Re: [Qemu-devel] RFC: DSO (dynamic shared objects) support

[Michael Tokarev <mjt@tls.msk.ru>]

18.06.2013 16:19, Michael Tokarev пишет:
> 18.06.2013 16:17, Laszlo Ersek wrote:
>> On 06/18/13 13:37, Michael Tokarev wrote:
>>
>>> Next, and this is the most complex part.  The build system for
>>> modules, and configuring it.   I heard there were plans to use
>>> something like kbuild system for that, has anything been done
>>> in this context?
>>
>> Sorry for responding separately... Some module/symbol versioning will be
>> necessary, as the binding will be delayed until runtime, and users
>> *will* mix and match qemu and modules, and get random crashes. AFAIK
>> versioning is a good way to avoid that (you would get an error in
>> dlopen(), and dlerror() would pinpoint problem).
>>
>> No idea how to implement this though, except I expect there's no chance
>> to do it halfway portably without libtool.
> 
> Well, I think this is trivial really.
> 
> Duding build, we re-#define register_module_init() to have a version
> number (or even a build id), for example register_module_init_1_6_0().
> This is a function which each plugin will call inside its constructor.
> Being unable to find this symbol in calling qemu it will fail to load.

$ ./x86_64-softmmu/qemu-system-x86_64 -hda http://foo/bar
warning: unable to load plugin plugins/block_curl.so: plugins/block_curl.so: undefined symbol: register_module_init_1_6_0
qemu-system-x86_64: -hda http://foo/bar: could not open disk image http://foo/bar: No such file or directory

Looks clear enough.

Also, we may add version number to the plugin name too.

/mjt