[v4, 1/3] kernel/modules: Add REL24 relocation support of livepatch symbols

[Michael Ellerman]

On Tue, 2017-11-14 at 09:29:08 UTC, Kamalesh Babulal wrote:
> Livepatch re-uses module loader function apply_relocate_add() to write
> relocations, instead of managing them by arch-dependent
> klp_write_module_reloc() function.
> 
> apply_relocate_add() doesn't understand livepatch symbols (marked with
> SHN_LIVEPATCH symbol section index) and assumes them to be local symbols
> by default for R_PPC64_REL24 relocation type. It fails with an error,
> when trying to calculate offset with local_entry_offset():
> 
>  module_64: kpatch_meminfo: REL24 -1152921504897399800 out of range!
> 
> Whereas livepatch symbols are essentially SHN_UNDEF, should be
> called via stub used for global calls. This issue can be fixed by
> teaching apply_relocate_add() to handle both SHN_UNDEF/SHN_LIVEPATCH
> symbols via the same stub. This patch extends SHN_UNDEF code to handle
> livepatch symbols too.
> 
> Signed-off-by: Kamalesh Babulal <kamalesh at linux.vnet.ibm.com>
> CC: Balbir Singh <bsingharora at gmail.com>
> Cc: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> Cc: Josh Poimboeuf <jpoimboe at redhat.com>
> Cc: Jessica Yu <jeyu at kernel.org>
> Cc: Ananth N Mavinakayanahalli <ananth at linux.vnet.ibm.com>
> Cc: Aravinda Prasad <aravinda at linux.vnet.ibm.com>
> Cc: Torsten Duwe <duwe at lst.de>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/a443bf6e8a7674b86221f4922cae82

cheers