[elrepo] building with retpoline-enabled compiler?

[Phil Perry]

On 18/03/18 23:30, Leon Fauster via elrepo wrote:
> OS: EL6
> 
> Must all kmod packages be rebuild with the new compiler (released recently)?
> 
> # dmesg  | grep -i retpo
> Spectre V2 : Mitigation: Full retpoline
> Spectre V2 : WARNING: module 'rr174x' built without retpoline-enabled compiler, may affect Spectre v2 mitigation
> 
> "Especially for kernel versions" -ge "kernel-2.6.32-696.23.1.el6.x86_64"
> 
> Just curious,
> 
> LF
> 
> 

I have a ticket open with Red Hat on that subject atm, but my feeling is 
potentially yes, but it may depend upon the driver code in question.

The warning message is slightly misleading as the package must also be 
rebuilt against a retpoline-aware kernel (e.g 
kernel-2.6.32-696.23.1.el6.x86_64) whereas we would normally build 
against a point release base kernel (e.g kernel-2.6.32-696.el6.x86_64).

The modules I've rebuilt so far that use any of the new 
__x86_indirect_thunk_* symbols obviously break backward compatibility as 
those symbols aren't available in pre-retpoline kernels.

We had discussed mass rebuilding all el7 kmod packages against el7.5 
when it is released shortly, but we could press ahead and rebuild el6 
modules as there is currently no el6 point release pending.