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>
(cherry picked from commit 4c315c27661502a0813b129e41c0bf640c34a8d6)

Conflicts:
	hw/arm/fsl-imx25.c
	hw/arm/fsl-imx31.c
	target-tilegx/cpu.c
	tests/device-introspect-test.c

* removed hunks pertaining to devices/tests not in 2.4

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

23 files changed, 166 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/xlnx-zynqmp.c b/hw/arm/xlnx-zynqmp.c
index 62ef4ceb32..5157565f99 100644
--- a/hw/arm/xlnx-zynqmp.c
+++ b/hw/arm/xlnx-zynqmp.c
@@ -248,6 +248,12 @@ 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 = {
diff --git a/hw/pci-host/versatile.c b/hw/pci-host/versatile.c
index 6d23553094..7172b90958 100644
--- a/hw/pci-host/versatile.c
+++ b/hw/pci-host/versatile.c
@@ -500,6 +500,8 @@ static void pci_vpb_class_init(ObjectClass *klass, void *data)
     dc->reset = pci_vpb_reset;
     dc->vmsd = &pci_vpb_vmstate;
     dc->props = pci_vpb_properties;
+    /* Reason: object_unref() hangs */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo pci_vpb_info = {
@@ -521,10 +523,19 @@ static void pci_realview_init(Object *obj)
     s->mem_win_size[2] = 0x08000000;
 }
 
+static void pci_realview_class_init(ObjectClass *class, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(class);
+
+    /* Reason: object_unref() hangs */
+    dc->cannot_destroy_with_object_finalize_yet = true;
+}
+
 static const TypeInfo pci_realview_info = {
     .name          = "realview_pci",
     .parent        = TYPE_VERSATILE_PCI,
     .instance_init = pci_realview_init,
+    .class_init    = pci_realview_class_init,
 };
 
 static void versatile_pci_register_types(void)
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 038b54d94b..8057aedaa6 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -114,6 +114,19 @@ typedef struct DeviceClass {
      * TODO remove once we're there
      */
     bool cannot_instantiate_with_device_add_yet;
+    /*
+     * Does this device model survive object_unref(object_new(TNAME))?
+     * All device models should, and this flag shouldn't exist.  Some
+     * devices crash in object_new(), some crash or hang in
+     * object_unref().  Makes introspecting properties with
+     * qmp_device_list_properties() dangerous.  Bad, because it's used
+     * by -device FOO,help.  This flag serves to protect that code.
+     * It should never be set without a comment explaining why it is
+     * set.
+     * TODO remove once we're there
+     */
+    bool cannot_destroy_with_object_finalize_yet;
+
     bool hotpluggable;
 
     /* callbacks */
diff --git a/qmp.c b/qmp.c
index 8603c46bdb..6998ca2fc6 100644
--- a/qmp.c
+++ b/qmp.c
@@ -520,6 +520,11 @@ DevicePropertyInfoList *qmp_device_list_properties(const char *typename,
         return NULL;
     }
 
+    if (DEVICE_CLASS(klass)->cannot_destroy_with_object_finalize_yet) {
+        error_setg(errp, "Can't list properties of device '%s'", typename);
+        return NULL;
+    }
+
     obj = object_new(typename);
 
     QTAILQ_FOREACH(prop, &obj->properties, node) {
diff --git a/target-alpha/cpu.c b/target-alpha/cpu.c
index 421d7e5364..ff1926a5d0 100644
--- a/target-alpha/cpu.c
+++ b/target-alpha/cpu.c
@@ -298,6 +298,13 @@ static void alpha_cpu_class_init(ObjectClass *oc, void *data)
     dc->vmsd = &vmstate_alpha_cpu;
 #endif
     cc->gdb_num_core_regs = 67;
+
+    /*
+     * Reason: alpha_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo alpha_cpu_type_info = {
diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 8b4323dd08..ce0b8c09c5 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -1403,6 +1403,17 @@ static void arm_cpu_class_init(ObjectClass *oc, void *data)
     cc->debug_excp_handler = arm_debug_excp_handler;
 
     cc->disas_set_info = arm_disas_set_info;
+
+    /*
+     * Reason: arm_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     *
+     * Once this is fixed, the devices that create ARM CPUs should be
+     * updated not to set cannot_destroy_with_object_finalize_yet,
+     * unless they still screw up something else.
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void cpu_register(const ARMCPUInfo *info)
diff --git a/target-cris/cpu.c b/target-cris/cpu.c
index b17e849e2a..aa5e1c57c1 100644
--- a/target-cris/cpu.c
+++ b/target-cris/cpu.c
@@ -308,6 +308,13 @@ static void cris_cpu_class_init(ObjectClass *oc, void *data)
     cc->gdb_stop_before_watchpoint = true;
 
