From: Bruno Larsen <blarsen@redhat.com>
To: gdb-patches@sourceware.org
Subject: [PATCH v3] [gdb/testsuite] test a function call by hand from pretty printer
Date: Mon, 14 Mar 2022 17:39:26 -0300 [thread overview]
Message-ID: <20220314203926.58662-1-blarsen@redhat.com> (raw)
In-Reply-To: <20220223185729.25609-1-blarsen@redhat.com>
The test case added here is testing the bug gdb/28856, where calling a
function by hand from a pretty printer makes GDB crash. There are 6
mechanisms to trigger this crash in the current test, using the commands
backtrace, up, down, finish, step and continue. Since the failure happens
because of use-after-free (more details below) the tests will always
have a chance of passing through sheer luck, but anecdotally they seem
to fail all of the time.
The reason GDB is crashing is a use-after-free problem. The above
mentioned functions save a pointer to the current frame's information,
then calls the pretty printer, and uses the saved pointer for different
reasons, depending on the function. The issue happens because
call_function_by_hand needs to reset the obstack to get the current
frame, invalidating the saved pointer.
---
Changes from v2:
* Make .c follow GDB's coding style 2 - electric boogaloo
* .exp tests outputs, not just if GDB breaks or not
* added copyright header to .py file
Changes from v1:
* make .c follow GDB's coding guidelines more closely
* Documented .exp file better
* renamed and refactored TCL proc to make it less confusing
---
.../gdb.python/pretty-print-call-by-hand.c | 53 ++++++++
.../gdb.python/pretty-print-call-by-hand.exp | 127 ++++++++++++++++++
.../gdb.python/pretty-print-call-by-hand.py | 41 ++++++
3 files changed, 221 insertions(+)
create mode 100644 gdb/testsuite/gdb.python/pretty-print-call-by-hand.c
create mode 100644 gdb/testsuite/gdb.python/pretty-print-call-by-hand.exp
create mode 100644 gdb/testsuite/gdb.python/pretty-print-call-by-hand.py
diff --git a/gdb/testsuite/gdb.python/pretty-print-call-by-hand.c b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.c
new file mode 100644
index 00000000000..3be5675b096
--- /dev/null
+++ b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.c
@@ -0,0 +1,53 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2022 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/>. */
+
+struct mytype
+{
+ char *x;
+};
+
+void
+rec (int i)
+{
+ if (i <= 0)
+ return;
+ rec (i-1);
+}
+
+int
+f ()
+{
+ rec (100);
+ return 2;
+}
+
+void
+g (struct mytype mt, int depth)
+{
+ if (depth <= 0)
+ return; /* TAG: final frame */
+ g (mt, depth - 1); /* TAG: first frame */
+}
+
+int
+main ()
+{
+ struct mytype mt;
+ mt.x = "hello world";
+ g (mt, 10); /* TAG: outside the frame */
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.python/pretty-print-call-by-hand.exp b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.exp
new file mode 100644
index 00000000000..0a6d014cf12
--- /dev/null
+++ b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.exp
@@ -0,0 +1,127 @@
+# Copyright (C) 2022 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/>.
+
+# This file is part of the GDB testsuite. It tests a pretty printer that
+# calls an inferior function by hand, triggering a Use-after-Free bug
+# (PR gdb/28856).
+
+load_lib gdb-python.exp
+
+standard_testfile
+
+# gdb needs to be started here for skip_python_tests to work.
+# prepare_for_testing could be used instead, but it could compile the program
+# unnecessarily, so starting GDB like this is preferable.
+gdb_start
+
+# Skip all tests if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
+ untested "failed to compile"
+ return -1
+}
+
+# This proc restarts GDB, makes the inferior reach the desired spot - marked
+# by a comment in the .c file - and turns on the pretty printer for testing.
+# Starting with a new GDB is important because the test may crash GDB. The
+# return values are here to avoid us trying to test the pretty printer if
+# there was a problem getting to main.
+proc start_test { breakpoint_comment } {
+ global srcdir subdir testfile binfile
+
+ # Start with a fresh gdb.
+ # This is important because the test can crash GDB.
+
+ clean_restart ${binfile}
+
+ if { ![runto_main] } then {
+ untested "couldn't run to breakpoint"
+ return -1
+ }
+
+ # Let GDB get to the return line.
+ gdb_breakpoint [gdb_get_line_number ${breakpoint_comment} ${testfile}.c ]
+ gdb_continue_to_breakpoint ${breakpoint_comment} ".*"
+
+ gdb_test_no_output "set print pretty on" "starting to pretty print"
+
+ set remote_python_file [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py]
+ gdb_test_no_output "source ${remote_python_file}" "load python file"
+
+ return 0
+}
+
+# Testing the backtrace command.
