int64_t error_code = 0;
        uint64_t result_low = 0;
        uint64_t result_high = 0;
        struct timeval tv;
        struct timezone tz;
        int descr;
        uint64_t length, mipsbuf, flags;
        unsigned char *charbuf;
        uint32_t sysctl_name, sysctl_namelen, sysctl_oldp,
            sysctl_oldlenp, sysctl_newp, sysctl_newlen;
        uint32_t name0, name1, name2, name3;

        switch (cpu->machine->arch) {
        case ARCH_MIPS:
                sysnr = cpu->cd.mips.gpr[MIPS_GPR_V0];
                if (sysnr == NETBSD_SYS___syscall) {
                        sysnr = cpu->cd.mips.gpr[MIPS_GPR_A0] +
                            (cpu->cd.mips.gpr[MIPS_GPR_A1] << 32);
                        arg0 = cpu->cd.mips.gpr[MIPS_GPR_A2];
                        arg1 = cpu->cd.mips.gpr[MIPS_GPR_A3];
                        /*  TODO:  stack arguments? Are these correct?  */
                        arg2 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 8);
                        arg3 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 16);
                        stack0 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 24);
                        stack1 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 32);
                        stack2 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 40);
                } else {
                        arg0 = cpu->cd.mips.gpr[MIPS_GPR_A0];
                        arg1 = cpu->cd.mips.gpr[MIPS_GPR_A1];
                        arg2 = cpu->cd.mips.gpr[MIPS_GPR_A2];
                        arg3 = cpu->cd.mips.gpr[MIPS_GPR_A3];
                        /*  TODO:  stack arguments? Are these correct?  */
                        stack0 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 4);
                        stack1 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 8);
                        stack2 = load_32bit_word(cpu,
                            cpu->cd.mips.gpr[MIPS_GPR_SP] + 12);
                }
                break;

        case ARCH_PPC:
                sysnr = cpu->cd.ppc.gpr[0];
                arg0 = cpu->cd.ppc.gpr[3];
                arg1 = cpu->cd.ppc.gpr[4];
                arg2 = cpu->cd.ppc.gpr[5];
                arg3 = cpu->cd.ppc.gpr[6];
                /*  TODO:  More arguments? Stack arguments?  */
                break;
        }

        /*
         *  NOTE: The following code should not be CPU arch dependant!
         *  (TODO)
         */

        switch (sysnr) {

        case NETBSD_SYS_exit:
                debug("[ exit(%i) ]\n", (int)arg0);
                cpu->running = 0;
                cpu->machine->exit_without_entering_debugger = 1;
                break;

        case NETBSD_SYS_read:
                debug("[ read(%i,0x%llx,%lli) ]\n",
                    (int)arg0, (long long)arg1, (long long)arg2);

                if (arg2 != 0) {
                        charbuf = malloc(arg2);
                        if (charbuf == NULL) {
                                fprintf(stderr, "out of memory in "
                                    "useremul__netbsd()\n");
                                exit(1);
                        }
                        result_low = read(arg0, charbuf, arg2);
                        if ((int64_t)result_low < 0) {
                                error_code = errno;
                                error_flag = 1;
                        }

                        /*  TODO: address validity check  */
                        cpu->memory_rw(cpu, cpu->mem, arg1, charbuf,
                            arg2, MEM_WRITE, CACHE_DATA);
                        free(charbuf);
                }
                break;

        case NETBSD_SYS_write:
                descr   = arg0;
                mipsbuf = arg1;
                length  = arg2;
                debug("[ write(%i,0x%llx,%lli) ]\n",
                    (int)descr, (long long)mipsbuf, (long long)length);
                if (length != 0) {
                        charbuf = malloc(length);
                        if (charbuf == NULL) {
                                fprintf(stderr, "out of memory in "
                                    "useremul__netbsd()\n");
                                exit(1);
                        }
                        /*  TODO: address validity check  */
                        cpu->memory_rw(cpu, cpu->mem, mipsbuf, charbuf,
                            length, MEM_READ, CACHE_DATA);
                        result_low = write(descr, charbuf, length);
                        if ((int64_t)result_low < 0) {
                                error_code = errno;
                                error_flag = 1;
                        }
                        free(charbuf);
                }
                break;

