gdb/nat/linux-waitpid.c

   1 /* Wrapper implementation for waitpid for GNU/Linux (LWP layer).
   2
   3    Copyright (C) 2001-2014 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 #ifdef GDBSERVER
  21 #include "server.h"
  22 #else
  23 #include "defs.h"
  24 #include "signal.h"
  25 #endif
  26
  27 #include "nat/linux-nat.h"
  28 #include "nat/linux-waitpid.h"
  29 #include "gdb_wait.h"
  30
  31 #include <string.h>
  32
  33 /* Print debugging output based on the format string FORMAT and
  34    its parameters.  */
  35
  36 static inline void
  37 linux_debug (const char *format, ...)
  38 {
  39 #ifdef GDBSERVER
  40   if (debug_threads)
  41     {
  42       va_list args;
  43       va_start (args, format);
  44       vfprintf (stderr, format, args);
  45       va_end (args);
  46     }
  47 #else
  48   /* GDB-specific debugging output.  */
  49 #endif
  50 }
  51
  52 /* Convert wait status STATUS to a string.  Used for printing debug
  53    messages only.  */
  54
  55 char *
  56 status_to_str (int status)
  57 {
  58   static char buf[64];
  59
  60   if (WIFSTOPPED (status))
  61     {
  62       if (WSTOPSIG (status) == SYSCALL_SIGTRAP)
  63         snprintf (buf, sizeof (buf), "%s (stopped at syscall)",
  64                   strsignal (SIGTRAP));
  65       else
  66         snprintf (buf, sizeof (buf), "%s (stopped)",
  67                   strsignal (WSTOPSIG (status)));
  68     }
  69   else if (WIFSIGNALED (status))
  70     snprintf (buf, sizeof (buf), "%s (terminated)",
  71               strsignal (WTERMSIG (status)));
  72   else
  73     snprintf (buf, sizeof (buf), "%d (exited)", WEXITSTATUS (status));
  74
  75   return buf;
  76 }
  77
  78 /* Wrapper function for waitpid which handles EINTR, and emulates
  79    __WALL for systems where that is not available.  */
  80
  81 int
  82 my_waitpid (int pid, int *status, int flags)
  83 {
  84   int ret, out_errno;
  85
  86   linux_debug ("my_waitpid (%d, 0x%x)\n", pid, flags);
  87
  88   if (flags & __WALL)
  89     {
  90       sigset_t block_mask, org_mask, wake_mask;
  91       int wnohang;
  92
  93       wnohang = (flags & WNOHANG) != 0;
  94       flags &= ~(__WALL | __WCLONE);
  95
  96       if (!wnohang)
  97         {
  98           flags |= WNOHANG;
  99
 100           /* Block all signals while here.  This avoids knowing about
 101              LinuxThread's signals.  */
 102           sigfillset (&block_mask);
 103           sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
 104
 105           /* ... except during the sigsuspend below.  */
 106           sigemptyset (&wake_mask);
 107         }
 108
 109       while (1)
 110         {
 111           /* Since all signals are blocked, there's no need to check
 112              for EINTR here.  */
 113           ret = waitpid (pid, status, flags);
 114           out_errno = errno;
 115
 116           if (ret == -1 && out_errno != ECHILD)
 117             break;
 118           else if (ret > 0)
 119             break;
 120
 121           if (flags & __WCLONE)
 122             {
 123               /* We've tried both flavors now.  If WNOHANG is set,
 124                  there's nothing else to do, just bail out.  */
 125               if (wnohang)
 126                 break;
 127
 128               linux_debug ("blocking\n");
 129
 130               /* Block waiting for signals.  */
 131               sigsuspend (&wake_mask);
 132             }
 133           flags ^= __WCLONE;
 134         }
 135
 136       if (!wnohang)
 137         sigprocmask (SIG_SETMASK, &org_mask, NULL);
 138     }
 139   else
 140     {
 141       do
 142         ret = waitpid (pid, status, flags);
 143       while (ret == -1 && errno == EINTR);
 144       out_errno = errno;
 145     }
 146
 147   linux_debug ("my_waitpid (%d, 0x%x): status(%x), %d\n",
 148                pid, flags, status ? *status : -1, ret);
 149
 150   errno = out_errno;
 151   return ret;
 152 }