+with_test_prefix "frame print" {
+ if { [start_test "TAG: final frame"] == 0 } {
+ setup_kfail gdb/28856 "*-*-*"
+ gdb_test "backtrace -frame-arguments all" [multi_line \
+ "#0 .*g \\(mt=mytype is .*\\).*"\
+ "#1 .*g \\(mt=mytype is .*\\).*"\
+ "#2 .*g \\(mt=mytype is .*\\).*"\
+ "#3 .*g \\(mt=mytype is .*\\).*"\
+ "#4 .*g \\(mt=mytype is .*\\).*"\
+ "#5 .*g \\(mt=mytype is .*\\).*"\
+ "#6 .*g \\(mt=mytype is .*\\).*"\
+ "#7 .*g \\(mt=mytype is .*\\).*"\
+ "#8 .*g \\(mt=mytype is .*\\).*"\
+ "#9 .*g \\(mt=mytype is .*\\).*"\
+ "#10 .*g \\(mt=mytype is .*\\).*"\
+ "#11 .*main \\(\\).*"] \
+ "backtrace test"
+ }
+}
+# Testing the down command.
+with_test_prefix "frame movement down" {
+ if { [start_test "TAG: first frame"] == 0 } {
+ gdb_test "up" [multi_line "#1 .*in main \\(\\) at .*" ".*outside the frame.*"]
+ setup_kfail gdb/28856 "*-*-*"
+ gdb_test "down" [multi_line "#0\\s+g \\(mt=mytype is .*\\).*" ".*first frame.*"]
+ }
+}
+
+# Testing the up command.
+with_test_prefix "frame movement up" {
+ if { [start_test "TAG: final frame"] == 0 } {
+ setup_kfail gdb/28856 "*-*-*"
+ gdb_test "up" [multi_line "#1 .*in g \\(mt=mytype is .*\\).*" ".*first frame.*"]
+ }
+}
+
+# Testing the finish command.
+with_test_prefix "frame exit through finish" {
+ if { [start_test "TAG: final frame"] == 0 } {
+ setup_kfail gdb/28856 "*-*-*"
+ gdb_test "finish" [multi_line "Run till exit from #0 .*" ".* g \\(mt=mytype is .*\\, depth=1\\).*" ".*first frame.*"]
+ }
+}
+
+# Testing the step command.
+with_test_prefix "frame enter through step" {
+ if { [start_test "TAG: outside the frame"] == 0 } {
+ setup_kfail gdb/28856 "*-*-*"
+ gdb_test "step" [multi_line "g \\(mt=mytype is .*\\, depth=10\\).*" "41.*if \\(depth \\<= 0\\)"]
+ }
+}
+
+# Testing the continue command.
+with_test_prefix "frame enter through continue" {
+ if { [start_test "TAG: outside the frame"] == 0 } {
+ setup_kfail gdb/28856 "*-*-*"
+ gdb_breakpoint [gdb_get_line_number "TAG: first frame" ${testfile}.c ]
+ gdb_continue_to_breakpoint "TAG: first frame" ".*TAG: first frame.*"
+ }
+}
diff --git a/gdb/testsuite/gdb.python/pretty-print-call-by-hand.py b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.py
new file mode 100644
index 00000000000..f8f5df678f8
--- /dev/null
+++ b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.py
@@ -0,0 +1,41 @@
+# Copyright (C) 2022 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/>.
+
+
+class MytypePrinter:
+ """pretty print my type"""
+
+ def __init__(self, val):
+ self.val = val
+
+ def to_string(self):
+ calls = gdb.parse_and_eval('f()')
+ return "mytype is %s" % self.val['x']
+
+def ec_lookup_function(val):
+ typ = val.type
+ if typ.code == gdb.TYPE_CODE_REF:
+ typ = typ.target()
+ if str(typ) == 'struct mytype':
+ return MytypePrinter(val)
+ return None
+
+def disable_lookup_function():
+ ec_lookup_function.enabled = False
+
+def enable_lookup_function():
+ ec_lookup_function.enabled = True
+
+gdb.pretty_printers.append(ec_lookup_function)
--
2.31.1
next prev parent reply other threads:[~2022-03-14 20:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-23 18:57 [PATCH] [gdb/testsuite] test a function call by hand fron " Bruno Larsen
2022-02-27 12:39 ` Joel Brobecker
2022-02-28 12:13 ` Bruno Larsen
2022-03-06 10:43 ` Joel Brobecker
2022-03-07 13:09 ` [PATCH v2] " Bruno Larsen
2022-03-13 6:13 ` Joel Brobecker
2022-03-14 20:39 ` Bruno Larsen [this message]
2022-03-19 14:41 ` [PATCH v3] [gdb/testsuite] test a function call by hand from " Joel Brobecker
2022-03-21 20:21 ` Simon Marchi
2022-03-23 15:37 ` Bruno Larsen
2022-03-24 14:18 ` Simon Marchi
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