        case NETBSD_SYS_open:
                charbuf = get_userland_string(cpu, arg0);
                debug("[ open(\"%s\", 0x%llx, 0x%llx) ]\n",
                    charbuf, (long long)arg1, (long long)arg2);
                result_low = open((char *)charbuf, arg1, arg2);
                if ((int64_t)result_low < 0) {
                        error_flag = 1;
                        error_code = errno;
                }
                free(charbuf);
                break;

        case NETBSD_SYS_close:
                descr   = arg0;
                debug("[ close(%i) ]\n", (int)descr);
                error_code = close(descr);
                if (error_code != 0)
                        error_flag = 1;
                break;

        case NETBSD_SYS_access:
                charbuf = get_userland_string(cpu, arg0);
                debug("[ access(\"%s\", 0x%llx) ]\n",
                    charbuf, (long long) arg1);
                result_low = access((char *)charbuf, arg1);
                if (result_low != 0) {
                        error_flag = 1;
                        error_code = errno;
                }
                free(charbuf);
                break;

        case NETBSD_SYS_getuid:
                result_low = useremul_getuid(cpu);
                break;

        case NETBSD_SYS_geteuid:
                debug("[ geteuid() ]\n");
                result_low = geteuid();
                break;

        case NETBSD_SYS_getgid:
                debug("[ getgid() ]\n");
                result_low = getgid();
                break;

        case NETBSD_SYS_getegid:
                debug("[ getegid() ]\n");
                result_low = getegid();
                break;

        case NETBSD_SYS_getfsstat:
                mipsbuf = arg0;
                length  = arg1;
                flags   = arg2;
                debug("[ getfsstat(0x%llx,%lli,0x%llx) ]\n",
                    (long long)mipsbuf, (long long)length,
                    (long long)flags);

                result_low = 0;         /*  nr of mounted filesystems,
                                            for now  (TODO)  */

                /*  Fill in the struct statfs buffer at arg0...
                        copy data from the host's getfsstat(). TODO  */
#if 1
                result_low = 1;
                store_32bit_word(cpu, mipsbuf + 0, 0);  /*  f_spare2  */
                store_32bit_word(cpu, mipsbuf + 4, 1024);       /*  f_bsize  */
                store_32bit_word(cpu, mipsbuf + 8, 65536);      /*  f_iosize  */
                store_32bit_word(cpu, mipsbuf + 12, 100);       /*  f_blocks  */
                store_32bit_word(cpu, mipsbuf + 16, 50);        /*  f_bfree  */
                store_32bit_word(cpu, mipsbuf + 20, 10);        /*  f_bavail  */
                store_32bit_word(cpu, mipsbuf + 24, 50);        /*  f_files  */
                store_32bit_word(cpu, mipsbuf + 28, 25);        /*  f_ffree  */
                store_32bit_word(cpu, mipsbuf + 28, 0x1234);    /*  f_fsid  */
                store_32bit_word(cpu, mipsbuf + 32, 0); /*  f_owner  */
                store_32bit_word(cpu, mipsbuf + 36, 0); /*  f_type  */
                store_32bit_word(cpu, mipsbuf + 40, 0); /*  f_flags  */
                store_32bit_word(cpu, mipsbuf + 44, 0); /*  f_fspare[0]  */
                store_32bit_word(cpu, mipsbuf + 48, 0); /*  f_fspare[1]  */
                store_string(cpu, mipsbuf + 52, "ffs"); /*  f_typename  */
#define MFSNAMELEN 16
#define MNAMELEN 90
                store_string(cpu, mipsbuf + 52 + MFSNAMELEN, "/");
                        /*  f_mntonname  */
                store_string(cpu, mipsbuf + 52 + MFSNAMELEN + MNAMELEN, "ffs");
                        /*  f_mntfromname  */
#endif
                break;

        case NETBSD_SYS_break:
                useremul_break(cpu, arg0);
                break;

        case NETBSD_SYS_readlink:
                result_low = useremul_readlink(cpu, &error_code,
                    arg0, arg1, arg2);
                break;

