gdb/nat/linux-waitpid.c

   1 /* Wrapper implementation for waitpid for GNU/Linux (LWP layer).
   2
   3    Copyright (C) 2001-2015 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "common-defs.h"
  21
  22 #ifdef GDBSERVER
  23 /* FIXME: server.h is required for the definition of debug_threads
  24    which is used in the gdbserver-specific debug printing in
  25    linux_debug.  This code should be made available to GDB also,
  26    but the lack of a suitable flag to enable it prevents this.  */
  27 #include "server.h"
  28 #endif
  29
  30 #include "linux-nat.h"
  31 #include "linux-waitpid.h"
  32 #include "gdb_wait.h"
  33
  34 /* Print debugging output based on the format string FORMAT and
  35    its parameters.  */
  36
  37 static inline void
  38 linux_debug (const char *format, ...)
  39 {
  40 #ifdef GDBSERVER
  41   if (debug_threads)
  42     {
  43       va_list args;
  44       va_start (args, format);
  45       vfprintf (stderr, format, args);
  46       va_end (args);
  47     }
  48 #endif
  49 }
  50
  51 /* Convert wait status STATUS to a string.  Used for printing debug
  52    messages only.  */
  53
  54 char *
  55 status_to_str (int status)
  56 {
  57   static char buf[64];
  58
  59   if (WIFSTOPPED (status))
  60     {
  61       if (WSTOPSIG (status) == SYSCALL_SIGTRAP)
  62         snprintf (buf, sizeof (buf), "%s (stopped at syscall)",
  63                   strsignal (SIGTRAP));
  64       else
  65         snprintf (buf, sizeof (buf), "%s (stopped)",
  66                   strsignal (WSTOPSIG (status)));
  67     }
  68   else if (WIFSIGNALED (status))
  69     snprintf (buf, sizeof (buf), "%s (terminated)",
  70               strsignal (WTERMSIG (status)));
  71   else
  72     snprintf (buf, sizeof (buf), "%d (exited)", WEXITSTATUS (status));
  73
  74   return buf;
  75 }
  76
  77 /* Wrapper function for waitpid which handles EINTR, and emulates
  78    __WALL for systems where that is not available.  */
  79
  80 int
  81 my_waitpid (int pid, int *status, int flags)
  82 {
  83   int ret, out_errno;
  84
  85   linux_debug ("my_waitpid (%d, 0x%x)\n", pid, flags);
  86
  87   if (flags & __WALL)
  88     {
  89       sigset_t block_mask, org_mask, wake_mask;
  90       int wnohang;
  91
  92       wnohang = (flags & WNOHANG) != 0;
  93       flags &= ~(__WALL | __WCLONE);
  94
  95       if (!wnohang)
  96         {
  97           flags |= WNOHANG;
  98
  99           /* Block all signals while here.  This avoids knowing about
 100              LinuxThread's signals.  */
 101           sigfillset (&block_mask);
 102           sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
 103
 104           /* ... except during the sigsuspend below.  */
 105           sigemptyset (&wake_mask);
 106         }
 107
 108       while (1)
 109         {
 110           /* Since all signals are blocked, there's no need to check
 111              for EINTR here.  */
 112           ret = waitpid (pid, status, flags);
 113           out_errno = errno;
 114
 115           if (ret == -1 && out_errno != ECHILD)
 116             break;
 117           else if (ret > 0)
 118             break;
 119
 120           if (flags & __WCLONE)
 121             {
 122               /* We've tried both flavors now.  If WNOHANG is set,
 123                  there's nothing else to do, just bail out.  */
 124               if (wnohang)
 125                 break;
 126
 127               linux_debug ("blocking\n");
 128
 129               /* Block waiting for signals.  */
 130               sigsuspend (&wake_mask);
 131             }
 132           flags ^= __WCLONE;
 133         }
 134
 135       if (!wnohang)
 136         sigprocmask (SIG_SETMASK, &org_mask, NULL);
 137     }
 138   else
 139     {
 140       do
 141         ret = waitpid (pid, status, flags);
 142       while (ret == -1 && errno == EINTR);
 143       out_errno = errno;
 144     }
 145
 146   linux_debug ("my_waitpid (%d, 0x%x): status(%x), %d\n",
 147                pid, flags, status ? *status : -1, ret);
 148
 149   errno = out_errno;
 150   return ret;
 151 }