Status: submitted for comments

2004-11-12  Daniel Jacobowitz  <dan@debian.org>

	* linux-nat.c (my_waitpid): New function.

	(linux_test_for_tracefork): Make more robust and verbose.  Take

	an ORIGINAL_PID argument and test for PTRACE_SETOPTIONS first.

	(linux_supports_tracefork, linux_supports_tracevforkdone): Take a PID

	argument.  Update calls to linux_test_for_tracefork.

	(linux_enable_event_reporting, child_follow_fork)

	(child_insert_fork_catchpoint, child_insert_vfork_catchpoint)

	(child_insert_exec_catchpoint): Update calls to

	linux_supports_tracefork and linux_supports_tracevforkdone.

Index: gdb-6.3/gdb/linux-nat.c

===================================================================

--- gdb-6.3.orig/gdb/linux-nat.c	2004-10-08 16:29:47.000000000 -0400

+++ gdb-6.3/gdb/linux-nat.c	2004-11-13 16:41:51.368720845 -0500

@@ -150,18 +150,47 @@ linux_tracefork_child (void)

   exit (0);

 }

-/* Determine if PTRACE_O_TRACEFORK can be used to follow fork events.  We

+/* Wrapper function for waitpid which handles EINTR.  */

+

+static int

+my_waitpid (int pid, int *status, int flags)

+{

+  int ret;

+  do

+    {

+      ret = waitpid (pid, status, flags);

+    }

+  while (ret == -1 && errno == EINTR);

+

+  return ret;

+}

+

+/* Determine if PTRACE_O_TRACEFORK can be used to follow fork events.

+

+   First, we try to enable fork tracing on ORIGINAL_PID.  If this fails,

+   we know that the feature is not available.  This may change the tracing

+   options for ORIGINAL_PID, but we'll be setting them shortly anyway.

+

+   However, if it succeeds, we don't know for sure that the feature is

+   available; old versions of PTRACE_SETOPTIONS ignored unknown options.  We

    create a child process, attach to it, use PTRACE_SETOPTIONS to enable

-   fork tracing, and let it fork.  If the process exits, we assume that

-   we can't use TRACEFORK; if we get the fork notification, and we can

-   extract the new child's PID, then we assume that we can.  */

+   fork tracing, and let it fork.  If the process exits, we assume that we

+   can't use TRACEFORK; if we get the fork notification, and we can extract

+   the new child's PID, then we assume that we can.  */

 static void

-linux_test_for_tracefork (void)

+linux_test_for_tracefork (int original_pid)

 {

   int child_pid, ret, status;

   long second_pid;

+  linux_supports_tracefork_flag = 0;

+  linux_supports_tracevforkdone_flag = 0;

+

+  ret = ptrace (PTRACE_SETOPTIONS, original_pid, 0, PTRACE_O_TRACEFORK);

+  if (ret != 0)

+    return;

+

   child_pid = fork ();

   if (child_pid == -1)

     perror_with_name ("linux_test_for_tracefork: fork");

@@ -169,7 +198,7 @@ linux_test_for_tracefork (void)

   if (child_pid == 0)

     linux_tracefork_child ();

-  ret = waitpid (child_pid, &status, 0);

+  ret = my_waitpid (child_pid, &status, 0);

   if (ret == -1)

     perror_with_name ("linux_test_for_tracefork: waitpid");

   else if (ret != child_pid)

@@ -177,13 +206,23 @@ linux_test_for_tracefork (void)

   if (! WIFSTOPPED (status))

     error ("linux_test_for_tracefork: waitpid: unexpected status %d.", status);

-  linux_supports_tracefork_flag = 0;

-

   ret = ptrace (PTRACE_SETOPTIONS, child_pid, 0, PTRACE_O_TRACEFORK);

   if (ret != 0)

     {

-      ptrace (PTRACE_KILL, child_pid, 0, 0);

-      waitpid (child_pid, &status, 0);

+      ret = ptrace (PTRACE_KILL, child_pid, 0, 0);

+      if (ret != 0)

+	{

+	  warning ("linux_test_for_tracefork: failed to kill child");

+	  return;

+	}

+

+      ret = my_waitpid (child_pid, &status, 0);

+      if (ret != child_pid)

+	warning ("linux_test_for_tracefork: failed to wait for killed child");

+      else if (!WIFSIGNALED (status))

+	warning ("linux_test_for_tracefork: unexpected wait status 0x%x from "