        case NETBSD_SYS_sync:
                useremul_sync(cpu);
                break;

        case NETBSD_SYS_gettimeofday:
                debug("[ gettimeofday(0x%llx,0x%llx) ]\n",
                    (long long)arg0, (long long)arg1);
                result_low = gettimeofday(&tv, &tz);
                if (result_low) {
                        error_flag = 1;
                        error_code = errno;
                } else {
                        if (arg0 != 0) {
                                /*  Store tv.tv_sec and tv.tv_usec as
                                    'long' (32-bit) values:  */
                                store_32bit_word(cpu, arg0 + 0,
                                    tv.tv_sec);
                                store_32bit_word(cpu, arg0 + 4,
                                    tv.tv_usec);
                        }
                        if (arg1 != 0) {
                                /*  Store tz.tz_minuteswest and
                                    tz.tz_dsttime as 'long'
                                    (32-bit) values:  */
                                store_32bit_word(cpu, arg1 + 0,
                                    tz.tz_minuteswest);
                                store_32bit_word(cpu, arg1 + 4,
                                    tz.tz_dsttime);
                        }
                }
                break;

        case NETBSD_SYS_mmap:
                debug("[ mmap(0x%x,%i,%i,%i,%i,0x%llx): TODO ]\n",
                    arg0, arg1, arg2, arg3, stack0, (long long)stack1);

                if ((int32_t)stack0 == -1) {
                        /*
                         *  Anonymous allocation:
                         *
                         *  TODO:  Fix this!!!
                         *
                         *  This quick hack simply allocates anonymous
                         *  mmap memory approximately below the stack.
                         *  This will probably not work with dynamically
                         *  loaded libraries and such.
                         */
                        static uint32_t mmap_anon_ptr = 0x70000000;
                        mmap_anon_ptr -= arg1;
                        /*  round down to page boundary:  */
                        mmap_anon_ptr &= ~4095;
                        debug("ANON: %i bytes at 0x%08x (TODO: not "
                            "working yet?)\n", (int)arg1,
                            mmap_anon_ptr);
                        result_low = mmap_anon_ptr;
                } else {
                        /*  Return NULL for now  */
                }
                break;

        case NETBSD_SYS_dup:
                debug("[ dup(%i) ]\n", (int)arg0);
                result_low = dup(arg0);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                break;

        case NETBSD_SYS_socket:
                debug("[ socket(%i,%i,%i) ]\n",
                    (int)arg0, (int)arg1, (int)arg2);
                result_low = socket(arg0,arg1,arg2);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                break;

        case NETBSD_SYS_issetugid:
                debug("[ issetugid() ]\n");
                /*  TODO: actually call the real issetugid?  */
                break;

        case NETBSD_SYS_nanosleep:
                debug("[ nanosleep(0x%llx,0x%llx) ]\n",
                    (long long)arg0, (long long)arg1);

                if (arg0 != 0) {
                        uint32_t sec = load_32bit_word(cpu, arg0 + 0);
                        uint32_t nsec = load_32bit_word(cpu, arg0 + 4);
                        struct timespec ts;
                        ts.tv_sec = sec;
                        ts.tv_nsec = nsec;
                        result_low = nanosleep(&ts, NULL);
                        if (result_low)
                                fprintf(stderr, "netbsd emulation "
                                    "nanosleep() failed\n");
                        /*  TODO: arg1  */
                } else {
                        error_flag = 1;
                        error_code = 14;  /*  EFAULT  */
                }
                break;

        case NETBSD_SYS___fstat13:
                debug("[ __fstat13(%lli,0x%llx): TODO ]\n",
                    (long long)arg0, (long long)arg1);
                error_flag = 1;
                error_code = 9;  /*  EBADF  */
                break;

        case NETBSD_SYS___getcwd:
                debug("[ __getcwd(0x%llx,%lli): TODO ]\n",
                    (long long)arg0, (long long)arg1);
                if (arg1 != 0 && arg1 < 500000) {
                        char *buf = malloc(arg1);
                        unsigned int i;

                        getcwd(buf, arg1);

                        /*  zero-terminate in host's space:  */
                        buf[arg1 - 1] = 0;

