Re: [PATCH] meson: -display dbus and CFI are incompatible

[Paolo Bonzini]

On Fri, Sep 30, 2022 at 9:59 AM Marc-André Lureau
<marcandre.lureau@gmail.com> wrote:
>
> Hi
>
> On Fri, Sep 30, 2022 at 11:53 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>> The generated skeletons for DBus call the finalize method of the parent
>> type using code like
>>
>>     G_OBJECT_CLASS 
>> (qemu_dbus_display1_chardev_skeleton_parent_class)->finalize (object);
>>
>> However, the finalize method is defined in a shared library that is not
>> compiled with CFI.  Do not enable anything that uses gdbus-codegen if
>> --enable-cfi was specified.
>
> I had the same analysis. But what if gdbus (or other dependencies) is 
> compiled with CFI ? Note: I have no idea if CFI is meant to be usable in 
> production or just for developers.

Yeah, in theory it's possible but I think it's very unlikely. For
libslirp QEMU ignores that possibility and requires a version with a
fixed API, but that's not really possible for the gdbus superclasses.

Paolo

>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>
>
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>
>
>>
>> ---
>>  meson.build | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/meson.build b/meson.build
>> index f6962834a3..6106daf267 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -515,6 +515,7 @@ meson.override_dependency('glib-2.0', glib)
>>
>>  gio = not_found
>>  gdbus_codegen = not_found
>> +gdbus_codegen_error = '@0@ requires gdbus-codegen, please install libgio'
>>  if not get_option('gio').auto() or have_system
>>    gio = dependency('gio-2.0', required: get_option('gio'),
>>                     method: 'pkg-config', kwargs: static_kwargs)
>> @@ -539,6 +540,10 @@ if not get_option('gio').auto() or have_system
>>                               version: gio.version())
>>    endif
>>  endif
>> +if gdbus_codegen.found() and get_option('cfi')
>> +  gdbus_codegen = not_found
>> +  gdbus_codegen_error = '@0@ uses gdbus-codegen, which does not support 
>> control flow integrity')
>> +endif
>>
>>  lttng = not_found
>>  if 'ust' in get_option('trace_backends')
>> @@ -1697,7 +1702,7 @@ dbus_display = get_option('dbus_display') \
>>    .require(gio.version().version_compare('>=2.64'),
>>             error_message: '-display dbus requires glib>=2.64') \
>>    .require(gdbus_codegen.found(),
>> -           error_message: '-display dbus requires gdbus-codegen') \
>> +           error_message: gdbus_codegen_error.format('-display dbus')) \
>>    .require(opengl.found() and gbm.found(),
>>             error_message: '-display dbus requires epoxy/egl and gbm') \
>>    .allowed()
>> --
>> 2.37.3
>>
>>
>
>
> --
> Marc-André Lureau