src/unix/os390.c

/* Copyright libuv project contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "uv.h"
#include "internal.h"
#include <sys/ioctl.h>
#include <net/if.h>
#include <utmpx.h>
#include <unistd.h>
#include <sys/ps.h>
#include <builtins.h>
#include <termios.h>
#include <sys/msg.h>
#include <sys/resource.h>
#include "zos-base.h"
#include "zos-sys-info.h"
#if defined(__clang__)
#include "csrsic.h"
#else
#include "//'SYS1.SAMPLIB(CSRSIC)'"
#endif

#define CVT_PTR           0x10
#define PSA_PTR           0x00
#define CSD_OFFSET        0x294

/*
    Long-term average CPU service used by this logical partition,
    in millions of service units per hour. If this value is above
    the partition's defined capacity, the partition will be capped.
    It is calculated using the physical CPU adjustment factor
    (RCTPCPUA) so it may not match other measures of service which
    are based on the logical CPU adjustment factor. It is available
    if the hardware supports LPAR cluster.
*/
#define RCTLACS_OFFSET    0xC4

/* 32-bit count of alive CPUs. This includes both CPs and IFAs */
#define CSD_NUMBER_ONLINE_CPUS        0xD4

/* Address of system resources manager (SRM) control table */
#define CVTOPCTP_OFFSET   0x25C

/* Address of the RCT table */
#define RMCTRCT_OFFSET    0xE4

/* Address of the rsm control and enumeration area. */
#define CVTRCEP_OFFSET    0x490

/* Total number of frames currently on all available frame queues. */
#define RCEAFC_OFFSET     0x088

/* Pointer to the home (current) ASCB. */
#define PSAAOLD           0x224

/* Pointer to rsm address space block extension. */
#define ASCBRSME          0x16C

/*
    NUMBER OF FRAMES CURRENTLY IN USE BY THIS ADDRESS SPACE.
    It does not include 2G frames.
*/
#define RAXFMCT           0x2C

/* Thread Entry constants */
#define PGTH_CURRENT  1
#define PGTH_LEN      26
#define PGTHAPATH     0x20
#pragma linkage(BPX4GTH, OS)
#pragma linkage(BPX1GTH, OS)

/* TOD Clock resolution in nanoseconds */
#define TOD_RES 4.096

typedef unsigned data_area_ptr_assign_type;

typedef union {
  struct {
#if defined(_LP64)
    data_area_ptr_assign_type lower;
#endif
    data_area_ptr_assign_type assign;
  };
  char* deref;
} data_area_ptr;


void uv_loadavg(double avg[3]) {
  /* TODO: implement the following */
  avg[0] = 0;
  avg[1] = 0;
  avg[2] = 0;
}


int uv__platform_loop_init(uv_loop_t* loop) {
  uv__os390_epoll* ep;

  ep = epoll_create1(0);
  loop->ep = ep;
  if (ep == NULL)
    return UV__ERR(errno);

  return 0;
}


void uv__platform_loop_delete(uv_loop_t* loop) {
  if (loop->ep != NULL) {
    epoll_queue_close(loop->ep);
    loop->ep = NULL;
  }
}


uint64_t uv__hrtime(uv_clocktype_t type) {
  unsigned long long timestamp;
  __stckf(&timestamp);
  /* Convert to nanoseconds */
  return timestamp / TOD_RES;
}


static int getexe(char* buf, size_t len) {
  return uv__strscpy(buf, __getargv()[0], len);
}


/*
 * We could use a static buffer for the path manipulations that we need outside
 * of the function, but this function could be called by multiple consumers and
 * we don't want to potentially create a race condition in the use of snprintf.
 * There is no direct way of getting the exe path in zOS - either through /procfs
 * or through some libc APIs. The below approach is to parse the argv[0]'s pattern
 * and use it in conjunction with PATH environment variable to craft one.
 */
int uv_exepath(char* buffer, size_t* size) {
  int res;
  char args[PATH_MAX];
  int pid;

  if (buffer == NULL || size == NULL || *size == 0)
    return UV_EINVAL;

