root/usr.bin/truss/syscalls.c
/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright 1997 Sean Eric Fagan
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Sean Eric Fagan
 * 4. Neither the name of the author may 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.
 */

/*
 * This file has routines used to print out system calls and their
 * arguments.
 */

#include <sys/aio.h>
#include <sys/capsicum.h>
#include <sys/types.h>
#define _WANT_FREEBSD11_KEVENT
#include <sys/event.h>
#include <sys/ioccom.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/poll.h>
#include <sys/procfs.h>
#include <sys/ptrace.h>
#include <sys/resource.h>
#include <sys/sched.h>
#include <sys/socket.h>
#define _WANT_FREEBSD11_STAT
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <netlink/netlink.h>
#include <arpa/inet.h>

#include <assert.h>
#include <ctype.h>
#include <err.h>
#define _WANT_KERNEL_ERRNO
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysdecode.h>
#include <unistd.h>
#include <vis.h>

#include "truss.h"
#include "extern.h"
#include "syscall.h"

/*
 * This should probably be in its own file, sorted alphabetically.
 *
 * Note: We only scan this table on the initial syscall number to calling
 * convention lookup, i.e. once each time a new syscall is encountered. This
 * is unlikely to be a performance issue, but if it is we could sort this array
 * and use a binary search instead.
 */
static const struct syscall_decode decoded_syscalls[] = {
        /* Native ABI */
        { .name = "__acl_aclcheck_fd", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_aclcheck_file", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_aclcheck_link", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_delete_fd", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Acltype, 1 } } },
        { .name = "__acl_delete_file", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Acltype, 1 } } },
        { .name = "__acl_delete_link", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Acltype, 1 } } },
        { .name = "__acl_get_fd", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_get_file", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_get_link", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_set_fd", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_set_file", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__acl_set_link", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Acltype, 1 }, { Ptr, 2 } } },
        { .name = "__cap_rights_get", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Int, 1 }, { CapRights | OUT, 2 } } },
        { .name = "__getcwd", .ret_type = 1, .nargs = 2,
          .args = { { Name | OUT, 0 }, { Int, 1 } } },
        { .name = "__realpathat", .ret_type = 1, .nargs = 5,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Name | OUT, 2 },
                    { Sizet, 3 }, { Int, 4} } },
        { .name = "_umtx_op", .ret_type = 1, .nargs = 5,
          .args = { { Ptr, 0 }, { Umtxop, 1 }, { LongHex, 2 }, { Ptr, 3 },
                    { Ptr, 4 } } },
        { .name = "accept", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Sockaddr | OUT, 1 }, { Ptr | OUT, 2 } } },
        { .name = "access", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Accessmode, 1 } } },
        { .name = "aio_cancel", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Aiocb, 1 } } },
        { .name = "aio_error", .ret_type = 1, .nargs = 1,
          .args = { { Aiocb, 0 } } },
        { .name = "aio_fsync", .ret_type = 1, .nargs = 2,
          .args = { { AiofsyncOp, 0 }, { Aiocb, 1 } } },
        { .name = "aio_mlock", .ret_type = 1, .nargs = 1,
          .args = { { Aiocb, 0 } } },
        { .name = "aio_read", .ret_type = 1, .nargs = 1,
          .args = { { Aiocb, 0 } } },
        { .name = "aio_return", .ret_type = 1, .nargs = 1,
          .args = { { Aiocb, 0 } } },
        { .name = "aio_suspend", .ret_type = 1, .nargs = 3,
          .args = { { AiocbArray, 0 }, { Int, 1 }, { Timespec, 2 } } },
        { .name = "aio_waitcomplete", .ret_type = 1, .nargs = 2,
          .args = { { AiocbPointer | OUT, 0 }, { Timespec, 1 } } },
        { .name = "aio_write", .ret_type = 1, .nargs = 1,
          .args = { { Aiocb, 0 } } },
        { .name = "bind", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Sockaddr | IN, 1 }, { Socklent, 2 } } },
        { .name = "bindat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Int, 1 }, { Sockaddr | IN, 2 },
                    { Int, 3 } } },
        { .name = "break", .ret_type = 1, .nargs = 1,
          .args = { { Ptr, 0 } } },
        { .name = "cap_fcntls_get", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { CapFcntlRights | OUT, 1 } } },
        { .name = "cap_fcntls_limit", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { CapFcntlRights, 1 } } },
        { .name = "cap_getmode", .ret_type = 1, .nargs = 1,
          .args = { { PUInt | OUT, 0 } } },
        { .name = "cap_rights_limit", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { CapRights, 1 } } },
        { .name = "chdir", .ret_type = 1, .nargs = 1,
          .args = { { Name, 0 } } },
        { .name = "chflags", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { FileFlags, 1 } } },
        { .name = "chflagsat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { FileFlags, 2 },
                    { Atflags, 3 } } },
        { .name = "chmod", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Octal, 1 } } },
        { .name = "chown", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Int, 1 }, { Int, 2 } } },
        { .name = "chroot", .ret_type = 1, .nargs = 1,
          .args = { { Name, 0 } } },
        { .name = "clock_gettime", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Timespec | OUT, 1 } } },
        { .name = "close", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "closefrom", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "close_range", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Int, 1 }, { Closerangeflags, 2 } } },
        { .name = "compat11.fstat", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Stat11 | OUT, 1 } } },
        { .name = "compat11.fstatat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Stat11 | OUT, 2 },
                    { Atflags, 3 } } },
        { .name = "compat11.kevent", .ret_type = 1, .nargs = 6,
          .args = { { Int, 0 }, { Kevent11, 1 }, { Int, 2 },
                    { Kevent11 | OUT, 3 }, { Int, 4 }, { Timespec, 5 } } },
        { .name = "compat11.lstat", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Stat11 | OUT, 1 } } },
        { .name = "compat11.mknod", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Octal, 1 }, { Int, 2 } } },
        { .name = "compat11.mknodat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name, 1 }, { Octal, 2 }, { Int, 3 } } },
        { .name = "compat11.stat", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Stat11 | OUT, 1 } } },
        { .name = "connect", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Sockaddr | IN, 1 }, { Socklent, 2 } } },
        { .name = "connectat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Int, 1 }, { Sockaddr | IN, 2 },
                    { Int, 3 } } },
        { .name = "dup", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "dup2", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Int, 1 } } },
        { .name = "eaccess", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Accessmode, 1 } } },
        { .name = "execve", .ret_type = 1, .nargs = 3,
          .args = { { Name | IN, 0 }, { ExecArgs | IN, 1 },
                    { ExecEnv | IN, 2 } } },
        { .name = "exit", .ret_type = 0, .nargs = 1,
          .args = { { Hex, 0 } } },
        { .name = "extattr_delete_fd", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Extattrnamespace, 1 }, { Name, 2 } } },
        { .name = "extattr_delete_file", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { Name, 2 } } },
        { .name = "extattr_delete_link", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { Name, 2 } } },
        { .name = "extattr_get_fd", .ret_type = 1, .nargs = 5,
          .args = { { Int, 0 }, { Extattrnamespace, 1 }, { Name, 2 },
                    { BinString | OUT, 3 }, { Sizet, 4 } } },
        { .name = "extattr_get_file", .ret_type = 1, .nargs = 5,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { Name, 2 },
                    { BinString | OUT, 3 }, { Sizet, 4 } } },
        { .name = "extattr_get_link", .ret_type = 1, .nargs = 5,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { Name, 2 },
                    { BinString | OUT, 3 }, { Sizet, 4 } } },
        { .name = "extattr_list_fd", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { Extattrnamespace, 1 }, { BinString | OUT, 2 },
                    { Sizet, 3 } } },
        { .name = "extattr_list_file", .ret_type = 1, .nargs = 4,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { BinString | OUT, 2 },
                    { Sizet, 3 } } },
        { .name = "extattr_list_link", .ret_type = 1, .nargs = 4,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { BinString | OUT, 2 },
                    { Sizet, 3 } } },
        { .name = "extattr_set_fd", .ret_type = 1, .nargs = 5,
          .args = { { Int, 0 }, { Extattrnamespace, 1 }, { Name, 2 },
                    { BinString | IN, 3 }, { Sizet, 4 } } },
        { .name = "extattr_set_file", .ret_type = 1, .nargs = 5,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { Name, 2 },
                    { BinString | IN, 3 }, { Sizet, 4 } } },
        { .name = "extattr_set_link", .ret_type = 1, .nargs = 5,
          .args = { { Name, 0 }, { Extattrnamespace, 1 }, { Name, 2 },
                    { BinString | IN, 3 }, { Sizet, 4 } } },
        { .name = "extattrctl", .ret_type = 1, .nargs = 5,
          .args = { { Name, 0 }, { Hex, 1 }, { Name, 2 },
                    { Extattrnamespace, 3 }, { Name, 4 } } },
        { .name = "faccessat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Accessmode, 2 },
                    { Atflags, 3 } } },
        { .name = "fchflags", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { FileFlags, 1 } } },
        { .name = "fchmod", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Octal, 1 } } },
        { .name = "fchmodat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name, 1 }, { Octal, 2 }, { Atflags, 3 } } },
        { .name = "fchown", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Int, 1 }, { Int, 2 } } },
        { .name = "fchownat", .ret_type = 1, .nargs = 5,
          .args = { { Atfd, 0 }, { Name, 1 }, { Int, 2 }, { Int, 3 },
                    { Atflags, 4 } } },
        { .name = "fcntl", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Fcntl, 1 }, { Fcntlflag, 2 } } },
        { .name = "fdatasync", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "flock", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Flockop, 1 } } },
        { .name = "fstat", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Stat | OUT, 1 } } },
        { .name = "fstatat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Stat | OUT, 2 },
                    { Atflags, 3 } } },
        { .name = "fstatfs", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { StatFs | OUT, 1 } } },
        { .name = "fsync", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "ftruncate", .ret_type = 1, .nargs = 2,
          .args = { { Int | IN, 0 }, { QuadHex | IN, 1 } } },
        { .name = "futimens", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Timespec2 | IN, 1 } } },
        { .name = "futimes", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Timeval2 | IN, 1 } } },
        { .name = "futimesat", .ret_type = 1, .nargs = 3,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Timeval2 | IN, 2 } } },
        { .name = "getdirentries", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { BinString | OUT, 1 }, { Int, 2 },
                    { PQuadHex | OUT, 3 } } },
        { .name = "getfsstat", .ret_type = 1, .nargs = 3,
          .args = { { Ptr, 0 }, { Long, 1 }, { Getfsstatmode, 2 } } },
        { .name = "getitimer", .ret_type = 1, .nargs = 2,
          .args = { { Itimerwhich, 0 }, { Itimerval | OUT, 2 } } },
        { .name = "getpeername", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Sockaddr | OUT, 1 }, { Ptr | OUT, 2 } } },
        { .name = "getpgid", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "getpriority", .ret_type = 1, .nargs = 2,
          .args = { { Priowhich, 0 }, { Int, 1 } } },
        { .name = "getrandom", .ret_type = 1, .nargs = 3,
          .args = { { BinString | OUT, 0 }, { Sizet, 1 }, { UInt, 2 } } },
        { .name = "getrlimit", .ret_type = 1, .nargs = 2,
          .args = { { Resource, 0 }, { Rlimit | OUT, 1 } } },
        { .name = "getrusage", .ret_type = 1, .nargs = 2,
          .args = { { RusageWho, 0 }, { Rusage | OUT, 1 } } },
        { .name = "getsid", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "getsockname", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Sockaddr | OUT, 1 }, { Ptr | OUT, 2 } } },
        { .name = "getsockopt", .ret_type = 1, .nargs = 5,
          .args = { { Int, 0 }, { Sockoptlevel, 1 }, { Sockoptname, 2 },
                    { Ptr | OUT, 3 }, { Ptr | OUT, 4 } } },
        { .name = "gettimeofday", .ret_type = 1, .nargs = 2,
          .args = { { Timeval | OUT, 0 }, { Ptr, 1 } } },
        { .name = "inotify_add_watch_at", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { Atfd, 1 }, { Name | IN, 2 },
                    { Inotifyflags, 3 } } },
        { .name = "ioctl", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Ioctl, 1 }, { Ptr, 2 } } },
        { .name = "kevent", .ret_type = 1, .nargs = 6,
          .args = { { Int, 0 }, { Kevent, 1 }, { Int, 2 }, { Kevent | OUT, 3 },
                    { Int, 4 }, { Timespec, 5 } } },
        { .name = "kill", .ret_type = 1, .nargs = 2,
          .args = { { Int | IN, 0 }, { Signal | IN, 1 } } },
        { .name = "kldfind", .ret_type = 1, .nargs = 1,
          .args = { { Name | IN, 0 } } },
        { .name = "kldfirstmod", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "kldload", .ret_type = 1, .nargs = 1,
          .args = { { Name | IN, 0 } } },
        { .name = "kldnext", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "kldstat", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Ptr, 1 } } },
        { .name = "kldsym", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Kldsymcmd, 1 }, { Ptr, 2 } } },
        { .name = "kldunload", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "kldunloadf", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Kldunloadflags, 1 } } },