+		 "killed child", status);

+

       return;

     }

@@ -192,8 +231,12 @@ linux_test_for_tracefork (void)

 		PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORKDONE);

   linux_supports_tracevforkdone_flag = (ret == 0);

-  ptrace (PTRACE_CONT, child_pid, 0, 0);

-  ret = waitpid (child_pid, &status, 0);

+  ret = ptrace (PTRACE_CONT, child_pid, 0, 0);

+  if (ret != 0)

+    warning ("linux_test_for_tracefork: failed to resume child");

+

+  ret = my_waitpid (child_pid, &status, 0);

+

   if (ret == child_pid && WIFSTOPPED (status)

       && status >> 16 == PTRACE_EVENT_FORK)

     {

@@ -204,34 +247,38 @@ linux_test_for_tracefork (void)

 	  int second_status;

 	  linux_supports_tracefork_flag = 1;

-	  waitpid (second_pid, &second_status, 0);

-	  ptrace (PTRACE_DETACH, second_pid, 0, 0);

+	  my_waitpid (second_pid, &second_status, 0);

+	  ret = ptrace (PTRACE_KILL, second_pid, 0, 0);

+	  if (ret != 0)

+	    warning ("linux_test_for_tracefork: failed to kill second child");

 	}

     }

+  else

+    warning ("linux_test_for_tracefork: unexpected result from waitpid "

+	     "(%d, status 0x%x)", ret, status);

-  if (WIFSTOPPED (status))

-    {

-      ptrace (PTRACE_DETACH, child_pid, 0, 0);

-      waitpid (child_pid, &status, 0);

-    }

+  ret = ptrace (PTRACE_KILL, child_pid, 0, 0);

+  if (ret != 0)

+    warning ("linux_test_for_tracefork: failed to kill child");

+  my_waitpid (child_pid, &status, 0);

 }

 /* Return non-zero iff we have tracefork functionality available.

    This function also sets linux_supports_tracefork_flag.  */

 static int

-linux_supports_tracefork (void)

+linux_supports_tracefork (int pid)

 {

   if (linux_supports_tracefork_flag == -1)

-    linux_test_for_tracefork ();

+    linux_test_for_tracefork (pid);

   return linux_supports_tracefork_flag;

 }

 static int

-linux_supports_tracevforkdone (void)

+linux_supports_tracevforkdone (int pid)

 {

   if (linux_supports_tracefork_flag == -1)

-    linux_test_for_tracefork ();

+    linux_test_for_tracefork (pid);

   return linux_supports_tracevforkdone_flag;

 }

@@ -242,12 +289,12 @@ linux_enable_event_reporting (ptid_t pti

   int pid = ptid_get_pid (ptid);

   int options;

-  if (! linux_supports_tracefork ())

+  if (! linux_supports_tracefork (pid))

     return;

   options = PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK | PTRACE_O_TRACEEXEC

     | PTRACE_O_TRACECLONE;

-  if (linux_supports_tracevforkdone ())

+  if (linux_supports_tracevforkdone (pid))

     options |= PTRACE_O_TRACEVFORKDONE;

   /* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to support

@@ -308,7 +355,8 @@ child_follow_fork (int follow_child)

       if (has_vforked)

 	{

-	  if (linux_supports_tracevforkdone ())

+	  gdb_assert (linux_supports_tracefork_flag >= 0);

+	  if (linux_supports_tracevforkdone (0))

 	    {

 	      int status;

@@ -476,7 +524,7 @@ linux_handle_extended_wait (int pid, int

 int

 child_insert_fork_catchpoint (int pid)

 {

-  if (! linux_supports_tracefork ())

+  if (! linux_supports_tracefork (pid))

     error ("Your system does not support fork catchpoints.");

   return 0;

@@ -485,7 +533,7 @@ child_insert_fork_catchpoint (int pid)

 int

 child_insert_vfork_catchpoint (int pid)

 {

-  if (!linux_supports_tracefork ())

+  if (!linux_supports_tracefork (pid))

     error ("Your system does not support vfork catchpoints.");

   return 0;

@@ -494,7 +542,7 @@ child_insert_vfork_catchpoint (int pid)

 int

 child_insert_exec_catchpoint (int pid)

 {

-  if (!linux_supports_tracefork ())

+  if (!linux_supports_tracefork (pid))

     error ("Your system does not support exec catchpoints.");

   return 0;