btrace: pretend we're not replaying when generating a core file

When generating a core file using the "generate-core-file" command while
replaying with the btrace record target, we won't be able to access all
registers and all memory.  This leads to the following assertion:

    gdb/regcache.c:1034: internal-error: regcache_raw_supply: Assertion `regnum >= 0 && regnum < regcache->descr->nr_raw_registers' failed.
    A problem internal to GDB has been detected,
    further debugging may prove unreliable.
    Quit this debugging session? (y or n) FAIL: gdb.btrace/gcore.exp: generate-core-file core (GDB internal error)
    Resyncing due to internal error.

Pretend that we are not replaying while generating a core file.  This will
forward fetch and store registers as well as xfer memory calls to the target
beneath.

gdb/
	* record-btrace.c (record_btrace_generating_corefile)
	(record_btrace_prepare_to_generate_core)
	(record_btrace_done_generating_core): New.
	(record_btrace_xfer_partial, record_btrace_fetch_registers)
	(record_btrace_store_registers, record_btrace_prepare_to_store):
	Forward request when generating a core file.
	(record_btrace_open): Set record_btrace_generating_corefile to zero.
	(init_record_btrace_ops): Set to_prepare_to_generate_core and
	to_done_generating_core.

testsuite/
	* gdb.btrace/gcore.exp: New.

1 files changed, 41 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.btrace/gcore.exp b/gdb/testsuite/gdb.btrace/gcore.exp
new file mode 100644
index 0000000..1ff4f27
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/gcore.exp
@@ -0,0 +1,41 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2014 Free Software Foundation, Inc.
+#
+# Contributed by Intel Corp. <markus.t.metzger@intel.com>
+#
+# 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/>.
+
+# check for btrace support
+if { [skip_btrace_tests] } { return -1 }
+
+# start inferior
+standard_testfile x86-record_goto.S
+if [prepare_for_testing gcore.exp $testfile $srcfile] {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+# trace the call to the test function
+gdb_test_no_output "record btrace"
+gdb_test "next" ".*main\.3.*"
+
+# start replaying
+gdb_test "record goto begin" ".*main\.2.*"
+
+# generate a core file - this used to assert
+gdb_test "generate-core-file core" "Saved corefile core"