        { .name = "kse_release", .ret_type = 0, .nargs = 1,
          .args = { { Timespec, 0 } } },
        { .name = "lchflags", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { FileFlags, 1 } } },
        { .name = "lchmod", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Octal, 1 } } },
        { .name = "lchown", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Int, 1 }, { Int, 2 } } },
        { .name = "link", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Name, 1 } } },
        { .name = "linkat", .ret_type = 1, .nargs = 5,
          .args = { { Atfd, 0 }, { Name, 1 }, { Atfd, 2 }, { Name, 3 },
                    { Atflags, 4 } } },
        { .name = "lio_listio", .ret_type = 1, .nargs = 4,
          .args = { { LioMode, 0 }, { AiocbArray, 1 }, { Int, 2 },
                    { Sigevent, 3 } } },
        { .name = "listen", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Int, 1 } } },
        { .name = "lseek", .ret_type = 2, .nargs = 3,
          .args = { { Int, 0 }, { QuadHex, 1 }, { Whence, 2 } } },
        { .name = "lstat", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Stat | OUT, 1 } } },
        { .name = "lutimes", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Timeval2 | IN, 1 } } },
        { .name = "madvise", .ret_type = 1, .nargs = 3,
          .args = { { Ptr, 0 }, { Sizet, 1 }, { Madvice, 2 } } },
        { .name = "minherit", .ret_type = 1, .nargs = 3,
          .args = { { Ptr, 0 }, { Sizet, 1 }, { Minherit, 2 } } },
        { .name = "mkdir", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Octal, 1 } } },
        { .name = "mkdirat", .ret_type = 1, .nargs = 3,
          .args = { { Atfd, 0 }, { Name, 1 }, { Octal, 2 } } },
        { .name = "mkfifo", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Octal, 1 } } },
        { .name = "mkfifoat", .ret_type = 1, .nargs = 3,
          .args = { { Atfd, 0 }, { Name, 1 }, { Octal, 2 } } },
        { .name = "mknod", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Octal, 1 }, { Quad, 2 } } },
        { .name = "mknodat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name, 1 }, { Octal, 2 }, { Quad, 3 } } },
        { .name = "mlock", .ret_type = 1, .nargs = 2,
          .args = { { Ptr, 0 }, { Sizet, 1 } } },
        { .name = "mlockall", .ret_type = 1, .nargs = 1,
          .args = { { Mlockall, 0 } } },
        { .name = "mmap", .ret_type = 1, .nargs = 6,
          .args = { { Ptr, 0 }, { Sizet, 1 }, { Mprot, 2 }, { Mmapflags, 3 },
                    { Int, 4 }, { QuadHex, 5 } } },
        { .name = "modfind", .ret_type = 1, .nargs = 1,
          .args = { { Name | IN, 0 } } },
        { .name = "mount", .ret_type = 1, .nargs = 4,
          .args = { { Name, 0 }, { Name, 1 }, { Mountflags, 2 }, { Ptr, 3 } } },
        { .name = "mprotect", .ret_type = 1, .nargs = 3,
          .args = { { Ptr, 0 }, { Sizet, 1 }, { Mprot, 2 } } },
        { .name = "msync", .ret_type = 1, .nargs = 3,
          .args = { { Ptr, 0 }, { Sizet, 1 }, { Msync, 2 } } },
        { .name = "munlock", .ret_type = 1, .nargs = 2,
          .args = { { Ptr, 0 }, { Sizet, 1 } } },
        { .name = "munmap", .ret_type = 1, .nargs = 2,
          .args = { { Ptr, 0 }, { Sizet, 1 } } },
        { .name = "nanosleep", .ret_type = 1, .nargs = 1,
          .args = { { Timespec, 0 } } },
        { .name = "nmount", .ret_type = 1, .nargs = 3,
          .args = { { Iovec | IN, 0 }, { UInt, 1 }, { Mountflags, 2 } } },
        { .name = "open", .ret_type = 1, .nargs = 3,
          .args = { { Name | IN, 0 }, { Open, 1 }, { Octal, 2 } } },
        { .name = "openat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Open, 2 },
                    { Octal, 3 } } },
        { .name = "pathconf", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Pathconf, 1 } } },
        { .name = "pipe", .ret_type = 1, .nargs = 1,
          .args = { { PipeFds | OUT, 0 } } },
        { .name = "pipe2", .ret_type = 1, .nargs = 2,
          .args = { { Ptr, 0 }, { Pipe2, 1 } } },
        { .name = "poll", .ret_type = 1, .nargs = 3,
          .args = { { Pollfd, 0 }, { Int, 1 }, { Int, 2 } } },
        { .name = "posix_fadvise", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { QuadHex, 1 }, { QuadHex, 2 },
                    { Fadvice, 3 } } },
        { .name = "posix_openpt", .ret_type = 1, .nargs = 1,
          .args = { { Open, 0 } } },
        { .name = "ppoll", .ret_type = 1, .nargs = 4,
          .args = { { Pollfd, 0 }, { Int, 1 }, { Timespec | IN, 2 },
                    { Sigset | IN, 3 } } },
        { .name = "pread", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { BinString | OUT, 1 }, { Sizet, 2 },
                    { QuadHex, 3 } } },
        { .name = "preadv", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { Iovec | OUT, 1 }, { Int, 2 },
                    { QuadHex, 3 } } },
        { .name = "procctl", .ret_type = 1, .nargs = 4,
          .args = { { Idtype, 0 }, { Quad, 1 }, { Procctl, 2 }, { Ptr, 3 } } },
        { .name = "ptrace", .ret_type = 1, .nargs = 4,
          .args = { { Ptraceop, 0 }, { Int, 1 }, { Ptr, 2 }, { Int, 3 } } },
        { .name = "pwrite", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { BinString | IN, 1 }, { Sizet, 2 },
                    { QuadHex, 3 } } },
        { .name = "pwritev", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { Iovec | IN, 1 }, { Int, 2 },
                    { QuadHex, 3 } } },
        { .name = "quotactl", .ret_type = 1, .nargs = 4,
          .args = { { Name, 0 }, { Quotactlcmd, 1 }, { Int, 2 }, { Ptr, 3 } } },
        { .name = "read", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { BinString | OUT, 1 }, { Sizet, 2 } } },
        { .name = "readlink", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Readlinkres | OUT, 1 }, { Sizet, 2 } } },
        { .name = "readlinkat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name, 1 }, { Readlinkres | OUT, 2 },
                    { Sizet, 3 } } },
        { .name = "readv", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Iovec | OUT, 1 }, { Int, 2 } } },
        { .name = "reboot", .ret_type = 1, .nargs = 1,
          .args = { { Reboothowto, 0 } } },
        { .name = "recvfrom", .ret_type = 1, .nargs = 6,
          .args = { { Int, 0 }, { BinString | OUT, 1 }, { Sizet, 2 },
                    { Msgflags, 3 }, { Sockaddr | OUT, 4 },
                    { Ptr | OUT, 5 } } },
        { .name = "recvmsg", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Msghdr | OUT, 1 }, { Msgflags, 2 } } },
        { .name = "rename", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Name, 1 } } },
        { .name = "renameat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name, 1 }, { Atfd, 2 }, { Name, 3 } } },
        { .name = "rfork", .ret_type = 1, .nargs = 1,
          .args = { { Rforkflags, 0 } } },
        { .name = "rmdir", .ret_type = 1, .nargs = 1,
          .args = { { Name, 0 } } },
        { .name = "rtprio", .ret_type = 1, .nargs = 3,
          .args = { { Rtpriofunc, 0 }, { Int, 1 }, { Ptr, 2 } } },
        { .name = "rtprio_thread", .ret_type = 1, .nargs = 3,
          .args = { { Rtpriofunc, 0 }, { Int, 1 }, { Ptr, 2 } } },
        { .name = "sched_get_priority_max", .ret_type = 1, .nargs = 1,
          .args = { { Schedpolicy, 0 } } },
        { .name = "sched_get_priority_min", .ret_type = 1, .nargs = 1,
          .args = { { Schedpolicy, 0 } } },
        { .name = "sched_getparam", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Schedparam | OUT, 1 } } },
        { .name = "sched_getscheduler", .ret_type = 1, .nargs = 1,
          .args = { { Int, 0 } } },
        { .name = "sched_rr_get_interval", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Timespec | OUT, 1 } } },
        { .name = "sched_setparam", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Schedparam, 1 } } },
        { .name = "sched_setscheduler", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Schedpolicy, 1 }, { Schedparam, 2 } } },
        { .name = "sctp_generic_recvmsg", .ret_type = 1, .nargs = 7,
          .args = { { Int, 0 }, { Iovec | OUT, 1 }, { Int, 2 },
                    { Sockaddr | OUT, 3 }, { Ptr | OUT, 4 },
                    { Sctpsndrcvinfo | OUT, 5 }, { Ptr | OUT, 6 } } },
        { .name = "sctp_generic_sendmsg", .ret_type = 1, .nargs = 7,
          .args = { { Int, 0 }, { BinString | IN, 1 }, { Int, 2 },
                    { Sockaddr | IN, 3 }, { Socklent, 4 },
                    { Sctpsndrcvinfo | IN, 5 }, { Msgflags, 6 } } },
        { .name = "sctp_generic_sendmsg_iov", .ret_type = 1, .nargs = 7,
          .args = { { Int, 0 }, { Iovec | IN, 1 }, { Int, 2 },
                    { Sockaddr | IN, 3 }, { Socklent, 4 },
                    { Sctpsndrcvinfo | IN, 5 }, { Msgflags, 6 } } },
        { .name = "sendfile", .ret_type = 1, .nargs = 7,
          .args = { { Int, 0 }, { Int, 1 }, { QuadHex, 2 }, { Sizet, 3 },
                    { Sendfilehdtr, 4 }, { QuadHex | OUT, 5 },
                    { Sendfileflags, 6 } } },
        { .name = "select", .ret_type = 1, .nargs = 5,
          .args = { { Int, 0 }, { Fd_set, 1 }, { Fd_set, 2 }, { Fd_set, 3 },
                    { Timeval, 4 } } },
        { .name = "sendmsg", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Msghdr | IN, 1 }, { Msgflags, 2 } } },
        { .name = "sendto", .ret_type = 1, .nargs = 6,
          .args = { { Int, 0 }, { BinString | IN, 1 }, { Sizet, 2 },
                    { Msgflags, 3 }, { Sockaddr | IN, 4 },
                    { Socklent | IN, 5 } } },
        { .name = "setitimer", .ret_type = 1, .nargs = 3,
          .args = { { Itimerwhich, 0 }, { Itimerval, 1 },
                    { Itimerval | OUT, 2 } } },
        { .name = "setpriority", .ret_type = 1, .nargs = 3,
          .args = { { Priowhich, 0 }, { Int, 1 }, { Int, 2 } } },
        { .name = "setrlimit", .ret_type = 1, .nargs = 2,
          .args = { { Resource, 0 }, { Rlimit | IN, 1 } } },
        { .name = "setsockopt", .ret_type = 1, .nargs = 5,
          .args = { { Int, 0 }, { Sockoptlevel, 1 }, { Sockoptname, 2 },
                    { Ptr | IN, 3 }, { Socklent, 4 } } },
        { .name = "shm_open", .ret_type = 1, .nargs = 3,
          .args = { { ShmName | IN, 0 }, { Open, 1 }, { Octal, 2 } } },
        { .name = "shm_open2", .ret_type = 1, .nargs = 5,
          .args = { { ShmName | IN, 0 }, { Open, 1 }, { Octal, 2 },
                    { ShmFlags, 3 }, { Name | IN, 4 } } },
        { .name = "shm_rename", .ret_type = 1, .nargs = 3,
          .args = { { Name | IN, 0 }, { Name | IN, 1 }, { Hex, 2 } } },
        { .name = "shm_unlink", .ret_type = 1, .nargs = 1,
          .args = { { Name | IN, 0 } } },
        { .name = "shutdown", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Shutdown, 1 } } },
        { .name = "sigaction", .ret_type = 1, .nargs = 3,
          .args = { { Signal, 0 }, { Sigaction | IN, 1 },
                    { Sigaction | OUT, 2 } } },
        { .name = "sigpending", .ret_type = 1, .nargs = 1,
          .args = { { Sigset | OUT, 0 } } },
        { .name = "sigprocmask", .ret_type = 1, .nargs = 3,
          .args = { { Sigprocmask, 0 }, { Sigset, 1 }, { Sigset | OUT, 2 } } },
        { .name = "sigqueue", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Signal, 1 }, { LongHex, 2 } } },
        { .name = "sigreturn", .ret_type = 1, .nargs = 1,
          .args = { { Ptr, 0 } } },
        { .name = "sigsuspend", .ret_type = 1, .nargs = 1,
          .args = { { Sigset | IN, 0 } } },
        { .name = "sigtimedwait", .ret_type = 1, .nargs = 3,
          .args = { { Sigset | IN, 0 }, { Siginfo | OUT, 1 },
                    { Timespec | IN, 2 } } },
        { .name = "sigwait", .ret_type = 1, .nargs = 2,
          .args = { { Sigset | IN, 0 }, { PSig | OUT, 1 } } },
        { .name = "sigwaitinfo", .ret_type = 1, .nargs = 2,
          .args = { { Sigset | IN, 0 }, { Siginfo | OUT, 1 } } },
        { .name = "socket", .ret_type = 1, .nargs = 3,
          .args = { { Sockdomain, 0 }, { Socktype, 1 }, { Sockprotocol, 2 } } },
        { .name = "stat", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Stat | OUT, 1 } } },
        { .name = "statfs", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { StatFs | OUT, 1 } } },
        { .name = "symlink", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Name, 1 } } },
        { .name = "symlinkat", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Atfd, 1 }, { Name, 2 } } },
        { .name = "sysarch", .ret_type = 1, .nargs = 2,
          .args = { { Sysarch, 0 }, { Ptr, 1 } } },
        { .name = "__sysctl", .ret_type = 1, .nargs = 6,
          .args = { { Sysctl, 0 }, { Sizet, 1 }, { Ptr, 2 }, { Ptr, 3 },
                    { Ptr, 4 }, { Sizet, 5 } } },
        { .name = "__sysctlbyname", .ret_type = 1, .nargs = 6,
          .args = { { Name, 0 }, { Sizet, 1 }, { Ptr, 2 }, { Ptr, 3 },
                    { Ptr, 4}, { Sizet, 5 } } },
        { .name = "thr_kill", .ret_type = 1, .nargs = 2,
          .args = { { Long, 0 }, { Signal, 1 } } },
        { .name = "thr_self", .ret_type = 1, .nargs = 1,
          .args = { { Ptr, 0 } } },
        { .name = "thr_set_name", .ret_type = 1, .nargs = 2,
          .args = { { Long, 0 }, { Name, 1 } } },
        { .name = "truncate", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { QuadHex | IN, 1 } } },
        { .name = "unlink", .ret_type = 1, .nargs = 1,
          .args = { { Name, 0 } } },
        { .name = "unlinkat", .ret_type = 1, .nargs = 3,
          .args = { { Atfd, 0 }, { Name, 1 }, { Atflags, 2 } } },
        { .name = "unmount", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Mountflags, 1 } } },
        { .name = "utimensat", .ret_type = 1, .nargs = 4,
          .args = { { Atfd, 0 }, { Name | IN, 1 }, { Timespec2 | IN, 2 },
                    { Atflags, 3 } } },
        { .name = "utimes", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Timeval2 | IN, 1 } } },
        { .name = "utrace", .ret_type = 1, .nargs = 1,
          .args = { { Utrace, 0 } } },
        { .name = "wait4", .ret_type = 1, .nargs = 4,
          .args = { { Int, 0 }, { ExitStatus | OUT, 1 }, { Waitoptions, 2 },
                    { Rusage | OUT, 3 } } },
        { .name = "wait6", .ret_type = 1, .nargs = 6,
          .args = { { Idtype, 0 }, { Quad, 1 }, { ExitStatus | OUT, 2 },
                    { Waitoptions, 3 }, { Rusage | OUT, 4 },
                    { Siginfo | OUT, 5 } } },
        { .name = "write", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { BinString | IN, 1 }, { Sizet, 2 } } },
        { .name = "writev", .ret_type = 1, .nargs = 3,
          .args = { { Int, 0 }, { Iovec | IN, 1 }, { Int, 2 } } },