  res = getexe(args, sizeof(args));
  if (res < 0)
    return UV_EINVAL;

  return uv__search_path(args, buffer, size);
}


uint64_t uv_get_free_memory(void) {
  uint64_t freeram;

  data_area_ptr cvt = {0};
  data_area_ptr rcep = {0};
  cvt.assign = *(data_area_ptr_assign_type*)(CVT_PTR);
  rcep.assign = *(data_area_ptr_assign_type*)(cvt.deref + CVTRCEP_OFFSET);
  freeram = (uint64_t)*((uint32_t*)(rcep.deref + RCEAFC_OFFSET)) * 4096;
  return freeram;
}


uint64_t uv_get_total_memory(void) {
  /* Use CVTRLSTG to get the size of actual real storage online at IPL in K. */
  return (uint64_t)((int)((char *__ptr32 *__ptr32 *)0)[4][214]) * 1024;
}


uint64_t uv_get_constrained_memory(void) {
  struct rlimit rl;

  /* RLIMIT_MEMLIMIT return value is in megabytes rather than bytes. */
  if (getrlimit(RLIMIT_MEMLIMIT, &rl) == 0)
    return rl.rlim_cur * 1024 * 1024;

  return 0; /* There is no memory limit set. */
}


uint64_t uv_get_available_memory(void) {
  return uv_get_free_memory();
}


int uv_resident_set_memory(size_t* rss) {
  char* ascb;
  char* rax;
  size_t nframes;

  ascb  = *(char* __ptr32 *)(PSA_PTR + PSAAOLD);
  rax = *(char* __ptr32 *)(ascb + ASCBRSME);
  nframes = *(unsigned int*)(rax + RAXFMCT);

  *rss = nframes * sysconf(_SC_PAGESIZE);
  return 0;
}


int uv_uptime(double* uptime) {
  struct utmpx u ;
  struct utmpx *v;
  time64_t t;

  u.ut_type = BOOT_TIME;
  v = getutxid(&u);
  if (v == NULL)
    return -1;
  *uptime = difftime64(time64(&t), v->ut_tv.tv_sec);
  return 0;
}


int uv_cpu_info(uv_cpu_info_t** cpu_infos, int* count) {
  uv_cpu_info_t* cpu_info;
  int idx;
  siv1v2 info;
  data_area_ptr cvt = {0};
  data_area_ptr csd = {0};
  data_area_ptr rmctrct = {0};
  data_area_ptr cvtopctp = {0};
  int cpu_usage_avg;

  cvt.assign = *(data_area_ptr_assign_type*)(CVT_PTR);

  csd.assign = *((data_area_ptr_assign_type *) (cvt.deref + CSD_OFFSET));
  cvtopctp.assign = *((data_area_ptr_assign_type *) (cvt.deref + CVTOPCTP_OFFSET));
  rmctrct.assign = *((data_area_ptr_assign_type *) (cvtopctp.deref + RMCTRCT_OFFSET));

  *count = *((int*) (csd.deref + CSD_NUMBER_ONLINE_CPUS));
  cpu_usage_avg = *((unsigned short int*) (rmctrct.deref + RCTLACS_OFFSET));

  *cpu_infos = uv__malloc(*count * sizeof(uv_cpu_info_t));
  if (!*cpu_infos)
    return UV_ENOMEM;

  cpu_info = *cpu_infos;
  idx = 0;
  while (idx < *count) {
    cpu_info->speed = *(int*)(info.siv1v2si22v1.si22v1cpucapability);
    cpu_info->model = uv__malloc(ZOSCPU_MODEL_LENGTH + 1);
    if (cpu_info->model == NULL) {
      uv_free_cpu_info(*cpu_infos, idx);
      return UV_ENOMEM;
    }
    __get_cpu_model(cpu_info->model, ZOSCPU_MODEL_LENGTH + 1);
    cpu_info->cpu_times.user = cpu_usage_avg;
    /* TODO: implement the following */
    cpu_info->cpu_times.sys = 0;
    cpu_info->cpu_times.idle = 0;
    cpu_info->cpu_times.irq = 0;
    cpu_info->cpu_times.nice = 0;
    ++cpu_info;
    ++idx;
  }

  return 0;
}


static int uv__interface_addresses_v6(uv_interface_address_t** addresses,
                                      int* count) {
  uv_interface_address_t* address;
  int sockfd;
  int maxsize;
  __net_ifconf6header_t ifc;
  __net_ifconf6entry_t* ifr;
  __net_ifconf6entry_t* p;
  unsigned int i;
  int count_names;
  unsigned char netmask[16] = {0};

