coregrind/vgdb.c

/*--------------------------------------------------------------------*/
/*--- Relay between gdb and gdbserver embedded in valgrind  vgdb.c ---*/
/*--------------------------------------------------------------------*/

/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2011-2015 Philippe Waroquiers

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/

#include "vgdb.h"

#include "config.h"

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>

/* vgdb has two usages:
   1. relay application between gdb and the gdbserver embedded in valgrind.
   2. standalone to send monitor commands to a running valgrind-ified process

   It is made of a main program which reads arguments.  If no
   arguments are given or only --pid and --vgdb-prefix, then usage 1 is
   assumed.
   
   As relay application, vgdb reads bytes from gdb on stdin and
   writes these bytes to valgrind.  Bytes read from valgrind are
   written to gdb on stdout.  Read/Write from/to valgrind is done
   using FIFOs.  There is one thread reading from stdin, writing to
   valgrind on a FIFO.  There is one thread reading from valgrind on a
   FIFO, writing to gdb on stdout

   As a standalone utility, vgdb builds command packets to write to valgrind,
   sends it and reads the reply. The same two threads are used to write/read.
   Once all the commands are sent and their replies received, vgdb will exit.
*/

int debuglevel;
struct timeval dbgtv;
static char *vgdb_prefix = NULL;

/* Will be set to True when any condition indicating we have to shutdown
   is encountered. */
Bool shutting_down = False;

VgdbShared32 *shared32;
VgdbShared64 *shared64;
#define VS_written_by_vgdb (shared32 != NULL ?        \
                            shared32->written_by_vgdb \
                            : shared64->written_by_vgdb)
#define VS_seen_by_valgrind (shared32 != NULL ?         \
                             shared32->seen_by_valgrind \
                             : shared64->seen_by_valgrind)

#define VS_vgdb_pid (shared32 != NULL ? shared32->vgdb_pid : shared64->vgdb_pid)

void *vmalloc(size_t size)
{
   void * mem = malloc(size);
   if (mem == NULL)
      XERROR (errno, "can't allocate memory\n");
   return mem;
}

void *vrealloc(void *ptr,size_t size)
{
   void * mem = realloc(ptr, size);
   if (mem == NULL)
      XERROR (errno, "can't reallocate memory\n");
   return mem;
}

/* Return the name of a directory for temporary files. */
static
const char *vgdb_tmpdir(void)
{
   const char *tmpdir;

   tmpdir = getenv("TMPDIR");
   if (tmpdir == NULL || *tmpdir == '\0')
     tmpdir = VG_TMPDIR;
   if (tmpdir == NULL || *tmpdir == '\0')
     tmpdir = "/tmp";    /* fallback */

   return tmpdir;
}

/* Return the default path prefix for the named pipes (FIFOs) used by vgdb/gdb
   to communicate with valgrind */
static
char *vgdb_prefix_default(void)
{
   static HChar *prefix;

   if (prefix == NULL) {
      const char *tmpdir = vgdb_tmpdir();
      prefix = vmalloc(strlen(tmpdir) + strlen("/vgdb-pipe") + 1);
      strcpy(prefix, tmpdir);
      strcat(prefix, "/vgdb-pipe");
   }
   return prefix;
}

/* add nrw to the written_by_vgdb field of shared32 or shared64 */ 
static
void add_written(int nrw)
{
   if (shared32 != NULL) 
      shared32->written_by_vgdb += nrw;
   else if (shared64 != NULL) 
      shared64->written_by_vgdb += nrw;
   else
      assert(0);
}

static int shared_mem_fd = -1;
static
void map_vgdbshared (char* shared_mem)
{
   struct stat fdstat;
   void **s;
   shared_mem_fd = open(shared_mem, O_RDWR);
   /* shared_mem_fd will not be closed till vgdb exits. */

   if (shared_mem_fd == -1)
      XERROR (errno, "error opening %s shared memory file\n", shared_mem);

   if (fstat(shared_mem_fd, &fdstat) != 0)
      XERROR (errno, "fstat");

   if (fdstat.st_size == sizeof(VgdbShared64))
      s = (void*) &shared64;
   else if (fdstat.st_size == sizeof(VgdbShared32))
      s = (void*) &shared32;
   else
#if VEX_HOST_WORDSIZE == 8
      XERROR (0,
              "error size shared memory file %s.\n"
              "expecting size %d (64bits) or %d (32bits) got %ld.\n",
              shared_mem,
              (int) sizeof(VgdbShared64), (int) sizeof(VgdbShared32), 
              (long int)fdstat.st_size);
#elif VEX_HOST_WORDSIZE == 4
      XERROR (0,
              "error size shared memory file %s.\n"
              "expecting size %d (32bits) got %ld.\n",
              shared_mem,
              (int) sizeof(VgdbShared32), 
              fdstat.st_size);
#else
# error "unexpected wordsize"
#endif

#if VEX_HOST_WORDSIZE == 4
   if (shared64 != NULL)
      XERROR (0, "cannot use 32 bits vgdb with a 64bits valgrind process\n");
   /* But we can use a 64 bits vgdb with a 32 bits valgrind */
#endif

   *s = (void*) mmap (NULL, fdstat.st_size, 
                      PROT_READ|PROT_WRITE, MAP_SHARED, 
                      shared_mem_fd, 0);

   if (*s == (void *) -1)
      XERROR (errno, "error mmap shared memory file %s\n", shared_mem);

}

/* This function loops till shutting_down becomes true.  In this loop,
   it verifies if valgrind process is reading the characters written
   by vgdb.  The verification is done every max_invoke_ms ms.  If
   valgrind is not reading characters, it will use invoker_invoke_gdbserver
   to ensure that the gdbserver code is called soon by valgrind. */
static int max_invoke_ms = 100;
#define NEVER 99999999
static int cmd_time_out = NEVER;
static
void *invoke_gdbserver_in_valgrind(void *v_pid)
{
   struct timeval cmd_max_end_time;
   Bool cmd_started = False;
   struct timeval invoke_time;

   int pid = *(int *)v_pid;
   int written_by_vgdb_before_sleep;
   int seen_by_valgrind_before_sleep;
   
   int invoked_written = -1;
   unsigned int usecs;

   pthread_cleanup_push(invoker_cleanup_restore_and_detach, v_pid);

