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Re: Suspicious QOM types without instance/class size

From: Roman Bolshakov
Subject: Re: Suspicious QOM types without instance/class size
Date: Mon, 24 Aug 2020 19:41:34 +0300 
On Fri, Aug 21, 2020 at 01:48:02PM -0400, Eduardo Habkost wrote:
> On Fri, Aug 21, 2020 at 01:29:38PM -0400, Eduardo Habkost wrote:
> > On Fri, Aug 21, 2020 at 01:53:52PM +0300, Roman Bolshakov wrote:
> > > On Thu, Aug 20, 2020 at 05:55:29PM -0400, Eduardo Habkost wrote:
> > > > While trying to convert TypeInfo declarations to the new
> > > > OBJECT_DECLARE* macros, I've stumbled on a few suspicious cases
> > > > where instance_size or class_size is not set, despite having type
> > > > checker macros that use a specific type.
> > > > 
> > > > The ones with "WARNING" are abstract types (maybe not serious if
> > > > subclasses set the appropriate sizes).  The ones with "ERROR"
> > > > don't seem to be abstract types.
> > > > 
> > > 
> > > > ERROR: target/i386/hvf/hvf.c:908:1: instance_size should be set to 
> > > > sizeof(HVFState)?
> > > 
> > 
> > > BTW, the object definition for hvf seems different from KVM (and perhaps
> > > wrong?), e.g. HVFState is allocated within init_machine handler and then
> > > assigned to a global variable:
> > 
> > Interesting.  It looks like hvf_state is _not_ the actual QOM
> > object instance.  The actual TYPE_HVF_ACCEL instance is created
> > by do_configure_accelerator().  That would explain why the lack
> > of instance_init never caused any problems.
> > 
> > Luckily, no code ever used the HVF_STATE macro.  If
> > HVF_STATE(hvf_state) got called, it would crash because of
> > uninitialized object instance data.  If HVF_STATE(machine->accel)
> > got called, it would return an invalid HVFState pointer (not
> > hvf_state).
> > 
> > I believe the simplest short term solution here is to just delete
> > the HVF_STATE macro and HVFState::parent field.  We can worry
> > about actually moving hvf_state to the machine->accel QOM object
> > later.
> 
> Actually, it might be easier to do the full QOM conversion in a
> single patch instead of deleting the incomplete code.
> 

I agree full QOM conversion is better, perhaps we can later move
certains bits to accel/hvf.c like it's done for kvm/tcg/qtest.

> Can you check if the following patch works?  I don't have a host
> where I can test it.
> 

Sure, thanks :)

> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> diff --git a/target/i386/hvf/hvf.c b/target/i386/hvf/hvf.c
> index d81f569aed..81d1662d06 100644
> --- a/target/i386/hvf/hvf.c
> +++ b/target/i386/hvf/hvf.c
> @@ -878,13 +878,11 @@ static int hvf_accel_init(MachineState *ms)
>  {
>      int x;
>      hv_return_t ret;
> -    HVFState *s;
> +    HVFState *s = HVF_STATE(ms->accelerator);

The file also needs definition of MachineState:
#include "hw/boards.h"

>  
>      ret = hv_vm_create(HV_VM_DEFAULT);
>      assert_hvf_ok(ret);
>  
> -    s = g_new0(HVFState, 1);
> - 
>      s->num_slots = 32;
>      for (x = 0; x < s->num_slots; ++x) {
>          s->slots[x].size = 0;
> @@ -908,6 +906,7 @@ static void hvf_accel_class_init(ObjectClass *oc, void 
> *data)
>  static const TypeInfo hvf_accel_type = {
>      .name = TYPE_HVF_ACCEL,
>      .parent = TYPE_ACCEL,
> +    .instance_size = sizeof(HVFState),
>      .class_init = hvf_accel_class_init,
>  };
>  
>  

Unfortunately it fails to start (even without the HVF patch):
ERROR:../qom/object.c:314:type_initialize: assertion failed: 
(parent->class_size <= ti->class_size)
Bail out! ERROR:../qom/object.c:314:type_initialize: assertion failed: 
(parent->class_size <= ti->class_size)