        /* Linux ABI */
        { .name = "linux_access", .ret_type = 1, .nargs = 2,
          .args = { { Name, 0 }, { Accessmode, 1 } } },
        { .name = "linux_execve", .ret_type = 1, .nargs = 3,
          .args = { { Name | IN, 0 }, { ExecArgs | IN, 1 },
                    { ExecEnv | IN, 2 } } },
        { .name = "linux_getitimer", .ret_type = 1, .nargs = 2,
          .args = { { Itimerwhich, 0 }, { Itimerval | OUT, 2 } } },
        { .name = "linux_lseek", .ret_type = 2, .nargs = 3,
          .args = { { Int, 0 }, { Int, 1 }, { Whence, 2 } } },
        { .name = "linux_mkdir", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Int, 1 } } },
        { .name = "linux_newfstat", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { Ptr | OUT, 1 } } },
        { .name = "linux_newlstat", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Ptr | OUT, 1 } } },
        { .name = "linux_newstat", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Ptr | OUT, 1 } } },
        { .name = "linux_open", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Hex, 1 }, { Octal, 2 } } },
        { .name = "linux_readlink", .ret_type = 1, .nargs = 3,
          .args = { { Name, 0 }, { Name | OUT, 1 }, { Sizet, 2 } } },
        { .name = "linux_setitimer", .ret_type = 1, .nargs = 3,
          .args = { { Itimerwhich, 0 }, { Itimerval, 1 },
                    { Itimerval | OUT, 2 } } },
        { .name = "linux_socketcall", .ret_type = 1, .nargs = 2,
          .args = { { Int, 0 }, { LinuxSockArgs, 1 } } },
        { .name = "linux_stat64", .ret_type = 1, .nargs = 2,
          .args = { { Name | IN, 0 }, { Ptr | OUT, 1 } } },
};
static STAILQ_HEAD(, syscall) seen_syscalls;

/* Xlat idea taken from strace */
struct xlat {
        int val;
        const char *str;
};

#define X(a)    { a, #a },
#define XEND    { 0, NULL }

static struct xlat poll_flags[] = {
        X(POLLSTANDARD) X(POLLIN) X(POLLPRI) X(POLLOUT) X(POLLERR)
        X(POLLHUP) X(POLLNVAL) X(POLLRDNORM) X(POLLRDBAND)
        X(POLLWRBAND) X(POLLINIGNEOF) X(POLLRDHUP) XEND
};

static struct xlat sigaction_flags[] = {
        X(SA_ONSTACK) X(SA_RESTART) X(SA_RESETHAND) X(SA_NOCLDSTOP)
        X(SA_NODEFER) X(SA_NOCLDWAIT) X(SA_SIGINFO) XEND
};

static struct xlat linux_socketcall_ops[] = {
        X(LINUX_SOCKET) X(LINUX_BIND) X(LINUX_CONNECT) X(LINUX_LISTEN)
        X(LINUX_ACCEPT) X(LINUX_GETSOCKNAME) X(LINUX_GETPEERNAME)
        X(LINUX_SOCKETPAIR) X(LINUX_SEND) X(LINUX_RECV) X(LINUX_SENDTO)
        X(LINUX_RECVFROM) X(LINUX_SHUTDOWN) X(LINUX_SETSOCKOPT)
        X(LINUX_GETSOCKOPT) X(LINUX_SENDMSG) X(LINUX_RECVMSG)
        XEND
};

static struct xlat lio_modes[] = {
        X(LIO_WAIT) X(LIO_NOWAIT)
        XEND
};

static struct xlat lio_opcodes[] = {
        X(LIO_WRITE) X(LIO_READ) X(LIO_READV) X(LIO_WRITEV) X(LIO_NOP)
        XEND
};

static struct xlat aio_fsync_ops[] = {
        X(O_SYNC)
        XEND
};

#undef X
#undef XEND

/*
 * Searches an xlat array for a value, and returns it if found.  Otherwise
 * return a string representation.
 */
static const char *
lookup(struct xlat *xlat, int val, int base)
{
        static char tmp[16];

        for (; xlat->str != NULL; xlat++)
                if (xlat->val == val)
                        return (xlat->str);
        switch (base) {
        case 8:
                sprintf(tmp, "0%o", val);
                break;
        case 16:
                sprintf(tmp, "0x%x", val);
                break;
        case 10:
                sprintf(tmp, "%u", val);
                break;
        default:
                errx(1, "Unknown lookup base");
        }
        return (tmp);
}

static const char *
xlookup(struct xlat *xlat, int val)
{

        return (lookup(xlat, val, 16));
}

/*
 * Searches an xlat array containing bitfield values.  Remaining bits
 * set after removing the known ones are printed at the end:
 * IN|0x400.
 */
static char *
xlookup_bits(struct xlat *xlat, int val)
{
        int len, rem;
        static char str[512];

        len = 0;
        rem = val;
        for (; xlat->str != NULL; xlat++) {
                if ((xlat->val & rem) == xlat->val) {
                        /*
                         * Don't print the "all-bits-zero" string unless all
                         * bits are really zero.
                         */
                        if (xlat->val == 0 && val != 0)
                                continue;
                        len += sprintf(str + len, "%s|", xlat->str);
                        rem &= ~(xlat->val);
                }
        }

        /*
         * If we have leftover bits or didn't match anything, print
         * the remainder.
         */
        if (rem || len == 0)
                len += sprintf(str + len, "0x%x", rem);
        if (len && str[len - 1] == '|')
                len--;
        str[len] = 0;
        return (str);
}

static void
print_integer_arg(const char *(*decoder)(int), FILE *fp, int value)
{
        const char *str;

        str = decoder(value);
        if (str != NULL)
                fputs(str, fp);
        else
                fprintf(fp, "%d", value);
}

static bool
print_mask_arg_part(bool (*decoder)(FILE *, int, int *), FILE *fp, int value,
    int *rem)
{

        return (decoder(fp, value, rem));
}

static void
print_mask_arg(bool (*decoder)(FILE *, int, int *), FILE *fp, int value)
{
        int rem;

        if (!print_mask_arg_part(decoder, fp, value, &rem))
                fprintf(fp, "0x%x", rem);
        else if (rem != 0)
                fprintf(fp, "|0x%x", rem);
}

static void
print_mask_arg32(bool (*decoder)(FILE *, uint32_t, uint32_t *), FILE *fp,
    uint32_t value)
{
        uint32_t rem;

        if (!decoder(fp, value, &rem))
                fprintf(fp, "0x%x", rem);
        else if (rem != 0)
                fprintf(fp, "|0x%x", rem);
}

/*
 * Add argument padding to subsequent system calls after Quad
 * syscall arguments as needed.  This used to be done by hand in the
 * decoded_syscalls table which was ugly and error prone.  It is
 * simpler to do the fixup of offsets at initialization time than when
 * decoding arguments.
 */
static void
quad_fixup(struct syscall_decode *sc)
{
        int offset, prev;
        u_int i;

        offset = 0;
        prev = -1;
        for (i = 0; i < sc->nargs; i++) {
                /* This arg type is a dummy that doesn't use offset. */
                if ((sc->args[i].type & ARG_MASK) == PipeFds)
                        continue;

                assert(prev < sc->args[i].offset);
                prev = sc->args[i].offset;
                sc->args[i].offset += offset;
                switch (sc->args[i].type & ARG_MASK) {
                case Quad:
                case QuadHex:
#if defined(__powerpc__) || defined(__arm__) || defined(__aarch64__)
                        /*
                         * 64-bit arguments on 32-bit powerpc and arm must be
                         * 64-bit aligned.  If the current offset is
                         * not aligned, the calling convention inserts
                         * a 32-bit pad argument that should be skipped.
                         */
                        if (sc->args[i].offset % 2 == 1) {
                                sc->args[i].offset++;
                                offset++;
                        }
#endif
                        offset++;
                default:
                        break;
                }
        }
}

static struct syscall *
find_syscall(struct procabi *abi, u_int number)
{
        struct extra_syscall *es;

        if (number < nitems(abi->syscalls))
                return (abi->syscalls[number]);
        STAILQ_FOREACH(es, &abi->extra_syscalls, entries) {
                if (es->number == number)
                        return (es->sc);
        }
        return (NULL);
}

static void
add_syscall(struct procabi *abi, u_int number, struct syscall *sc)
{
        struct extra_syscall *es;

        /*
         * quad_fixup() is currently needed for all 32-bit ABIs.
         * TODO: This should probably be a function pointer inside struct
         *  procabi instead.
         */
        if (abi->pointer_size == 4)
                quad_fixup(&sc->decode);

        if (number < nitems(abi->syscalls)) {
                assert(abi->syscalls[number] == NULL);
                abi->syscalls[number] = sc;
        } else {
                es = malloc(sizeof(*es));
                es->sc = sc;
                es->number = number;
                STAILQ_INSERT_TAIL(&abi->extra_syscalls, es, entries);
        }

        STAILQ_INSERT_HEAD(&seen_syscalls, sc, entries);
}

/*
 * If/when the list gets big, it might be desirable to do it
 * as a hash table or binary search.
 */
struct syscall *
get_syscall(struct threadinfo *t, u_int number, u_int nargs)
{
        struct syscall *sc;
        struct procabi *procabi;
        const char *sysdecode_name;
        const char *lookup_name;
        const char *name;
        u_int i;

        procabi = t->proc->abi;
        sc = find_syscall(procabi, number);
        if (sc != NULL)
                return (sc);