   while (!shutting_down) {
      written_by_vgdb_before_sleep = VS_written_by_vgdb;
      seen_by_valgrind_before_sleep = VS_seen_by_valgrind;
      DEBUG(3, 
            "written_by_vgdb_before_sleep %d "
            "seen_by_valgrind_before_sleep %d\n",
            written_by_vgdb_before_sleep,
            seen_by_valgrind_before_sleep);
      if (cmd_time_out != NEVER
          && !cmd_started
          && written_by_vgdb_before_sleep > seen_by_valgrind_before_sleep) {
         /* A command was started. Record the time at which it was started. */
         DEBUG(1, "IO for command started\n");
         gettimeofday(&cmd_max_end_time, NULL);
         cmd_max_end_time.tv_sec += cmd_time_out;
         cmd_started = True;
      }
      if (max_invoke_ms > 0) {
         usecs = 1000 * max_invoke_ms;
         gettimeofday(&invoke_time, NULL);
         invoke_time.tv_sec += max_invoke_ms / 1000;
         invoke_time.tv_usec += 1000 * (max_invoke_ms % 1000);
         invoke_time.tv_sec += invoke_time.tv_usec / (1000 * 1000);
         invoke_time.tv_usec = invoke_time.tv_usec % (1000 * 1000);
      } else {
         usecs = 0;
      }
      if (cmd_started) {
         // 0 usecs here means the thread just has to check gdbserver eats
         // the characters in <= cmd_time_out seconds.
         // We will just wait by 1 second max at a time.
         if (usecs == 0 || usecs > 1000 * 1000)
            usecs = 1000 * 1000;
      }
      usleep(usecs);

      /* If nothing happened during our sleep, let's try to wake up valgrind
         or check for cmd time out. */
      if (written_by_vgdb_before_sleep == VS_written_by_vgdb
          && seen_by_valgrind_before_sleep == VS_seen_by_valgrind
          && VS_written_by_vgdb > VS_seen_by_valgrind) {
         struct timeval now;
         gettimeofday(&now, NULL);
         DEBUG(2,
               "after sleep "
               "written_by_vgdb %d "
               "seen_by_valgrind %d "
               "invoked_written %d\n",
               VS_written_by_vgdb,
               VS_seen_by_valgrind,
               invoked_written);
         /* if the pid does not exist anymore, we better stop */
         if (kill(pid, 0) != 0)
           XERROR (errno, 
                   "invoke_gdbserver_in_valgrind: "
                   "check for pid %d existence failed\n", pid);
         if (cmd_started) {
            if (timercmp (&now, &cmd_max_end_time, >))
               XERROR (0, 
                       "pid %d did not handle a command in %d seconds\n",
                       pid, cmd_time_out);
         }
         if (max_invoke_ms > 0 && timercmp (&now, &invoke_time, >=)) {
            /* only need to wake up if the nr written has changed since
               last invoke. */
            if (invoked_written != written_by_vgdb_before_sleep) {
               if (invoker_invoke_gdbserver(pid)) {
                  /* If invoke successful, no need to invoke again
                     for the same value of written_by_vgdb_before_sleep. */
                  invoked_written = written_by_vgdb_before_sleep;
               }
            }
         }
      } else {
         // Something happened => restart timer check.
         if (cmd_time_out != NEVER) {
            DEBUG(2, "some IO was done => restart command\n");
            cmd_started = False;
         }
      }
   }
   pthread_cleanup_pop(0);
   return NULL;
}

static
int open_fifo (const char* name, int flags, const char* desc)
{
   int fd;
   DEBUG(1, "opening %s %s\n", name, desc);
   fd = open(name, flags);
   if (fd == -1)
      XERROR (errno, "error opening %s %s\n", name, desc);

   DEBUG(1, "opened %s %s fd %d\n", name, desc, fd);
   return fd;
}

/* acquire a lock on the first byte of the given fd. If not successful,
   exits with error.
   This allows to avoid having two vgdb speaking with the same Valgrind
   gdbserver as this causes serious headaches to the protocol. */
static
void acquire_lock (int fd, int valgrind_pid)
{
   struct flock fl;
   fl.l_type = F_WRLCK;
   fl.l_whence = SEEK_SET;
   fl.l_start = 0;
   fl.l_len = 1;
   if (fcntl(fd, F_SETLK, &fl) < 0) {
      if (errno == EAGAIN || errno == EACCES) {
         XERROR(errno, 
                "Cannot acquire lock.\n"
                "Probably vgdb pid %d already speaks with Valgrind pid %d\n",
                VS_vgdb_pid,
                valgrind_pid);
      } else {
         XERROR(errno, "cannot acquire lock.\n");
      }
   }

   /* Here, we have the lock. It will be released when fd will be closed. */
   /* We indicate our pid to Valgrind gdbserver */
   if (shared32 != NULL)
      shared32->vgdb_pid = getpid();
   else if (shared64 != NULL)
      shared64->vgdb_pid = getpid();
   else
      assert(0);
}

#define PBUFSIZ 16384 /* keep in sync with server.h */

/* read some characters from fd.
   Returns the nr of characters read, -1 if error.
   desc is a string used in tracing */
static
int read_buf (int fd, char* buf, const char* desc)
{
   int nrread;
   DEBUG(2, "reading %s\n", desc);
   nrread = read(fd, buf, PBUFSIZ);
   if (nrread == -1) {
      ERROR (errno, "error reading %s\n", desc);
      return -1;
   }
   buf[nrread] = '\0';
   DEBUG(2, "read %s %s\n", desc, buf);
   return nrread;
}

/* write size bytes from buf to fd.
   desc is a description of the action for which the write is done.
   If notify, then add size to the shared cntr indicating to the 
   valgrind process that there is new data.
   Returns True if write is ok, False if there was a problem. */
static
Bool write_buf(int fd, const char* buf, int size, const char* desc, Bool notify)
{
   int nrwritten;
   int nrw;
   DEBUG(2, "writing %s len %d %.*s notify: %d\n", desc, size,
         size, buf, notify);
   nrwritten = 0;
   while (nrwritten < size) {
      nrw = write (fd, buf+nrwritten, size - nrwritten);
      if (nrw == -1) {
         ERROR(errno, "error write %s\n", desc);
         return False;
      }
      nrwritten = nrwritten + nrw;
      if (notify)
         add_written(nrw);
   }
   return True;
} 

typedef enum {
   FROM_GDB,
   TO_GDB,
   FROM_PID,
   TO_PID } ConnectionKind;
static const int NumConnectionKind = TO_PID+1;
static 
const char *ppConnectionKind (ConnectionKind con)
{
   switch (con) {
   case FROM_GDB: return "FROM_GDB";
   case TO_GDB:   return "TO_GDB";
   case FROM_PID: return "FROM_PID";
   case TO_PID:   return "TO_PID";
   default:       return "invalid connection kind";
   }
}

static char *shared_mem;