  *count = 0;
  /* Assume maximum buffer size allowable */
  maxsize = 16384;

  if (0 > (sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP)))
    return UV__ERR(errno);

  ifc.__nif6h_buffer = uv__calloc(1, maxsize);

  if (ifc.__nif6h_buffer == NULL) {
    uv__close(sockfd);
    return UV_ENOMEM;
  }

  ifc.__nif6h_version = 1;
  ifc.__nif6h_buflen = maxsize;

  if (ioctl(sockfd, SIOCGIFCONF6, &ifc) == -1) {
    /* This will error on a system that does not support IPv6. However, we want
     * to treat this as there being 0 interfaces so we can continue to get IPv4
     * interfaces in uv_interface_addresses(). So return 0 instead of the error.
     */
    uv__free(ifc.__nif6h_buffer);
    uv__close(sockfd);
    errno = 0;
    return 0;
  }

  ifr = (__net_ifconf6entry_t*)(ifc.__nif6h_buffer);
  while ((char*)ifr < (char*)ifc.__nif6h_buffer + ifc.__nif6h_buflen) {
    p = ifr;
    ifr = (__net_ifconf6entry_t*)((char*)ifr + ifc.__nif6h_entrylen);

    if (!(p->__nif6e_addr.sin6_family == AF_INET6))
      continue;

    if (!(p->__nif6e_flags & _NIF6E_FLAGS_ON_LINK_ACTIVE))
      continue;

    ++(*count);
  }

  if ((*count) == 0) {
    uv__free(ifc.__nif6h_buffer);
    uv__close(sockfd);
    return 0;
  }

  /* Alloc the return interface structs */
  *addresses = uv__calloc(1, *count * sizeof(uv_interface_address_t));
  if (!(*addresses)) {
    uv__free(ifc.__nif6h_buffer);
    uv__close(sockfd);
    return UV_ENOMEM;
  }
  address = *addresses;

  count_names = 0;
  ifr = (__net_ifconf6entry_t*)(ifc.__nif6h_buffer);
  while ((char*)ifr < (char*)ifc.__nif6h_buffer + ifc.__nif6h_buflen) {
    p = ifr;
    ifr = (__net_ifconf6entry_t*)((char*)ifr + ifc.__nif6h_entrylen);

    if (!(p->__nif6e_addr.sin6_family == AF_INET6))
      continue;

    if (!(p->__nif6e_flags & _NIF6E_FLAGS_ON_LINK_ACTIVE))
      continue;

    /* All conditions above must match count loop */

    i = 0;
    /* Ignore EBCDIC space (0x40) padding in name */
    while (i < ARRAY_SIZE(p->__nif6e_name) &&
           p->__nif6e_name[i] != 0x40 &&
           p->__nif6e_name[i] != 0)
      ++i;
    address->name = uv__malloc(i + 1);
    if (address->name == NULL) {
      uv_free_interface_addresses(*addresses, count_names);
      uv__free(ifc.__nif6h_buffer);
      uv__close(sockfd);
      return UV_ENOMEM;
    }
    memcpy(address->name, p->__nif6e_name, i);
    address->name[i] = '\0';
    __e2a_s(address->name);
    count_names++;

    address->address.address6 = *((struct sockaddr_in6*) &p->__nif6e_addr);

    for (i = 0; i < (p->__nif6e_prefixlen / 8); i++)
      netmask[i] = 0xFF;

    if (p->__nif6e_prefixlen % 8)
      netmask[i] = 0xFF << (8 - (p->__nif6e_prefixlen % 8));

