btrace: do not return out of TRY/CATCH

In btrace_pt_readmem_callback, we read memory inside TRY/CATCH and return in
case of an error return value.  This corrupts the cleanup chain, which
eventually results in a SEGV when doing or discarding cleanups later on.

gdb/
	* btrace.c (btrace_pt_readmem_callback): Do not return in TRY/CATCH.

testsuite/
	* gdb.btrace/dlopen.exp: New.
	* gdb.btrace/dlopen.c: New.
	* gdb.btrace/dlopen-dso.c: New.

3 files changed, 124 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.btrace/dlopen-dso.c b/gdb/testsuite/gdb.btrace/dlopen-dso.c
new file mode 100644
index 0000000..3a1733e
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/dlopen-dso.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015-2016 Free Software Foundation, Inc.
+
+   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/>.  */
+
+int
+answer (void)
+{
+  return 42;
+}
diff --git a/gdb/testsuite/gdb.btrace/dlopen.c b/gdb/testsuite/gdb.btrace/dlopen.c
new file mode 100644
index 0000000..7e01f79
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/dlopen.c
@@ -0,0 +1,50 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015-2016 Free Software Foundation, Inc.
+
+   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 <dlfcn.h>
+#include <assert.h>
+#include <stdlib.h>
+
+static int
+test (void)
+{
+  void *dso;
+  int (*fun) (void);
+  int answer;
+
+  dso = dlopen (DSO_NAME, RTLD_NOW | RTLD_GLOBAL);
+  assert (dso != NULL);
+
+  fun = (int (*) (void)) dlsym (dso, "answer");
+  assert (fun != NULL);
+
+  answer = fun ();
+
+  dlclose (dso);
+
+  return answer;
+}
+
+int
+main (void)
+{
+  int answer;
+
+  answer = test ();
+
+  return answer;
+}
diff --git a/gdb/testsuite/gdb.btrace/dlopen.exp b/gdb/testsuite/gdb.btrace/dlopen.exp
new file mode 100644
index 0000000..2afb42b
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/dlopen.exp
@@ -0,0 +1,52 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2015-2016 Free Software Foundation, Inc.
+#
+# 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/>.
+
+if { [skip_btrace_tests] } { return -1 }
+if { [skip_shlib_tests]  } { return -1 }
+
+standard_testfile
+
+set basename_lib dlopen-dso
+set srcfile_lib $srcdir/$subdir/$basename_lib.c
+set binfile_lib [standard_output_file $basename_lib.so]
+
+if { [gdb_compile_shlib $srcfile_lib $binfile_lib \
+	  [list additional_flags=-fPIC]] != "" } {
+    untested "Could not compile $binfile_lib."
+    return -1
+}
+
+if { [prepare_for_testing $testfile.exp $testfile $srcfile \
+	  [list additional_flags=-DDSO_NAME=\"$binfile_lib\" libs=-ldl]] } {
+    return -1
+}
+
+if ![runto_main] {
+    return 0
+}
+
+# Trace the test function
+#
+gdb_test_no_output "record btrace"
+gdb_test "next"
+
+# The memory containing the library call we traced is already gone.
+# Trace decode used to run into a SEGV after corrupting the cleanup chain.
+#
+# The test passes if we don't crash GDB.
+#
+gdb_test "info record"