static int from_gdb = 0; /* stdin by default, changed if --port is given. */
static char *from_gdb_to_pid; /* fifo name to write gdb command to pid */
/* Returns True in case read/write operations were done properly.
   Returns False in case of error.
   to_pid is the file descriptor to write to the process pid. */
static
Bool read_from_gdb_write_to_pid(int to_pid)
{
   char buf[PBUFSIZ+1]; // +1 for trailing \0
   int nrread;

   nrread = read_buf(from_gdb, buf, "from gdb on stdin");
   if (nrread <= 0) {
      if (nrread == 0) 
         DEBUG(1, "read 0 bytes from gdb => assume exit\n");
      else
         DEBUG(1, "error reading bytes from gdb\n");
      close (from_gdb);
      shutting_down = True;
      return False;
   }
   return write_buf(to_pid, buf, nrread, "to_pid", /* notify */ True);
}

static int to_gdb = 1; /* stdout by default, changed if --port is given. */
static char *to_gdb_from_pid; /* fifo name to read pid replies */
/* Returns True in case read/write operations were done properly.
   Returns False in case of error.
   from_pid is the file descriptor to read data from the process pid. */
static
Bool read_from_pid_write_to_gdb(int from_pid)
{
   char buf[PBUFSIZ+1]; // +1 for trailing \0
   int nrread;

   nrread = read_buf(from_pid, buf, "from pid");
   if (nrread <= 0) {
      if (nrread == 0) 
         DEBUG(1, "read 0 bytes from pid => assume exit\n");
      else
         DEBUG(1, "error reading bytes from pid\n");
      close (from_pid);
      shutting_down = True;
      return False;
   }
   return write_buf(to_gdb, buf, nrread, "to_gdb", /* notify */ False);
}

static
void wait_for_gdb_connect (int in_port)
{
   struct sockaddr_in addr;

   int listen_gdb = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
   int gdb_connect;
 
   if (-1 == listen_gdb) {
      XERROR(errno, "cannot create socket");
   }
 
    memset(&addr, 0, sizeof(addr));
 
    addr.sin_family = AF_INET;
    addr.sin_port = htons((unsigned short int)in_port);
    addr.sin_addr.s_addr = INADDR_ANY;
 
    if (-1 == bind(listen_gdb,(struct sockaddr *)&addr, sizeof(addr))) {
      XERROR(errno, "bind failed");
    }
    fprintf(stderr, "listening on port %d ...", in_port);
    fflush(stderr);
    if (-1 == listen(listen_gdb, 1)) {
      XERROR(errno, "error listen failed");
    }

    gdb_connect = accept(listen_gdb, NULL, NULL);
    if (gdb_connect < 0) {
        XERROR(errno, "accept failed");
    }
    fprintf(stderr, "connected.\n");
    fflush(stderr);
    close(listen_gdb);
    from_gdb = gdb_connect;
    to_gdb = gdb_connect;
}

/* prepares the FIFOs filenames, map the shared memory. */
static
void prepare_fifos_and_shared_mem(int pid)
{
   const HChar *user, *host;
   unsigned len;

   user = getenv("LOGNAME");
   if (user == NULL) user = getenv("USER");
   if (user == NULL) user = "???";
   if (strchr(user, '/')) user = "???";

   host = getenv("HOST");
   if (host == NULL) host = getenv("HOSTNAME");
   if (host == NULL) host = "???";
   if (strchr(host, '/')) host = "???";

   len = strlen(vgdb_prefix) + strlen(user) + strlen(host) + 40;
   from_gdb_to_pid = vmalloc (len);
   to_gdb_from_pid = vmalloc (len);
   shared_mem      = vmalloc (len);
   /* below 3 lines must match the equivalent in remote-utils.c */
   sprintf(from_gdb_to_pid, "%s-from-vgdb-to-%d-by-%s-on-%s",    vgdb_prefix,
           pid, user, host);
   sprintf(to_gdb_from_pid, "%s-to-vgdb-from-%d-by-%s-on-%s",    vgdb_prefix,
           pid, user, host);
   sprintf(shared_mem,      "%s-shared-mem-vgdb-%d-by-%s-on-%s", vgdb_prefix,
           pid, user, host);
   DEBUG (1, "vgdb: using %s %s %s\n", 
          from_gdb_to_pid, to_gdb_from_pid, shared_mem);

   map_vgdbshared(shared_mem);
}

/* Convert hex digit A to a number.  */

static int
fromhex (int a)
{
   if (a >= '0' && a <= '9')
      return a - '0';
   else if (a >= 'a' && a <= 'f')
      return a - 'a' + 10;
   else
      XERROR(0, "Reply contains invalid hex digit %c\n", a);
  return 0;
}

/* Returns next char from fd.  -1 if error, -2 if EOF.
   NB: must always call it with the same fd */
static int
readchar (int fd)
{
  static char buf[PBUFSIZ+1]; // +1 for trailing \0
  static int bufcnt = 0;
  static unsigned char *bufp; 
  // unsigned bufp to e.g. avoid having 255 converted to int -1

  if (bufcnt-- > 0)
     return *bufp++;

  bufcnt = read_buf (fd, buf, "static buf readchar");

  if (bufcnt <= 0) {
     if (bufcnt == 0) {
        fprintf (stderr, "readchar: Got EOF\n");
        return -2;
     } else {
        ERROR (errno, "readchar\n");
        return -1;
     }
  }

  bufp = (unsigned char *)buf;
  bufcnt--;
  return *bufp++;
}

/* Read a packet from fromfd, with error checking,
   and store it in BUF.
   If checksum incorrect, writes a - on ackfd.
   Returns length of packet, or -1 if error or -2 if EOF. */
static int
getpkt (char *buf, int fromfd, int ackfd)
{
  char *bp;
  unsigned char csum, c1, c2;
  int c;
  
  while (1) {
     csum = 0;

     while (1) {
        c = readchar (fromfd);
        if (c == '$')
           break;
        DEBUG(2, "[getpkt: discarding char '%c']\n", c);
        if (c < 0)
           return c;
     }

     bp = buf;
     while (1) {
        c = readchar (fromfd);
        if (c < 0)
           return c;
        if (c == '#')
           break;
        if (c == '*') {
           int repeat;
           int r;
           int prev;
           prev = *(bp-1);
           csum += c;
           repeat = readchar (fromfd);
           csum += repeat;
           for (r = 0; r < repeat - 29; r ++)
              *bp++ = prev;
        } else {
           *bp++ = c;
           csum += c;
        }
     }
     *bp = 0;

     c1 = fromhex (readchar (fromfd));
     c2 = fromhex (readchar (fromfd));

     if (csum == (c1 << 4) + c2)
	break;

     fprintf (stderr, "Bad checksum, sentsum=0x%x, csum=0x%x, buf=%s\n",
              (c1 << 4) + c2, csum, buf);
     if (write (ackfd, "-", 1) != 1)
        ERROR(0, "error when writing - (nack)\n");
     else
        add_written(1);
  }