     cc->disas_set_info = cris_disas_set_info;
+
+    /*
+     * Reason: cris_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo cris_cpu_type_info = {
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 7a779b1653..4d1b085332 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -1475,6 +1475,8 @@ static void host_x86_cpu_class_init(ObjectClass *oc, void *data)
      */
 
     dc->props = host_x86_cpu_properties;
+    /* Reason: host_x86_cpu_initfn() dies when !kvm_enabled() */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void host_x86_cpu_initfn(Object *obj)
@@ -3200,6 +3202,12 @@ static void x86_cpu_common_class_init(ObjectClass *oc, void *data)
 #endif
     cc->cpu_exec_enter = x86_cpu_exec_enter;
     cc->cpu_exec_exit = x86_cpu_exec_exit;
+
+    /*
+     * Reason: x86_cpu_initfn() calls cpu_exec_init(), which saves the
+     * object in cpus -> dangling pointer after final object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo x86_cpu_type_info = {
diff --git a/target-lm32/cpu.c b/target-lm32/cpu.c
index c2b77c6986..d0ab2786ae 100644
--- a/target-lm32/cpu.c
+++ b/target-lm32/cpu.c
@@ -275,6 +275,13 @@ static void lm32_cpu_class_init(ObjectClass *oc, void *data)
     cc->gdb_num_core_regs = 32 + 7;
     cc->gdb_stop_before_watchpoint = true;
     cc->debug_excp_handler = lm32_debug_excp_handler;
+
+    /*
+     * Reason: lm32_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void lm32_register_cpu_type(const LM32CPUInfo *info)
diff --git a/target-m68k/cpu.c b/target-m68k/cpu.c
index 4f246da748..97527ef32a 100644
--- a/target-m68k/cpu.c
+++ b/target-m68k/cpu.c
@@ -212,6 +212,13 @@ static void m68k_cpu_class_init(ObjectClass *c, void *data)
     dc->vmsd = &vmstate_m68k_cpu;
     cc->gdb_num_core_regs = 18;
     cc->gdb_core_xml_file = "cf-core.xml";
+
+    /*
+     * Reason: m68k_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void register_cpu_type(const M68kCPUInfo *info)
diff --git a/target-microblaze/cpu.c b/target-microblaze/cpu.c
index 9ac509af3e..15b46f7686 100644
--- a/target-microblaze/cpu.c
+++ b/target-microblaze/cpu.c
@@ -264,6 +264,12 @@ static void mb_cpu_class_init(ObjectClass *oc, void *data)
     cc->gdb_num_core_regs = 32 + 5;
 
     cc->disas_set_info = mb_disas_set_info;
+
+    /*
+     * Reason: mb_cpu_initfn() calls cpu_exec_init(), which saves the
+     * object in cpus -> dangling pointer after final object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo mb_cpu_type_info = {
diff --git a/target-mips/cpu.c b/target-mips/cpu.c
index 4027d0f417..7fe1f0407f 100644
--- a/target-mips/cpu.c
+++ b/target-mips/cpu.c
@@ -153,6 +153,13 @@ static void mips_cpu_class_init(ObjectClass *c, void *data)
 
     cc->gdb_num_core_regs = 73;
     cc->gdb_stop_before_watchpoint = true;
+
+    /*
+     * Reason: mips_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo mips_cpu_type_info = {
diff --git a/target-moxie/cpu.c b/target-moxie/cpu.c
index 6b035aaab3..3af37799b7 100644
--- a/target-moxie/cpu.c
+++ b/target-moxie/cpu.c
@@ -114,6 +114,13 @@ static void moxie_cpu_class_init(ObjectClass *oc, void *data)
     cc->get_phys_page_debug = moxie_cpu_get_phys_page_debug;
     cc->vmsd = &vmstate_moxie_cpu;
 #endif
+
+    /*
+     * Reason: moxie_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void moxielite_initfn(Object *obj)
diff --git a/target-openrisc/cpu.c b/target-openrisc/cpu.c
index d97f3c03c2..cc5e2d1c5d 100644
--- a/target-openrisc/cpu.c
+++ b/target-openrisc/cpu.c
@@ -177,6 +177,13 @@ static void openrisc_cpu_class_init(ObjectClass *oc, void *data)
     dc->vmsd = &vmstate_openrisc_cpu;
 #endif
     cc->gdb_num_core_regs = 32 + 3;
+
+    /*
+     * Reason: openrisc_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void cpu_register(const OpenRISCCPUInfo *info)
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 110436d088..a307a13deb 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -2188,6 +2188,7 @@ static void kvmppc_host_cpu_initfn(Object *obj)
 