    address->netmask.netmask6.sin6_len = p->__nif6e_prefixlen;
    memcpy(&(address->netmask.netmask6.sin6_addr), netmask, 16);
    address->netmask.netmask6.sin6_family = AF_INET6;

    address->is_internal = p->__nif6e_flags & _NIF6E_FLAGS_LOOPBACK ? 1 : 0;
    address++;
  }

  uv__free(ifc.__nif6h_buffer);
  uv__close(sockfd);
  return 0;
}


int uv_interface_addresses(uv_interface_address_t** addresses, int* count) {
  uv_interface_address_t* address;
  int sockfd;
  int maxsize;
  struct ifconf ifc;
  struct ifreq flg;
  struct ifreq* ifr;
  struct ifreq* p;
  uv_interface_address_t* addresses_v6;
  int count_v6;
  unsigned int i;
  int rc;
  int count_names;

  *count = 0;
  *addresses = NULL;

  /* get the ipv6 addresses first */
  if ((rc = uv__interface_addresses_v6(&addresses_v6, &count_v6)) != 0)
    return rc;

  /* now get the ipv4 addresses */

  /* Assume maximum buffer size allowable */
  maxsize = 16384;

  sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
  if (0 > sockfd) {
    if (count_v6)
      uv_free_interface_addresses(addresses_v6, count_v6);
    return UV__ERR(errno);
  }

  ifc.ifc_req = uv__calloc(1, maxsize);

  if (ifc.ifc_req == NULL) {
    if (count_v6)
      uv_free_interface_addresses(addresses_v6, count_v6);
    uv__close(sockfd);
    return UV_ENOMEM;
  }

  ifc.ifc_len = maxsize;

  if (ioctl(sockfd, SIOCGIFCONF, &ifc) == -1) {
    if (count_v6)
      uv_free_interface_addresses(addresses_v6, count_v6);
    uv__free(ifc.ifc_req);
    uv__close(sockfd);
    return UV__ERR(errno);
  }

#define MAX(a,b) (((a)>(b))?(a):(b))
#define ADDR_SIZE(p) MAX((p).sa_len, sizeof(p))

  /* Count all up and running ipv4/ipv6 addresses */
  ifr = ifc.ifc_req;
  while ((char*)ifr < (char*)ifc.ifc_req + ifc.ifc_len) {
    p = ifr;
    ifr = (struct ifreq*)
      ((char*)ifr + sizeof(ifr->ifr_name) + ADDR_SIZE(ifr->ifr_addr));

    if (!(p->ifr_addr.sa_family == AF_INET6 ||
          p->ifr_addr.sa_family == AF_INET))
      continue;

    memcpy(flg.ifr_name, p->ifr_name, sizeof(flg.ifr_name));
    if (ioctl(sockfd, SIOCGIFFLAGS, &flg) == -1) {
      if (count_v6)
        uv_free_interface_addresses(addresses_v6, count_v6);
      uv__free(ifc.ifc_req);
      uv__close(sockfd);
      return UV__ERR(errno);
    }

    if (!(flg.ifr_flags & IFF_UP && flg.ifr_flags & IFF_RUNNING))
      continue;

    (*count)++;
  }

  if (*count == 0 && count_v6 == 0) {
    uv__free(ifc.ifc_req);
    uv__close(sockfd);
    return 0;
  }

  /* Alloc the return interface structs */
  *addresses = uv__calloc(1, (*count + count_v6) *
                          sizeof(uv_interface_address_t));

  if (!(*addresses)) {
    if (count_v6)
      uv_free_interface_addresses(addresses_v6, count_v6);
    uv__free(ifc.ifc_req);
    uv__close(sockfd);
    return UV_ENOMEM;
  }
  address = *addresses;