  DEBUG(2, "getpkt (\"%s\");  [no ack] \n", buf);
  return bp - buf;
}

static int sigint = 0;
static int sigterm = 0;
static int sigpipe = 0;
static int sighup = 0;
static int sigusr1 = 0;
static int sigalrm = 0;
static int sigusr1_fd = -1;
static pthread_t invoke_gdbserver_in_valgrind_thread;

static
void received_signal (int signum)
{
   if (signum == SIGINT)
      sigint++;
   else if (signum == SIGUSR1) {
      sigusr1++;
      if (sigusr1_fd >= 0) {
         char control_c = '\003';
         write_buf(sigusr1_fd, &control_c, 1,
                   "write \\003 on SIGUSR1", /* notify */ True);
      }
   }
   else if (signum == SIGTERM) {
      shutting_down = True;
      sigterm++;
   } else if (signum == SIGHUP) {
      shutting_down = True;
      sighup++;
   } else if (signum == SIGPIPE) {
      sigpipe++;
   } else if (signum == SIGALRM) {
      sigalrm++;
#if defined(VGPV_amd64_linux_android) \
    || defined(VGPV_arm_linux_android) \
    || defined(VGPV_x86_linux_android) \
    || defined(VGPV_mips32_linux_android) \
    || defined(VGPV_arm64_linux_android)
      /* Android has no pthread_cancel. As it also does not have
         an invoker implementation, there is no need for cleanup action.
         So, we just do nothing. */
      DEBUG(1, "sigalrm received, no action on android\n");
#else
      /* Note: we cannot directly invoke restore_and_detach : this must
         be done by the thread that has attached. 
         We have in this thread pushed a cleanup handler that will
         cleanup what is needed. */
      DEBUG(1, "pthread_cancel invoke_gdbserver_in_valgrind_thread\n");
      pthread_cancel(invoke_gdbserver_in_valgrind_thread);
#endif
   } else {
      ERROR(0, "unexpected signal %d\n", signum);
   }
}

/* install the signal handlers allowing e.g. vgdb to cleanup in
   case of termination. */
static
void install_handlers(void)
{
   struct sigaction action, oldaction;

   action.sa_handler = received_signal;
   sigemptyset (&action.sa_mask);
   action.sa_flags = 0;
   
   /* SIGINT: when user types C-c in gdb, this sends
      a SIGINT to vgdb + causes a character to be sent to remote gdbserver.
      The later is enough to wakeup the valgrind process. */
   if (sigaction (SIGINT, &action, &oldaction) != 0)
      XERROR (errno, "vgdb error sigaction SIGINT\n");
   /* We might do something more intelligent than just
      reporting this SIGINT E.g. behave similarly to the gdb: two
      control-C without feedback from the debugged process would
      mean to stop debugging it. */

   /* SIGUSR1: this is used to facilitate automatic testing.  When
      vgdb receives this signal, it will simulate the user typing C-c. */
   if (sigaction (SIGUSR1, &action, &oldaction) != 0)
      XERROR (errno, "vgdb error sigaction SIGUSR1\n");
   

   /* SIGTERM: can receive this signal (e.g. from gdb) to terminate vgdb
      when detaching or similar. A clean shutdown will be done as both
      the read and write side will detect an end of file. */
   if (sigaction (SIGTERM, &action, &oldaction) != 0)
      XERROR (errno, "vgdb error sigaction SIGTERM\n");
   
   /* SIGPIPE: can receive this signal when gdb detaches or kill the
      process debugged: gdb will close its pipes to vgdb. vgdb
      must resist to this signal to allow a clean shutdown. */
   if (sigaction (SIGPIPE, &action, &oldaction) != 0)
      XERROR (errno, "vgdb error sigaction SIGPIPE\n");
   
   /* SIGALRM: in case invoke thread is blocked, alarm is used
      to cleanup.  */
   if (sigaction (SIGALRM, &action, &oldaction) != 0)
      XERROR (errno, "vgdb error sigaction SIGALRM\n");

   /* unmask all signals, in case the process that launched vgdb
      masked some. */
   if (sigprocmask (SIG_SETMASK, &action.sa_mask, NULL) != 0)
      XERROR (errno, "vgdb error sigprocmask");
}

/* close the FIFOs provided connections, terminate the invoker thread.  */
static
void close_connection(int to_pid, int from_pid)
{
   DEBUG(1, "nr received signals: sigint %d sigterm %d sighup %d sigpipe %d\n",
         sigint, sigterm, sighup, sigpipe);
   /* Note that we do not forward sigterm to the valgrind process:
      a sigterm signal is (probably) received from gdb if the user wants to
      kill the debugged process. The kill instruction has been given to
      the valgrind process, which should execute a clean exit. */

   /* We first close the connection to pid. The pid will then
      terminates its gdbserver work. We keep the from pid
      fifo opened till the invoker thread is finished.
      This allows the gdbserver to finish sending its last reply. */
   if (close(to_pid) != 0)
      ERROR(errno, "close to_pid\n");

   /* if there is a task that was busy trying to wake up valgrind
      process, we wait for it to be terminated otherwise threads
      in the valgrind process can stay stopped if vgdb main
      exits before the invoke thread had time to detach from
      all valgrind threads. */
   if (max_invoke_ms > 0 || cmd_time_out != NEVER) {
      int join;

      /* It is surprisingly complex to properly shutdown or exit the
         valgrind process in which gdbserver has been invoked through
         ptrace.  In the normal case (gdb detaches from the process,
         or process is continued), the valgrind process will reach the
         breakpoint place.  Using ptrace, vgdb will ensure the
         previous activity of the process is resumed (e.g. restart a
         blocking system call).  The special case is when gdb asks the
         valgrind process to exit (using either the "kill" command or
         "monitor exit").  In such a case, the valgrind process will
         call exit.  But a ptraced process will be blocked in exit,
         waiting for the ptracing process to detach or die. vgdb
         cannot detach unconditionally as otherwise, in the normal
         case, the valgrind process would stop abnormally with SIGSTOP
         (as vgdb would not be there to catch it). vgdb can also not
         die unconditionally otherwise again, similar problem.  So, we
         assume that most of the time, we arrive here in the normal
         case, and so, the breakpoint has been encountered by the
         valgrind process, so the invoker thread will exit and the
         join will succeed.  For the "kill" case, we cause an alarm
         signal to be sent after a few seconds. This means that in the
         normal case, the gdbserver code in valgrind process must have
         returned the control in less than the alarm nr of seconds,
         otherwise, valgrind will stop abnormally with SIGSTOP. */
      (void) alarm (3);