        /* Memory is not explicitly deallocated, it's released on exit(). */
        sysdecode_name = sysdecode_syscallname(procabi->abi, number);
        if (sysdecode_name == NULL)
                asprintf(__DECONST(char **, &name), "#%d", number);
        else
                name = sysdecode_name;

        sc = calloc(1, sizeof(*sc));
        sc->name = name;

        /* Also decode compat syscalls arguments by stripping the prefix. */
        lookup_name = name;
        if (procabi->compat_prefix != NULL && strncmp(procabi->compat_prefix,
            name, strlen(procabi->compat_prefix)) == 0)
                lookup_name += strlen(procabi->compat_prefix);

        for (i = 0; i < nitems(decoded_syscalls); i++) {
                if (strcmp(lookup_name, decoded_syscalls[i].name) == 0) {
                        sc->decode = decoded_syscalls[i];
                        add_syscall(t->proc->abi, number, sc);
                        return (sc);
                }
        }

        /* It is unknown.  Add it into the list. */
#if DEBUG
        fprintf(stderr, "unknown syscall %s -- setting args to %d\n", name,
            nargs);
#endif
        sc->unknown = sysdecode_name == NULL;
        sc->decode.ret_type = 1; /* Assume 1 return value. */
        sc->decode.nargs = nargs;
        for (i = 0; i < nargs; i++) {
                sc->decode.args[i].offset = i;
                /* Treat all unknown arguments as LongHex. */
                sc->decode.args[i].type = LongHex;
        }
        add_syscall(t->proc->abi, number, sc);
        return (sc);
}

/*
 * Copy a fixed amount of bytes from the process.
 */
static int
get_struct(pid_t pid, psaddr_t offset, void *buf, size_t len)
{
        struct ptrace_io_desc iorequest;

        iorequest.piod_op = PIOD_READ_D;
        iorequest.piod_offs = (void *)(uintptr_t)offset;
        iorequest.piod_addr = buf;
        iorequest.piod_len = len;
        if (ptrace(PT_IO, pid, (caddr_t)&iorequest, 0) < 0)
                return (-1);
        return (0);
}

#define MAXSIZE         4096

/*
 * Copy a string from the process.  Note that it is
 * expected to be a C string, but if max is set, it will
 * only get that much.
 */
static char *
get_string(pid_t pid, psaddr_t addr, int max)
{
        struct ptrace_io_desc iorequest;
        char *buf, *nbuf;
        size_t offset, size, totalsize;

        offset = 0;
        if (max)
                size = max + 1;
        else {
                /* Read up to the end of the current page. */
                size = PAGE_SIZE - (addr % PAGE_SIZE);
                if (size > MAXSIZE)
                        size = MAXSIZE;
        }
        totalsize = size;
        buf = malloc(totalsize);
        if (buf == NULL)
                return (NULL);
        for (;;) {
                iorequest.piod_op = PIOD_READ_D;
                iorequest.piod_offs = (void *)((uintptr_t)addr + offset);
                iorequest.piod_addr = buf + offset;
                iorequest.piod_len = size;
                if (ptrace(PT_IO, pid, (caddr_t)&iorequest, 0) < 0) {
                        free(buf);
                        return (NULL);
                }
                if (memchr(buf + offset, '\0', size) != NULL)
                        return (buf);
                offset += size;
                if (totalsize < MAXSIZE && max == 0) {
                        size = MAXSIZE - totalsize;
                        if (size > PAGE_SIZE)
                                size = PAGE_SIZE;
                        nbuf = realloc(buf, totalsize + size);
                        if (nbuf == NULL) {
                                buf[totalsize - 1] = '\0';
                                return (buf);
                        }
                        buf = nbuf;
                        totalsize += size;
                } else {
                        buf[totalsize - 1] = '\0';
                        return (buf);
                }
        }
}

static const char *
strsig2(int sig)
{
        static char tmp[32];
        const char *signame;

        signame = sysdecode_signal(sig);
        if (signame == NULL) {
                snprintf(tmp, sizeof(tmp), "%d", sig);
                signame = tmp;
        }
        return (signame);
}

static void
print_kevent(FILE *fp, struct kevent *ke)
{

        switch (ke->filter) {
        case EVFILT_READ:
        case EVFILT_WRITE:
        case EVFILT_VNODE:
        case EVFILT_PROC:
        case EVFILT_TIMER:
        case EVFILT_PROCDESC:
        case EVFILT_EMPTY:
                fprintf(fp, "%ju", (uintmax_t)ke->ident);
                break;
        case EVFILT_SIGNAL:
                fputs(strsig2(ke->ident), fp);
                break;
        default:
                fprintf(fp, "%p", (void *)ke->ident);
        }
        fprintf(fp, ",");
        print_integer_arg(sysdecode_kevent_filter, fp, ke->filter);
        fprintf(fp, ",");
        print_mask_arg(sysdecode_kevent_flags, fp, ke->flags);
        fprintf(fp, ",");
        sysdecode_kevent_fflags(fp, ke->filter, ke->fflags, 16);
        fprintf(fp, ",%#jx,%p", (uintmax_t)ke->data, ke->udata);
}

static void
print_utrace(FILE *fp, void *utrace_addr, size_t len)
{
        unsigned char *utrace_buffer;

        fprintf(fp, "{ ");
        if (sysdecode_utrace(fp, utrace_addr, len)) {
                fprintf(fp, " }");
                return;
        }

        utrace_buffer = utrace_addr;
        fprintf(fp, "%zu:", len);
        while (len--)
                fprintf(fp, " %02x", *utrace_buffer++);
        fprintf(fp, " }");
}

static void
print_pointer(FILE *fp, uintptr_t arg)
{

        fprintf(fp, "%p", (void *)arg);
}

static void
print_sockaddr(FILE *fp, struct trussinfo *trussinfo, uintptr_t arg,
    socklen_t len)
{
        char addr[64];
        struct sockaddr_in *lsin;
        struct sockaddr_in6 *lsin6;
        struct sockaddr_un *sun;
        struct sockaddr *sa;
        u_char *q;
        pid_t pid = trussinfo->curthread->proc->pid;

        if (arg == 0) {
                fputs("NULL", fp);
                return;
        }
        /* If the length is too small, just bail. */
        if (len < sizeof(*sa)) {
                print_pointer(fp, arg);
                return;
        }

        sa = calloc(1, len);
        if (get_struct(pid, arg, sa, len) == -1) {
                free(sa);
                print_pointer(fp, arg);
                return;
        }

        switch (sa->sa_family) {
        case AF_INET:
                if (len < sizeof(*lsin))
                        goto sockaddr_short;
                lsin = (struct sockaddr_in *)(void *)sa;
                inet_ntop(AF_INET, &lsin->sin_addr, addr, sizeof(addr));
                fprintf(fp, "{ AF_INET %s:%d }", addr,
                    htons(lsin->sin_port));
                break;
        case AF_INET6:
                if (len < sizeof(*lsin6))
                        goto sockaddr_short;
                lsin6 = (struct sockaddr_in6 *)(void *)sa;
                inet_ntop(AF_INET6, &lsin6->sin6_addr, addr,
                    sizeof(addr));
                fprintf(fp, "{ AF_INET6 [%s]:%d }", addr,
                    htons(lsin6->sin6_port));
                break;
        case AF_UNIX:
                sun = (struct sockaddr_un *)sa;
                fprintf(fp, "{ AF_UNIX \"%.*s\" }",
                    (int)(len - offsetof(struct sockaddr_un, sun_path)),
                    sun->sun_path);
                break;
        default:
        sockaddr_short:
                fprintf(fp,
                    "{ sa_len = %d, sa_family = %d, sa_data = {",
                    (int)sa->sa_len, (int)sa->sa_family);
                for (q = (u_char *)sa->sa_data;
                     q < (u_char *)sa + len; q++)
                        fprintf(fp, "%s 0x%02x",
                            q == (u_char *)sa->sa_data ? "" : ",",
                            *q);
                fputs(" } }", fp);
        }
        free(sa);
}

#define IOV_LIMIT 16

static void
print_iovec(FILE *fp, struct trussinfo *trussinfo, uintptr_t arg, int iovcnt)
{
        struct iovec iov[IOV_LIMIT];
        size_t max_string = trussinfo->strsize;
        char tmp2[max_string + 1], *tmp3;
        size_t len;
        pid_t pid = trussinfo->curthread->proc->pid;
        int i;
        bool buf_truncated, iov_truncated;

        if (iovcnt <= 0) {
                print_pointer(fp, arg);
                return;
        }
        if (iovcnt > IOV_LIMIT) {
                iovcnt = IOV_LIMIT;
                iov_truncated = true;
        } else {
                iov_truncated = false;
        }
        if (get_struct(pid, arg, &iov, iovcnt * sizeof(struct iovec)) == -1) {
                print_pointer(fp, arg);
                return;
        }

        fputs("[", fp);
        for (i = 0; i < iovcnt; i++) {
                len = iov[i].iov_len;
                if (len > max_string) {
                        len = max_string;
                        buf_truncated = true;
                } else {
                        buf_truncated = false;
                }
                fprintf(fp, "%s{", (i > 0) ? "," : "");
                if (len && get_struct(pid, (uintptr_t)iov[i].iov_base, &tmp2, len) != -1) {
                        tmp3 = malloc(len * 4 + 1);
                        while (len) {
                                if (strvisx(tmp3, tmp2, len,
                                    VIS_CSTYLE|VIS_TAB|VIS_NL) <=
                                    (int)max_string)
                                        break;
                                len--;
                                buf_truncated = true;
                        }
                        fprintf(fp, "\"%s\"%s", tmp3,
                            buf_truncated ? "..." : "");
                        free(tmp3);
                } else {
                        print_pointer(fp, (uintptr_t)iov[i].iov_base);
                }
                fprintf(fp, ",%zu}", iov[i].iov_len);
        }
        fprintf(fp, "%s%s", iov_truncated ? ",..." : "", "]");
}

static void
print_sigval(FILE *fp, union sigval *sv)
{
        fprintf(fp, "{ %d, %p }", sv->sival_int, sv->sival_ptr);
}

static void
print_sigevent(FILE *fp, struct sigevent *se)
{
        fputs("{ sigev_notify=", fp);
        switch (se->sigev_notify) {
        case SIGEV_NONE:
                fputs("SIGEV_NONE", fp);
                break;
        case SIGEV_SIGNAL:
                fprintf(fp, "SIGEV_SIGNAL, sigev_signo=%s, sigev_value=",
                                strsig2(se->sigev_signo));
                print_sigval(fp, &se->sigev_value);
                break;
        case SIGEV_THREAD:
                fputs("SIGEV_THREAD, sigev_value=", fp);
                print_sigval(fp, &se->sigev_value);
                break;
        case SIGEV_KEVENT:
                fprintf(fp, "SIGEV_KEVENT, sigev_notify_kqueue=%d, sigev_notify_kevent_flags=",
                                se->sigev_notify_kqueue);
                print_mask_arg(sysdecode_kevent_flags, fp, se->sigev_notify_kevent_flags);
                break;
        case SIGEV_THREAD_ID:
                fprintf(fp, "SIGEV_THREAD_ID, sigev_notify_thread_id=%d, sigev_signo=%s, sigev_value=",
                                se->sigev_notify_thread_id, strsig2(se->sigev_signo));
                print_sigval(fp, &se->sigev_value);
                break;
        default:
                fprintf(fp, "%d", se->sigev_notify);
                break;
        }
        fputs(" }", fp);
}

static void
print_aiocb(FILE *fp, struct aiocb *cb)
{
        fprintf(fp, "{ %d,%jd,%p,%zu,%s,",
                        cb->aio_fildes,
                        cb->aio_offset,
                        cb->aio_buf,
                        cb->aio_nbytes,
                        xlookup(lio_opcodes, cb->aio_lio_opcode));
        print_sigevent(fp, &cb->aio_sigevent);
        fputs(" }", fp);
}

static void
print_gen_cmsg(FILE *fp, struct cmsghdr *cmsghdr)
{
        u_char *q;

        fputs("{", fp);
        for (q = CMSG_DATA(cmsghdr);
             q < (u_char *)cmsghdr + cmsghdr->cmsg_len; q++) {
                fprintf(fp, "%s0x%02x", q == CMSG_DATA(cmsghdr) ? "" : ",", *q);
        }
        fputs("}", fp);
}

static void
print_sctp_initmsg(FILE *fp, struct sctp_initmsg *init)
{
        fprintf(fp, "{out=%u,", init->sinit_num_ostreams);
        fprintf(fp, "in=%u,", init->sinit_max_instreams);
        fprintf(fp, "max_rtx=%u,", init->sinit_max_attempts);
        fprintf(fp, "max_rto=%u}", init->sinit_max_init_timeo);
}

