qdev: Protect device-list-properties against broken devices

Several devices don't survive object_unref(object_new(T)): they crash
or hang during cleanup, or they leave dangling pointers behind.

This breaks at least device-list-properties, because
qmp_device_list_properties() needs to create a device to find its
properties.  Broken in commit f4eb32b "qmp: show QOM properties in
device-list-properties", v2.1.  Example reproducer:

    $ qemu-system-aarch64 -nodefaults -display none -machine none -S -qmp stdio
    {"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2}, "package": ""}, "capabilities": []}}
    { "execute": "qmp_capabilities" }
    {"return": {}}
    { "execute": "device-list-properties", "arguments": { "typename": "pxa2xx-pcmcia" } }
    qemu-system-aarch64: /home/armbru/work/qemu/memory.c:1307: memory_region_finalize: Assertion `((&mr->subregions)->tqh_first == ((void *)0))' failed.
    Aborted (core dumped)
    [Exit 134 (SIGABRT)]

Unfortunately, I can't fix the problems in these devices right now.
Instead, add DeviceClass member cannot_destroy_with_object_finalize_yet
to mark them:

* Hang during cleanup (didn't debug, so I can't say why):
  "realview_pci", "versatile_pci".

* Dangling pointer in cpus: most CPUs, plus "allwinner-a10", "digic",
  "fsl,imx25", "fsl,imx31", "xlnx,zynqmp", because they create such
  CPUs

* Assert kvm_enabled(): "host-x86_64-cpu", host-i386-cpu",
  "host-powerpc64-cpu", "host-embedded-powerpc-cpu",
  "host-powerpc-cpu" (the powerpc ones can't currently reach the
  assertion, because the CPUs are only registered when KVM is enabled,
  but the assertion is arguably in the wrong place all the same)

Make qmp_device_list_properties() fail cleanly when the device is so
marked.  This improves device-list-properties from "crashes, hangs or
leaves dangling pointers behind" to "fails".  Not a complete fix, just
a better-than-nothing work-around.  In the above reproducer,
device-list-properties now fails with "Can't list properties of device
'pxa2xx-pcmcia'".

This also protects -device FOO,help, which uses the same machinery
since commit ef52358 "qdev-monitor: include QOM properties in -device
FOO, help output", v2.2.  Example reproducer:

    $ qemu-system-aarch64 -machine none -device pxa2xx-pcmcia,help

Before:

    qemu-system-aarch64: .../memory.c:1307: memory_region_finalize: Assertion `((&mr->subregions)->tqh_first == ((void *)0))' failed.

After:

    Can't list properties of device 'pxa2xx-pcmcia'

Cc: "Andreas Färber" <afaerber@suse.de>
Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Anthony Green <green@moxielogic.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Jia Liu <proljc@gmail.com>
Cc: Leon Alrae <leon.alrae@imgtec.com>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Walle <michael@walle.cc>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: qemu-ppc@nongnu.org
Cc: qemu-stable@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1443689999-12182-10-git-send-email-armbru@redhat.com>

5 files changed, 30 insertions, 0 deletions

diff --git a/hw/arm/allwinner-a10.c b/hw/arm/allwinner-a10.c
index ff249af335..43dc0a12de 100644
--- a/hw/arm/allwinner-a10.c
+++ b/hw/arm/allwinner-a10.c
@@ -103,6 +103,12 @@ static void aw_a10_class_init(ObjectClass *oc, void *data)
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = aw_a10_realize;
+
+    /*
+     * Reason: creates an ARM CPU, thus use after free(), see
+     * arm_cpu_class_init()
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo aw_a10_type_info = {
diff --git a/hw/arm/digic.c b/hw/arm/digic.c
index ec8c330602..90f8190c48 100644
--- a/hw/arm/digic.c
+++ b/hw/arm/digic.c
@@ -97,6 +97,12 @@ static void digic_class_init(ObjectClass *oc, void *data)
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = digic_realize;
+
+    /*
+     * Reason: creates an ARM CPU, thus use after free(), see
+     * arm_cpu_class_init()
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo digic_type_info = {
diff --git a/hw/arm/fsl-imx25.c b/hw/arm/fsl-imx25.c
index 86fde42e34..e1cadac997 100644
--- a/hw/arm/fsl-imx25.c
+++ b/hw/arm/fsl-imx25.c
@@ -284,6 +284,12 @@ static void fsl_imx25_class_init(ObjectClass *oc, void *data)
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = fsl_imx25_realize;
+
+    /*
+     * Reason: creates an ARM CPU, thus use after free(), see
+     * arm_cpu_class_init()
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo fsl_imx25_type_info = {
diff --git a/hw/arm/fsl-imx31.c b/hw/arm/fsl-imx31.c
index 8e1ed4811b..53d4473250 100644
--- a/hw/arm/fsl-imx31.c
+++ b/hw/arm/fsl-imx31.c
@@ -258,6 +258,12 @@ static void fsl_imx31_class_init(ObjectClass *oc, void *data)
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = fsl_imx31_realize;
+
+    /*
+     * Reason: creates an ARM CPU, thus use after free(), see
+     * arm_cpu_class_init()
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo fsl_imx31_type_info = {
diff --git a/hw/arm/xlnx-zynqmp.c b/hw/arm/xlnx-zynqmp.c
index a9097f9b72..b36ca3da74 100644
--- a/hw/arm/xlnx-zynqmp.c
+++ b/hw/arm/xlnx-zynqmp.c
@@ -271,6 +271,12 @@ static void xlnx_zynqmp_class_init(ObjectClass *oc, void *data)
 
     dc->props = xlnx_zynqmp_props;
     dc->realize = xlnx_zynqmp_realize;
+
+    /*
+     * Reason: creates an ARM CPU, thus use after free(), see
+     * arm_cpu_class_init()
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo xlnx_zynqmp_type_info = {