From 6cf99a70c551b2a672d7732442f2da13154cab0c Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Fri, 1 Jun 2018 19:54:38 -0500 Subject: [PATCH] (windows) GDB/MI crash when using "-list-thread-groups --available" On Windows, using the "-list-thread-groups --available" GDB/MI command before an inferior is being debugged: % gdb -q -i=mi =thread-group-added,id="i1" =cmd-param-changed,param="auto-load safe-path",value="/" (gdb) -list-thread-groups --available Segmentation fault Ooops! The SEGV happens because the -list-thread-groups --available command triggers a windows_nat_target::xfer_partial call for a TARGET_OBJECT_OSDATA object. Until a program is being debugged, the target_ops layer that gets the call is the Windows "native" layer. Except for a couple of specific objects (TARGET_OBJECT_MEMORY and TARGET_OBJECT_LIBRARIES), this layer's xfer_partial method delegates the xfer of other objects to the target beneath: default: return beneath->xfer_partial (object, annex, readbuf, writebuf, offset, len, xfered_len); Unfortunately, there is no "beneath layer" in this case, so beneath is NULL and dereferencing it leads to the SEGV. This patch fixes the issue by checking beneath before trying to delegate the request. gdb/ChangeLog: * windows-nat.c (windows_nat_target::xfer_partial): Return TARGET_XFER_E_IO if we need to delegate to the target beneath but BENEATH is NULL. gdb/testsuite/ChangeLog: * gdb.mi/mi-list-thread-groups-no-inferior.exp: New testcase. --- .../gdb.mi/mi-list-thread-groups-no-inferior.exp | 43 ++++++++++++++++++++++ gdb/windows-nat.c | 7 ++++ 2 files changed, 50 insertions(+) create mode 100644 gdb/testsuite/gdb.mi/mi-list-thread-groups-no-inferior.exp diff --git a/gdb/testsuite/gdb.mi/mi-list-thread-groups-no-inferior.exp b/gdb/testsuite/gdb.mi/mi-list-thread-groups-no-inferior.exp new file mode 100644 index 0000000..381f6f1 --- /dev/null +++ b/gdb/testsuite/gdb.mi/mi-list-thread-groups-no-inferior.exp @@ -0,0 +1,43 @@ +# Copyright 2018 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 . + +load_lib mi-support.exp +set MIFLAGS "-i=mi" + +gdb_exit +if [mi_gdb_start] { + continue +} + +# Try the "-list-thread-groups --available". This command can generate +# a very large amount of output, potentially exceeding expect's buffer +# size. So we consume the output in chunks. + +set test "-list-thread-groups --available" +gdb_test_multiple $test $test { + -re ".*\}" { + exp_continue + } + -re "\r\n$gdb_prompt " { + pass $test + } +} + +# Verify that GDB is still alive. + +mi_gdb_test "-data-evaluate-expression 1" \ + ".*\\^done,value=\"1\"" \ + "check GDB is still alive" + diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c index 0f24257..e3e36cd 100644 --- a/gdb/windows-nat.c +++ b/gdb/windows-nat.c @@ -2966,6 +2966,13 @@ windows_nat_target::xfer_partial (enum target_object object, writebuf, offset, len, xfered_len); default: + if (beneath == NULL) + { + /* This can happen when requesting the transfer of unsupported + objects before a program has been started (and therefore + with the current_target having no target beneath). */ + return TARGET_XFER_E_IO; + } return beneath->xfer_partial (object, annex, readbuf, writebuf, offset, len, xfered_len); -- 2.1.4