[PATCH v2] Fix inconsistent breakpoint kinds between breakpoints and tracepoints in GDBServer.

[Antoine Tremblay]

This patch fixes a regression introduced by :
https://sourceware.org/ml/gdb-patches/2015-10/msg00369.html

Tests : gdb.trace/trace-break.exp and gdb.trace/trace-mt.exp would fail on x86
with gdbserver-{native,extended}.

Before this patch, the breakpoint kind set by GDB with a Z packet and the one
set in the case of a tracepoint would be inconsistent on targets that did not
implement breakpoint_kind_from_pc. On x86 for example a breakpoint set by GDB
would have a kind of 1 but a breakpoint set by a tracepoint would have a kind of
0.

This created a missmatch when trying to insert a tracepoint and a breakpoint at
the same location. One of the two breakpoints would be removed with debug
message : "Inconsistent breakpoint kind".

This patch fixes the issue by changing the default 0 breakpoint kind to be
the size of the breakpoint according to sw_breakpoint_from_kind.

The default breakpoint kind must be the breakpoint length to keep consistency
between breakpoints set via GDB and the ones set internally by GDBServer.

No regression on Ubuntu 14.04 x86-64 with gdbserver-{native-extended}

gdb/gdbserver/ChangeLog:

	* linux-low.c (default_breakpoint_kind_from_pc): New function.
	(linux_breakpoint_kind_from_pc): Use default_breakpoint_kind_from_pc for
	the default breakpoint kind.
---
 gdb/gdbserver/linux-low.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index c20e257..8d1730b 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -6937,6 +6937,19 @@ current_lwp_ptid (void)
   return ptid_of (current_thread);
 }
 
+/* Return the default breakpoint kind as the size of the breakpoint.  */
+
+int
+default_breakpoint_kind_from_pc (CORE_ADDR *pcptr)
+{
+  int size = 0;
+
+  gdb_assert (the_low_target.sw_breakpoint_from_kind != NULL);
+
+  (*the_low_target.sw_breakpoint_from_kind) (0, &size);
+  return size;
+}
+
 /* Implementation of the target_ops method "breakpoint_kind_from_pc".  */
 
 static int
@@ -6945,8 +6958,7 @@ linux_breakpoint_kind_from_pc (CORE_ADDR *pcptr)
   if (the_low_target.breakpoint_kind_from_pc != NULL)
     return (*the_low_target.breakpoint_kind_from_pc) (pcptr);
   else
-    /* Default breakpoint kind value.  */
-    return 0;
+    return default_breakpoint_kind_from_pc (pcptr);
 }
 
 /* Implementation of the target_ops method "sw_breakpoint_from_kind".  */
-- 
1.9.1