Re: Library auditing interface stability?

[Steven Munroe <munroesj at linux dot vnet dot ibm dot com>]

On Thu, 2016-05-05 at 11:57 -0400, Carlos O'Donell wrote:
> 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.
> 
Not VSX or TAR but VMX regs are, which GLIBC was library audit
added? ...