[PATCH/RFC] Support rthreads on OpenBSD 5.2 and later.

[Mark Kettenis <mark dot kettenis at xs4all dot nl>]

OpenBSD 5.2 and later has a proper threads implementation based on
kernel threads.  Debugging support is provided through additional
ptrace(2) requests, so this diff extends the generic code in
inf-ptrace.c with OpenBSD-specific code to discover additional
threads.

I intend to commit this in a couple of days as I don't really expect
other people to care.  But comments are welcome...


gdb/ChangeLog:

        * obsd-nat.h: New file.
        * obsd-nat.c: New file.
---
 gdb/obsd-nat.c | 185 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/obsd-nat.h |  25 ++++++++
 2 files changed, 210 insertions(+)
 create mode 100644 gdb/obsd-nat.c
 create mode 100644 gdb/obsd-nat.h

diff --git a/gdb/obsd-nat.c b/gdb/obsd-nat.c
new file mode 100644
index 0000000..c17a565
--- /dev/null
+++ b/gdb/obsd-nat.c
@@ -0,0 +1,185 @@
+/* Native-dependent code for OpenBSD.
+
+   Copyright (C) 2012-2014 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 3 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, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "gdbthread.h"
+#include "inferior.h"
+#include "target.h"
+
+#include "gdb_assert.h"
+#include <sys/types.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+
+#include "inf-child.h"
+#include "obsd-nat.h"
+
+/* OpenBSD 5.2 and later include rthreads which uses a thread model
+   that maps userlan threads directly onto kernel threads in a 1:1
+   fashion.  */
+
+#ifdef PT_GET_THREAD_FIRST
+
+static char *
+obsd_pid_to_str (struct target_ops *ops, ptid_t ptid)
+{
+  if (ptid_get_lwp (ptid) != 0)
+    {
+      static char buf[64];
+
+      xsnprintf (buf, sizeof buf, "thread %ld", ptid_get_lwp (ptid));
+      return buf;
+    }
+
+  return normal_pid_to_str (ptid);
+}
+
+static void
+obsd_find_new_threads (struct target_ops *ops)
+{
+  pid_t pid = ptid_get_pid (inferior_ptid);
+  struct ptrace_thread_state pts;
+
+  if (ptrace(PT_GET_THREAD_FIRST, pid, (caddr_t)&pts, sizeof pts) == -1)
+    perror_with_name (("ptrace"));
+
+  while (pts.pts_tid != -1)
+    {
+      ptid_t ptid = ptid_build (pid, pts.pts_tid, 0);
+
+      if (!in_thread_list (ptid))
+	{
+	  if (ptid_get_lwp (inferior_ptid) == 0)
+	    thread_change_ptid (inferior_ptid, ptid);
+	  else
+	    add_thread (ptid);
+	}
+
+      if (ptrace(PT_GET_THREAD_NEXT, pid, (caddr_t)&pts, sizeof pts) == -1)
+	perror_with_name (("ptrace"));
+    }
+}
+
+static ptid_t
+obsd_wait (struct target_ops *ops,
+	   ptid_t ptid, struct target_waitstatus *ourstatus, int options)
+{
+  pid_t pid;
+  int status, save_errno;
+
+  do
+    {
+      set_sigint_trap ();
+
+      do
+	{
+	  pid = waitpid (ptid_get_pid (ptid), &status, 0);
+	  save_errno = errno;
+	}
+      while (pid == -1 && errno == EINTR);
+
+      clear_sigint_trap ();
+
+      if (pid == -1)
+	{
+	  fprintf_unfiltered (gdb_stderr,
+			      _("Child process unexpectedly missing: %s.\n"),
+			      safe_strerror (save_errno));
+
+	  /* Claim it exited with unknown signal.  */
+	  ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
+	  ourstatus->value.sig = GDB_SIGNAL_UNKNOWN;
+	  return inferior_ptid;
+	}
+
+      /* Ignore terminated detached child processes.  */
+      if (!WIFSTOPPED (status) && pid != ptid_get_pid (inferior_ptid))
+	pid = -1;
+    }
+  while (pid == -1);
+
+  ptid = pid_to_ptid (pid);
+
+  if (WIFSTOPPED (status))
+    {
+      ptrace_state_t pe;
+      pid_t fpid;
+
+      if (ptrace (PT_GET_PROCESS_STATE, pid, (caddr_t)&pe, sizeof pe) == -1)
+	perror_with_name (("ptrace"));
+
+      switch (pe.pe_report_event)
+	{
+	case PTRACE_FORK:
+	  ourstatus->kind = TARGET_WAITKIND_FORKED;
+	  ourstatus->value.related_pid = pid_to_ptid (pe.pe_other_pid);
+
+	  /* Make sure the other end of the fork is stopped too.  */
+	  fpid = waitpid (pe.pe_other_pid, &status, 0);
+	  if (fpid == -1)
+	    perror_with_name (("waitpid"));
+
+	  if (ptrace (PT_GET_PROCESS_STATE, fpid,
+		      (caddr_t)&pe, sizeof pe) == -1)
+	    perror_with_name (("ptrace"));
+
+	  gdb_assert (pe.pe_report_event == PTRACE_FORK);
+	  gdb_assert (pe.pe_other_pid == pid);
+	  if (fpid == ptid_get_pid (inferior_ptid))
+	    {
+	      ourstatus->value.related_pid = pid_to_ptid (pe.pe_other_pid);
+	      return pid_to_ptid (fpid);
+	    }
+
+	  return pid_to_ptid (pid);
+	}
+
+      ptid = ptid_build (pid, pe.pe_tid, 0);
+      if (!in_thread_list (ptid))
+	{
+	  if (ptid_get_lwp (inferior_ptid) == 0)
+	    thread_change_ptid (inferior_ptid, ptid);
+	  else
+	    add_thread (ptid);
+	}
+    }
+
+  store_waitstatus (ourstatus, status);
+  return ptid;
+}
+
+void
+obsd_add_target (struct target_ops *t)
+{
+  /* Override some methods to support threads.  */
+  t->to_pid_to_str = obsd_pid_to_str;
+  t->to_find_new_threads = obsd_find_new_threads;
+  t->to_wait = obsd_wait;
+  add_target (t);
+}
+
+#else
+
+void
+obsd_add_target (struct target_ops *t)
+{
+  add_target (t);
+}
+
+#endif /* PT_GET_THREAD_FIRST */
diff --git a/gdb/obsd-nat.h b/gdb/obsd-nat.h
new file mode 100644
index 0000000..ad021fc
--- /dev/null
+++ b/gdb/obsd-nat.h
@@ -0,0 +1,25 @@
+/* Native-dependent code for OpenBSD.
+
+   Copyright (C) 2014 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 3 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, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef OBSD_NAT_H
+#define OBSD_NAT_H
+
+extern void obsd_add_target (struct target_ops *);
+
+#endif /* obsd-nat.h */
-- 
1.8.5.3