 static void kvmppc_host_cpu_class_init(ObjectClass *oc, void *data)
 {
+    DeviceClass *dc = DEVICE_CLASS(oc);
     PowerPCCPUClass *pcc = POWERPC_CPU_CLASS(oc);
     uint32_t vmx = kvmppc_get_vmx();
     uint32_t dfp = kvmppc_get_dfp();
@@ -2214,6 +2215,9 @@ static void kvmppc_host_cpu_class_init(ObjectClass *oc, void *data)
     if (icache_size != -1) {
         pcc->l1_icache_size = icache_size;
     }
+
+    /* Reason: kvmppc_host_cpu_initfn() dies when !kvm_enabled() */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 bool kvmppc_has_cap_epr(void)
diff --git a/target-s390x/cpu.c b/target-s390x/cpu.c
index c3e21b445c..ccfaa8a919 100644
--- a/target-s390x/cpu.c
+++ b/target-s390x/cpu.c
@@ -353,6 +353,13 @@ static void s390_cpu_class_init(ObjectClass *oc, void *data)
 #endif
     cc->gdb_num_core_regs = S390_NUM_CORE_REGS;
     cc->gdb_core_xml_file = "s390x-core64.xml";
+
+    /*
+     * Reason: s390_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo s390_cpu_type_info = {
diff --git a/target-sh4/cpu.c b/target-sh4/cpu.c
index 5c65ab4df5..64e4467c04 100644
--- a/target-sh4/cpu.c
+++ b/target-sh4/cpu.c
@@ -290,6 +290,13 @@ static void superh_cpu_class_init(ObjectClass *oc, void *data)
 #endif
     dc->vmsd = &vmstate_sh_cpu;
     cc->gdb_num_core_regs = 59;
+
+    /*
+     * Reason: superh_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo superh_cpu_type_info = {
diff --git a/target-sparc/cpu.c b/target-sparc/cpu.c
index 9528e3afbb..82bb72ab79 100644
--- a/target-sparc/cpu.c
+++ b/target-sparc/cpu.c
@@ -854,6 +854,13 @@ static void sparc_cpu_class_init(ObjectClass *oc, void *data)
 #else
     cc->gdb_num_core_regs = 72;
 #endif
+
+    /*
+     * Reason: sparc_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo sparc_cpu_type_info = {
diff --git a/target-tricore/cpu.c b/target-tricore/cpu.c
index 2029ef651a..ed8b030ef5 100644
--- a/target-tricore/cpu.c
+++ b/target-tricore/cpu.c
@@ -170,6 +170,12 @@ static void tricore_cpu_class_init(ObjectClass *c, void *data)
     cc->set_pc = tricore_cpu_set_pc;
     cc->synchronize_from_tb = tricore_cpu_synchronize_from_tb;
 
+    /*
+     * Reason: tricore_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void cpu_register(const TriCoreCPUInfo *info)
diff --git a/target-unicore32/cpu.c b/target-unicore32/cpu.c
index fc451a1a35..e5252ebaf8 100644
--- a/target-unicore32/cpu.c
+++ b/target-unicore32/cpu.c
@@ -155,6 +155,13 @@ static void uc32_cpu_class_init(ObjectClass *oc, void *data)
     cc->get_phys_page_debug = uc32_cpu_get_phys_page_debug;
 #endif
     dc->vmsd = &vmstate_uc32_cpu;
+
+    /*
+     * Reason: uc32_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static void uc32_register_cpu_type(const UniCore32CPUInfo *info)
diff --git a/target-xtensa/cpu.c b/target-xtensa/cpu.c
index da8129db50..4e49bee9b5 100644
--- a/target-xtensa/cpu.c
+++ b/target-xtensa/cpu.c
@@ -155,6 +155,13 @@ static void xtensa_cpu_class_init(ObjectClass *oc, void *data)
 #endif
     cc->debug_excp_handler = xtensa_breakpoint_handler;
     dc->vmsd = &vmstate_xtensa_cpu;
+
+    /*
+     * Reason: xtensa_cpu_initfn() calls cpu_exec_init(), which saves
+     * the object in cpus -> dangling pointer after final
+     * object_unref().
+     */
+    dc->cannot_destroy_with_object_finalize_yet = true;
 }
 
 static const TypeInfo xtensa_cpu_type_info = {