                        for (i = 0; i<arg1 && i < arg1; i++)
                                cpu->memory_rw(cpu, cpu->mem, arg0 + i,
                                    (unsigned char *)&buf[i], 1,
                                    MEM_WRITE, CACHE_NONE);

                        /*  zero-terminate in emulated space:  */
                        cpu->memory_rw(cpu, cpu->mem, arg0 + arg1-1,
                            (unsigned char *)&buf[arg1 - 1],
                            1, MEM_WRITE, CACHE_NONE);

                        free(buf);
                }
                result_low = arg0;
                break;

        case NETBSD_SYS___sigaction14:
                debug("[ __sigaction14(%lli,0x%llx,0x%llx): TODO ]\n",
                    (long long)arg0, (long long)arg1, (long long)arg2);
                error_flag = 1;
                error_code = 9;  /*  EBADF  */
                break;

        case NETBSD_SYS___sysctl:
                sysctl_name    = arg0;
                sysctl_namelen = arg1;
                sysctl_oldp    = arg2;
                sysctl_oldlenp = arg3;
                sysctl_newp    = load_32bit_word(cpu,
                    cpu->cd.mips.gpr[MIPS_GPR_SP]);
                    /*  TODO: +4 and +8 ??  */
                sysctl_newlen  = load_32bit_word(cpu,
                    cpu->cd.mips.gpr[MIPS_GPR_SP] + 4);
                debug("[ __sysctl(");

                name0 = load_32bit_word(cpu, sysctl_name + 0);
                name1 = load_32bit_word(cpu, sysctl_name + 4);
                name2 = load_32bit_word(cpu, sysctl_name + 8);
                name3 = load_32bit_word(cpu, sysctl_name + 12);
                debug("name (@ 0x%08x) = %i, %i, %i, %i) ]\n",
                    sysctl_name, name0, name1, name2, name3);

                if (name0 == CTL_KERN && name1 == KERN_HOSTNAME) {
                        char hname[256];
                        hname[0] = '\0';
                        gethostname(hname, sizeof(hname));
                        hname[sizeof(hname)-1] = '\0';
                        if (sysctl_oldp != 0)
                                store_string(cpu, sysctl_oldp, hname);
                        if (sysctl_oldlenp != 0)
                                store_32bit_word(cpu, sysctl_oldlenp,
                                    strlen(hname));
                } else if (name0 == CTL_HW && name1 == HW_PAGESIZE) {
                        if (sysctl_oldp != 0)
                                store_32bit_word(cpu,
                                    sysctl_oldp, 4096);
                        if (sysctl_oldlenp != 0)
                                store_32bit_word(cpu,
                                    sysctl_oldlenp, sizeof(uint32_t));
                } else {
                        error_flag = 1;
                        error_code = 2;  /*  ENOENT  */
                }
                break;

        default:
                fatal("[ UNIMPLEMENTED netbsd syscall %i ]\n", sysnr);
                error_flag = 1;
                error_code = 78;  /*  ENOSYS  */
        }


        switch (cpu->machine->arch) {
        case ARCH_MIPS:
                /*
                 *  NetBSD/mips return values:
                 *
                 *  a3 is 0 if the syscall was ok, otherwise 1.
                 *  v0 (and sometimes v1) contain the result value.
                 */
                cpu->cd.mips.gpr[MIPS_GPR_A3] = error_flag;
                if (error_flag)
                        cpu->cd.mips.gpr[MIPS_GPR_V0] = error_code;
                else
                        cpu->cd.mips.gpr[MIPS_GPR_V0] = result_low;

                if (result_high_set)
                        cpu->cd.mips.gpr[MIPS_GPR_V1] = result_high;
                break;
        case ARCH_PPC:
                /*
                 *  NetBSD/powerpc return values:
                 *
                 *  TODO
                 */
                cpu->cd.ppc.gpr[3] = result_low;

                if (result_high_set)
                        cpu->cd.ppc.gpr[4] = result_high;
                break;
        }
}