      DEBUG(1, "joining with invoke_gdbserver_in_valgrind_thread\n");
      join = pthread_join(invoke_gdbserver_in_valgrind_thread, NULL);
      if (join != 0)
         XERROR 
            (join, 
             "vgdb error pthread_join invoke_gdbserver_in_valgrind_thread\n");
   }
   if (close(from_pid) != 0)
      ERROR(errno, "close from_pid\n");
}

/* Relay data between gdb and Valgrind gdbserver, till EOF or an
   error is encountered. */
static
void gdb_relay (int pid)
{
   int from_pid = -1; /* fd to read from pid */
   int to_pid = -1; /* fd to write to pid */

   int shutdown_loop = 0;
   fprintf (stderr, "relaying data between gdb and process %d\n", pid);
   fflush (stderr);

   if (max_invoke_ms > 0)
      pthread_create(&invoke_gdbserver_in_valgrind_thread, NULL, 
                     invoke_gdbserver_in_valgrind, (void *) &pid);
   to_pid = open_fifo(from_gdb_to_pid, O_WRONLY, "write to pid");
   acquire_lock (shared_mem_fd, pid);
   
   from_pid = open_fifo (to_gdb_from_pid, O_RDONLY|O_NONBLOCK, 
                         "read mode from pid");

   sigusr1_fd = to_pid; /* allow simulating user typing control-c */

   while (1) {
      ConnectionKind ck;
      int ret;
      struct pollfd pollfds[NumConnectionKind];
      
      /* watch data written by gdb, watch POLLERR on both gdb fd */
      pollfds[FROM_GDB].fd = from_gdb;
      pollfds[FROM_GDB].events = POLLIN;
      pollfds[FROM_GDB].revents = 0;
      pollfds[TO_GDB].fd = to_gdb;
      pollfds[TO_GDB].events = 0;
      pollfds[TO_GDB].revents = 0;
      
      /* watch data written by pid, watch POLLERR on both pid fd */
      pollfds[FROM_PID].fd = from_pid;
      pollfds[FROM_PID].events = POLLIN;
      pollfds[FROM_PID].revents = 0;
      pollfds[TO_PID].fd = to_pid;
      pollfds[TO_PID].events = 0;
      pollfds[TO_PID].revents = 0;
      
      ret = poll(pollfds, 
                 NumConnectionKind, 
                 (shutting_down ? 
                  1 /* one second */ 
                  : -1 /* infinite */));
      DEBUG(2, "poll ret %d errno %d\n", ret, errno);

      /* check for unexpected error */
      if (ret <= 0 && errno != EINTR) {
         ERROR (errno, "unexpected poll ret %d\n", ret);
         shutting_down = True;
         break;
      }
      
      /* check for data to read */
      for (ck = 0; ck < NumConnectionKind; ck ++) {
         if (pollfds[ck].revents & POLLIN) {
            switch (ck) {
            case FROM_GDB: 
               if (!read_from_gdb_write_to_pid(to_pid))
                  shutting_down = True;
               break;
            case FROM_PID:
               if (!read_from_pid_write_to_gdb(from_pid))
                  shutting_down = True;
               break;
            default: XERROR(0, "unexpected POLLIN on %s\n",
                               ppConnectionKind(ck));
            }
         }
      }

      /* check for an fd being in error condition */
      for (ck = 0; ck < NumConnectionKind; ck ++) {
         if (pollfds[ck].revents & POLLERR) {
            DEBUG(1, "connection %s fd %d POLLERR error condition\n",
                     ppConnectionKind(ck), pollfds[ck].fd);
            invoker_valgrind_dying();
            shutting_down = True;
         }
         if (pollfds[ck].revents & POLLHUP) {
            DEBUG(1, "connection %s fd %d POLLHUP error condition\n",
                  ppConnectionKind(ck), pollfds[ck].fd);
            invoker_valgrind_dying();
            shutting_down = True;
         }
         if (pollfds[ck].revents & POLLNVAL) {
            DEBUG(1, "connection %s fd %d POLLNVAL error condition\n",
                  ppConnectionKind(ck), pollfds[ck].fd);
            invoker_valgrind_dying();
            shutting_down = True;
         }
      }
      
      if (shutting_down) {
         /* we let some time to the final packets to be transferred */
         shutdown_loop++;
         if (shutdown_loop > 3)
            break;
      }
   }
   close_connection(to_pid, from_pid);
}

static int packet_len_for_command(char *cmd)
{
   /* cmd will be send as a packet $qRcmd,xxxx....................xx#cc      */
   return                          7+     2*strlen(cmd)             +3  + 1;
}

/* hyper-minimal protocol implementation that
   sends the provided commands (using qRcmd packets)
   and read and display their replies. */
static
void standalone_send_commands(int pid, 
                              int last_command,
                              char *commands[] )
{
   int from_pid = -1; /* fd to read from pid */
   int to_pid = -1; /* fd to write to pid */

   int i;
   int hi;
   char hex[3];
   unsigned char cksum;
   char *hexcommand;
   char buf[PBUFSIZ+1]; // +1 for trailing \0
   int buflen;
   int nc;


   if (max_invoke_ms > 0 || cmd_time_out != NEVER)
      pthread_create(&invoke_gdbserver_in_valgrind_thread, NULL, 
                     invoke_gdbserver_in_valgrind, (void *) &pid);

   to_pid = open_fifo(from_gdb_to_pid, O_WRONLY, "write to pid");
   acquire_lock (shared_mem_fd, pid);

   /* first send a C-c \003 to pid, so that it wakes up the process
      After that, we can open the fifo from the pid in read mode
      We then start to wait for packets (normally first a resume reply)
      At that point, we send our command and expect replies */
   buf[0] = '\003';
   i = 0;
   while (!write_buf(to_pid, buf, 1, 
                     "write \\003 to wake up", /* notify */ True)) {
      /* If write fails, retries up to 10 times every 0.5 seconds
         This aims at solving the race condition described in
         remote-utils.c remote_finish function. */
      usleep(500*1000);
      i++;
      if (i >= 10)
         XERROR (errno, "failed to send wake up char after 10 trials\n");
   }
   from_pid = open_fifo(to_gdb_from_pid, O_RDONLY, 
                        "read cmd result from pid");