  /* copy over the ipv6 addresses if any are found */
  if (count_v6) {
    memcpy(address, addresses_v6, count_v6 * sizeof(uv_interface_address_t));
    address += count_v6;
    *count += count_v6;
    /* free ipv6 addresses, but keep address names */
    uv__free(addresses_v6);
  }

  count_names = *count;
  ifr = ifc.ifc_req;
  while ((char*)ifr < (char*)ifc.ifc_req + ifc.ifc_len) {
    p = ifr;
    ifr = (struct ifreq*)
      ((char*)ifr + sizeof(ifr->ifr_name) + ADDR_SIZE(ifr->ifr_addr));

    if (!(p->ifr_addr.sa_family == AF_INET6 ||
          p->ifr_addr.sa_family == AF_INET))
      continue;

    memcpy(flg.ifr_name, p->ifr_name, sizeof(flg.ifr_name));
    if (ioctl(sockfd, SIOCGIFFLAGS, &flg) == -1) {
      uv_free_interface_addresses(*addresses, count_names);
      uv__free(ifc.ifc_req);
      uv__close(sockfd);
      return UV_ENOSYS;
    }

    if (!(flg.ifr_flags & IFF_UP && flg.ifr_flags & IFF_RUNNING))
      continue;

    /* All conditions above must match count loop */

    i = 0;
    /* Ignore EBCDIC space (0x40) padding in name */
    while (i < ARRAY_SIZE(p->ifr_name) &&
           p->ifr_name[i] != 0x40 &&
           p->ifr_name[i] != 0)
      ++i;
    address->name = uv__malloc(i + 1);
    if (address->name == NULL) {
      uv_free_interface_addresses(*addresses, count_names);
      uv__free(ifc.ifc_req);
      uv__close(sockfd);
      return UV_ENOMEM;
    }
    memcpy(address->name, p->ifr_name, i);
    address->name[i] = '\0';
    __e2a_s(address->name);
    count_names++;

    address->address.address4 = *((struct sockaddr_in*) &p->ifr_addr);

    if (ioctl(sockfd, SIOCGIFNETMASK, p) == -1) {
      uv_free_interface_addresses(*addresses, count_names);
      uv__free(ifc.ifc_req);
      uv__close(sockfd);
      return UV__ERR(errno);
    }

    address->netmask.netmask4 = *((struct sockaddr_in*) &p->ifr_addr);
    address->netmask.netmask4.sin_family = AF_INET;
    address->is_internal = flg.ifr_flags & IFF_LOOPBACK ? 1 : 0;
    address++;
  }

#undef ADDR_SIZE
#undef MAX

  uv__free(ifc.ifc_req);
  uv__close(sockfd);
  return 0;
}


void uv_free_interface_addresses(uv_interface_address_t* addresses,
                                 int count) {
  int i;
  for (i = 0; i < count; ++i)
    uv__free(addresses[i].name);
  uv__free(addresses);
}


void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {
  struct epoll_event* events;
  struct epoll_event dummy;
  uintptr_t i;
  uintptr_t nfds;

  assert(loop->watchers != NULL);
  assert(fd >= 0);

  events = (struct epoll_event*) loop->watchers[loop->nwatchers];
  nfds = (uintptr_t) loop->watchers[loop->nwatchers + 1];
  if (events != NULL)
    /* Invalidate events with same file descriptor */
    for (i = 0; i < nfds; i++)
      if ((int) events[i].fd == fd)
        events[i].fd = -1;

  /* Remove the file descriptor from the epoll. */
  if (loop->ep != NULL)
    epoll_ctl(loop->ep, EPOLL_CTL_DEL, fd, &dummy);
}


int uv__io_check_fd(uv_loop_t* loop, int fd) {
  struct pollfd p[1];
  int rv;

  p[0].fd = fd;
  p[0].events = POLLIN;

  do
    rv = poll(p, 1, 0);
  while (rv == -1 && errno == EINTR);

  if (rv == -1)
    abort();

  if (p[0].revents & POLLNVAL)
    return -1;

  return 0;
}


int uv_fs_event_init(uv_loop_t* loop, uv_fs_event_t* handle) {
  uv__handle_init(loop, (uv_handle_t*)handle, UV_FS_EVENT);
  return 0;
}


static int os390_regfileint(uv_fs_event_t* handle, char* path) {
  uv__os390_epoll* ep;
  _RFIS reg_struct;
  int rc;

  ep = handle->loop->ep;
  assert(ep->msg_queue != -1);

