[PATCH 2/3 v4] Remove some GDBSERVER checks from linux-ptrace

[Gary Benson <gbenson@redhat.com>]

This patch removes some GDBSERVER checks from nat/linux-ptrace.c.
Currently the code uses a compile-time check to decide whether some
flags should be used.  This changes the code to instead let users of
the module specify an additional set of flags; and then changes gdb's
linux-nat.c to call this function.  At some later date, when the back
ends are fully merged, we will be able to remove this function again.

gdb/
2014-07-24  Tom Tromey  <tromey@redhat.com>
	    Gary Benson  <gbenson@redhat.com>

	* nat/linux-ptrace.c (additional_flags): New global.
	(linux_test_for_tracesysgood, linux_test_for_tracefork): Use
	additional_flags; don't check GDBSERVER.
	(linux_ptrace_set_additional_flags): New function.
	* nat/linux-ptrace.h (linux_ptrace_set_additional_flags):
	Declare.
	* linux-nat.c (_initialize_linux_nat): Call
	linux_ptrace_set_additional_flags.
---
 gdb/ChangeLog          |   12 ++++++++++
 gdb/linux-nat.c        |    8 ++++++
 gdb/nat/linux-ptrace.c |   57 ++++++++++++++++++++++++++---------------------
 gdb/nat/linux-ptrace.h |    1 +
 4 files changed, 52 insertions(+), 26 deletions(-)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index b50a88e..7db1b3d 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -5033,6 +5033,14 @@ Enables printf debugging output."),
   sigdelset (&suspend_mask, SIGCHLD);
 
   sigemptyset (&blocked_mask);
+
+  /* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to
+     support read-only process state.  */
+  linux_ptrace_set_additional_flags (PTRACE_O_TRACESYSGOOD
+				     | PTRACE_O_TRACEVFORKDONE
+				     | PTRACE_O_TRACEVFORK
+				     | PTRACE_O_TRACEFORK
+				     | PTRACE_O_TRACEEXEC);
 }
 \f
 
diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index 3ad2113..7893073 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -37,6 +37,10 @@
    there are no supported features.  */
 static int current_ptrace_options = -1;
 
+/* Additional flags to test.  */
+
+static int additional_flags;
+
 /* Find all possible reasons we could fail to attach PID and append
    these as strings to the already initialized BUFFER.  '\0'
    termination of BUFFER must be done by the caller.  */
@@ -359,16 +363,16 @@ linux_check_ptrace_features (void)
 static void
 linux_test_for_tracesysgood (int child_pid)
 {
-#ifdef GDBSERVER
-  /* gdbserver does not support PTRACE_O_TRACESYSGOOD.  */
-#else
   int ret;
 
+  if ((additional_flags & PTRACE_O_TRACESYSGOOD) == 0)
+    return;
+
   ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
 		(PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);
+
   if (ret == 0)
     current_ptrace_options |= PTRACE_O_TRACESYSGOOD;
-#endif
 }
 
 /* Determine if PTRACE_O_TRACEFORK can be used to follow fork
@@ -388,16 +392,15 @@ linux_test_for_tracefork (int child_pid)
   if (ret != 0)
     return;
 
-#ifdef GDBSERVER
-  /* gdbserver does not support PTRACE_O_TRACEVFORKDONE yet.  */
-#else
-  /* Check if the target supports PTRACE_O_TRACEVFORKDONE.  */
-  ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
-		(PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
-				    | PTRACE_O_TRACEVFORKDONE));
-  if (ret == 0)
-    current_ptrace_options |= PTRACE_O_TRACEVFORKDONE;
-#endif
+  if ((additional_flags & PTRACE_O_TRACEVFORKDONE) != 0)
+    {
+      /* Check if the target supports PTRACE_O_TRACEVFORKDONE.  */
+      ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
+		    (PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
+					| PTRACE_O_TRACEVFORKDONE));
+      if (ret == 0)
+	current_ptrace_options |= PTRACE_O_TRACEVFORKDONE;
+    }
 
   /* Setting PTRACE_O_TRACEFORK did not cause an error, however we
      don't know for sure that the feature is available; old
@@ -433,18 +436,9 @@ linux_test_for_tracefork (int child_pid)
 
 	  /* We got the PID from the grandchild, which means fork
 	     tracing is supported.  */
-#ifdef GDBSERVER
-	  /* Do not enable all the options for now since gdbserver does not
-	     properly support them.  This restriction will be lifted when
-	     gdbserver is augmented to support them.  */
-	  current_ptrace_options |= PTRACE_O_TRACECLONE;
-#else
-	  current_ptrace_options |= PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK
-	    | PTRACE_O_TRACECLONE | PTRACE_O_TRACEEXEC;
-
-	  /* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to
-	     support read-only process state.  */
-#endif
+	  current_ptrace_options |= PTRACE_O_TRACECLONE |
+	    (additional_flags & ~(PTRACE_O_TRACESYSGOOD
+				  | PTRACE_O_TRACEVFORKDONE));
 
 	  /* Do some cleanup and kill the grandchild.  */
 	  my_waitpid (second_pid, &second_status, 0);
@@ -551,3 +545,14 @@ linux_ptrace_init_warnings (void)
 
   linux_ptrace_test_ret_to_nx ();
 }
+
+/* Set additional ptrace flags to use.  Some such flags may be checked
+   by the implementation above.  This function must be called before
+   any other function in this file; otherwise the flags may not take
+   effect appropriately.  */
+
+void
+linux_ptrace_set_additional_flags (int flags)
+{
+  additional_flags = flags;
+}
diff --git a/gdb/nat/linux-ptrace.h b/gdb/nat/linux-ptrace.h
index cffb5ce..41b3198 100644
--- a/gdb/nat/linux-ptrace.h
+++ b/gdb/nat/linux-ptrace.h
@@ -91,5 +91,6 @@ extern int linux_supports_tracefork (void);
 extern int linux_supports_traceclone (void);
 extern int linux_supports_tracevforkdone (void);
 extern int linux_supports_tracesysgood (void);
+extern void linux_ptrace_set_additional_flags (int);
 
 #endif /* COMMON_LINUX_PTRACE_H */
-- 
1.7.1