   /* Enable no ack mode. */
   write_buf(to_pid, "$QStartNoAckMode#b0", 19, "write start no ack mode",
             /* notify */ True);
   buflen = getpkt(buf, from_pid, to_pid);
   if (buflen != 2 || strcmp(buf, "OK") != 0) {
      if (buflen != 2)
         ERROR (0, "no ack mode: unexpected buflen %d\n", buflen);
      else
         ERROR (0, "no ack mode: unexpected packet %s\n", buf);
   }
   
   for (nc = 0; nc <= last_command; nc++) {
      fprintf (stderr, "sending command %s to pid %d\n", commands[nc], pid);
      fflush (stderr);
      
      /* prepare hexcommand $qRcmd,xxxx....................xx#cc      */
      hexcommand = vmalloc (packet_len_for_command(commands[nc]));
      hexcommand[0] = 0;
      strcat (hexcommand, "$qRcmd,");
      for (i = 0; i < strlen(commands[nc]); i++) {
         sprintf(hex, "%02x", (unsigned char) commands[nc][i]);
         // Need to use unsigned char, to avoid sign extension.
         strcat (hexcommand, hex);
      }
      /* checksum (but without the $) */
      cksum = 0;
      for (hi = 1; hi < strlen(hexcommand); hi++)
         cksum+=hexcommand[hi];
      strcat(hexcommand, "#");
      sprintf(hex, "%02x", cksum);
      strcat(hexcommand, hex);
      write_buf(to_pid, hexcommand, strlen(hexcommand), 
                "writing hex command to pid", /* notify */ True);

      /* we exit of the below loop explicitely when the command has
         been handled or because a signal handler will set
         shutting_down. */
      while (!shutting_down) {
         buflen = getpkt(buf, from_pid, to_pid);
         if (buflen < 0) {
            ERROR (0, "error reading packet\n");
            if (buflen == -2)
               invoker_valgrind_dying();
            break;
         }
         if (strlen(buf) == 0) {
            DEBUG(0, "empty packet rcvd (packet qRcmd not recognised?)\n");
            break;
         }
         if (strcmp(buf, "OK") == 0) {
            DEBUG(1, "OK packet rcvd\n");
            break;
         }
         if (buf[0] == 'E') {
            DEBUG(0, 
                  "E NN error packet rcvd: %s (unknown monitor command?)\n",
                  buf);
            break;
         }
         if (buf[0] == 'W') {
            DEBUG(0, "W stopped packet rcvd: %s\n", buf);
            break;
         }
         if (buf[0] == 'T') {
            DEBUG(1, "T resume reply packet received: %s\n", buf);
            continue;
         }
         
         /* must be here an O packet with hex encoded string reply 
            => decode and print it */
         if (buf[0] != 'O') {
            DEBUG(0, "expecting O packet, received: %s\n", buf);
            continue;
         }
         {
            char buf_print[buflen/2 + 1];
            for (i = 1; i < buflen; i = i + 2)
               buf_print[i/2] = (fromhex(*(buf+i)) << 4) 
                     + fromhex(*(buf+i+1));
            buf_print[buflen/2] = 0;
            printf("%s", buf_print);
            fflush(stdout);
         }
      }
      free (hexcommand);
   }
   shutting_down = True;

   close_connection(to_pid, from_pid);
}

/* report to user the existence of a vgdb-able valgrind process 
   with given pid.
   Note: this function does not use XERROR if an error is encountered
   while producing the command line for pid, as this is not critical
   and at least on MacOS, reading cmdline is not available. */
static
void report_pid (int pid, Bool on_stdout)
{
   char cmdline_file[50];   // large enough
   int fd, i;
   FILE *out = on_stdout ? stdout : stderr;

   fprintf(out, "use --pid=%d for ", pid);

   sprintf(cmdline_file, "/proc/%d/cmdline", pid);
   fd = open (cmdline_file, O_RDONLY);
   if (fd == -1) {
      DEBUG(1, "error opening cmdline file %s %s\n", 
            cmdline_file, strerror(errno));
      fprintf(out, "(could not open process command line)\n");
   } else {
      char cmdline[100];
      ssize_t sz;
      while ((sz = read(fd, cmdline, sizeof cmdline - 1)) != 0) {
         for (i = 0; i < sz; i++)
            if (cmdline[i] == 0)
               cmdline[i] = ' ';
         cmdline[sz] = 0;
         fprintf(out, "%s", cmdline);
      }
      if (sz == -1) {
         DEBUG(1, "error reading cmdline file %s %s\n", 
               cmdline_file, strerror(errno));
         fprintf(out, "(error reading process command line)");
      }
      fprintf(out, "\n");
      close (fd);
   }  
   fflush(out);
}

static
void usage(void)
{
   fprintf(stderr,
"Usage: vgdb [OPTION]... [[-c] COMMAND]...\n"
"vgdb (valgrind gdb) has two usages\n"
"  1. standalone to send monitor commands to a Valgrind gdbserver.\n"
"     The OPTION(s) must be followed by the command to send\n"
"     To send more than one command, separate the commands with -c\n"
"  2. relay application between gdb and a Valgrind gdbserver.\n"
"     Only OPTION(s) can be given.\n"
"\n"
" OPTIONS are [--pid=<number>] [--vgdb-prefix=<prefix>]\n"
"             [--wait=<number>] [--max-invoke-ms=<number>]\n"
"             [--port=<portnr>\n"
"             [--cmd-time-out=<number>] [-l] [-D] [-d]\n"
"             \n"
"  --pid arg must be given if multiple Valgrind gdbservers are found.\n"
"  --vgdb-prefix arg must be given to both Valgrind and vgdb utility\n"
"      if you want to change the prefix (default %s) for the FIFOs communication\n"
"      between the Valgrind gdbserver and vgdb.\n"
"  --wait (default 0) tells vgdb to check during the specified number\n"
"      of seconds if a Valgrind gdbserver can be found.\n"
"  --max-invoke-ms (default 100) gives the nr of milli-seconds after which vgdb\n"
"      will force the invocation of the Valgrind gdbserver (if the Valgrind\n"
"         process is blocked in a system call).\n"
"  --port instructs vgdb to listen for gdb on the specified port nr.\n"
"  --cmd-time-out (default 99999999) tells vgdb to exit if the found Valgrind\n"
"     gdbserver has not processed a command after number seconds\n"
"  -l  arg tells to show the list of running Valgrind gdbserver and then exit.\n"
"  -D  arg tells to show shared mem status and then exit.\n"
"  -d  arg tells to show debug info. Multiple -d args for more debug info\n"
"\n"
"  -h --help shows this message\n"
"  To get help from the Valgrind gdbserver, use vgdb help\n"
"\n", vgdb_prefix_default()
           );
   invoker_restrictions_msg();  
}

/* If show_list, outputs on stdout the list of Valgrind processes with gdbserver activated.
                 and then exits.

   else if arg_pid == -1, waits maximum check_trials seconds to discover
   a valgrind pid appearing.