static void
print_sctp_sndrcvinfo(FILE *fp, bool receive, struct sctp_sndrcvinfo *info)
{
        fprintf(fp, "{sid=%u,", info->sinfo_stream);
        if (receive) {
                fprintf(fp, "ssn=%u,", info->sinfo_ssn);
        }
        fputs("flgs=", fp);
        sysdecode_sctp_sinfo_flags(fp, info->sinfo_flags);
        fprintf(fp, ",ppid=%u,", ntohl(info->sinfo_ppid));
        if (!receive) {
                fprintf(fp, "ctx=%u,", info->sinfo_context);
                fprintf(fp, "ttl=%u,", info->sinfo_timetolive);
        }
        if (receive) {
                fprintf(fp, "tsn=%u,", info->sinfo_tsn);
                fprintf(fp, "cumtsn=%u,", info->sinfo_cumtsn);
        }
        fprintf(fp, "id=%u}", info->sinfo_assoc_id);
}

static void
print_sctp_sndinfo(FILE *fp, struct sctp_sndinfo *info)
{
        fprintf(fp, "{sid=%u,", info->snd_sid);
        fputs("flgs=", fp);
        print_mask_arg(sysdecode_sctp_snd_flags, fp, info->snd_flags);
        fprintf(fp, ",ppid=%u,", ntohl(info->snd_ppid));
        fprintf(fp, "ctx=%u,", info->snd_context);
        fprintf(fp, "id=%u}", info->snd_assoc_id);
}

static void
print_sctp_rcvinfo(FILE *fp, struct sctp_rcvinfo *info)
{
        fprintf(fp, "{sid=%u,", info->rcv_sid);
        fprintf(fp, "ssn=%u,", info->rcv_ssn);
        fputs("flgs=", fp);
        print_mask_arg(sysdecode_sctp_rcv_flags, fp, info->rcv_flags);
        fprintf(fp, ",ppid=%u,", ntohl(info->rcv_ppid));
        fprintf(fp, "tsn=%u,", info->rcv_tsn);
        fprintf(fp, "cumtsn=%u,", info->rcv_cumtsn);
        fprintf(fp, "ctx=%u,", info->rcv_context);
        fprintf(fp, "id=%u}", info->rcv_assoc_id);
}

static void
print_sctp_nxtinfo(FILE *fp, struct sctp_nxtinfo *info)
{
        fprintf(fp, "{sid=%u,", info->nxt_sid);
        fputs("flgs=", fp);
        print_mask_arg(sysdecode_sctp_nxt_flags, fp, info->nxt_flags);
        fprintf(fp, ",ppid=%u,", ntohl(info->nxt_ppid));
        fprintf(fp, "len=%u,", info->nxt_length);
        fprintf(fp, "id=%u}", info->nxt_assoc_id);
}

static void
print_sctp_prinfo(FILE *fp, struct sctp_prinfo *info)
{
        fputs("{pol=", fp);
        print_integer_arg(sysdecode_sctp_pr_policy, fp, info->pr_policy);
        fprintf(fp, ",val=%u}", info->pr_value);
}

static void
print_sctp_authinfo(FILE *fp, struct sctp_authinfo *info)
{
        fprintf(fp, "{num=%u}", info->auth_keynumber);
}

static void
print_sctp_ipv4_addr(FILE *fp, struct in_addr *addr)
{
        char buf[INET_ADDRSTRLEN];
        const char *s;

        s = inet_ntop(AF_INET, addr, buf, INET_ADDRSTRLEN);
        if (s != NULL)
                fprintf(fp, "{addr=%s}", s);
        else
                fputs("{addr=???}", fp);
}

static void
print_sctp_ipv6_addr(FILE *fp, struct in6_addr *addr)
{
        char buf[INET6_ADDRSTRLEN];
        const char *s;

        s = inet_ntop(AF_INET6, addr, buf, INET6_ADDRSTRLEN);
        if (s != NULL)
                fprintf(fp, "{addr=%s}", s);
        else
                fputs("{addr=???}", fp);
}

static void
print_sctp_cmsg(FILE *fp, bool receive, struct cmsghdr *cmsghdr)
{
        void *data;
        socklen_t len;

        len = cmsghdr->cmsg_len;
        data = CMSG_DATA(cmsghdr);
        switch (cmsghdr->cmsg_type) {
        case SCTP_INIT:
                if (len == CMSG_LEN(sizeof(struct sctp_initmsg)))
                        print_sctp_initmsg(fp, (struct sctp_initmsg *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_SNDRCV:
                if (len == CMSG_LEN(sizeof(struct sctp_sndrcvinfo)))
                        print_sctp_sndrcvinfo(fp, receive,
                            (struct sctp_sndrcvinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
#if 0
        case SCTP_EXTRCV:
                if (len == CMSG_LEN(sizeof(struct sctp_extrcvinfo)))
                        print_sctp_extrcvinfo(fp,
                            (struct sctp_extrcvinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
#endif
        case SCTP_SNDINFO:
                if (len == CMSG_LEN(sizeof(struct sctp_sndinfo)))
                        print_sctp_sndinfo(fp, (struct sctp_sndinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_RCVINFO:
                if (len == CMSG_LEN(sizeof(struct sctp_rcvinfo)))
                        print_sctp_rcvinfo(fp, (struct sctp_rcvinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_NXTINFO:
                if (len == CMSG_LEN(sizeof(struct sctp_nxtinfo)))
                        print_sctp_nxtinfo(fp, (struct sctp_nxtinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_PRINFO:
                if (len == CMSG_LEN(sizeof(struct sctp_prinfo)))
                        print_sctp_prinfo(fp, (struct sctp_prinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_AUTHINFO:
                if (len == CMSG_LEN(sizeof(struct sctp_authinfo)))
                        print_sctp_authinfo(fp, (struct sctp_authinfo *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_DSTADDRV4:
                if (len == CMSG_LEN(sizeof(struct in_addr)))
                        print_sctp_ipv4_addr(fp, (struct in_addr *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        case SCTP_DSTADDRV6:
                if (len == CMSG_LEN(sizeof(struct in6_addr)))
                        print_sctp_ipv6_addr(fp, (struct in6_addr *)data);
                else
                        print_gen_cmsg(fp, cmsghdr);
                break;
        default:
                print_gen_cmsg(fp, cmsghdr);
        }
}

static void
print_cmsgs(FILE *fp, pid_t pid, bool receive, struct msghdr *msghdr)
{
        struct cmsghdr *cmsghdr;
        char *cmsgbuf;
        const char *temp;
        socklen_t len;
        int level, type;
        bool first;

        len = msghdr->msg_controllen;
        if (len == 0) {
                fputs("{}", fp);
                return;
        }
        cmsgbuf = calloc(1, len);
        if (get_struct(pid, (uintptr_t)msghdr->msg_control, cmsgbuf, len) == -1) {
                print_pointer(fp, (uintptr_t)msghdr->msg_control);
                free(cmsgbuf);
                return;
        }
        msghdr->msg_control = cmsgbuf;
        first = true;
        fputs("{", fp);
        for (cmsghdr = CMSG_FIRSTHDR(msghdr);
           cmsghdr != NULL;
           cmsghdr = CMSG_NXTHDR(msghdr, cmsghdr)) {
                if (cmsghdr->cmsg_len < sizeof(*cmsghdr)) {
                        fprintf(fp, "{<invalid cmsg, len=%u>}",
                            cmsghdr->cmsg_len);
                        if (cmsghdr->cmsg_len == 0) {
                                /* Avoid looping forever. */
                                break;
                        }
                        continue;
                }

                level = cmsghdr->cmsg_level;
                type = cmsghdr->cmsg_type;
                len = cmsghdr->cmsg_len;
                fprintf(fp, "%s{level=", first ? "" : ",");
                print_integer_arg(sysdecode_sockopt_level, fp, level);
                fputs(",type=", fp);
                temp = sysdecode_cmsg_type(level, type);
                if (temp) {
                        fputs(temp, fp);
                } else {
                        fprintf(fp, "%d", type);
                }
                fputs(",data=", fp);
                switch (level) {
                case IPPROTO_SCTP:
                        print_sctp_cmsg(fp, receive, cmsghdr);
                        break;
                default:
                        print_gen_cmsg(fp, cmsghdr);
                        break;
                }
                fputs("}", fp);
                first = false;
        }
        fputs("}", fp);
        free(cmsgbuf);
}

static void
print_sysctl_oid(FILE *fp, int *oid, size_t len)
{
        size_t i;
        bool first;

        first = true;
        fprintf(fp, "{ ");
        for (i = 0; i < len; i++) {
                fprintf(fp, "%s%d", first ? "" : ".", oid[i]);
                first = false;
        }
        fprintf(fp, " }");
}

static void
print_sysctl(FILE *fp, int *oid, size_t len)
{
        char name[BUFSIZ];
        int qoid[CTL_MAXNAME + 2];
        size_t i;

        qoid[0] = CTL_SYSCTL;
        qoid[1] = CTL_SYSCTL_NAME;
        memcpy(qoid + 2, oid, len * sizeof(int));
        i = sizeof(name);
        if (sysctl(qoid, len + 2, name, &i, 0, 0) == -1)
                print_sysctl_oid(fp, oid, len);
        else
                fprintf(fp, "%s", name);
}

/*
 * Convert a 32-bit user-space pointer to psaddr_t by zero-extending.
 */
static psaddr_t
user_ptr32_to_psaddr(int32_t user_pointer)
{
        return ((psaddr_t)(uintptr_t)user_pointer);
}

#define NETLINK_MAX_DECODE 4096

/*
 * Reads the first IOV and attempts to print it as Netlink using libsysdecode.
 * Returns true if successful, false if fallback to standard print is needed.
 */
static bool
print_netlink(FILE *fp, struct trussinfo *trussinfo, struct msghdr *msg)
{
        struct sockaddr_storage ss;
        struct iovec iov;
        struct ptrace_io_desc piod;
        char *buf;
        pid_t pid = trussinfo->curthread->proc->pid;
        bool success = false;

        /* Only decode AF_NETLINK sockets. */
        if (msg->msg_name == NULL || msg->msg_namelen < offsetof(struct sockaddr, sa_data)
                || msg->msg_iovlen == 0 || msg->msg_iov == NULL)
                return (false);

        if (get_struct(pid, (uintptr_t)msg->msg_name, &ss,
            MIN(sizeof(ss), msg->msg_namelen)) == -1)
                return (false);

        if (ss.ss_family != AF_NETLINK)
                return (false);

        if (get_struct(pid, (uintptr_t)msg->msg_iov, &iov, sizeof(iov)) == -1)
                return (false);

        /* Cap read size to avoid unbounded allocations. */
        size_t read_len = MIN(iov.iov_len, NETLINK_MAX_DECODE);
        if (read_len == 0)
                return (false);

        buf = malloc(read_len);
        if (buf == NULL)
                return (false);

        /* Snapshot User Memory using PTRACE. */
        piod.piod_op = PIOD_READ_D;
        piod.piod_offs = iov.iov_base;
        piod.piod_addr = buf;
        piod.piod_len = read_len;

        if (ptrace(PT_IO, pid, (caddr_t)&piod, 0) == -1) {
                free(buf);
                return (false);
        }

        /* Delegate Decoding to libsysdecode. */
        if (sysdecode_netlink(fp, buf, read_len)) {
                success = true;
        }
        free(buf);

        return (success);
}

/*
 * Converts a syscall argument into a string.  Said string is
 * allocated via malloc(), so needs to be free()'d.  sc is
 * a pointer to the syscall description (see above); args is
 * an array of all of the system call arguments.
 */
char *
print_arg(struct syscall_arg *sc, syscallarg_t *args, syscallarg_t *retval,
    struct trussinfo *trussinfo)
{
        FILE *fp;
        char *tmp;
        size_t tmplen;
        pid_t pid;

        fp = open_memstream(&tmp, &tmplen);
        pid = trussinfo->curthread->proc->pid;
        switch (sc->type & ARG_MASK) {
        case Hex:
                fprintf(fp, "0x%x", (int)args[sc->offset]);
                break;
        case Octal:
                fprintf(fp, "0%o", (int)args[sc->offset]);
                break;
        case Int:
                fprintf(fp, "%d", (int)args[sc->offset]);
                break;
        case UInt:
                fprintf(fp, "%u", (unsigned int)args[sc->offset]);
                break;
        case PUInt: {
                unsigned int val;

                if (get_struct(pid, args[sc->offset], &val,
                    sizeof(val)) == 0) 
                        fprintf(fp, "{ %u }", val);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case LongHex:
                fprintf(fp, "0x%lx", (long)args[sc->offset]);
                break;
        case Long:
                fprintf(fp, "%ld", (long)args[sc->offset]);
                break;
        case Sizet:
                fprintf(fp, "%zu", (size_t)args[sc->offset]);
                break;
        case ShmName:
                /* Handle special SHM_ANON value. */
                if ((char *)(uintptr_t)args[sc->offset] == SHM_ANON) {
                        fprintf(fp, "SHM_ANON");
                        break;
                }
                /* FALLTHROUGH */
        case Name: {
                /* NULL-terminated string. */
                char *tmp2;

                tmp2 = get_string(pid, args[sc->offset], 0);
                fprintf(fp, "\"%s\"", tmp2);
                free(tmp2);
                break;
        }
        case BinString: {
                /*
                 * Binary block of data that might have printable characters.
                 * XXX If type|OUT, assume that the length is the syscall's
                 * return value.  Otherwise, assume that the length of the block
                 * is in the next syscall argument.
                 */
                int max_string = trussinfo->strsize;
                char tmp2[max_string + 1], *tmp3;
                int len;
                int truncated = 0;

                if (sc->type & OUT)
                        len = retval[0];
                else
                        len = args[sc->offset + 1];

