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

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 <redacted>
CC: Balbir Singh <bsingharora@gmail.com>
Cc: Naveen N. Rao <redacted>
Cc: Josh Poimboeuf <redacted>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Ananth N Mavinakayanahalli <redacted>
Cc: Aravinda Prasad <redacted>
Cc: Torsten Duwe <redacted>

Applied to powerpc next, thanks.

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

cheers