Re: [ptxdist] [PATCH v4 1/2] Add libfaketime as a core component of ptxdist for patchin support

[Jon Ringle <jon@ringle.org>]

On Wed, Aug 8, 2018 at 6:58 AM Jon Ringle <jon@ringle.org> wrote:
> On Wed, Aug 8, 2018 at 5:50 AM Roland Hieber <r.hieber@pengutronix.de> wrote:
>> On Fri, Aug 03, 2018 at 11:44:55AM -0400, jon@ringle.org wrote:
>> > From: Jon Ringle <jringle@gridpoint.com>
>> >
>> > libfaketime will be used during patchin so that committer timestamps always
>> > have a fixed value and therefore making the ${PKG}_SERIES_SHA256 value
>> > repeatable
>> >
>> > The minimal set of source files was picked out of libfaketime-0.9.7
>> >
>> > Signed-off-by: Jon Ringle <jringle@gridpoint.com>
>> > ---
>> >  Makefile.in                           |   14 +-
>> >  scripts/libfaketime/Makefile          |  118 ++
>> >  scripts/libfaketime/faketime.c        |  385 ++++++
>> >  scripts/libfaketime/faketime_common.h |   61 +
>> >  scripts/libfaketime/libfaketime.c     | 2410 +++++++++++++++++++++++++++++++++
>> >  scripts/libfaketime/libfaketime.map   |   10 +
>> >  scripts/libfaketime/time_ops.h        |  104 ++
>>
>> Uh. Does it really make more sense to vendor libfaketime instead of
>> using the package from the host system, like we do it with python, bash,
>> etc.?
>
>
> The reason that this is needed as a core component of ptxdist rather than just being built as a host package is that patchin step uses libfaketime and therefore is potentially needed before even a single package is ever built. What would happen if we just used a host-libfaketime package and someone adds a patch series for libfaketime? (In fact, I actually do have such a patch series locally that I will be sending to the ptxdist ml later). This is a chicken vs egg problem that is resolved by making libfaketime an integral part of ptxdist. The ptxdist usage of libfaketime in the patchin step does not need a patched version of libfaketime (it just needs to set an absolute date time and the libfaketime code I have here does that). It doesn’t need new configuration features or bug fixes for fixing the time manipulation via some specific system call.

Roland, I think I see now what you are getting at. However, do you
think it is ok to ask everyone to install libfaketime on their system
(`sudo apt-get install libfaketime`) before they are able to configure
the next version of ptxdist? On ubuntu 14.04 this package installs the
following files for me:

/usr/lib/x86_64-linux-gnu/faketime/libfaketime.so.1
/usr/lib/x86_64-linux-gnu/faketime/libfaketimeMT.so.1
/usr/share/doc/libfaketime/README.gz
/usr/share/doc/libfaketime/changelog.Debian.gz
/usr/share/doc/libfaketime/copyright

There is nothing here that I see that can be used to properly set the
correct location of the libfaketime.so.1 when setting LD_PRELOAD
environment. It could be in a different location on some other
distribution.
The libfaketime code is fairly small and making it a part of ptxdist
like kconfig is just makes sense to me given the use case where it is
needed

-Jon

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