                /*
                 * Don't print more than max_string characters, to avoid word
                 * wrap.  If we have to truncate put some ... after the string.
                 */
                if (len > max_string) {
                        len = max_string;
                        truncated = 1;
                }
                if (len && get_struct(pid, args[sc->offset], &tmp2, len)
                    != -1) {
                        tmp3 = malloc(len * 4 + 1);
                        while (len) {
                                if (strvisx(tmp3, tmp2, len,
                                    VIS_CSTYLE|VIS_TAB|VIS_NL) <= max_string)
                                        break;
                                len--;
                                truncated = 1;
                        }
                        fprintf(fp, "\"%s\"%s", tmp3, truncated ?
                            "..." : "");
                        free(tmp3);
                } else {
                        print_pointer(fp, args[sc->offset]);
                }
                break;
        }
        case ExecArgs:
        case ExecEnv:
        case StringArray: {
                psaddr_t addr;
                union {
                        int32_t strarray32[PAGE_SIZE / sizeof(int32_t)];
                        int64_t strarray64[PAGE_SIZE / sizeof(int64_t)];
                        char buf[PAGE_SIZE];
                } u;
                char *string;
                size_t len;
                u_int first, i;
                size_t pointer_size =
                    trussinfo->curthread->proc->abi->pointer_size;

                /*
                 * Only parse argv[] and environment arrays from exec calls
                 * if requested.
                 */
                if (((sc->type & ARG_MASK) == ExecArgs &&
                    (trussinfo->flags & EXECVEARGS) == 0) ||
                    ((sc->type & ARG_MASK) == ExecEnv &&
                    (trussinfo->flags & EXECVEENVS) == 0)) {
                        print_pointer(fp, args[sc->offset]);
                        break;
                }

                /*
                 * Read a page of pointers at a time.  Punt if the top-level
                 * pointer is not aligned.  Note that the first read is of
                 * a partial page.
                 */
                addr = args[sc->offset];
                if (!__is_aligned(addr, pointer_size)) {
                        print_pointer(fp, args[sc->offset]);
                        break;
                }

                len = PAGE_SIZE - (addr & PAGE_MASK);
                if (get_struct(pid, addr, u.buf, len) == -1) {
                        print_pointer(fp, args[sc->offset]);
                        break;
                }
                assert(len > 0);

                fputc('[', fp);
                first = 1;
                i = 0;
                for (;;) {
                        psaddr_t straddr;
                        if (pointer_size == 4) {
                                straddr = user_ptr32_to_psaddr(u.strarray32[i]);
                        } else if (pointer_size == 8) {
                                straddr = (psaddr_t)u.strarray64[i];
                        } else {
                                errx(1, "Unsupported pointer size: %zu",
                                    pointer_size);
                        }

                        /* Stop once we read the first NULL pointer. */
                        if (straddr == 0)
                                break;
                        string = get_string(pid, straddr, 0);
                        fprintf(fp, "%s \"%s\"", first ? "" : ",", string);
                        free(string);
                        first = 0;

                        i++;
                        if (i == len / pointer_size) {
                                addr += len;
                                len = PAGE_SIZE;
                                if (get_struct(pid, addr, u.buf, len) == -1) {
                                        fprintf(fp, ", <inval>");
                                        break;
                                }
                                i = 0;
                        }
                }
                fputs(" ]", fp);
                break;
        }
        case Quad:
        case QuadHex: {
                uint64_t value;
                size_t pointer_size =
                    trussinfo->curthread->proc->abi->pointer_size;

                if (pointer_size == 4) {
#if _BYTE_ORDER == _LITTLE_ENDIAN
                        value = (uint64_t)args[sc->offset + 1] << 32 |
                            args[sc->offset];
#else
                        value = (uint64_t)args[sc->offset] << 32 |
                            args[sc->offset + 1];
#endif
                } else {
                        value = (uint64_t)args[sc->offset];
                }
                if ((sc->type & ARG_MASK) == Quad)
                        fprintf(fp, "%jd", (intmax_t)value);
                else
                        fprintf(fp, "0x%jx", (intmax_t)value);
                break;
        }
        case PQuadHex: {
                uint64_t val;

                if (get_struct(pid, args[sc->offset], &val,
                    sizeof(val)) == 0) 
                        fprintf(fp, "{ 0x%jx }", (uintmax_t)val);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Ptr:
                print_pointer(fp, args[sc->offset]);
                break;
        case Readlinkres: {
                char *tmp2;

                if (retval[0] == -1)
                        break;
                tmp2 = get_string(pid, args[sc->offset], retval[0]);
                fprintf(fp, "\"%s\"", tmp2);
                free(tmp2);
                break;
        }
        case Ioctl: {
                const char *temp;
                unsigned long cmd;

                cmd = args[sc->offset];
                temp = sysdecode_ioctlname(cmd);
                if (temp)
                        fputs(temp, fp);
                else {
                        fprintf(fp, "0x%lx { IO%s%s 0x%lx('%c'), %lu, %lu }",
                            cmd, cmd & IOC_OUT ? "R" : "",
                            cmd & IOC_IN ? "W" : "", IOCGROUP(cmd),
                            isprint(IOCGROUP(cmd)) ? (char)IOCGROUP(cmd) : '?',
                            cmd & 0xFF, IOCPARM_LEN(cmd));
                }
                break;
        }
        case Timespec: {
                struct timespec ts;

                if (get_struct(pid, args[sc->offset], &ts, sizeof(ts)) != -1)
                        fprintf(fp, "{ %jd.%09ld }", (intmax_t)ts.tv_sec,
                            ts.tv_nsec);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Timespec2: {
                struct timespec ts[2];
                const char *sep;
                unsigned int i;

                if (get_struct(pid, args[sc->offset], &ts, sizeof(ts)) != -1) {
                        fputs("{ ", fp);
                        sep = "";
                        for (i = 0; i < nitems(ts); i++) {
                                fputs(sep, fp);
                                sep = ", ";
                                switch (ts[i].tv_nsec) {
                                case UTIME_NOW:
                                        fprintf(fp, "UTIME_NOW");
                                        break;
                                case UTIME_OMIT:
                                        fprintf(fp, "UTIME_OMIT");
                                        break;
                                default:
                                        fprintf(fp, "%jd.%09ld",
                                            (intmax_t)ts[i].tv_sec,
                                            ts[i].tv_nsec);
                                        break;
                                }
                        }
                        fputs(" }", fp);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Timeval: {
                struct timeval tv;

                if (get_struct(pid, args[sc->offset], &tv, sizeof(tv)) != -1)
                        fprintf(fp, "{ %jd.%06ld }", (intmax_t)tv.tv_sec,
                            tv.tv_usec);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Timeval2: {
                struct timeval tv[2];

                if (get_struct(pid, args[sc->offset], &tv, sizeof(tv)) != -1)
                        fprintf(fp, "{ %jd.%06ld, %jd.%06ld }",
                            (intmax_t)tv[0].tv_sec, tv[0].tv_usec,
                            (intmax_t)tv[1].tv_sec, tv[1].tv_usec);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Itimerval: {
                struct itimerval itv;

                if (get_struct(pid, args[sc->offset], &itv, sizeof(itv)) != -1)
                        fprintf(fp, "{ %jd.%06ld, %jd.%06ld }",
                            (intmax_t)itv.it_interval.tv_sec,
                            itv.it_interval.tv_usec,
                            (intmax_t)itv.it_value.tv_sec,
                            itv.it_value.tv_usec);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case LinuxSockArgs:
        {
                struct linux_socketcall_args largs;

                if (get_struct(pid, args[sc->offset], (void *)&largs,
                    sizeof(largs)) != -1)
                        fprintf(fp, "{ %s, 0x%lx }",
                            lookup(linux_socketcall_ops, largs.what, 10),
                            (long unsigned int)largs.args);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Pollfd: {
                /*
                 * XXX: A Pollfd argument expects the /next/ syscall argument
                 * to be the number of fds in the array. This matches the poll
                 * syscall.
                 */
                struct pollfd *pfd;
                int numfds = args[sc->offset + 1];
                size_t bytes = sizeof(struct pollfd) * numfds;
                int i;

                if ((pfd = malloc(bytes)) == NULL)
                        err(1, "Cannot malloc %zu bytes for pollfd array",
                            bytes);
                if (get_struct(pid, args[sc->offset], pfd, bytes) != -1) {
                        fputs("{", fp);
                        for (i = 0; i < numfds; i++) {
                                fprintf(fp, " %d/%s", pfd[i].fd,
                                    xlookup_bits(poll_flags, pfd[i].events));
                        }
                        fputs(" }", fp);
                } else {
                        print_pointer(fp, args[sc->offset]);
                }
                free(pfd);
                break;
        }
        case Fd_set: {
                /*
                 * XXX: A Fd_set argument expects the /first/ syscall argument
                 * to be the number of fds in the array.  This matches the
                 * select syscall.
                 */
                fd_set *fds;
                int numfds = args[0];
                size_t bytes = _howmany(numfds, _NFDBITS) * _NFDBITS;
                int i;

                if ((fds = malloc(bytes)) == NULL)
                        err(1, "Cannot malloc %zu bytes for fd_set array",
                            bytes);
                if (get_struct(pid, args[sc->offset], fds, bytes) != -1) {
                        fputs("{", fp);
                        for (i = 0; i < numfds; i++) {
                                if (FD_ISSET(i, fds))
                                        fprintf(fp, " %d", i);
                        }
                        fputs(" }", fp);
                } else
                        print_pointer(fp, args[sc->offset]);
                free(fds);
                break;
        }
        case Signal:
                fputs(strsig2(args[sc->offset]), fp);
                break;
        case Sigset: {
                sigset_t ss;
                int i, first;

                if (get_struct(pid, args[sc->offset], (void *)&ss,
                    sizeof(ss)) == -1) {
                        print_pointer(fp, args[sc->offset]);
                        break;
                }
                fputs("{ ", fp);
                first = 1;
                for (i = 1; i < sys_nsig; i++) {
                        if (sigismember(&ss, i)) {
                                fprintf(fp, "%s%s", !first ? "|" : "",
                                    strsig2(i));
                                first = 0;
                        }
                }
                if (!first)
                        fputc(' ', fp);
                fputc('}', fp);
                break;
        }
        case Sigprocmask:
                print_integer_arg(sysdecode_sigprocmask_how, fp,
                    args[sc->offset]);
                break;
        case Fcntlflag:
                /* XXX: Output depends on the value of the previous argument. */
                if (sysdecode_fcntl_arg_p(args[sc->offset - 1]))
                        sysdecode_fcntl_arg(fp, args[sc->offset - 1],
                            args[sc->offset], 16);
                break;
        case Open:
                print_mask_arg(sysdecode_open_flags, fp, args[sc->offset]);
                break;
        case Fcntl:
                print_integer_arg(sysdecode_fcntl_cmd, fp, args[sc->offset]);
                break;
        case Closerangeflags:
                print_mask_arg(sysdecode_close_range_flags, fp, args[sc->offset]);
                break;
        case Mprot:
                print_mask_arg(sysdecode_mmap_prot, fp, args[sc->offset]);
                break;
        case Mmapflags:
                print_mask_arg(sysdecode_mmap_flags, fp, args[sc->offset]);
                break;
        case Whence:
                print_integer_arg(sysdecode_whence, fp, args[sc->offset]);
                break;
        case ShmFlags:
                print_mask_arg(sysdecode_shmflags, fp, args[sc->offset]);
                break;
        case Sockdomain:
                print_integer_arg(sysdecode_socketdomain, fp, args[sc->offset]);
                break;
        case Socktype:
                print_mask_arg(sysdecode_socket_type, fp, args[sc->offset]);
                break;
        case Shutdown:
                print_integer_arg(sysdecode_shutdown_how, fp, args[sc->offset]);
                break;
        case Resource:
                print_integer_arg(sysdecode_rlimit, fp, args[sc->offset]);
                break;
        case RusageWho:
                print_integer_arg(sysdecode_getrusage_who, fp, args[sc->offset]);
                break;
        case Pathconf:
                print_integer_arg(sysdecode_pathconf_name, fp, args[sc->offset]);
                break;
        case Rforkflags:
                print_mask_arg(sysdecode_rfork_flags, fp, args[sc->offset]);
                break;
        case Sockaddr: {
                socklen_t len;

                if (args[sc->offset] == 0) {
                        fputs("NULL", fp);
                        break;
                }

