Purpose of gen_tar

Purpose of gen_tar

[Marcos Paulo de Souza]

Hi,

while testing a new patch on the livepatch kselftests, I was testing the gen_tar
target and I figured that we only copy the resulting binaries to the final tar
file.

Per the kselftests documentation[1], the gen_tar target is used to package the
tests to run "on different systems". But what if the different system has
different libraries/library versions? Wouldn't it be a problem?

This question came when I was working to build the livepatch modules as part of
the kselftests testing suit. The plan was to just package the test
scripts/programs/modules and then run the tests on a different system, likewise
a different SLE version. Since the kernel would be different in this case, I
expected that gen_tar would copy the module source files so they can be compiled
on the target system.

While the current approach can work when the selftests rely solely on shell scripts(cpufreq, kexec),
those who compile userspace binaries (cgroup, alsa, sched, ...) may not work.

Am I missing something? Is gen_tar only meant to copy the tests to be run on
systems with the same libraries or with the libraries with the exactly the same
version?

Thanks in advance,
  Marcos

[1]: https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html

RE: Purpose of gen_tar

[Bird, Tim]

> -----Original Message-----
> From: Marcos Paulo de Souza <mpdesouza@suse.de>
> 
...
> Per the kselftests documentation[1], the gen_tar target is used to package the
> tests to run "on different systems". But what if the different system has
> different libraries/library versions? Wouldn't it be a problem?
> 
...
> 
> While the current approach can work when the selftests rely solely on shell scripts(cpufreq, kexec),
> those who compile userspace binaries (cgroup, alsa, sched, ...) may not work.
> 
> Am I missing something? Is gen_tar only meant to copy the tests to be run on
> systems with the same libraries or with the libraries with the exactly the same
> version?

gen_tar was originally intended (I believe) for developers doing cross-compilation.
The SDK used for cross-compilation of the executables should handle issues such as
library versions (and of course, CPU architecture and endian-ness).

I've never done cross-compilation for the same architecture, so I don't know how that
would work, but I presume there is some way to compile code for another system
with the same architecture but different libraries.
 -- Tim

Re: Purpose of gen_tar

[Shuah Khan]

On 10/24/23 12:34, Bird, Tim wrote:
> 
> 
>> -----Original Message----- From: Marcos Paulo de Souza
>> <mpdesouza@suse.de>
>> 
> ...
>> Per the kselftests documentation[1], the gen_tar target is used to
>> package the tests to run "on different systems". But what if the
>> different system has different libraries/library versions? Wouldn't
>> it be a problem?
>> 
> ...
>> 
>> While the current approach can work when the selftests rely solely
>> on shell scripts(cpufreq, kexec), those who compile userspace
>> binaries (cgroup, alsa, sched, ...) may not work.
>> 
>> Am I missing something? Is gen_tar only meant to copy the tests to
>> be run on systems with the same libraries or with the libraries
>> with the exactly the same version?
> 
> gen_tar was originally intended (I believe) for developers doing
> cross-compilation. The SDK used for cross-compilation of the
> executables should handle issues such as library versions (and of
> course, CPU architecture and endian-ness).
> 
> I've never done cross-compilation for the same architecture, so I
> don't know how that would work, but I presume there is some way to
> compile code for another system with the same architecture but
> different libraries.

Right. gen_tar was intended to be used when a user wants to generate tar
archive of all the complied tests/installed tests. Running kselftest_install
creates a directory with artifacts necessary to execute tests.

This functionality is now part of the selftests Makefile - gen_tar target will
do the same.

thanks,
-- Shuah