   Otherwise verify arg_pid is valid and corresponds to a Valgrind process
   with gdbserver activated.

   Returns the pid to work with
   or exits in case of error (e.g. no pid found corresponding to arg_pid */

static
int search_arg_pid(int arg_pid, int check_trials, Bool show_list)
{
   int i;
   int pid = -1;

   if (arg_pid == 0 || arg_pid < -1) {
      fprintf (stderr, "vgdb error: invalid pid %d given\n", arg_pid);
      exit (1);
   } else {
      /* search for a matching named fifo. 
         If we have been given a pid, we will check that the matching FIFO is
         there (or wait the nr of check_trials for this to appear).
         If no pid has been given, then if we find only one FIFO,
         we will use this to build the pid to use.
         If we find multiple processes with valid FIFO, we report them and will
         exit with an error. */
      DIR *vgdb_dir;
      char *vgdb_dir_name = vmalloc (strlen (vgdb_prefix) + 3);
      struct dirent *f;
      int is;
      int nr_valid_pid = 0;
      const char *suffix = "-from-vgdb-to-"; /* followed by pid */
      char *vgdb_format = vmalloc (strlen(vgdb_prefix) + strlen(suffix) + 1);
      
      strcpy (vgdb_format, vgdb_prefix);
      strcat (vgdb_format, suffix);
      
      if (strchr(vgdb_prefix, '/') != NULL) {
         strcpy (vgdb_dir_name, vgdb_prefix);
         for (is = strlen(vgdb_prefix) - 1; is >= 0; is--)
            if (vgdb_dir_name[is] == '/') {
               vgdb_dir_name[is+1] = '\0';
               break;
            }
      } else {
         strcpy (vgdb_dir_name, "");
      }

      DEBUG(1, "searching pid in directory %s format %s\n", 
            vgdb_dir_name, vgdb_format);

      /* try to find FIFOs with valid pid.
         On exit of the loop, pid is set to:
         the last pid found if show_list (or -1 if no process was listed)
         -1 if no FIFOs matching a running process is found
         -2 if multiple FIFOs of running processes are found
         otherwise it is set to the (only) pid found that can be debugged
      */
      for (i = 0; i < check_trials; i++) {
         DEBUG(1, "check_trial %d \n", i);
         if (i > 0)
           /* wait one second before checking again */
           sleep(1);

         vgdb_dir = opendir (strlen (vgdb_dir_name) ? vgdb_dir_name : "./");
         if (vgdb_dir == NULL)
            XERROR (errno, 
                    "vgdb error: opening directory %s searching vgdb fifo\n", 
                    vgdb_dir_name);
      
         errno = 0; /* avoid complain if vgdb_dir is empty */
         while ((f = readdir (vgdb_dir))) {
            struct stat st;
            char pathname[strlen(vgdb_dir_name) + strlen(f->d_name) + 1];
            char *wrongpid;
            int newpid;

            strcpy (pathname, vgdb_dir_name);
            strcat (pathname, f->d_name);
            DEBUG(3, "checking pathname is FIFO %s\n", pathname);
            if (stat (pathname, &st) != 0) {
               if (debuglevel >= 3)
                  ERROR (errno, "vgdb error: stat %s searching vgdb fifo\n", 
                         pathname);
            } else if (S_ISFIFO (st.st_mode)) {
               DEBUG(3, "trying FIFO %s\n", pathname);
               if (strncmp (pathname, vgdb_format, 
                            strlen (vgdb_format)) == 0) {
                  newpid = strtol(pathname + strlen (vgdb_format), 
                                  &wrongpid, 10);
                  if (*wrongpid == '-' && newpid > 0 
                      && kill (newpid, 0) == 0) {
                     nr_valid_pid++;
                     if (show_list) {
                        report_pid (newpid, /*on_stdout*/ True);
                        pid = newpid;
                     } else if (arg_pid != -1) {
                        if (arg_pid == newpid) {
                           pid = newpid;
                        }
                     } else if (nr_valid_pid > 1) {
                        if (nr_valid_pid == 2) {
                           fprintf 
                              (stderr, 
                               "no --pid= arg given"
                               " and multiple valgrind pids found:\n");
                           report_pid (pid, /*on_stdout*/ False);
                        }
                        pid = -2;
                        report_pid (newpid, /*on_stdout*/ False);
                     } else {
                        pid = newpid;
                     }
                  }
               }
            }
            errno = 0; /* avoid complain if at the end of vgdb_dir */
         }
         if (f == NULL && errno != 0)
            XERROR (errno, "vgdb error: reading directory %s for vgdb fifo\n", 
                    vgdb_dir_name);

         closedir (vgdb_dir);
         if (pid != -1)
            break;
      }

      free (vgdb_dir_name);
      free (vgdb_format);
   }
   
   if (show_list) {
      exit (1);
   } else if (pid == -1) {
      if (arg_pid == -1)
         fprintf (stderr, "vgdb error: no FIFO found and no pid given\n");
      else
         fprintf (stderr, "vgdb error: no FIFO found matching pid %d\n", 
                  arg_pid);
      exit (1);
   }
   else if (pid == -2) {
      /* no arg_pid given, multiple FIFOs found */
      exit (1);
   }
   else {
      return pid;
   }
}

/* return true if the numeric value of an option of the 
   form --xxxxxxxxx=<number> could properly be extracted
   from arg. If True is returned, *value contains the
   extracted value.*/
static
Bool numeric_val(char* arg, int *value)
{
   const char *eq_pos = strchr(arg, '=');
   char *wrong;
   long long int long_value;

   if (eq_pos == NULL)
      return False;

   long_value = strtoll(eq_pos+1, &wrong, 10);
   if (long_value < 0 || long_value > INT_MAX)
      return False;
   if (*wrong)
      return False;

   *value = (int) long_value;
   return True;
}

/* true if arg matches the provided option */
static
Bool is_opt(char* arg, const char *option)
{
   int option_len = strlen(option);
   if (option[option_len-1] == '=')
      return (0 == strncmp(option, arg, option_len));
   else
      return (0 == strcmp(option, arg));
}