(lldb) bt
* thread #3, stop reason = signal SIGABRT
  * frame #0: 0x00007fff6a75e33a libsystem_kernel.dylib`__pthread_kill + 10
    frame #1: 0x00007fff6a81ae60 libsystem_pthread.dylib`pthread_kill + 430
    frame #2: 0x00007fff6a6e5808 libsystem_c.dylib`abort + 120
    frame #3: 0x0000000101289c36 libglib-2.0.0.dylib`g_assertion_message + 406
    frame #4: 0x0000000101289c9e libglib-2.0.0.dylib`g_assertion_message_expr + 
94
    frame #5: 0x0000000100353c00 
qemu-system-x86_64`type_initialize(ti=0x00000001032403e0) at object.c:314:9 
[opt]
    frame #6: 0x000000010035378b 
qemu-system-x86_64`type_initialize(ti=0x000000010323fd70) at object.c:310:9 
[opt]
    frame #7: 0x0000000100353de8 
qemu-system-x86_64`object_class_foreach_tramp(key=<unavailable>, 
value=0x000000010323fd70, opaque=0x0000700005cb8d98) at object.c:1030:5 [opt]
    frame #8: 0x000000010124b83d libglib-2.0.0.dylib`g_hash_table_foreach + 125
    frame #9: 0x0000000100354079 qemu-system-x86_64`object_class_get_list 
[inlined] object_class_foreach(fn=<unavailable>, implements_type=<unavailable>, 
include_abstract=<unavailable>, opaque=0x0000700005cb8d90) at object.c:1052:5 
[opt]
    frame #10: 0x000000010035401e 
qemu-system-x86_64`object_class_get_list(implements_type=<unavailable>, 
include_abstract=<unavailable>) at object.c:1109 [opt]
    frame #11: 0x000000010030875d qemu-system-x86_64`qemu_init [inlined] 
select_machine at vl.c:2438:24 [opt]
    frame #12: 0x000000010030874c 
qemu-system-x86_64`qemu_init(argc=<unavailable>, argv=<unavailable>, 
envp=<unavailable>) at vl.c:3842 [opt]
    frame #13: 0x0000000100008ef9 
qemu-system-x86_64`qemu_main(argc=<unavailable>, argv=<unavailable>, 
envp=<unavailable>) at main.c:49:5 [opt]
    frame #14: 0x00000001000386f6 
qemu-system-x86_64`call_qemu_main(opaque=<unavailable>) at cocoa.m:1710:14 [opt]
    frame #15: 0x000000010045f7ae 
qemu-system-x86_64`qemu_thread_start(args=<unavailable>) at 
qemu-thread-posix.c:521:9 [opt]
    frame #16: 0x00007fff6a81b109 libsystem_pthread.dylib`_pthread_start + 148
    frame #17: 0x00007fff6a816b8b libsystem_pthread.dylib`thread_start + 15

(lldb) f 6
frame #6: 0x000000010035378b 
qemu-system-x86_64`type_initialize(ti=0x000000010323fd70) at object.c:310:9 
[opt]
   307
   308      parent = type_get_parent(ti);
   309      if (parent) {
-> 310          type_initialize(parent);
   311          GSList *e;
   312          int i;
   313
(lldb) p *ti
(TypeImpl) $3 = {
  name = 0x000000010323fee0 "tls-creds-anon"
  class_size = 80
  instance_size = 88
  class_init = 0x0000000100365160 
(qemu-system-x86_64`qcrypto_tls_creds_anon_class_init at tlscredsanon.c:186)
  class_base_init = 0x0000000000000000
  class_data = 0x0000000000000000
  instance_init = 0x00000001003650d0 
(qemu-system-x86_64`qcrypto_tls_creds_anon_init at tlscredsanon.c:199)
  instance_post_init = 0x0000000000000000
  instance_finalize = 0x00000001003650e0 
(qemu-system-x86_64`qcrypto_tls_creds_anon_finalize at tlscredsanon.c:177)
  abstract = false
  parent = 0x000000010323fef0 "tls-creds"
  parent_type = 0x00000001032403e0
  class = 0x00000001032844f0
  num_interfaces = 1
  interfaces = {
    [0] = (typename = "user-creatable")
    [1] = (typename = 0x0000000000000000)
    [2] = (typename = 0x0000000000000000)
    [3] = (typename = 0x0000000000000000)
    [4] = (typename = 0x0000000000000000)
    [5] = (typename = 0x0000000000000000)
    [6] = (typename = 0x0000000000000000)
    [7] = (typename = 0x0000000000000000)
    [8] = (typename = 0x0000000000000000)
    [9] = (typename = 0x0000000000000000)
    [10] = (typename = 0x0000000000000000)
    [11] = (typename = 0x0000000000000000)
    [12] = (typename = 0x0000000000000000)
    [13] = (typename = 0x0000000000000000)
    [14] = (typename = 0x0000000000000000)
    [15] = (typename = 0x0000000000000000)
    [16] = (typename = 0x0000000000000000)
    [17] = (typename = 0x0000000000000000)
    [18] = (typename = 0x0000000000000000)
    [19] = (typename = 0x0000000000000000)
    [20] = (typename = 0x0000000000000000)
    [21] = (typename = 0x0000000000000000)
    [22] = (typename = 0x0000000000000000)
    [23] = (typename = 0x0000000000000000)
    [24] = (typename = 0x0000000000000000)
    [25] = (typename = 0x0000000000000000)
    [26] = (typename = 0x0000000000000000)
    [27] = (typename = 0x0000000000000000)
    [28] = (typename = 0x0000000000000000)
    [29] = (typename = 0x0000000000000000)
    [30] = (typename = 0x0000000000000000)
    [31] = (typename = 0x0000000000000000)
  }
}