  reg_struct.__rfis_cmd  = _RFIS_REG;
  reg_struct.__rfis_qid  = ep->msg_queue;
  reg_struct.__rfis_type = 1;
  memcpy(reg_struct.__rfis_utok, &handle, sizeof(handle));

  rc = __w_pioctl(path, _IOCC_REGFILEINT, sizeof(reg_struct), &reg_struct);
  if (rc != 0)
    return UV__ERR(errno);

  memcpy(handle->rfis_rftok, reg_struct.__rfis_rftok,
         sizeof(handle->rfis_rftok));

  return 0;
}


int uv_fs_event_start(uv_fs_event_t* handle, uv_fs_event_cb cb,
                      const char* filename, unsigned int flags) {
  char* path;
  int rc;

  if (uv__is_active(handle))
    return UV_EINVAL;

  path = uv__strdup(filename);
  if (path == NULL)
    return UV_ENOMEM;

  rc = os390_regfileint(handle, path);
  if (rc != 0) {
    uv__free(path);
    return rc;
  }

  uv__handle_start(handle);
  handle->path = path;
  handle->cb = cb;

  return 0;
}


int uv__fs_event_stop(uv_fs_event_t* handle) {
  uv__os390_epoll* ep;
  _RFIS reg_struct;
  int rc;

  if (!uv__is_active(handle))
    return 0;

  ep = handle->loop->ep;
  assert(ep->msg_queue != -1);

  reg_struct.__rfis_cmd  = _RFIS_UNREG;
  reg_struct.__rfis_qid  = ep->msg_queue;
  reg_struct.__rfis_type = 1;
  memcpy(reg_struct.__rfis_rftok, handle->rfis_rftok,
         sizeof(handle->rfis_rftok));

  /*
   * This call will take "/" as the path argument in case we
   * don't care to supply the correct path. The system will simply
   * ignore it.
   */
  rc = __w_pioctl("/", _IOCC_REGFILEINT, sizeof(reg_struct), &reg_struct);
  if (rc != 0 && errno != EALREADY && errno != ENOENT)
    abort();

  if (handle->path != NULL) {
    uv__free(handle->path);
    handle->path = NULL;
  }

  if (rc != 0 && errno == EALREADY)
    return -1;

  uv__handle_stop(handle);

  return 0;
}


int uv_fs_event_stop(uv_fs_event_t* handle) {
  uv__fs_event_stop(handle);
  return 0;
}


void uv__fs_event_close(uv_fs_event_t* handle) {
  /*
   * If we were unable to unregister file interest here, then it is most likely
   * that there is a pending queued change notification. When this happens, we
   * don't want to complete the close as it will free the underlying memory for
   * the handle, causing a use-after-free problem when the event is processed.
   * We defer the final cleanup until after the event is consumed in
   * os390_message_queue_handler().
   */
  if (uv__fs_event_stop(handle) == 0)
    uv__make_close_pending((uv_handle_t*) handle);
}


static int os390_message_queue_handler(uv__os390_epoll* ep) {
  uv_fs_event_t* handle;
  int msglen;
  int events;
  _RFIM msg;

  if (ep->msg_queue == -1)
    return 0;

  msglen = msgrcv(ep->msg_queue, &msg, sizeof(msg), 0, IPC_NOWAIT);

  if (msglen == -1 && errno == ENOMSG)
    return 0;

  if (msglen == -1)
    abort();

  events = 0;
  if (msg.__rfim_event == _RFIM_ATTR || msg.__rfim_event == _RFIM_WRITE)
    events = UV_CHANGE;
  else if (msg.__rfim_event == _RFIM_RENAME || msg.__rfim_event == _RFIM_UNLINK)
    events = UV_RENAME;
  else if (msg.__rfim_event == 156)
    /* TODO(gabylb): zos - this event should not happen, need to investigate.
     *
     * This event seems to occur when the watched file is [re]moved, or an
     * editor (like vim) renames then creates the file on save (for vim, that's
     * when backupcopy=no|auto).
     */
    events = UV_RENAME;
  else
    /* Some event that we are not interested in. */
    return 0;