/* Parse command lines options. If error(s), exits.
   Otherwise returns the options in *p_... args.
   commands must be big enough for the commands extracted from argv.
   On return, *p_last_command gives the position in commands where
   the last command has been allocated (using vmalloc). */
static
void parse_options(int argc, char** argv,
                   Bool *p_show_shared_mem,
                   Bool *p_show_list,
                   int *p_arg_pid,
                   int *p_check_trials,
                   int *p_port,
                   int *p_last_command,
                   char *commands[])
{
   Bool show_shared_mem = False;
   Bool show_list = False;
   int arg_pid = -1;
   int check_trials = 1;
   int last_command = -1;
   int int_port = 0;

   int i;
   int arg_errors = 0;

   for (i = 1; i < argc; i++) {
      if (is_opt(argv[i], "--help") || is_opt(argv[i], "-h")) {
         usage();
         exit(0);
      } else if (is_opt(argv[i], "-d")) {
         debuglevel++;
      } else if (is_opt(argv[i], "-D")) {
         show_shared_mem = True;
      } else if (is_opt(argv[i], "-l")) {
         show_list = True;
      } else if (is_opt(argv[i], "--pid=")) {
         int newpid;
         if (!numeric_val(argv[i], &newpid)) {
            fprintf (stderr, "invalid --pid argument %s\n", argv[i]);
            arg_errors++;
         } else if (arg_pid != -1) {
            fprintf (stderr, "multiple --pid arguments given\n");
            arg_errors++;
         } else {
            arg_pid = newpid;
         }
      } else if (is_opt(argv[i], "--wait=")) {
         if (!numeric_val(argv[i], &check_trials)) {
            fprintf (stderr, "invalid --wait argument %s\n", argv[i]);
            arg_errors++;
         }
      } else if (is_opt(argv[i], "--max-invoke-ms=")) {
         if (!numeric_val(argv[i], &max_invoke_ms)) {
            fprintf (stderr, "invalid --max-invoke-ms argument %s\n", argv[i]);
            arg_errors++;
         }
      } else if (is_opt(argv[i], "--cmd-time-out=")) {
         if (!numeric_val(argv[i], &cmd_time_out)) {
            fprintf (stderr, "invalid --cmd-time-out argument %s\n", argv[i]);
            arg_errors++;
         }
      } else if (is_opt(argv[i], "--port=")) {
         if (!numeric_val(argv[i], &int_port)) {
            fprintf (stderr, "invalid --port argument %s\n", argv[i]);
            arg_errors++;
         }
      } else if (is_opt(argv[i], "--vgdb-prefix=")) {
         vgdb_prefix = argv[i] + 14;
      } else if (is_opt(argv[i], "-c")) {
         last_command++;
         commands[last_command] = vmalloc (1);
         commands[last_command][0] = '\0';
      } else if (0 == strncmp(argv[i], "-", 1)) {
         fprintf (stderr, "unknown or invalid argument %s\n", argv[i]);
         arg_errors++;
      } else {
         int len;
         if (last_command == -1) {
            /* only one command, no -c command indicator */
            last_command++;
            commands[last_command] = vmalloc (1);
            commands[last_command][0] = '\0';
         }
         len = strlen(commands[last_command]);
         commands[last_command] = vrealloc (commands[last_command], 
                                            len + 1 + strlen(argv[i]) + 1);
         if (len > 0)
            strcat (commands[last_command], " ");
         strcat (commands[last_command], argv[i]);
         if (packet_len_for_command(commands[last_command]) > PBUFSIZ) {
            fprintf (stderr, "command %s too long\n", commands[last_command]);
            arg_errors++;
         }
            
      }
   }

   if (vgdb_prefix == NULL)
      vgdb_prefix = vgdb_prefix_default();

   if (isatty(0) 
       && !show_shared_mem 
       && !show_list
       && int_port == 0
       && last_command == -1) {
      arg_errors++;
      fprintf (stderr, 
               "Using vgdb standalone implies to give -D or -l or a COMMAND\n");
   }

   if (show_shared_mem && show_list) {
      arg_errors++;
      fprintf (stderr,
               "Can't use both -D and -l options\n");
   }

   if (max_invoke_ms > 0 
       && cmd_time_out != NEVER
       && (cmd_time_out * 1000) <= max_invoke_ms) {
      arg_errors++;
      fprintf (stderr,
               "--max-invoke-ms must be < --cmd-time-out * 1000\n");
   }

   if (show_list && arg_pid != -1) {
      arg_errors++;
      fprintf (stderr,
               "Can't use both --pid and -l options\n");
   }

   if (int_port > 0 && last_command != -1) {
      arg_errors++;
      fprintf (stderr,
               "Can't use --port to send commands\n");
   }

   if (arg_errors > 0) {
      fprintf (stderr, "args error. Try `vgdb --help` for more information\n");
      exit(1);
   }

   *p_show_shared_mem = show_shared_mem;
   *p_show_list = show_list;
   *p_arg_pid = arg_pid;
   *p_check_trials = check_trials;
   *p_port = int_port;
   *p_last_command = last_command;
}

int main(int argc, char** argv)
{
   int i;
   int pid;

   Bool show_shared_mem;
   Bool show_list;
   int arg_pid;
   int check_trials;
   int in_port;
   int last_command;
   char *commands[argc]; // we will never have more commands than args.

   parse_options(argc, argv,
                 &show_shared_mem,
                 &show_list,
                 &arg_pid,
                 &check_trials,
                 &in_port,
                 &last_command,
                 commands);
  
   /* when we are working as a relay for gdb, handle some signals by
      only reporting them (according to debug level). Also handle these
      when ptrace will be used: vgdb must clean up the ptrace effect before
      dying. */
   if (max_invoke_ms > 0 || last_command == -1)
      install_handlers();

   pid = search_arg_pid (arg_pid, check_trials, show_list);

   prepare_fifos_and_shared_mem(pid);

   if (in_port > 0)
      wait_for_gdb_connect(in_port);

   if (show_shared_mem) {
      fprintf(stderr, 
              "vgdb %d "
              "written_by_vgdb %d "
              "seen_by_valgrind %d\n"
              "vgdb pid %d\n",
              VS_vgdb_pid,
              VS_written_by_vgdb,
              VS_seen_by_valgrind,
              VS_vgdb_pid);
      exit (0);
   }

   if (last_command >= 0) {
      standalone_send_commands(pid, last_command, commands);
   } else {
      gdb_relay(pid);
   }
      

   free (from_gdb_to_pid);
   free (to_gdb_from_pid);
   free (shared_mem);

   for (i = 0; i <= last_command; i++)
      free (commands[i]);
   return 0;
}