Re: [PATCH v2 0/4] s390: compile relocatable kernel with/without fPIE

[Joe Lawrence <joe.lawrence@redhat.com>]

On 6/19/24 14:23, Joe Lawrence wrote:
> On 6/19/24 13:01, Sumanth Korikkar wrote:
>> Other Note:
>> The latest kernel is built with -fPIC and linked with -no-pie (reference
>> commit: ca888b17da9b ("s390: Compile kernel with -fPIC and link with
>> -no-pie")) which also avoids generation of dynamic symbols and helps
>> kpatch usecases (when num of sections >=64k sections).  Also the build
>> options would be similar (-fPIC in kernel and -fPIC in kpatch-build)
>>
>> For latest kernel, there is no need to add explicit -fPIC again
>> in kpatch tool.
>>
>> But for the intermediate commits, yes, makes sense to add
>> it in kpatch-build tools and will create one PR.
>>
> 
> Interesting!  With 00cda11d3b2e ("s390: Compile kernel with -fPIC and
> link with -no-pie") it sounds like the original vmlinux would be built
> with -fPIC as well, so the optimization decisions re: __mmput() would
> likely be the same.  I can retry the tests with v6.10-rcX to verify.
> 

To follow up, all of the kpatch-build integration tests work with
v6.10.0-rc4 :) as the kernel is built with -fPIC and so are the kpatch
reference and patched builds.  For pre-v6.10 kernels, I think there may
be some instances where a patch author may need to account for slight
build differences to appease kpatch-build expectations as I noticed here.

-- 
Joe