Re: Library auditing interface stability?

[Carlos O'Donell <carlos at redhat dot com>]

On 04/28/2016 04:20 AM, Florian Weimer wrote:
> On 04/20/2016 04:24 PM, Ulrich Drepper wrote:
>> On Tue, Apr 19, 2016 at 5:03 PM, Carlos O'Donell
>> <carlos@redhat.com> wrote:
>>> In particular the La_*_regs and La_*_retval which contains 
>>> additional registers as we expand the supported ISAs.
>> 
>> la_version is there to preserve unlimited backward compatibility.
> 
> We have not used this mechanism when we added support for additional
> registers to be passed to the PLT callbacks.  Looking at commits
> 14c5cbabc2d11004ab223ae5eae761ddf83ef99e and 
> 5cdd1989d1d2f135d02e66250f37ba8e767f9772, there is no way for an
> audit module to notice if these additional fields are maintained by
> glibc.

I think we should have bumped the la_version number for all changes
to the structure for any architecture.

Do we fix this by bumping LAV_CURRENT?

diff --git a/elf/link.h b/elf/link.h
index f448141..cbf94a3 100644
--- a/elf/link.h
+++ b/elf/link.h
@@ -95,8 +95,13 @@ struct link_map
 
 #ifdef __USE_GNU
 
-/* Version numbers for la_version handshake interface.  */
-#define LAV_CURRENT    1
+/* Version numbers for la_version handshake interface.
+   1 - Initial implementation.
+   2 - Added lrv_bnd0 and lrv_bnd1 to La_i86_retval.
+   3 - Added lr_v[24,25,26,27,28,29,30,31] to La_s390_64_regs, and
+       La_s390_32_regs. Added lrv_v24 to La_s390_64_retval and
+       La_s390_64_retval.  */
+#define LAV_CURRENT    3
 
 /* Activity types signaled through la_activity.  */
 enum
---

We can't fix audit modules in the field which return 1.

We can fix newly compiled audit modules, making them expect
a LAV_CURRENT of 3, such that they can't be run with older
LAV_CURRENT 1 glibc which doesn't have BIND on x86 or
VSX on s390?

-- 
Cheers,
Carlos.