  /* `__rfim_utok` is treated as text when it should be treated as binary while
   * running in ASCII mode, resulting in an unwanted autoconversion.
   */
  __a2e_l(msg.__rfim_utok, sizeof(msg.__rfim_utok));
  handle = *(uv_fs_event_t**)(msg.__rfim_utok);
  assert(handle != NULL);

  assert((handle->flags & UV_HANDLE_CLOSED) == 0);
  if (uv__is_closing(handle)) {
    uv__handle_stop(handle);
    uv__make_close_pending((uv_handle_t*) handle);
    return 0;
  } else if (handle->path == NULL) {
    /* _RFIS_UNREG returned EALREADY. */
    uv__handle_stop(handle);
    return 0;
  }

  /* The file is implicitly unregistered when the change notification is
   * sent, only one notification is sent per registration. So we need to
   * re-register interest in a file after each change notification we
   * receive.
   */
  assert(handle->path != NULL);
  os390_regfileint(handle, handle->path);
  handle->cb(handle, uv__basename_r(handle->path), events, 0);
  return 1;
}


void uv__io_poll(uv_loop_t* loop, int timeout) {
  static const int max_safe_timeout = 1789569;
  uv__loop_internal_fields_t* lfields;
  struct epoll_event events[1024];
  struct epoll_event* pe;
  struct epoll_event e;
  uv__os390_epoll* ep;
  int have_signals;
  int real_timeout;
  struct uv__queue* q;
  uv__io_t* w;
  uint64_t base;
  int count;
  int nfds;
  int fd;
  int op;
  int i;
  int user_timeout;
  int reset_timeout;

  if (loop->nfds == 0) {
    assert(uv__queue_empty(&loop->watcher_queue));
    return;
  }

  lfields = uv__get_internal_fields(loop);

  while (!uv__queue_empty(&loop->watcher_queue)) {
    uv_stream_t* stream;

    q = uv__queue_head(&loop->watcher_queue);
    uv__queue_remove(q);
    uv__queue_init(q);
    w = uv__queue_data(q, uv__io_t, watcher_queue);

    assert(w->pevents != 0);
    assert(w->fd >= 0);

    stream= container_of(w, uv_stream_t, io_watcher);

    assert(w->fd < (int) loop->nwatchers);

    e.events = w->pevents;
    e.fd = w->fd;

    if (w->events == 0)
      op = EPOLL_CTL_ADD;
    else
      op = EPOLL_CTL_MOD;

    /* XXX Future optimization: do EPOLL_CTL_MOD lazily if we stop watching
     * events, skip the syscall and squelch the events after epoll_wait().
     */
    if (epoll_ctl(loop->ep, op, w->fd, &e)) {
      if (errno != EEXIST)
        abort();

      assert(op == EPOLL_CTL_ADD);

      /* We've reactivated a file descriptor that's been watched before. */
      if (epoll_ctl(loop->ep, EPOLL_CTL_MOD, w->fd, &e))
        abort();
    }

    w->events = w->pevents;
  }

  assert(timeout >= -1);
  base = loop->time;
  count = 48; /* Benchmarks suggest this gives the best throughput. */
  real_timeout = timeout;
  int nevents = 0;
  have_signals = 0;

  if (lfields->flags & UV_METRICS_IDLE_TIME) {
    reset_timeout = 1;
    user_timeout = timeout;
    timeout = 0;
  } else {
    reset_timeout = 0;
  }

  nfds = 0;
  for (;;) {
    /* Only need to set the provider_entry_time if timeout != 0. The function
     * will return early if the loop isn't configured with UV_METRICS_IDLE_TIME.
     */
    if (timeout != 0)
      uv__metrics_set_provider_entry_time(loop);

    if (sizeof(int32_t) == sizeof(long) && timeout >= max_safe_timeout)
      timeout = max_safe_timeout;

    /* Store the current timeout in a location that's globally accessible so
     * other locations like uv__work_done() can determine whether the queue
     * of events in the callback were waiting when poll was called.
     */
    lfields->current_timeout = timeout;

    nfds = epoll_wait(loop->ep, events,
                      ARRAY_SIZE(events), timeout);

