Re: Library auditing interface stability?

[Carlos O'Donell <carlos@redhat.com>]

On 05/05/2016 10:56 AM, Steven Munroe wrote:
> On Thu, 2016-04-28 at 15:21 -0400, Carlos O'Donell wrote:
>> 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?
>>
> 
> I am not sure if the audit modules need to now or care about PPC VSX or
> TAR, but if memory serves. VSX was added after the audit API.
 
Is VSX or TAR part of the procedure call sequence?

The La_*_regs structure allows an audit module to modify incoming
registers to the function using the PLT hook being provided by the
audit infrastructure.

Cheers,
Carlos.

 


-- 
Cheers,
Carlos.