/*
 *  useremul__ultrix():
 *
 *  Ultrix syscall emulation.
 */
static void useremul__ultrix(struct cpu *cpu, uint32_t code)
{
        int error_flag = 0, result_high_set = 0;
        uint64_t arg0,arg1,arg2,arg3,stack0=0,stack1=0,stack2;
        int sysnr = 0;
        int64_t error_code = 0;
        uint64_t result_low = 0;
        uint64_t result_high = 0;
        struct timeval tv;
        struct timezone tz;
        int descr;
        uint64_t length, mipsbuf;
        unsigned char *charbuf;

        /*
         *  Ultrix/pmax gets the syscall number in register v0,
         *  and syscall arguments in registers a0, a1, ...
         *
         *  TODO:  If there is a __syscall-like syscall (as in NetBSD)
         *  then 64-bit args may be passed in two registers or something...
         *  If so, then copy from the section above (NetBSD).
         */
        sysnr = cpu->cd.mips.gpr[MIPS_GPR_V0];

        arg0 = cpu->cd.mips.gpr[MIPS_GPR_A0];
        arg1 = cpu->cd.mips.gpr[MIPS_GPR_A1];
        arg2 = cpu->cd.mips.gpr[MIPS_GPR_A2];
        arg3 = cpu->cd.mips.gpr[MIPS_GPR_A3];
        /*  TODO:  stack arguments? Are these correct?  */
        stack0 = load_32bit_word(cpu, cpu->cd.mips.gpr[MIPS_GPR_SP] + 0);
        stack1 = load_32bit_word(cpu, cpu->cd.mips.gpr[MIPS_GPR_SP] + 4);
        stack2 = load_32bit_word(cpu, cpu->cd.mips.gpr[MIPS_GPR_SP] + 8);

        switch (sysnr) {

        case ULTRIX_SYS_exit:
                debug("[ exit(%i) ]\n", (int)arg0);
                cpu->running = 0;
                cpu->machine->exit_without_entering_debugger = 1;
                break;

        case ULTRIX_SYS_read:
                debug("[ read(%i,0x%llx,%lli) ]\n",
                    (int)arg0, (long long)arg1, (long long)arg2);

                if (arg2 != 0) {
                        charbuf = malloc(arg2);
                        if (charbuf == NULL) {
                                fprintf(stderr, "out of memory in "
                                    "useremul__ultrix()\n");
                                exit(1);
                        }

                        result_low = read(arg0, charbuf, arg2);
                        if ((int64_t)result_low < 0) {
                                error_code = errno;
                                error_flag = 1;
                        }

                        /*  TODO: address validity check  */
                        cpu->memory_rw(cpu, cpu->mem, arg1, charbuf,
                            arg2, MEM_WRITE, CACHE_DATA);

                        free(charbuf);
                }
                break;

        case ULTRIX_SYS_write:
                descr   = arg0;
                mipsbuf = arg1;
                length  = arg2;
                debug("[ write(%i,0x%llx,%lli) ]\n",
                    (int)descr, (long long)mipsbuf, (long long)length);

                if (length != 0) {
                        charbuf = malloc(length);
                        if (charbuf == NULL) {
                                fprintf(stderr, "out of memory in "
                                    "useremul__ultrix()\n");
                                exit(1);
                        }

                        /*  TODO: address validity check  */
                        cpu->memory_rw(cpu, cpu->mem, mipsbuf, charbuf,
                            length, MEM_READ, CACHE_DATA);

                        result_low = write(descr, charbuf, length);
                        if ((int64_t)result_low < 0) {
                                error_code = errno;
                                error_flag = 1;
                        }
                        free(charbuf);
                }
                break;

        case ULTRIX_SYS_open:
                charbuf = get_userland_string(cpu, arg0);
                debug("[ open(\"%s\", 0x%llx, 0x%llx) ]\n",
                    charbuf, (long long)arg1, (long long)arg2);

                result_low = open((char *)charbuf, arg1, arg2);
                if ((int64_t)result_low < 0) {
                        error_flag = 1;
                        error_code = errno;
                }
                free(charbuf);
                break;

        case ULTRIX_SYS_close:
                descr = arg0;
                debug("[ close(%i) ]\n", (int)descr);