                /*
                 * Extract the address length from the next argument.  If
                 * this is an output sockaddr (OUT is set), then the
                 * next argument is a pointer to a socklen_t.  Otherwise
                 * the next argument contains a socklen_t by value.
                 */
                if (sc->type & OUT) {
                        if (get_struct(pid, args[sc->offset + 1], &len,
                            sizeof(len)) == -1) {
                                print_pointer(fp, args[sc->offset]);
                                break;
                        }
                } else
                        len = args[sc->offset + 1];

                print_sockaddr(fp, trussinfo, args[sc->offset], len);
                break;
        }
        case Sigaction: {
                struct sigaction sa;

                if (get_struct(pid, args[sc->offset], &sa, sizeof(sa)) != -1) {
                        fputs("{ ", fp);
                        if (sa.sa_handler == SIG_DFL)
                                fputs("SIG_DFL", fp);
                        else if (sa.sa_handler == SIG_IGN)
                                fputs("SIG_IGN", fp);
                        else
                                fprintf(fp, "%p", sa.sa_handler);
                        fprintf(fp, " %s ss_t }",
                            xlookup_bits(sigaction_flags, sa.sa_flags));
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Sigevent: {
                struct sigevent se;

                if (get_struct(pid, args[sc->offset], &se, sizeof(se)) != -1)
                        print_sigevent(fp, &se);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Kevent: {
                /*
                 * XXX XXX: The size of the array is determined by either the
                 * next syscall argument, or by the syscall return value,
                 * depending on which argument number we are.  This matches the
                 * kevent syscall, but luckily that's the only syscall that uses
                 * them.
                 */
                struct kevent *ke;
                int numevents = -1;
                size_t bytes;
                int i;

                if (sc->offset == 1)
                        numevents = args[sc->offset+1];
                else if (sc->offset == 3 && retval[0] != -1)
                        numevents = retval[0];

                if (numevents >= 0) {
                        bytes = sizeof(struct kevent) * numevents;
                        if ((ke = malloc(bytes)) == NULL)
                                err(1,
                                    "Cannot malloc %zu bytes for kevent array",
                                    bytes);
                } else
                        ke = NULL;
                if (numevents >= 0 && get_struct(pid, args[sc->offset],
                    ke, bytes) != -1) {
                        fputc('{', fp);
                        for (i = 0; i < numevents; i++) {
                                fputc(' ', fp);
                                print_kevent(fp, &ke[i]);
                        }
                        fputs(" }", fp);
                } else {
                        print_pointer(fp, args[sc->offset]);
                }
                free(ke);
                break;
        }
        case Kevent11: {
                struct freebsd11_kevent *ke11;
                struct kevent ke;
                int numevents = -1;
                size_t bytes;
                int i;

                if (sc->offset == 1)
                        numevents = args[sc->offset+1];
                else if (sc->offset == 3 && retval[0] != -1)
                        numevents = retval[0];

                if (numevents >= 0) {
                        bytes = sizeof(struct freebsd11_kevent) * numevents;
                        if ((ke11 = malloc(bytes)) == NULL)
                                err(1,
                                    "Cannot malloc %zu bytes for kevent array",
                                    bytes);
                } else
                        ke11 = NULL;
                memset(&ke, 0, sizeof(ke));
                if (numevents >= 0 && get_struct(pid, args[sc->offset],
                    ke11, bytes) != -1) {
                        fputc('{', fp);
                        for (i = 0; i < numevents; i++) {
                                fputc(' ', fp);
                                ke.ident = ke11[i].ident;
                                ke.filter = ke11[i].filter;
                                ke.flags = ke11[i].flags;
                                ke.fflags = ke11[i].fflags;
                                ke.data = ke11[i].data;
                                ke.udata = ke11[i].udata;
                                print_kevent(fp, &ke);
                        }
                        fputs(" }", fp);
                } else {
                        print_pointer(fp, args[sc->offset]);
                }
                free(ke11);
                break;
        }
        case Stat: {
                struct stat st;

                if (get_struct(pid, args[sc->offset], &st, sizeof(st))
                    != -1) {
                        char mode[12];

                        strmode(st.st_mode, mode);
                        fprintf(fp,
                            "{ mode=%s,inode=%ju,size=%jd,blksize=%ld }", mode,
                            (uintmax_t)st.st_ino, (intmax_t)st.st_size,
                            (long)st.st_blksize);
                } else {
                        print_pointer(fp, args[sc->offset]);
                }
                break;
        }
        case Stat11: {
                struct freebsd11_stat st;

                if (get_struct(pid, args[sc->offset], &st, sizeof(st))
                    != -1) {
                        char mode[12];

                        strmode(st.st_mode, mode);
                        fprintf(fp,
                            "{ mode=%s,inode=%ju,size=%jd,blksize=%ld }", mode,
                            (uintmax_t)st.st_ino, (intmax_t)st.st_size,
                            (long)st.st_blksize);
                } else {
                        print_pointer(fp, args[sc->offset]);
                }
                break;
        }
        case StatFs: {
                unsigned int i;
                struct statfs buf;

                if (get_struct(pid, args[sc->offset], &buf,
                    sizeof(buf)) != -1) {
                        char fsid[17];

                        bzero(fsid, sizeof(fsid));
                        if (buf.f_fsid.val[0] != 0 || buf.f_fsid.val[1] != 0) {
                                for (i = 0; i < sizeof(buf.f_fsid); i++)
                                        snprintf(&fsid[i*2],
                                            sizeof(fsid) - (i*2), "%02x",
                                            ((u_char *)&buf.f_fsid)[i]);
                        }
                        fprintf(fp,
                            "{ fstypename=%s,mntonname=%s,mntfromname=%s,"
                            "fsid=%s }", buf.f_fstypename, buf.f_mntonname,
                            buf.f_mntfromname, fsid);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }

        case Rusage: {
                struct rusage ru;

                if (get_struct(pid, args[sc->offset], &ru, sizeof(ru))
                    != -1) {
                        fprintf(fp,
                            "{ u=%jd.%06ld,s=%jd.%06ld,in=%ld,out=%ld }",
                            (intmax_t)ru.ru_utime.tv_sec, ru.ru_utime.tv_usec,
                            (intmax_t)ru.ru_stime.tv_sec, ru.ru_stime.tv_usec,
                            ru.ru_inblock, ru.ru_oublock);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Rlimit: {
                struct rlimit rl;

                if (get_struct(pid, args[sc->offset], &rl, sizeof(rl))
                    != -1) {
                        fprintf(fp, "{ cur=%ju,max=%ju }",
                            rl.rlim_cur, rl.rlim_max);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case ExitStatus: {
                int status;

                if (get_struct(pid, args[sc->offset], &status,
                    sizeof(status)) != -1) {
                        fputs("{ ", fp);
                        if (WIFCONTINUED(status))
                                fputs("CONTINUED", fp);
                        else if (WIFEXITED(status))
                                fprintf(fp, "EXITED,val=%d",
                                    WEXITSTATUS(status));
                        else if (WIFSIGNALED(status))
                                fprintf(fp, "SIGNALED,sig=%s%s",
                                    strsig2(WTERMSIG(status)),
                                    WCOREDUMP(status) ? ",cored" : "");
                        else
                                fprintf(fp, "STOPPED,sig=%s",
                                    strsig2(WTERMSIG(status)));
                        fputs(" }", fp);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Waitoptions:
                print_mask_arg(sysdecode_wait6_options, fp, args[sc->offset]);
                break;
        case Idtype:
                print_integer_arg(sysdecode_idtype, fp, args[sc->offset]);
                break;
        case Procctl:
                print_integer_arg(sysdecode_procctl_cmd, fp, args[sc->offset]);
                break;
        case Umtxop: {
                int rem;

                if (print_mask_arg_part(sysdecode_umtx_op_flags, fp,
                    args[sc->offset], &rem))
                        fprintf(fp, "|");
                print_integer_arg(sysdecode_umtx_op, fp, rem);
                break;
        }
        case Atfd:
                print_integer_arg(sysdecode_atfd, fp, args[sc->offset]);
                break;
        case Atflags:
                print_mask_arg(sysdecode_atflags, fp, args[sc->offset]);
                break;
        case Accessmode:
                print_mask_arg(sysdecode_access_mode, fp, args[sc->offset]);
                break;
        case Sysarch:
                print_integer_arg(sysdecode_sysarch_number, fp,
                    args[sc->offset]);
                break;
        case Sysctl: {
                char name[BUFSIZ];
                int oid[CTL_MAXNAME + 2];
                size_t len;

                memset(name, 0, sizeof(name));
                len = args[sc->offset + 1];
                if (get_struct(pid, args[sc->offset], oid,
                    len * sizeof(oid[0])) != -1) {
                        fprintf(fp, "\"");
                        if (oid[0] == CTL_SYSCTL) {
                                fprintf(fp, "sysctl.");
                                switch (oid[1]) {
                                case CTL_SYSCTL_DEBUG:
                                        fprintf(fp, "debug");
                                        break;
                                case CTL_SYSCTL_NAME:
                                        fprintf(fp, "name ");
                                        print_sysctl_oid(fp, oid + 2, len - 2);
                                        break;
                                case CTL_SYSCTL_NEXT:
                                        fprintf(fp, "next");
                                        break;
                                case CTL_SYSCTL_NAME2OID:
                                        fprintf(fp, "name2oid %s",
                                            get_string(pid,
                                                args[sc->offset + 4],
                                                args[sc->offset + 5]));
                                        break;
                                case CTL_SYSCTL_OIDFMT:
                                        fprintf(fp, "oidfmt ");
                                        print_sysctl(fp, oid + 2, len - 2);
                                        break;
                                case CTL_SYSCTL_OIDDESCR:
                                        fprintf(fp, "oiddescr ");
                                        print_sysctl(fp, oid + 2, len - 2);
                                        break;
                                case CTL_SYSCTL_OIDLABEL:
                                        fprintf(fp, "oidlabel ");
                                        print_sysctl(fp, oid + 2, len - 2);
                                        break;
                                case CTL_SYSCTL_NEXTNOSKIP:
                                        fprintf(fp, "nextnoskip");
                                        break;
                                default:
                                        print_sysctl(fp, oid + 1, len - 1);
                                }
                        } else {
                                print_sysctl(fp, oid, len);
                        }
                        fprintf(fp, "\"");
                }
                break;
        }
        case PipeFds:
                /*
                 * The pipe() system call in the kernel returns its
                 * two file descriptors via return values.  However,
                 * the interface exposed by libc is that pipe()
                 * accepts a pointer to an array of descriptors.
                 * Format the output to match the libc API by printing
                 * the returned file descriptors as a fake argument.
                 *
                 * Overwrite the first retval to signal a successful
                 * return as well.
                 */
                fprintf(fp, "{ %d, %d }", (int)retval[0], (int)retval[1]);
                retval[0] = 0;
                break;
        case Utrace: {
                size_t len;
                void *utrace_addr;

                len = args[sc->offset + 1];
                utrace_addr = calloc(1, len);
                if (get_struct(pid, args[sc->offset],
                    (void *)utrace_addr, len) != -1)
                        print_utrace(fp, utrace_addr, len);
                else
                        print_pointer(fp, args[sc->offset]);
                free(utrace_addr);
                break;
        }
        case IntArray: {
                int descriptors[16];
                unsigned long i, ndescriptors;
                bool truncated;

                ndescriptors = args[sc->offset + 1];
                truncated = false;
                if (ndescriptors > nitems(descriptors)) {
                        ndescriptors = nitems(descriptors);
                        truncated = true;
                }
                if (get_struct(pid, args[sc->offset],
                    descriptors, ndescriptors * sizeof(descriptors[0])) != -1) {
                        fprintf(fp, "{");
                        for (i = 0; i < ndescriptors; i++)
                                fprintf(fp, i == 0 ? " %d" : ", %d",
                                    descriptors[i]);
                        fprintf(fp, truncated ? ", ... }" : " }");
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Pipe2:
                print_mask_arg(sysdecode_pipe2_flags, fp, args[sc->offset]);
                break;
        case CapFcntlRights: {
                uint32_t rights;

                if (sc->type & OUT) {
                        if (get_struct(pid, args[sc->offset], &rights,
                            sizeof(rights)) == -1) {
                                print_pointer(fp, args[sc->offset]);
                                break;
                        }
                } else
                        rights = args[sc->offset];
                print_mask_arg32(sysdecode_cap_fcntlrights, fp, rights);
                break;
        }
        case Fadvice:
                print_integer_arg(sysdecode_fadvice, fp, args[sc->offset]);
                break;
        case FileFlags: {
                fflags_t rem;