(lldb) f 5 (NB, it's from the different run of lldb, so addresses can be
different due to KASLR)
qemu-system-x86_64 was compiled with optimization - stepping may behave oddly; 
variables may not be available.
frame #5: 0x0000000100353c00 
qemu-system-x86_64`type_initialize(ti=0x0000000101e409d0) at object.c:314:9 
[opt]
   311          GSList *e;
   312          int i;
   313
-> 314          g_assert(parent->class_size <= ti->class_size);
   315          g_assert(parent->instance_size <= ti->instance_size);
   316          memcpy(ti->class, parent->class, parent->class_size);
   317          ti->class->interfaces = NULL;
(lldb) p *ti
(TypeImpl) $0 = {
  name = 0x0000000101e40b40 "tls-creds"
  class_size = 40
  instance_size = 80
  class_init = 0x0000000100369740 
(qemu-system-x86_64`qcrypto_tls_creds_class_init at tlscreds.c:229)
  class_base_init = 0x0000000000000000
  class_data = 0x0000000000000000
  instance_init = 0x00000001003696d0 (qemu-system-x86_64`qcrypto_tls_creds_init 
at tlscreds.c:249)
  instance_post_init = 0x0000000000000000
  instance_finalize = 0x0000000100369700 
(qemu-system-x86_64`qcrypto_tls_creds_finalize at tlscreds.c:258)
  abstract = true
  parent = 0x0000000101e40b50 "object"
  parent_type = 0x0000000101e3f360
  class = 0x0000000101e84b30
  num_interfaces = 0
  interfaces = {
    [0] = (typename = 0x0000000000000000)
    [1] = (typename = 0x0000000000000000)
    [2] = (typename = 0x0000000000000000)
    [3] = (typename = 0x0000000000000000)
    [4] = (typename = 0x0000000000000000)
    [5] = (typename = 0x0000000000000000)
    [6] = (typename = 0x0000000000000000)
    [7] = (typename = 0x0000000000000000)
    [8] = (typename = 0x0000000000000000)
    [9] = (typename = 0x0000000000000000)
    [10] = (typename = 0x0000000000000000)
    [11] = (typename = 0x0000000000000000)
    [12] = (typename = 0x0000000000000000)
    [13] = (typename = 0x0000000000000000)
    [14] = (typename = 0x0000000000000000)
    [15] = (typename = 0x0000000000000000)
    [16] = (typename = 0x0000000000000000)
    [17] = (typename = 0x0000000000000000)
    [18] = (typename = 0x0000000000000000)
    [19] = (typename = 0x0000000000000000)
    [20] = (typename = 0x0000000000000000)
    [21] = (typename = 0x0000000000000000)
    [22] = (typename = 0x0000000000000000)
    [23] = (typename = 0x0000000000000000)
    [24] = (typename = 0x0000000000000000)
    [25] = (typename = 0x0000000000000000)
    [26] = (typename = 0x0000000000000000)
    [27] = (typename = 0x0000000000000000)
    [28] = (typename = 0x0000000000000000)
    [29] = (typename = 0x0000000000000000)
    [30] = (typename = 0x0000000000000000)
    [31] = (typename = 0x0000000000000000)
  }
}

It doesn't seem related to HVF QOM changes 🤔

Bisected it to:

b717702de21461138ac0e1d6775da0bd0482c013 is the first bad commit
commit b717702de21461138ac0e1d6775da0bd0482c013
Author: Daniel P. Berrangé <berrange@redhat.com>
Date:   Wed Aug 19 20:12:35 2020 -0400

    crypto: use QOM macros for declaration/definition of secret types

    This introduces the use of the OBJECT_DEFINE and OBJECT_DECLARE macro
    families in the secret types, in order to eliminate boilerplate code.

    Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
    Message-Id: <20200723181410.3145233-4-berrange@redhat.com>
    [ehabkost: rebase, update to pass additional arguments to macro]
    Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
    Message-Id: <20200820001236.1284548-58-ehabkost@redhat.com>

Regards,
Roman
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