                /*  Special case because some Ultrix programs tend
                    to close low descriptors:  */
                if (descr <= 2) {
                        error_flag = 1;
                        error_code = 2; /*  TODO: Ultrix ENOENT error code  */
                        break;
                }

                error_code = close(descr);
                if (error_code != 0)
                        error_flag = 1;
                break;

        case ULTRIX_SYS_break:
                useremul_break(cpu, arg0);
                break;

        case ULTRIX_SYS_sync:
                useremul_sync(cpu);
                break;

        case ULTRIX_SYS_getuid:
                result_low = useremul_getuid(cpu);
                break;

        case ULTRIX_SYS_getgid:
                debug("[ getgid() ]\n");
                result_low = getgid();
                break;

        case ULTRIX_SYS_dup:
                debug("[ dup(%i) ]\n", (int)arg0);
                result_low = dup(arg0);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                break;

        case ULTRIX_SYS_socket:
                debug("[ socket(%i,%i,%i) ]\n",
                    (int)arg0, (int)arg1, (int)arg2);
                result_low = socket(arg0,arg1,arg2);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                break;

        case ULTRIX_SYS_select:
                debug("[ select(%i,0x%x,0x%x,0x%x,0x%x): TODO ]\n",
                    (int)arg0, (int)arg1, (int)arg2, (int)arg3, (int)stack0);

                /*  TODO  */
                {
                        fd_set fdset;
                        FD_SET(3, &fdset);
                        result_low = select(4, &fdset, NULL, NULL, NULL);
                }
                break;

        case ULTRIX_SYS_setsockopt:
                debug("[ setsockopt(%i,%i,%i,0x%x,%i): TODO ]\n",
                    (int)arg0, (int)arg1, (int)arg2, (int)arg3, (int)stack0);
                /*  TODO: len is not 4, len is stack0?  */
                charbuf = get_userland_buf(cpu, arg3, 4);
                /*  TODO: endianness of charbuf, etc  */
                result_low = setsockopt(arg0, arg1, arg2, (void *)charbuf, 4);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                free(charbuf);
                printf("setsockopt!!!! res = %i error=%i\n",
                    (int)result_low, (int)error_code);
                break;

        case ULTRIX_SYS_connect:
                debug("[ connect(%i,0x%x,%i) ]\n",
                    (int)arg0, (int)arg1, (int)arg2);
                charbuf = get_userland_buf(cpu, arg1, arg2);
                result_low = connect(arg0, (void *)charbuf, arg2);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                printf("connect!!!! res = %i error=%i\n",
                    (int)result_low, (int)error_code);
                free(charbuf);
                break;

        case ULTRIX_SYS_fcntl:
                debug("[ fcntl(%i,%i,0x%x): TODO ]\n",
                    (int)arg0, (int)arg1, (int)arg2);
                /*  TODO:  how about that third argument?  */
                result_low = fcntl(arg0, arg1, arg2);
                if ((int64_t)result_low < 0) {
                        error_code = errno;
                        error_flag = 1;
                }
                printf("fcntl!!!! res = %i error=%i\n",
                    (int)result_low, (int)error_code);
                break;

        case ULTRIX_SYS_stat43:
                charbuf = get_userland_string(cpu, arg0);
                debug("[ stat(\"%s\", 0x%llx): TODO ]\n",
                    charbuf, (long long)arg1);

                if (arg1 != 0) {
                        struct stat st;
                        result_low = stat((char *)charbuf, &st);
                        if ((int64_t)result_low < 0) {
                                error_flag = 1;
                                error_code = errno;
                        } else {
                                /*  Fill in the Ultrix stat struct at arg1:  */

                                /*  TODO  */
                        }
                } else {
                        error_flag = 1;
                        error_code = 1111;      /*  TODO: ultrix ENOMEM?  */
                }
                free(charbuf);
                break;

        case ULTRIX_SYS_fstat:
                result_low = useremul_fstat(cpu, &error_code, arg0, arg1);
                break;

        case ULTRIX_SYS_getpagesize:
                debug("[ getpagesize() ]\n");
                result_low = 4096;
                break;

        case ULTRIX_SYS_getdtablesize:
                debug("[ getdtablesize() ]\n");
                result_low = getdtablesize();
                break;

        case ULTRIX_SYS_gethostname:
                debug("[ gethostname(0x%llx,%lli) ]\n",
                    (long long)arg0, (long long)arg1);
                result_low = 0;
                if (arg1 != 0 && arg1 < 500000) {
                        unsigned char *buf = malloc(arg1);
                        unsigned int i;

