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Re: [PATCH 05/11] qdev: Make DeviceState.id independent of QemuOpts

From: Vladimir Sementsov-Ogievskiy
Subject: Re: [PATCH 05/11] qdev: Make DeviceState.id independent of QemuOpts
Date: Fri, 24 Sep 2021 18:14:34 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 
24.09.2021 18:10, Kevin Wolf wrote:

Am 24.09.2021 um 16:02 hat Vladimir Sementsov-Ogievskiy geschrieben:

24.09.2021 12:04, Kevin Wolf wrote:

DeviceState.id is a pointer to a string that is stored in the QemuOpts
object DeviceState.opts and freed together with it. We want to create
devices without going through QemuOpts in the future, so make this a
separately allocated string.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>


Interesting that in hw/xen/xen-legacy-backend.c
g_strdup_printf-allocated id is passed to qdev_set_id prior this
patch. So, the patch seems to fix that small leak. Worth to mention?


Ok, I can mention it explicitly.


---
   include/hw/qdev-core.h              | 2 +-
   include/monitor/qdev.h              | 2 +-
   hw/arm/virt.c                       | 2 +-
   hw/core/qdev.c                      | 1 +
   hw/pci-bridge/pci_expander_bridge.c | 2 +-
   hw/ppc/e500.c                       | 2 +-
   softmmu/qdev-monitor.c              | 5 +++--
   7 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 34c8a7506a..1857d9698e 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -176,7 +176,7 @@ struct DeviceState {
       Object parent_obj;
       /*< public >*/
-    const char *id;
+    char *id;
       char *canonical_path;
       bool realized;
       bool pending_deleted_event;
diff --git a/include/monitor/qdev.h b/include/monitor/qdev.h
index eaa947d73a..389287eb44 100644
--- a/include/monitor/qdev.h
+++ b/include/monitor/qdev.h
@@ -9,6 +9,6 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error 
**errp);
   int qdev_device_help(QemuOpts *opts);
   DeviceState *qdev_device_add(QemuOpts *opts, Error **errp);
-void qdev_set_id(DeviceState *dev, const char *id);
+void qdev_set_id(DeviceState *dev, char *id);
   #endif
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 1d59f0e59f..f933d48d3b 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1459,7 +1459,7 @@ static void create_platform_bus(VirtMachineState *vms)
       MemoryRegion *sysmem = get_system_memory();
       dev = qdev_new(TYPE_PLATFORM_BUS_DEVICE);
-    dev->id = TYPE_PLATFORM_BUS_DEVICE;
+    dev->id = g_strdup(TYPE_PLATFORM_BUS_DEVICE);
       qdev_prop_set_uint32(dev, "num_irqs", PLATFORM_BUS_NUM_IRQS);
       qdev_prop_set_uint32(dev, "mmio_size", 
vms->memmap[VIRT_PLATFORM_BUS].size);
       sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index cefc5eaa0a..d918b50a1d 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -956,6 +956,7 @@ static void device_finalize(Object *obj)
       }
       qemu_opts_del(dev->opts);
+    g_free(dev->id);
   }
   static void device_class_base_init(ObjectClass *class, void *data)
diff --git a/hw/pci-bridge/pci_expander_bridge.c 
b/hw/pci-bridge/pci_expander_bridge.c
index 7112dc3062..10e6e7c2ab 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -245,7 +245,7 @@ static void pxb_dev_realize_common(PCIDevice *dev, bool 
pcie, Error **errp)
       } else {
           bus = pci_root_bus_new(ds, "pxb-internal", NULL, NULL, 0, 
TYPE_PXB_BUS);
           bds = qdev_new("pci-bridge");
-        bds->id = dev_name;
+        bds->id = g_strdup(dev_name);
           qdev_prop_set_uint8(bds, PCI_BRIDGE_DEV_PROP_CHASSIS_NR, 
pxb->bus_nr);
           qdev_prop_set_bit(bds, PCI_BRIDGE_DEV_PROP_SHPC, false);
       }
diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
index 95451414dd..960e7efcd3 100644
--- a/hw/ppc/e500.c
+++ b/hw/ppc/e500.c
@@ -1006,7 +1006,7 @@ void ppce500_init(MachineState *machine)
       /* Platform Bus Device */
       if (pmc->has_platform_bus) {
           dev = qdev_new(TYPE_PLATFORM_BUS_DEVICE);
-        dev->id = TYPE_PLATFORM_BUS_DEVICE;
+        dev->id = g_strdup(TYPE_PLATFORM_BUS_DEVICE);
           qdev_prop_set_uint32(dev, "num_irqs", pmc->platform_bus_num_irqs);
           qdev_prop_set_uint32(dev, "mmio_size", pmc->platform_bus_size);
           sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
index 034b999401..1207e57a46 100644
--- a/softmmu/qdev-monitor.c
+++ b/softmmu/qdev-monitor.c
@@ -592,7 +592,8 @@ static BusState *qbus_find(const char *path, Error **errp)
       return bus;
   }
-void qdev_set_id(DeviceState *dev, const char *id)
+/* Takes ownership of @id, will be freed when deleting the device */
+void qdev_set_id(DeviceState *dev, char *id)
   {
       if (id) {
           dev->id = id;
@@ -690,7 +691,7 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
           }
       }
-    qdev_set_id(dev, qemu_opts_id(opts));
+    qdev_set_id(dev, g_strdup(qemu_opts_id(opts)));
       /* set properties */
       if (qemu_opt_foreach(opts, set_property, dev, errp)) {



In hw/pci/pci_bridge.c

we do

    br->bus_name = dev->qdev.id

It seems bad, as we now stole dynamic pointer, that may be freed later.


If it's bad now, it was as bad before because previously it was just a
pointer stolen from the QemuOpts that is freed in the same function as
dev->id after this patch.



Ah, right, OK.


I think the code is correct (it's just another field of the same device,
the real bus name is just a copy of it, and the bus can't outlive the
device that owns it anyway), but it might be bad style.




Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>


--
Best regards,
Vladimir
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