                if (!sysdecode_fileflags(fp, args[sc->offset], &rem))
                        fprintf(fp, "0x%x", rem);
                else if (rem != 0)
                        fprintf(fp, "|0x%x", rem);
                break;
        }
        case Flockop:
                print_mask_arg(sysdecode_flock_operation, fp, args[sc->offset]);
                break;
        case Getfsstatmode:
                print_integer_arg(sysdecode_getfsstat_mode, fp,
                    args[sc->offset]);
                break;
        case Inotifyflags:
                print_mask_arg(sysdecode_inotifyflags, fp, args[sc->offset]);
                break;
        case Itimerwhich:
                print_integer_arg(sysdecode_itimer, fp, args[sc->offset]);
                break;
        case Kldsymcmd:
                print_integer_arg(sysdecode_kldsym_cmd, fp, args[sc->offset]);
                break;
        case Kldunloadflags:
                print_integer_arg(sysdecode_kldunload_flags, fp,
                    args[sc->offset]);
                break;
        case AiofsyncOp:
                fputs(xlookup(aio_fsync_ops, args[sc->offset]), fp);
                break;
        case LioMode:
                fputs(xlookup(lio_modes, args[sc->offset]), fp);
                break;
        case Madvice:
                print_integer_arg(sysdecode_madvice, fp, args[sc->offset]);
                break;
        case Socklent:
                fprintf(fp, "%u", (socklen_t)args[sc->offset]);
                break;
        case Sockprotocol: {
                const char *temp;
                int domain, protocol;

                domain = args[sc->offset - 2];
                protocol = args[sc->offset];
                if (protocol == 0) {
                        fputs("0", fp);
                } else {
                        temp = sysdecode_socket_protocol(domain, protocol);
                        if (temp) {
                                fputs(temp, fp);
                        } else {
                                fprintf(fp, "%d", protocol);
                        }
                }
                break;
        }
        case Sockoptlevel:
                print_integer_arg(sysdecode_sockopt_level, fp,
                    args[sc->offset]);
                break;
        case Sockoptname: {
                const char *temp;
                int level, name;

                level = args[sc->offset - 1];
                name = args[sc->offset];
                temp = sysdecode_sockopt_name(level, name);
                if (temp) {
                        fputs(temp, fp);
                } else {
                        fprintf(fp, "%d", name);
                }
                break;
        }
        case Msgflags:
                print_mask_arg(sysdecode_msg_flags, fp, args[sc->offset]);
                break;
        case CapRights: {
                cap_rights_t rights;

                if (get_struct(pid, args[sc->offset], &rights,
                    sizeof(rights)) != -1) {
                        fputs("{ ", fp);
                        sysdecode_cap_rights(fp, &rights);
                        fputs(" }", fp);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Acltype:
                print_integer_arg(sysdecode_acltype, fp, args[sc->offset]);
                break;
        case Extattrnamespace:
                print_integer_arg(sysdecode_extattrnamespace, fp,
                    args[sc->offset]);
                break;
        case Minherit:
                print_integer_arg(sysdecode_minherit_inherit, fp,
                    args[sc->offset]);
                break;
        case Mlockall:
                print_mask_arg(sysdecode_mlockall_flags, fp, args[sc->offset]);
                break;
        case Mountflags:
                print_mask_arg(sysdecode_mount_flags, fp, args[sc->offset]);
                break;
        case Msync:
                print_mask_arg(sysdecode_msync_flags, fp, args[sc->offset]);
                break;
        case Priowhich:
                print_integer_arg(sysdecode_prio_which, fp, args[sc->offset]);
                break;
        case Ptraceop:
                print_integer_arg(sysdecode_ptrace_request, fp,
                    args[sc->offset]);
                break;
        case Sendfileflags:
                print_mask_arg(sysdecode_sendfile_flags, fp, args[sc->offset]);
                break;
        case Sendfilehdtr: {
                struct sf_hdtr hdtr;

                if (get_struct(pid, args[sc->offset], &hdtr, sizeof(hdtr)) !=
                    -1) {
                        fprintf(fp, "{");
                        print_iovec(fp, trussinfo, (uintptr_t)hdtr.headers,
                            hdtr.hdr_cnt);
                        print_iovec(fp, trussinfo, (uintptr_t)hdtr.trailers,
                            hdtr.trl_cnt);
                        fprintf(fp, "}");
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Quotactlcmd:
                if (!sysdecode_quotactl_cmd(fp, args[sc->offset]))
                        fprintf(fp, "%#x", (int)args[sc->offset]);
                break;
        case Reboothowto:
                print_mask_arg(sysdecode_reboot_howto, fp, args[sc->offset]);
                break;
        case Rtpriofunc:
                print_integer_arg(sysdecode_rtprio_function, fp,
                    args[sc->offset]);
                break;
        case Schedpolicy:
                print_integer_arg(sysdecode_scheduler_policy, fp,
                    args[sc->offset]);
                break;
        case Schedparam: {
                struct sched_param sp;

                if (get_struct(pid, args[sc->offset], &sp, sizeof(sp)) != -1)
                        fprintf(fp, "{ %d }", sp.sched_priority);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case PSig: {
                int sig;

                if (get_struct(pid, args[sc->offset], &sig, sizeof(sig)) == 0)
                        fprintf(fp, "{ %s }", strsig2(sig));
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Siginfo: {
                siginfo_t si;

                if (get_struct(pid, args[sc->offset], &si, sizeof(si)) != -1) {
                        fprintf(fp, "{ signo=%s", strsig2(si.si_signo));
                        decode_siginfo(fp, &si);
                        fprintf(fp, " }");
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Iovec:
                /*
                 * Print argument as an array of struct iovec, where the next
                 * syscall argument is the number of elements of the array.
                 */

                print_iovec(fp, trussinfo, args[sc->offset],
                    (int)args[sc->offset + 1]);
                break;
        case Aiocb: {
                struct aiocb cb;

                if (get_struct(pid, args[sc->offset], &cb, sizeof(cb)) != -1)
                        print_aiocb(fp, &cb);
                else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case AiocbArray: {
                /*
                 * Print argment as an array of pointers to struct aiocb, where
                 * the next syscall argument is the number of elements.
                 */
                uintptr_t cbs[16];
                unsigned int nent;
                bool truncated;

                nent = args[sc->offset + 1];
                truncated = false;
                if (nent > nitems(cbs)) {
                        nent = nitems(cbs);
                        truncated = true;
                }

                if (get_struct(pid, args[sc->offset], cbs, sizeof(uintptr_t) * nent) != -1) {
                        unsigned int i;
                        fputs("[", fp);
                        for (i = 0; i < nent; ++i) {
                                struct aiocb cb;
                                if (i > 0)
                                        fputc(',', fp);
                                if (get_struct(pid, cbs[i], &cb, sizeof(cb)) != -1)
                                        print_aiocb(fp, &cb);
                                else
                                        print_pointer(fp, cbs[i]);
                        }
                        if (truncated)
                                fputs(",...", fp);
                        fputs("]", fp);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case AiocbPointer: {
                /*
                 * aio_waitcomplete(2) assigns a pointer to a pointer to struct
                 * aiocb, so we need to handle the extra layer of indirection.
                 */
                uintptr_t cbp;
                struct aiocb cb;

                if (get_struct(pid, args[sc->offset], &cbp, sizeof(cbp)) != -1) {
                        if (get_struct(pid, cbp, &cb, sizeof(cb)) != -1)
                                print_aiocb(fp, &cb);
                        else
                                print_pointer(fp, cbp);
                } else
                        print_pointer(fp, args[sc->offset]);
                break;
        }
        case Sctpsndrcvinfo: {
                struct sctp_sndrcvinfo info;

                if (get_struct(pid, args[sc->offset],
                    &info, sizeof(struct sctp_sndrcvinfo)) == -1) {
                        print_pointer(fp, args[sc->offset]);
                        break;
                }
                print_sctp_sndrcvinfo(fp, sc->type & OUT, &info);
                break;
        }
        case Msghdr: {
                struct msghdr msghdr;

                if (get_struct(pid, args[sc->offset],
                    &msghdr, sizeof(struct msghdr)) == -1) {
                        print_pointer(fp, args[sc->offset]);
                        break;
                }
                fputs("{", fp);
                print_sockaddr(fp, trussinfo, (uintptr_t)msghdr.msg_name, msghdr.msg_namelen);
                fprintf(fp, ",%d,", msghdr.msg_namelen);
                /* Attempt Netlink decode; fallback to standard iovec if it fails. */
                if (!print_netlink(fp, trussinfo, &msghdr)) {
                        print_iovec(fp, trussinfo, (uintptr_t)msghdr.msg_iov,
                            msghdr.msg_iovlen);
                }
                fprintf(fp, ",%d,", msghdr.msg_iovlen);
                print_cmsgs(fp, pid, sc->type & OUT, &msghdr);
                fprintf(fp, ",%u,", msghdr.msg_controllen);
                print_mask_arg(sysdecode_msg_flags, fp, msghdr.msg_flags);
                fputs("}", fp);
                break;
        }

        default:
                errx(1, "Invalid argument type %d\n", sc->type & ARG_MASK);
        }
        fclose(fp);
        return (tmp);
}

/*
 * Print (to outfile) the system call and its arguments.
 */
void
print_syscall(struct trussinfo *trussinfo)
{
        struct threadinfo *t;
        const char *name;
        char **s_args;
        int i, len, nargs;

        t = trussinfo->curthread;

        name = t->cs.sc->name;
        nargs = t->cs.nargs;
        s_args = t->cs.s_args;

        len = print_line_prefix(trussinfo);
        len += fprintf(trussinfo->outfile, "%s(", name);

        for (i = 0; i < nargs; i++) {
                if (s_args[i] != NULL)
                        len += fprintf(trussinfo->outfile, "%s", s_args[i]);
                else
                        len += fprintf(trussinfo->outfile,
                            "<missing argument>");
                len += fprintf(trussinfo->outfile, "%s", i < (nargs - 1) ?
                    "," : "");
        }
        len += fprintf(trussinfo->outfile, ")");
        for (i = 0; i < 6 - (len / 8); i++)
                fprintf(trussinfo->outfile, "\t");
}

void
print_syscall_ret(struct trussinfo *trussinfo, int error, syscallarg_t *retval)
{
        struct timespec timediff;
        struct threadinfo *t;
        struct syscall *sc;

        t = trussinfo->curthread;
        sc = t->cs.sc;
        if (trussinfo->flags & COUNTONLY) {
                timespecsub(&t->after, &t->before, &timediff);
                timespecadd(&sc->time, &timediff, &sc->time);
                sc->ncalls++;
                if (error != 0)
                        sc->nerror++;
                return;
        }

        print_syscall(trussinfo);
        fflush(trussinfo->outfile);

        if (retval == NULL) {
                /*
                 * This system call resulted in the current thread's exit,
                 * so there is no return value or error to display.
                 */
                fprintf(trussinfo->outfile, "\n");
                return;
        }

        if (error == ERESTART)
                fprintf(trussinfo->outfile, " ERESTART\n");
        else if (error == EJUSTRETURN)
                fprintf(trussinfo->outfile, " EJUSTRETURN\n");
        else if (error != 0) {
                fprintf(trussinfo->outfile, " ERR#%d '%s'\n",
                    sysdecode_freebsd_to_abi_errno(t->proc->abi->abi, error),
                    strerror(error));
        } else if (sc->decode.ret_type == 2 &&
            t->proc->abi->pointer_size == 4) {
                off_t off;
#if _BYTE_ORDER == _LITTLE_ENDIAN
                off = (off_t)retval[1] << 32 | retval[0];
#else
                off = (off_t)retval[0] << 32 | retval[1];
#endif
                fprintf(trussinfo->outfile, " = %jd (0x%jx)\n", (intmax_t)off,
                    (intmax_t)off);
        } else {
                fprintf(trussinfo->outfile, " = %jd (0x%jx)\n",
                    (intmax_t)retval[0], (intmax_t)retval[0]);
        }
}

void
print_summary(struct trussinfo *trussinfo)
{
        struct timespec total = {0, 0};
        struct syscall *sc;
        int ncall, nerror;

        fprintf(trussinfo->outfile, "%-20s%15s%8s%8s\n",
            "syscall", "seconds", "calls", "errors");
        ncall = nerror = 0;
        STAILQ_FOREACH(sc, &seen_syscalls, entries) {
                if (sc->ncalls) {
                        fprintf(trussinfo->outfile, "%-20s%5jd.%09ld%8d%8d\n",
                            sc->name, (intmax_t)sc->time.tv_sec,
                            sc->time.tv_nsec, sc->ncalls, sc->nerror);
                        timespecadd(&total, &sc->time, &total);
                        ncall += sc->ncalls;
                        nerror += sc->nerror;
                }
        }
        fprintf(trussinfo->outfile, "%20s%15s%8s%8s\n",
            "", "-------------", "-------", "-------");
        fprintf(trussinfo->outfile, "%-20s%5jd.%09ld%8d%8d\n",
            "", (intmax_t)total.tv_sec, total.tv_nsec, ncall, nerror);
}