                        result_low = gethostname((char *)buf, arg1);
                        for (i = 0; i<arg1 && i < arg1; i++)
                                cpu->memory_rw(cpu, cpu->mem, arg0 + i,
                                    &buf[i], 1, MEM_WRITE, CACHE_NONE);

                        free(buf);
                } else {
                        error_flag = 1;
                        error_code = 5555; /* TODO */  /*  ENOMEM  */
                }
                break;

        case ULTRIX_SYS_writev:
                descr = arg0;
                debug("[ writev(%lli,0x%llx,%lli) ]\n",
                    (long long)arg0, (long long)arg1, (long long)arg2);

                if (arg1 != 0) {
                        unsigned int i, total = 0;

                        for (i=0; i<arg2; i++) {
                                uint32_t iov_base, iov_len;
                                iov_base = load_32bit_word(cpu,
                                    arg1 + 8*i + 0);    /*  char *  */
                                iov_len  = load_32bit_word(cpu,
                                    arg1 + 8*i + 4);    /*  size_t  */

                                if (iov_len != 0) {
                                        unsigned char *charbuf =
                                            malloc(iov_len);
                                        if (charbuf == NULL) {
                                                fprintf(stderr, "out of memory"
                                                    " in useremul__ultrix()\n");
                                                exit(1);
                                        }

                                        /*  TODO: address validity check  */
                                        cpu->memory_rw(cpu, cpu->mem, (uint64_t)
                                            iov_base, charbuf, iov_len,
                                            MEM_READ, CACHE_DATA);
                                        total += write(descr, charbuf, iov_len);
                                        free(charbuf);
                                }
                        }

                        result_low = total;
                }
                break;

        case ULTRIX_SYS_gethostid:
                debug("[ gethostid() ]\n");
                /*  This is supposed to return a unique 32-bit host id.  */
                result_low = 0x12345678;
                break;

        case ULTRIX_SYS_gettimeofday:
                debug("[ gettimeofday(0x%llx,0x%llx) ]\n",
                    (long long)arg0, (long long)arg1);
                result_low = gettimeofday(&tv, &tz);
                if (result_low) {
                        error_flag = 1;
                        error_code = errno;
                } else {
                        if (arg0 != 0) {
                                /*  Store tv.tv_sec and tv.tv_usec
                                    as 'long' (32-bit) values:  */
                                store_32bit_word(cpu, arg0 + 0, tv.tv_sec);
                                store_32bit_word(cpu, arg0 + 4, tv.tv_usec);
                        }
                        if (arg1 != 0) {
                                /*  Store tz.tz_minuteswest and
                                    tz.tz_dsttime as 'long' (32-bit) values:  */
                                store_32bit_word(cpu, arg1 + 0,
                                    tz.tz_minuteswest);
                                store_32bit_word(cpu, arg1 + 4, tz.tz_dsttime);
                        }
                }
                break;

        default:
                fatal("[ UNIMPLEMENTED ultrix syscall %i ]\n", sysnr);
                error_flag = 1;
                error_code = 78;  /*  ENOSYS  */
        }

        /*
         *  Ultrix/mips return values:
         *
         *  TODO
         *
         *  a3 is 0 if the syscall was ok, otherwise 1.
         *  v0 (and sometimes v1) contain the result value.
         */
        cpu->cd.mips.gpr[MIPS_GPR_A3] = error_flag;
        if (error_flag)
                cpu->cd.mips.gpr[MIPS_GPR_V0] = error_code;
        else
                cpu->cd.mips.gpr[MIPS_GPR_V0] = result_low;

        if (result_high_set)
                cpu->cd.mips.gpr[MIPS_GPR_V1] = result_high;