    /* Update loop->time unconditionally. It's tempting to skip the update when
     * timeout == 0 (i.e. non-blocking poll) but there is no guarantee that the
     * operating system didn't reschedule our process while in the syscall.
     */
    base = loop->time;
    SAVE_ERRNO(uv__update_time(loop));
    if (nfds == 0) {
      assert(timeout != -1);

      if (reset_timeout != 0) {
        timeout = user_timeout;
        reset_timeout = 0;
      }

      if (timeout == -1)
        continue;

      if (timeout == 0)
        return;

      /* We may have been inside the system call for longer than |timeout|
       * milliseconds so we need to update the timestamp to avoid drift.
       */
      goto update_timeout;
    }

    if (nfds == -1) {

      if (errno != EINTR)
        abort();

      if (reset_timeout != 0) {
        timeout = user_timeout;
        reset_timeout = 0;
      }

      if (timeout == -1)
        continue;

      if (timeout == 0)
        return;

      /* Interrupted by a signal. Update timeout and poll again. */
      goto update_timeout;
    }


    assert(loop->watchers != NULL);
    loop->watchers[loop->nwatchers] = (void*) events;
    loop->watchers[loop->nwatchers + 1] = (void*) (uintptr_t) nfds;
    for (i = 0; i < nfds; i++) {
      pe = events + i;
      fd = pe->fd;

      /* Skip invalidated events, see uv__platform_invalidate_fd */
      if (fd == -1)
        continue;

      ep = loop->ep;
      if (pe->is_msg) {
        os390_message_queue_handler(ep);
        nevents++;
        continue;
      }

      assert(fd >= 0);
      assert((unsigned) fd < loop->nwatchers);

      w = loop->watchers[fd];

      if (w == NULL) {
        /* File descriptor that we've stopped watching, disarm it.
         *
         * Ignore all errors because we may be racing with another thread
         * when the file descriptor is closed.
         */
        epoll_ctl(loop->ep, EPOLL_CTL_DEL, fd, pe);
        continue;
      }

      /* Give users only events they're interested in. Prevents spurious
       * callbacks when previous callback invocation in this loop has stopped
       * the current watcher. Also, filters out events that users has not
       * requested us to watch.
       */
      pe->events &= w->pevents | POLLERR | POLLHUP;

      if (pe->events == POLLERR || pe->events == POLLHUP)
        pe->events |= w->pevents & (POLLIN | POLLOUT);

      if (pe->events != 0) {
        /* Run signal watchers last.  This also affects child process watchers
         * because those are implemented in terms of signal watchers.
         */
        if (w == &loop->signal_io_watcher) {
          have_signals = 1;
        } else {
          uv__metrics_update_idle_time(loop);
          w->cb(loop, w, pe->events);
        }
        nevents++;
      }
    }

    uv__metrics_inc_events(loop, nevents);
    if (reset_timeout != 0) {
      timeout = user_timeout;
      reset_timeout = 0;
      uv__metrics_inc_events_waiting(loop, nevents);
    }

    if (have_signals != 0) {
      uv__metrics_update_idle_time(loop);
      loop->signal_io_watcher.cb(loop, &loop->signal_io_watcher, POLLIN);
    }

    loop->watchers[loop->nwatchers] = NULL;
    loop->watchers[loop->nwatchers + 1] = NULL;

    if (have_signals != 0)
      return;  /* Event loop should cycle now so don't poll again. */

    if (nevents != 0) {
      if (nfds == ARRAY_SIZE(events) && --count != 0) {
        /* Poll for more events but don't block this time. */
        timeout = 0;
        continue;
      }
      return;
    }

    if (timeout == 0)
      return;

    if (timeout == -1)
      continue;

update_timeout:
    assert(timeout > 0);

    real_timeout -= (loop->time - base);
    if (real_timeout <= 0)
      return;

    timeout = real_timeout;
  }
}


int uv__io_fork(uv_loop_t* loop) {
  /*
    Nullify the msg queue but don't close it because
    it is still being used by the parent.
  */
  loop->ep = NULL;

  return uv__platform_loop_init(loop);
}