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* [PATCH] [gdb/testsuite] test a function call by hand fron pretty printer
@ 2022-02-23 18:57 Bruno Larsen
  2022-02-27 12:39 ` Joel Brobecker
                   ` (2 more replies)
  0 siblings, 3 replies; 11+ messages in thread
From: Bruno Larsen @ 2022-02-23 18:57 UTC (permalink / raw)
  To: gdb-patches

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.
---
 .../gdb.python/pretty-print-call-by-hand.c    |  44 ++++++
 .../gdb.python/pretty-print-call-by-hand.exp  | 148 ++++++++++++++++++
 .../gdb.python/pretty-print-call-by-hand.py   |  25 +++
 3 files changed, 217 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..0dcddc9c1e6
--- /dev/null
+++ b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.c
@@ -0,0 +1,44 @@
+/* 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: inside the frame */
+    g (mt, depth - 1);
+}
+
+int main (){
+    struct mytype mt;
+    mt.x = "hello world";
+    g (mt, 10); /* TAG: break here */
+    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..6ba3fdcc7b3
--- /dev/null
+++ b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.exp
@@ -0,0 +1,148 @@
+# 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 Python-based
+# pretty-printing for the CLI.
+
+load_lib gdb-python.exp
+
+standard_testfile
+
+# Start with a fresh gdb.
+gdb_exit
+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
+}
+
+proc start_test_no_pretty {} {
+    global srcdir subdir testfile binfile
+
+    # Start with a fresh gdb.
+    # This is important because the test can crash GDB.
+
+    gdb_exit
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    if { ![runto_main] } then {
+	perror "couldn't run to breakpoint"
+	return -1
+    }
+    #gdb_test_no_output "source ${testfile}.py" "load python file"
+
+    #let GDB get to the return line
+    gdb_breakpoint [gdb_get_line_number "TAG: break here" ${testfile}.c ]
+    gdb_continue_to_breakpoint "TAG: break here" ".*TAG: break here.*"
+
+    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
+}
+
+proc start_test_pretty {} {
+    global srcdir subdir testfile binfile
+
+    # Start with a fresh gdb.
+    # This is important because the test can crash GDB.
+
+    gdb_exit
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    if { ![runto_main] } then {
+	perror "couldn't run to breakpoint"
+	return -1
+    }
+    #gdb_test_no_output "source ${testfile}.py" "load python file"
+
+    #let GDB get to the return line
+    gdb_breakpoint [gdb_get_line_number "TAG: break here" ${testfile}.c ]
+    gdb_continue_to_breakpoint "TAG: break here" ".*TAG: break here.*"
+
+    gdb_test "step" ".*" #enter the problematic frame
+
+    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_pretty] == 0 } {
+	setup_kfail gdb/28856 "*-*-*"
+	gdb_test "backtrace -frame-arguments all" ".*"
+    }
+}
+
+# Testing the down command
+with_test_prefix "frame movement up" {
+    if { [start_test_pretty] == 0 } {
+	gdb_test "up" ".*"
+	setup_kfail gdb/28856 "*-*-*"
+	gdb_test "down" ".*"
+    }
+}
+
+# Testing the up command
+with_test_prefix "frame movement down" {
+    if { [start_test_pretty] == 0 } {
+	gdb_test_no_output "set print pretty off" "removing pretty printing"
+	gdb_breakpoint [gdb_get_line_number "TAG: inside the frame" ${testfile}.c ]
+	gdb_continue_to_breakpoint "TAG: inside the frame" ".*TAG: inside the frame.*"
+	gdb_test_no_output "set print pretty on" "removing pretty printing"
+	setup_kfail gdb/28856 "*-*-*"
+	gdb_test "up" ".*"
+    }
+}
+
+# Testing the finish command
+with_test_prefix "frame exit through finish" {
+    if { [start_test_pretty] == 0 } {
+	setup_kfail gdb/28856 "*-*-*"
+	gdb_test "finish" ".*"
+    }
+}
+
+# Testing the step command
+with_test_prefix "frame enter through step" {
+    if { [start_test_no_pretty] == 0 } {
+	setup_kfail gdb/28856 "*-*-*"
+	gdb_test "step" ".*"
+    }
+}
+
+# Testing the continue command
+with_test_prefix "frame enter through continue" {
+    if { [start_test_no_pretty] == 0 } {
+	gdb_test "backtrace -frame-arguments all" ".*"
+	setup_kfail gdb/28856 "*-*-*"
+	gdb_breakpoint [gdb_get_line_number "TAG: inside the frame" ${testfile}.c ]
+	gdb_continue_to_breakpoint "TAG: inside the frame" ".*TAG: inside the 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..978876723fc
--- /dev/null
+++ b/gdb/testsuite/gdb.python/pretty-print-call-by-hand.py
@@ -0,0 +1,25 @@
+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


^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2022-03-24 14:18 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-23 18:57 [PATCH] [gdb/testsuite] test a function call by hand fron pretty printer 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 ` [PATCH v3] [gdb/testsuite] test a function call by hand from " Bruno Larsen
2022-03-19 14:41   ` 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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