        /* TODO */
}


/*
 *  useremul_name_to_useremul():
 *
 *  Example:
 *     Input:  name = "netbsd/pmax"
 *     Output: sets *arch = ARCH_MIPS, *machine_name = "NetBSD/pmax",
 *             and *cpu_name = "R3000".
 */
void useremul_name_to_useremul(struct cpu *cpu, char *name, int *arch,
        char **machine_name, char **cpu_name)
{
        struct syscall_emul *sep;

        sep = first_syscall_emul;

        while (sep != NULL) {
                if (strcasecmp(name, sep->name) == 0) {
                        if (cpu_family_ptr_by_number(sep->arch) == NULL) {
                                printf("\nSupport for the CPU family needed"
                                    " for '%s' userland emulation was not"
                                    " enabled at configuration time.\n",
                                    sep->name);
                                exit(1);
                        }

                        if (cpu != NULL)
                                cpu->useremul_syscall = sep->f;

                        if (arch != NULL)
                                *arch = sep->arch;

                        if (machine_name != NULL) {
                                *machine_name = strdup(sep->name);
                                if (*machine_name == NULL) {
                                        printf("out of memory\n");
                                        exit(1);
                                }
                        }

                        if (cpu_name != NULL) {
                                *cpu_name = strdup(sep->cpu_name);
                                if (*cpu_name == NULL) {
                                        printf("out of memory\n");
                                        exit(1);
                                }
                        }
                        return;
                }

                sep = sep->next;
        }

        fatal("Unknown userland emulation '%s'\n", name);
        exit(1);
}


/*
 *  add_useremul():
 *
 *  For internal use, from useremul_init() only. Adds an emulation mode.
 */
static void add_useremul(char *name, int arch, char *cpu_name,
        void (*f)(struct cpu *, uint32_t),
        void (*setup)(struct cpu *, int, char **))
{
        struct syscall_emul *sep;

        sep = malloc(sizeof(struct syscall_emul));
        if (sep == NULL) {
                printf("add_useremul(): out of memory\n");
                exit(1);
        }
        memset(sep, 0, sizeof(sep));

        sep->name     = name;
        sep->arch     = arch;
        sep->cpu_name = cpu_name;
        sep->f        = f;
        sep->setup    = setup;

        sep->next = first_syscall_emul;
        first_syscall_emul = sep;
}


/*
 *  useremul_list_emuls():
 *
 *  List all available userland emulation modes.  (Actually, only those which
 *  have CPU support enabled.)
 */
void useremul_list_emuls(void)
{
        struct syscall_emul *sep;
        int iadd = 8;

        sep = first_syscall_emul;

        if (sep == NULL)
                return;

        debug("The following userland-only (syscall) emulation modes are"
            " available:\n\n");
        debug_indentation(iadd);

        while (sep != NULL) {
                if (cpu_family_ptr_by_number(sep->arch) != NULL) {
                        debug("%s (default CPU \"%s\")\n",
                            sep->name, sep->cpu_name);
                }

                sep = sep->next;
        }

        debug_indentation(-iadd);
        debug("\n(Most of these modes are bogus.)\n\n");
}


/*
 *  useremul_init():
 *
 *  This function should be called before any other useremul_*() function
 *  is used.
 */
void useremul_init(void)
{
        /*  Note: These are in reverse alphabetic order:  */

        add_useremul("Ultrix", ARCH_MIPS, "R3000",
            useremul__ultrix, useremul__ultrix_setup);

        add_useremul("NetBSD/powerpc", ARCH_PPC, "PPC750",
            useremul__netbsd, useremul__netbsd_setup);

        add_useremul("NetBSD/pmax", ARCH_MIPS, "R3000",
            useremul__netbsd, useremul__netbsd_setup);

        add_useremul("NetBSD/arm", ARCH_ARM, "ARM",
            useremul__netbsd, useremul__netbsd_setup);

        add_useremul("NetBSD/amd64", ARCH_X86, "AMD64",
            useremul__netbsd, useremul__netbsd_setup);

        add_useremul("Linux/PPC64", ARCH_PPC, "PPC970",
            useremul__linux, useremul__linux_setup);

        add_useremul("FreeBSD/Alpha", ARCH_ALPHA, "Alpha",
            useremul__freebsd, useremul__freebsd_setup);
}
